Genetics, Physiology and Cultivation of Moth Bean, Cowpea and Horse Gram 9811999554, 9789811999550

Citation preview

Rakesh Pathak

Genetics, Physiology and Cultivation of Moth Bean, Cowpea and Horse Gram

Genetics, Physiology and Cultivation of Moth Bean, Cowpea and Horse Gram

Rakesh Pathak

Genetics, Physiology and Cultivation of Moth Bean, Cowpea and Horse Gram

Rakesh Pathak Central Arid Zone Research Institute Jodhpur, Rajasthan, India

ISBN 978-981-19-9955-0 ISBN 978-981-19-9956-7 https://doi.org/10.1007/978-981-19-9956-7

(eBook)

# The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 This work is subject to copyright. All rights are solely and exclusively licensed by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors, and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, expressed or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. This Springer imprint is published by the registered company Springer Nature Singapore Pte Ltd. The registered company address is: 152 Beach Road, #21-01/04 Gateway East, Singapore 189721, Singapore

Dedicated to my parents Mrs. Urmila-Mr. R.S. Pathak, my wife Mrs. Sheela and my son Mayank

Preface

Legumes utilized as pulses or grains play an important role in the sustainable agriculture, improving livelihood and nutritional security of population of developing countries and also provide raw materials to the food and feed industries. They are valuable for soil-building, improving soil quality and biological nitrogen fixation. Legumes have acquired global importance due to the presence of higher protein content. Traditionally, legumes have been an integral component of vegetarian diet in India and fulfill the need of required protein. India is one of the largest producers as well as consumers of legumes globally. These are cultivated over a vast area nearly 30.37 million hectares in the country and produced about 26.96 million metric tonnes, which is all time highest in the world. Arid legumes are crops characterized by inherent features and capabilities to withstand under adverse and harsh climatic conditions, significantly replenish the soil, provide rich protein and micronutrients. Adaptability to several stresses including drought makes them key to agriculture in the areas receiving scanty rainfall. Physiology and genetics provides an inimitable source of information on the distinct aspects of basic and applied legume research for general readers, students, academicians, and researchers. This book gives insight into morphology, physiology, genetics, plant protection, and biotechnology of three important arid legumes, viz., moth bean, cowpea, and horse gram. This book has been organized in three sections (moth bean, cowpea, and horse gram) and each section has seven chapters. Chapter 1 introduces the crops and describes the basic introduction including prospects and constraints. Chapter 2 covers genetic improvement and variability of the crops and includes various tools and techniques used for the genetic improvement and creation of variability in the crops. Chapter 3 is dedicated to quality and nutrition of the crop and covers the nutritional composition, anti-nutritional factors, nutraceutical and medicinal properties. Chapter 4 is devoted to the cultivation of the crops and also gives information on the varieties of the crops developed in India. Chapter 5 presents the plant protection aspect of moth bean, cowpea, and horse gram. Chapter 6 addresses physiological and abiotic stress-related aspects of the crops. Chapter 7 covers the reviews on the genetic markers and biotechnological works accomplished with respect to these legumes. All the included chapters present research findings and brief reviews concerning the advances made in the improvement of these legumes. The study has been systematically referred to the research vii

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Preface

papers and data from industry and markets. The book is of importance to teachers, researchers, and policy makers who are interested to acquire knowledge about moth bean, cowpea, and horse gram. It also serves as an additional reading material for postgraduate students of agriculture and environmental sciences. Jodhpur, Rajasthan, India

Rakesh Pathak

About the Book

Legumes are utilized as pulses or grains aiding as an important source of protein for both human and animal consumption and also provide raw materials to the food and feed industries. They are also valuable for soil-building, improving soil quality and biological nitrogen fixation. Physiology and genetics provides an inimitable source of information on the distinct aspects of basic and applied legume research for general readers, students, academicians, and researchers. Arid legumes are crops characterized by inherent features and capabilities to withstand under adverse and harsh climatic conditions, significantly replenish the soil, as well as proteins and micronutrients. Adaptability to several stresses including drought makes them key to agriculture in the areas receiving scanty rainfall. This book gives insight into morphology, physiology, genetics, plant protection, and biotechnology of three important arid legumes, viz., moth bean, cowpea, and horse gram. There are seven chapters for each crop that provide in-depth information on cultivation, genetic improvement, plant protection measures, management of physiological and abiotic stresses along with related genetic markers and biotechnological advances pertaining to these legumes. The chapters that are included present research findings and brief reviews concerning the advances made in the improvement of these legumes. This comprehensive book disseminates significant information on the genetic diversity, cultivation, manipulation through mutagenic techniques, molecular biology, and other breeding techniques. The book, therefore, is of importance to teachers, researchers, and policy makers who are interested to acquire knowledge about moth bean, cowpea, and horse gram. It also serves as an additional reading material for M.Sc. and Ph.D. students of agriculture and environmental sciences.

ix

Contents

Part I

Cowpea

1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2 Floral Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3 Taxonomic Classification . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.4 Botany . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.5 Origin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.6 Cytogenetics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.7 Molecular Biology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.8 Uses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.9 Prospects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.10 Constraints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3 3 5 5 6 7 8 8 9 9 10 10

2

Genetic Improvement and Variability . . . . . . . . . . . . . . . . . . . . . . . 2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2 Morphometric Characterization . . . . . . . . . . . . . . . . . . . . . . . 2.3 Genetic Divergence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.4 Correlation and Path Coefficient Analysis . . . . . . . . . . . . . . . . 2.5 Hybridization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.6 Inheritance Studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.7 Combining Ability and Diallel Analysis . . . . . . . . . . . . . . . . . 2.8 Heterosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.9 Genetic Variability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.9.1 Genotypic and Phenotypic Coefficient of Variation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.9.2 Heritability and Genetic Advance . . . . . . . . . . . . . . 2.10 Genotype-Environmental Interaction . . . . . . . . . . . . . . . . . . . . 2.11 Mutation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.12 Nitrogen-Fixing Ability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15 15 16 17 20 25 26 27 30 31 32 34 38 39 40 41

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3

Quality and Nutrition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2 Nutrient Value . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3 Anti-nutritional Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4 Cooking Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.5 Medicinal Values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.6 Nutraceutical Properties of Cowpea . . . . . . . . . . . . . . . . . . . . 3.7 Uses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

55 55 56 58 59 59 60 61 61

4

Cultivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2 Climate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3 Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4 Field Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.5 Sowing Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.6 Seed Rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.7 Method of Sowing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.8 Germination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.9 Irrigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.10 Fertilizer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.11 Weed Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.12 Cowpea Under Intercropping System . . . . . . . . . . . . . . . . . . . 4.13 Cowpea Under Crop Rotation System . . . . . . . . . . . . . . . . . . . 4.14 Seed Treatment and Inoculation with Bacterial Culture . . . . . . 4.15 Harvesting and Threshing . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.16 Photoperiodism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.17 Cowpea Varieties Developed in India . . . . . . . . . . . . . . . . . . . 4.18 Cowpea Production in India . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

67 67 68 68 69 69 69 70 70 71 71 73 74 75 76 76 77 78 92 94

5

Plant Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2 Fungal Disease . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2.1 Cowpea Rust . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2.2 Anthracnose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2.3 Blight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2.4 Wilt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2.5 Leaf Spot . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2.6 Powdery Mildew . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2.7 Root Rot . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2.8 Basal Stem Rot . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2.9 Seedling Mortality . . . . . . . . . . . . . . . . . . . . . . . . .

99 99 100 100 101 102 102 103 103 104 105 106

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5.3

Bacterial Diseases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.3.1 Blight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.3.2 Bacterial Spot . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.4 Viral Diseases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.4.1 Cowpea Mosaic . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.4.2 Cowpea Yellow Mosaic . . . . . . . . . . . . . . . . . . . . . 5.5 Insect Pests of Cowpea and Their Management . . . . . . . . . . . . 5.5.1 Pod Borer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.5.2 Leaf Hopper and Foliage Beetles . . . . . . . . . . . . . . . 5.5.3 Thrips . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.5.4 Weevil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.5.5 Aphids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.5.6 Pod-Sucking Bugs . . . . . . . . . . . . . . . . . . . . . . . . . 5.5.7 Blister Beetle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.5.8 Bean Fly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.5.9 White Fly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.5.10 Jassids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.5.11 Cut Worm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.5.12 White Grub . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.6 Striga Gesnerioides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.7 Nematodes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.8 Storage Grain Pest . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.9 Disease and Pest Linked Resistance Markers . . . . . . . . . . . . . . 5.10 Termites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.11 Integrated Pest Management . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

106 106 107 107 108 108 108 109 109 110 110 111 112 112 113 113 113 114 114 114 115 115 116 116 116 117

6

Physiology and Abiotic Stresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2 Seed Coat Colour . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3 Germination and Seedling Growth . . . . . . . . . . . . . . . . . . . . . 6.4 Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.5 Water Stress and Drought Tolerance . . . . . . . . . . . . . . . . . . . . 6.6 Salt Tolerance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.7 Other Abiotic Stress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

125 125 126 126 127 128 130 131 132

7

Genetic Markers and Biotechnology . . . . . . . . . . . . . . . . . . . . . . . . 7.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.2 Biochemical Markers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.3 Molecular Markers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.4 PCR-Based Markers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.4.1 Random Amplified Polymorphic DNA (RAPD) . . . . 7.4.2 Simple Sequence Repeat (SSR) . . . . . . . . . . . . . . . .

139 139 140 141 142 142 143

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7.4.3

Amplified Fragment Length Polymorphism (AFLP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.4.4 Inter Simple Sequence Repeats (ISSR) . . . . . . . . . . . 7.4.5 DNA Amplification Fingerprinting (DAF) . . . . . . . . 7.4.6 Sequence-Related Amplified Polymorphism (SRAP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.5 Genetic Linkage Studies and Inheritance . . . . . . . . . . . . . . . . . 7.6 Genetic Map Studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.7 Restriction Fragment Length Polymorphism (RFLP) . . . . . . . . 7.8 Transcriptomic Studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.9 Callus Induction and Regeneration Protocol . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Part II

144 145 146 147 147 148 150 150 151 154

Horsegram

8

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.2 Origin and Distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.3 Descriptive Botany and Taxonomy . . . . . . . . . . . . . . . . . . . . . 8.4 Taxonomic Classification . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.5 Botany . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.6 Constraints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.7 Prospects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

165 165 167 168 169 170 171 171 171

9

Genetic Improvement and Variability . . . . . . . . . . . . . . . . . . . . . . . 9.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.2 Morphometric Characterization . . . . . . . . . . . . . . . . . . . . . . . 9.3 Genetic Divergence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.4 Correlation and Path Coefficient Analysis . . . . . . . . . . . . . . . . 9.5 Hybridization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.6 Inheritance Studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.7 Diallel Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.8 Heterosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.9 Genetic Variability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.9.1 Genotypic and Phenotypic Coefficient of Variation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.9.2 Heritability and Genetic Advances . . . . . . . . . . . . . . 9.10 Genotype-Environmental Interaction . . . . . . . . . . . . . . . . . . . . 9.11 Mutation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.12 Nitrogen Fixing Ability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

177 177 179 179 181 184 185 185 186 186

10

187 189 190 191 194 195

Quality and Nutrition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203 10.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203 10.2 Nutrient Value . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204

Contents

10.3 Anti-nutritional Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.4 Medicinal Values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.5 Nutraceutical Properties of Horsegram . . . . . . . . . . . . . . . . . 10.6 Chemical Compound . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.7 Uses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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207 208 209 210 211 212

11

Cultivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.2 Soil and Climate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.3 Horsegram Under Intercropping System . . . . . . . . . . . . . . . . . 11.4 Horsegram Under Crop Rotation System . . . . . . . . . . . . . . . . 11.5 Sowing Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.6 Seed Rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.7 Spacing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.8 Sowing Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.9 Fertilizer Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.10 Seed Treatment and Inoculation with Bacterial Culture . . . . . . 11.11 Irrigation Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.12 Weed Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.13 Harvesting and Threshing . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.14 Photoperiodism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.15 Horsegram Production in India . . . . . . . . . . . . . . . . . . . . . . . . 11.16 Horsegram Varieties Developed in India . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

219 219 220 220 221 222 222 222 223 223 225 226 226 226 226 227 237 241

12

Plant Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.2 Proteases and Bowman–Birk Inhibitors . . . . . . . . . . . . . . . . . . 12.3 Fungal Disease . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.3.1 Anthracnose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.3.2 Powdery Mildew . . . . . . . . . . . . . . . . . . . . . . . . . . 12.3.3 Dry Root Rot . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.3.4 Leaf Spot . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.3.5 Rust . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.3.6 Blight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.3.7 Wilt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.4 Viral Diseases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.4.1 Yellow Mosaic Virus . . . . . . . . . . . . . . . . . . . . . . . 12.5 Bacterial Disease . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.5.1 Bacterial Leaf Spot . . . . . . . . . . . . . . . . . . . . . . . . . 12.6 Nematode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.7 Insect Pests of Horsegram . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.7.1 Pod Caterpillar . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.7.2 Leaf Miner . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

245 245 246 247 247 248 248 249 249 250 250 251 251 252 252 252 253 253 253

xvi

Contents

12.7.3 Leaf Hopper . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.7.4 Pod Bug . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.7.5 Pod Fly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.7.6 Thrips . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.7.7 White Fly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.7.8 Pod Borer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.7.9 Leaf Roller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.7.10 Hairy Caterpillar . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.8 Integrated Disease Management . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

254 254 254 254 255 255 255 255 255 256

13

Physiology and Abiotic Stresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.2 Seed Coat Colour . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.3 Germination and Seedling Growth . . . . . . . . . . . . . . . . . . . . . 13.4 Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.5 Water Stress and Drought Tolerance . . . . . . . . . . . . . . . . . . . . 13.6 Salt Tolerance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.7 Heavy Metal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

261 261 262 263 263 264 265 266 267

14

Genetic Markers and Biotechnology . . . . . . . . . . . . . . . . . . . . . . . . 14.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.2 Biochemical Markers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.3 Molecular Markers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.4 PCR-Based Markers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.4.1 RAPD and ISSR . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.4.2 SSR, EST and ILP . . . . . . . . . . . . . . . . . . . . . . . . . 14.5 Transcriptomic Studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.6 Callus Induction and Regeneration Protocol . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

273 273 274 275 277 277 278 280 281 283

Part III 15

Moth Bean

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.2 Origin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.3 Taxonomic Classification . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.4 Botany . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.5 Floral Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.6 Cytogenetics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.7 Molecular Biology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.8 Uses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.9 Prospects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.10 Constraints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

289 289 290 291 291 292 292 293 294 294 295 296

Contents

xvii

Genetic Improvement and Variability . . . . . . . . . . . . . . . . . . . . . . . 16.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.2 Genetic Divergence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.3 Correlation and Path Coefficient Analysis . . . . . . . . . . . . . . . . 16.4 Hybridization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.5 Genetic Variability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.5.1 Genotypic and Phenotypic Coefficient of Variation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.5.2 Heritability and Genetic Advance . . . . . . . . . . . . . . 16.6 Genotype-Environmental Interaction . . . . . . . . . . . . . . . . . . . . 16.7 Mutation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.8 Nitrogen Fixing Ability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

305 306 308 309 311 311

17

Quality and Nutrition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.2 Phytochemical Composition . . . . . . . . . . . . . . . . . . . . . . . . . . 17.3 Nutrient Value . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.4 Anti-nutritional Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.5 Cooking Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.6 Nutraceutical Properties of Moth Bean . . . . . . . . . . . . . . . . . . 17.7 Uses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

317 317 319 320 322 324 325 326 327

18

Cultivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.2 Climate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.3 Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.4 Field Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.5 Sowing Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.6 Row Spacing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.7 Seed Rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.8 Method of Sowing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.9 Irrigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.10 Fertilizer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.11 Weed Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.12 Moth Bean Under Intercropping System . . . . . . . . . . . . . . . . . 18.13 Seed Treatment and Inoculation with Bacterial Culture . . . . . . 18.14 Harvesting and Threshing . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.15 Moth Bean Varieties Developed in India . . . . . . . . . . . . . . . . . 18.16 Moth Bean Production in India . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

333 333 334 335 335 335 336 337 337 338 338 339 340 341 341 342 345 349

16

299 299 300 302 304 305

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Contents

19

Plant Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.2 Fungal Disease . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.2.1 Anthracnose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.2.2 Web Blight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.2.3 Wilt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.2.4 Leaf Spot and Pod Infection . . . . . . . . . . . . . . . . . . 19.2.5 Cercospora Species . . . . . . . . . . . . . . . . . . . . . . . . 19.2.6 Colletotrichum . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.2.7 Myrothecium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.2.8 Alternaria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.2.9 Curvularia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.2.10 Powdery Mildew . . . . . . . . . . . . . . . . . . . . . . . . . . 19.2.11 Root Rot . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.2.12 Seedling Mortality . . . . . . . . . . . . . . . . . . . . . . . . . 19.2.13 Seedling Rot . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.2.14 Pod Rot . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.2.15 Seed Microflora . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.3 Bacterial Diseases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.3.1 Blight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.3.2 Bacterial Leaf Spot . . . . . . . . . . . . . . . . . . . . . . . . . 19.3.3 Witches’ Broom of Moth Bean . . . . . . . . . . . . . . . . 19.4 Viral Diseases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.4.1 Yellow Mosaic Virus . . . . . . . . . . . . . . . . . . . . . . . 19.4.2 Leaf Crinkle Virus . . . . . . . . . . . . . . . . . . . . . . . . . 19.5 Insect Pests of Moth Bean and Their Management . . . . . . . . . . 19.5.1 Thrips . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.5.2 Weevil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.5.3 Aphids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.5.4 Storage Grain Pest . . . . . . . . . . . . . . . . . . . . . . . . . 19.5.5 White Fly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.5.6 Jassids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.5.7 White Grub . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.6 Termites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.7 Disease- and Pest-Linked Resistance Markers . . . . . . . . . . . . . 19.8 Parasitic Plant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.8.1 Cuscuta . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.8.2 Striga Species . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.9 Nematodes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.10 Integrated Pest Management . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

353 353 354 354 354 355 355 356 356 356 357 357 357 358 359 359 359 360 360 360 360 361 361 361 363 363 364 365 365 365 366 366 367 367 367 368 368 368 368 368 369

20

Physiology and Abiotic Stresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . 373 20.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 373 20.2 Seed Coat Colour . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 374

Contents

20.3 Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.4 Water Stress and Drought Tolerance . . . . . . . . . . . . . . . . . . . 20.5 Salt Tolerance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.6 Other Abiotic Stresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

xix

. . . . .

374 374 378 379 379

Genetic Markers and Biotechnology . . . . . . . . . . . . . . . . . . . . . . . . 21.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21.2 Classical Markers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21.2.1 Morphological Markers . . . . . . . . . . . . . . . . . . . . . . 21.2.2 Biochemical Markers . . . . . . . . . . . . . . . . . . . . . . . 21.2.3 Molecular Markers . . . . . . . . . . . . . . . . . . . . . . . . . 21.2.4 PCR-Based Molecular Markers . . . . . . . . . . . . . . . . 21.3 Genetic Map Studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21.4 Protein Profiling and Expressed Sequence Tags . . . . . . . . . . . . 21.5 Callus Induction and Regeneration Protocol . . . . . . . . . . . . . . 21.6 Protoplast Culture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

383 383 384 384 385 386 387 388 389 390 392 393

About the Author

Rakesh Pathak obtained Ph.D. from the Jai Narain Vyas University, Jodhpur in 2008. He is an Assistant Chief Technical Officer in the Central Arid Zone Research Institute, Jodhpur, Rajasthan and is a Fellow of Institution of Chemists (India). Dr. Pathak has published more than 100 research papers and book chapters on molecular characterization and genetic diversity studies of several crops and trees in journals and books of national and international repute. He has molecularly characterized and submitted more than 200 novel gene sequences belonging to plant varieties/germplasm, macro-fungi, fungal pathogens, and PGPRs with NCBI, USA, to address Indian biodiversity. Dr. Pathak has delivered several oral and poster presentation in national and international conferences. He has been regularly reviewing manuscripts as a referee for high-impact journals.

xxi

Part I Cowpea

1

Introduction

Abstract

Cowpea is an annual legume having erect, semi-erect, and trailing type of growth habits and varied flowers color. It is drought resilient, hardy, and highly adaptive to poor soils and adverse climatic condition. Cowpea is grown both for vegetable and seed purpose. It is an excellent source of protein, carbohydrates, dietary fiber, micronutrients, and feed and fodder for animals. The chapter briefly describes the taxonomic classification, floral characteristics, origin, and uses of cowpea.

1.1

Introduction

Cowpea (Vigna unguiculata L. Walp), an annual legume having large seeds, belongs to the genus Vigna of family Fabaceae. The species is morphologically and genetically variable in nature and is found in form of wild perennial, wild annual, and in annual cultivated forms (Pasquet 1999). It is considered one of the oldest sources of human food of developing countries of Africa and Asia due to protein-rich green pods and grains (Ortiz 2003). The crop has high adaptation to various stresses and is grown under varied range of soils and rainfall patterns, but its cultivation is mainly confined to the arid and semiarid regions of the world (Ehlers and Hall 1997). It has good potential for soil manuring and increasing microbial population in the soil. The crop helps in conserving the soil moisture, reducing the soil temperature and weed canopy in the field. The nutritional, medical significance and staple fodder quality have established cowpea as one of choices of arid and semiarid region crops of the world. It is grown throughout the semiarid regions of Asia, Africa, Southern Europe, Southern United States, and Central and South America (Singh 2005; Timko et al. 2007). Nigeria is the single largest producers of cowpea in the world. International Institute for Tropical Agriculture (IITA), Ibadan, situated in Nigeria has wide collection of cowpea germplasm (Davis et al. 1991). # The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 R. Pathak, Genetics, Physiology and Cultivation of Moth Bean, Cowpea and Horse Gram, https://doi.org/10.1007/978-981-19-9956-7_1

3

4

1 Introduction

Cowpea is cultivated in India since prehistoric times, and it was suggested that India is the major center of its origin (Vavilov 1939). Africa and China were suggested to be other centers, but later, it was strongly hypothesized that West Africa was the main center of origin of cowpeas (Faris 1965; Pasquet and Baudoin 2001). The marginal and submarginal farmers of Africa are major producers and consumers of the crop (Pasquet and Baudoin 2001). Cowpea is cultivated under about 11.2 million hectares throughout world with a total production of 3.2 million tons (FAO 2009). India, Sri Lanka, Bangladesh, Myanmar, China, Korea, Thailand, Indonesia, Nepal, Pakistan, Malaysia, and Philippines are major cowpea-growing countries in Asia. India is the largest producers of cowpea in Asia. Cowpea is also known as Lobia (Hindi), Barbati (Bengali), Chavali (Marathi), Alasande (Kannada), Mampayar (Malayalm), southern pea, and black eyed pea in different parts of India. In some states of India including Maharashtra, it is grown in all three cropping seasons. Nitrogen-fixing ability, fast growing habit, tolerant to drought, higher temperatures (Hall et al. 2002; Hall 2004) and soil acidity (Fery 1990) are the potential that makes the crop one of the important choices for the regions having low rainfall, high temperature, and low fertile soils (Ortiz 2003). The crop provides food for human being and feed for livestock. It is used as green manuring and cover crop to minimize moisture losses and maintain soil fertility (Bado et al. 2006) under rainfed conditions. Cowpea is one of the choices of intercrop and mixed crop with various other crops including pearl millet, sorghum, etc. to ensure the soil fertility and crop sustainability (Bado et al. 2006). It provides good source of nutrition, and therefore, its grain, green pods, and leaves are consumed throughout the world. Its seeds contain 21–30% protein that is rich in amino acids, lysine, and tryptophan, while methionine and cysteine are found in lesser quantity (Nielson et al. 1993; Mwasaru et al. 1999a, 1999b; Hall et al. 2003). Cowpea is rich in calcium, magnesium, phosphorus, iron, zinc, and carbohydrates. It has good quantities of various vitamins, namely, thiamine, riboflavin, ascorbic acid, niacin, folic acid, and low fatty acids (Jayathilake et al. 2018). Non-nutritional factors, presence of high quantity of lysine along with other essential amino acids, and low quantity of methionine and cysteine make cowpea a good balance to cereal-based diets (Ohler and Mitchell 1995; Nielson et al. 1993). Cowpea has small dicotyledonous kidney or globular shaped seeds consisting of seed coat, micropyle, hilum, and cotyledon. The chemical composition of cowpea seed is given in Table 1.1. The weight of 100 seeds of cowpea ranges from 2 to 28 g (Olapade et al. 2002; Langyintuo et al. 2004). The color of its seeds is white to black or their mixture, and sometimes it has colored spots on its seeds (Taiwo 1998). Cotyledon of the seed is the reservoir of carbohydrates and proteins. Larger seed having wrinkled seed coats are favored by the consumers (Langyintuo et al. 2004) as it soaks water easily, and therefore, its seed coat can be removed easily. Aphids, flower thrips, cowpea pod borer, pod-sucking bugs, and storage weevil are the important insect pests that attack the crop and reduce the production (Raheja 1976). Various fungal diseases, namely, anthracnose, ascochyta blight, leaf smut, leaf spot, brown rust, powdery mildew, pythium soft stem rot, stem canker, and web

1.3 Taxonomic Classification Table 1.1 Chemical constitute of cowpea seed

Constitute Moisture Crude protein Fat extract Ash Crude fibre Starch

5

Per cent 10.4 28.0 1.9 3.8 3.1 40.6

Source: Longe (1980)

blight; bacterial diseases namely, bacteria blight and bacterial pustules; viral diseases, namely, cowpea yellow mosaic comovirus, mottle virus, aphid-borne mosaic potyvirus, cucumber mosaic virus, cucumovirus, cowpea golden mosaic virus, mild mottle virus, sunn-hemp mosaic tobamovirus, and mungbean yellow mosaic virus; nematodes; and parasitic weeds are the major limitation in the production of the crop.

1.2

Floral Characteristics

The flowers of cowpea are racemose, bisexual papilionaceous type having indeterminate inflorescence and are borne in multiple racemes at the distal ends of peduncles in the leaf axil (Davis et al. 1991). The flower has five sepals in gamosepalous and five petals in polypetalous conditions. The outer posterior petal is standard; two lateral petals are clawed almost covering two boat-shaped interior petals. The 15–30 cm long flowers have various colors, namely, purple, pink, white, blue, or yellow. They are self-pollinated with little amount (2%) of out-crossing.

1.3

Taxonomic Classification

Vigna is characterized by the genus of most pulse crops of the family Fabaceae. There are two approaches for the taxonomic classification of the species. The first approach includes identification of three groups on the basis of seed and pod characteristics (Piper 1912), while the second approach includes three cultivargroup rank (Westphal 1974). The cultivar-group (cv. gr.) rank cv. gr. Unguiculata, Biflora, and Sesquipedalis was accepted and widely used. Later, it was realized that it is difficult to differentiate cultivar-group Unguiculata and Biflora (Pasquet 1998); therefore, it was suggested to include fourth cultivar-group, that is, cv. gr. Melanophthalmus, on the basis of phenetic analysis of the gene pool. The cultivargroup Unguiculata includes cowpea, which is the most widespread and economically most important group of the species. The primary cultivation regions of this cultivar group are in the Sahel belt in Africa, Brazil, and Venezuela; nevertheless, it is also cultivated in other African, Asian, Australian, and American countries.

6

1 Introduction

Cultivar-group Melanophthalmus (Pasquet 1998) is the recently documented cultivar group, which is based on the taxon proposed by Chevalier (1944) and is cultivated mainly in West Africa. Cultivar-group Biflora (Westphal 1974) includes the bean, Catjang, which is cultivated in South Asia, Southeast, or East Asia and subtropical regions. The variability of the bean is less as compared to the true cowpea. Cultivar-group Sesquipedalis (Westphal 1974) includes yard-long bean/ asparagus bean. It is produced in South and Southeast Asia, from India to Indonesia. Some of hybrids developed from hybridization of cowpea and yard-long bean have also been grouped under this cultivar group. The detailed taxonomic classification of the crop is given below: Domain: Eukaryota Kingdom: Plantae Subkingdom: Viridiplantae Infra kingdom: Streptophyta Super division: Embryophyta Division: Tracheophyta Subdivision: Spermatophytina Class: Magnoliopsida Superorder: Rosanae Order: Fabales Family: Fabaceae Genus: Vigna Species: V. unguiculata

1.4

Botany

The genus has eight genera (Verdcourt 1970) comprising of about 150 species. Out of which only seven species, that is, Vigna unguiculata, V. mungo, V. radiate, V. subterranean, V. aconitifolia, V. angularis, and V. umbellate, are cultivated as leguminous crop. V. unguiculata, V. mungo, and V. radiate are the widely cultivated species of the genus, while V. subterranean, V. angularis, and V. umbellate are cultivated to a lesser extent. Cowpea was earlier documented as Vigna sinensis (L) Savi that was later changed to V. unguiculata L. Walp (Gunn 1982). Cowpea has 22 chromosomes (2n = 22), and its genome is estimated to be 613 Mb. V. unguiculata is known by various names, but cowpea is its most common name through the world. In the United States, it is known as black eye beans or pea (Miller et al. 1989); in Africa, it is called as cowpea, niebe, and southern peas (Duke 1981); in Senegal, it is known as seub and niao; in Brazil, it is called caupi, while in Indian subcontinent, it is known as lobia. Cowpea is a self-pollinated, warm season, day neutral, annual herbaceous legume having erect, semi-erect, prostrate, or climbing plants with deep rooted and spreading lateral root system. It has determinate and indeterminate growth habits. Its leaves are alternate and trifoliate with ovate leaflets. The flowers of cowpea are bisexual papilionaceous type and are borne in multiple racemes (Davis et al. 1991). Its fruits

1.5 Origin

7

are found in 8–30 cm long, straight, or slightly curved pods. Pods are pendulous, smooth, long, and cylindrical with a thick decurved beak. Each pod contains about 7–25 seeds of variable size and shape. The seeds are mostly laterally compressed, oblong to globose having variable colors, namely, white, black, pale brown, or brown. Most of the varieties are sensitive to photoperiodism. The crop has tendency to flower as the length of day become shorter.

1.5

Origin

It has been postulated that origin of a cultivated plant could be found where it grows wild (De Candolle 1908); therefore, cowpea is known as a crop of African origin due to the presence of its wild forms in tropical Africa (Marechal et al. 1978). Reports also suggest its origin in Ethiopia followed by African savanna (Sauer 1952). Origin of the crop in Africa is a matter of debate, and its domestication in Ethiopia, West Africa, and sub-Saharan belt has also been proposed. Therefore, the particular location or region of its first domestication is under assumption. It has been reported that during the evolution process of V. unguiculata, it has experienced a major change in its growth cycle, that is, from perennial habit, it has become annual (Ng 1995). The African continent has wide genetic diversity of wild-type cowpea. West Africa, Burkina Faso, Ghana, Togo, Benin, Niger, Nigeria, and Cameroon are known for the presence of its cultivated species. The crop was primarily domesticated in North-east Africa (Pasquet 1999) with the secondary center of domestication in West Africa (Pasquet 1996; Garba and Pasquet 1998) and the Indian subcontinent (Steele et al. 1985). The seeds of cowpea were perhaps taken to Europe during 300 BC and to India during 200 BC. It is speculated that probably Spanish has introduced the crop to tropical America during seventeenth century, and consequently, it is widely cultivated in the United States, the Caribbean region, and Brazil. The crop has experienced diversification and produced two cultivar groups, that is, Sesquipedalis and Biflora. The Sesquipedalis cultivar group has long pods and was used as a vegetable, while the cultivars under Biflora group were mainly grown for pods, dry seeds, and fodder. It has also been emphasized that both cultivar groups of cowpea were evolved in Asian countries including China and India. Tropical Africa and Southeast Asia are considered as the center of diversification of the crop. Hanelt (2001) suggested that the crop spread to the Mediterranean countries to Southeast and East Asia and near East to India during eighteenth and nineteenth century BC, respectively. The origin of cultivar-group Sesquipedalis and Biflora took place as a result of selection of grain.

8

1.6

1 Introduction

Cytogenetics

Cowpea has comparatively small genome of 613–620 Mb having 22 chromosomes and has close lineages with Glycine max, Phaseolus vulgaris, and Cajanus cajan (Arumuganathan and Earle 1991). It is one of the multipurpose leguminous crops, but little information is available in the literatures pertaining to cytogenetics of the plant (Naylor et al. 2004). However, a consensus genetic map based on expressed sequence tags (EST) derived single nucleotide polymorphism (Muchero et al. 2009), bacterial artificial chromosome (BAC) libraries, BAC end sequences, and physical maps are available. The whole genome sequencing of Vigna radiata and Vigna angularis (Kang et al. 2014, 2015) may be used to study the genetics of cowpea. BAC clone mapping has been used for cytogenetic studies in cowpea (Vasconcelos et al. 2015). The mitotic indices was studied during cell division of cowpea (Willie and Aikpokpodion 2015), and it was observed that the active cell division occurred between 7.00 AM and 2.00 PM, and it was at peak levels between 11.00 AM and 1.00 PM. The enhanced cell division during the day hours may be due to cellular metabolism and photosynthesis (Adesoye and Nnadi 2011) leading to the higher mitotic index, germination, growth, and development of the plant (Isabelle et al. 2000). Molecular cytogenetics was employed to characterize the structure of pachytene chromosomes of cowpea (Iwata-Otsubo et al. 2016), and it was observed that the crop has highly diverse chromosomal structures with the presence of centromeric and pericentromeric regions in the centromere pairs.

1.7

Molecular Biology

Genetic diversity studies in cowpea have been exploited using various molecular markers including random amplified polymorphic DNA (RAPD), simple sequence repeats (SSR), inter simple sequence repeats (ISSRs), amplified fragment length polymorphism (AFLP), and combination of RAPD-ISSR, RAPD-SSR, AFLPSAMPL, etc. during the last decades. Allozyme (Pasquet 2000) has also been used in the diversity studies of cowpea. RAPD has been widely employed in the genetic diversity studies due to the simplicity of the technique by various workers (Zannou et al. 2008; Malviya et al. 2012; Ba et al. 2004; Nkongolo 2003; Chen et al. 2008; Patil et al. 2013; Khan et al. 2015). SSR markers have also been used to assess genetic variability in cowpea (Li et al. 2001; Ogunkanmi et al. 2008; Asare et al. 2010; Badiane et al. 2012; Sawadogo et al. 2010; Lee et al. 2009; Xu et al. 2010; Xu et al. 2007; Wamalwa et al. 2016). AFLP (Coulibaly et al. 2002; Fang et al. 2007), and AFLP-SAMPL (Tosti and Negri 2005; Gillaspie et al. 2005) has also been applied for various molecular studies in cowpea.

1.9 Prospects

1.8

9

Uses

Cowpea is highly valued for its protein-rich seeds, vitamins, and mineral-rich young plants and has ability to sustain in drought conditions and fix the atmospheric nitrogen (Fall et al. 2003). Generally, its seed is consumed, but young leaves and pods are also consumed at various parts of the world. Snacks and various food preparations are prepared from its dried grains. The crop is also cultivated for fodder and fiber purposes (Pasquet and Baudoin 2001). The crop matures earlier as compared to other cereal crop during the season providing source of monetary benefits to the farmers. In Western Africa, the cowpea are used as traditional medicines to treat various diseases (Duke 1981). The dried leaves are also rich in protein content (Ohler et al. 1996). Crop residues are used as nutritive fodder for the animals (Grings et al. 2012). Cowpea is known for having protein-rich (20–40%) seeds, nitrogen-fixing ability (73–354 kg N/ha per year), and utilization of its fodder (Kamara et al. 2017). The nitrogen-fixing ability of the crop adds to sustainable productivity of the agroecosystem (Martins et al. 2003). The crop is usually cultivated in fields having low organic carbon and nutrient content. It is a short cycle crop, requires low water, and has the ability to fix the atmospheric nitrogen. It is one of the important herbaceous legumes of tropics and subtropics area of the world (Lopes et al. 2018) known for important source of protein, carbohydrates, lipids, sodium, potassium, and iron for the human diet (Cheng et al. 2013; Murdock et al. 2012) and provides food security and monetary benefits (Tharanathan and Mahadevamma 2003). The area under cultivation of cowpea is about 21 million acres with the production of 12.5 million tons and is mainly confined to West and Central Africa (Mellor et al. 2012; Shui et al. 2013). The cultivated cowpea is mainly bushy, short podded, and climbing, long podded (Xu et al. 2017). The vegetable purpose cowpea has long pods, and young pods are collected for sale and storage (Xu et al. 2017).

1.9

Prospects

Cowpea is one of the important leguminous crops of arid and semiarid parts of the world and has major importance for the livelihood and nutrition security of the poor people in the developing countries. An outline of the prospects of the crop is given below: • The immature pods, grains, and fresh leaves of cowpea provide the basic nutrition, that is, protein, carbohydrate, vitamins, and minerals in appreciable quantity. Its grains have 22–23% protein with good quantity of vitamins, iron, and calcium. Its leaves are good source of β-carotene and ascorbic acid. • It provides protein, vitamin, and mineral-rich fodder to the cattle, sheep, and goats.

10

1 Introduction

• The crop has spreading indeterminate and semi-determinate bushy growth habit. The growth habit provides good covering over the field and protection against soil erosion. • The broad and drooping leaves of the crop help in conserving the soil moisture and reducing the soil temperature. The residues of root stem and haulm provide organic matter after harvest. • It is fast-growing legume and helps in reducing the weed canopy and growth of various weeds in the field. • The crop fixes atmospheric nitrogen and improves the nitrogen content of the soil. It has been observed that the soil nitrogen in the field followed by cowpea increases about 40–80 kg per ha. Therefore, cowpea is one of the choices of crops in inter- and intra-cropping system to improve the soil fertility. • Cowpea is a drought hardy legume and can survive in the dry conditions where other crops cannot grow. It provides a good source of income during drought condition. • Its seeds take comparatively lesser time to cook and may be one the important consideration of food in the developing countries.

1.10

Constraints

Cowpea is one of the robust crops of arid and semiarid regions and requires less care for its cultivation. Some of the constraints affecting its production are summarized below: • Various insect pests and viral, fungal, and bacterial diseases are the major constraints in the production of the crop. • The viny growth habit, compulsive photoperiodism, low flowering, and seed setting abilities also affect its production potential. • Presence of tannins, trypsin inhibitors, and raffinose in its grain causes bloating of stomach upon consumption. • Shattering of matured pods leads to major loss of seeds. • Indeterminate growth habit is again a constraint to realize better yields.

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(Cajanus cajan) and cowpea (Vigna unguiculata) protein isolates. II Functional properties. Food Chem 67(4):445–452 Naylor RL, Falcon WP, Goodman RM et al (2004) Biotechnology in the developing world: a case for increased investments in orphan crops. Food Policy 29:15–44 Ng NQ (1995) Cowpea Vigna unguiculata (Leguminosae-Papilionoideae). In: Smartt J, Simmonds NW (eds) Evolution of crop plants, 2nd edn. Longman Group Ltd, London, pp 326–332 Nielson SS, Brandt WE, Singh BB (1993) Genetic variability for nutritional composition and cooking time of improved cowpea lines. Crop Sci 33:469–472 Nkongolo KK (2003) Genetic characterization of Malawian cowpea (Vigna unguiculata (L.) Walp.) landraces: diversity and gene flow among accessions. Euphytica 129:219–228 Ogunkanmi LA, Ogundipe OT, Ng NQ, Fatokun CA (2008) Genetic diversity in wild relatives of cowpea (Vigna unguiculata) as revealed by simple sequence repeats (SSR) markers. J Food Agric Environ 6:263–268 Ohler TA, Mitchell CA (1995) Effects of carbon dioxide level and plant density on cowpea canopy productivity for a bioregenerative life-support system. Life Support Biosph Sci 2:3–9 Ohler TA, Nielsen SS, Mitchell CA (1996) Varying plant density and harvest time to optimize cowpea leaf yield and nutrient content. HortSci 31(2):193–197 Olapade A, Okafor GI, Ozumba AU, Olatunji O (2002) Characterization of common Nigerian cowpea (Vigna unguiculata L. Walp) varieties. J Food Eng 55:101–105 Ortiz R (2003) An international public partnership for genetic enhancement of cowpea using a holistic approach to biotechnology. Genomic/Proteomic Technol 3:45–47 Pasquet RS (1996) Wild cowpea (Vigna unguiculata) evolution. In: Pickersgill B, Lock JM (eds) Advances in legume systematics: legumes of economic importance. Royal Botanic Gardens, Kew, pp 95–100 Pasquet RS (1998) Morphological study of cultivated cowpea Vigna unguiculata (L.) Walp: importance of ovule number and definition of cv gr Melanophthalmus. Agron 18(1):61–70 Pasquet RS (1999) Genetic relationships among subspecies of Vigna unguiculata (L.) Walp. Based on allozyme variation. Theor Appl Genet 98(6–7):1104–1119 Pasquet RS (2000) Allozyme diversity of cultivated cowpea Vigna unguiculata (L.) Walp. Theor Appl Genet 101(1–2):211–219 Pasquet RS, Baudoin JP (2001) Cowpea. In: Charrier A, Jacquot M, Hamon S, Nicolas D (eds) Tropical plant breeding. Science Publishers, Enfield, pp 177–198 Patil DM, Sawardekar SV, Gokhale NB et al (2013) Genetic diversity analysis in cowpea [Vigna unguiculata (L.) Walp.] by using RAPD markers. Int J Innov Biotechnol Biochem 1:15–23 Piper CV (1912) Agricultural varieties of the cowpea and immediately related species. USDA, Bureau of Plant Industry, Bulletin No. 229, p 160 Raheja AK (1976) Assessment of losses caused by insect pests to cowpeas in northern Nigeria. PANS 22(2):229–233 Sauer CO (1952) Agricultural origins and dispersal. American Geographical Society, New York Sawadogo M, Ouedraogo JT, Gowda BS, Timko MP (2010) Genetic diversity of cowpea (Vigna unguiculata L. Walp.) cultivars in Burkina Faso resistant to Striga gesnerioides. Afr J Biotechnol 9(48):8146–8153 Shui XR, Chen ZW, Li JX (2013) MicroRNA prediction and its function in regulating droughtrelated genes in cowpea. Plant Sci 210:25–35 Singh BB (2005) Cowpea [Vigna unguiculata (L.) Walp]. In: Singh RJ, Jauhar PP (eds) Genetic resources, chromosome engineering and crop improvement, vol 1. CRC Press, Boca Raton, pp 117–162 Steele WM, Allen DJ, Summerfield RJ (1985) Cowpea [Vigna unguiculata (L.) Walp]. In: Summerfield RJ, Roberts EH (eds) Grain legume crops. Collins Professional and Technical Books, London, pp 520–583 Taiwo KA (1998) The potential of cowpea as human food in Nigeria. Technovation 18(5/6): 469–481

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1 Introduction

Tharanathan RN, Mahadevamma S (2003) Grain legumes-a boon to human nutrition. Trends Food Sci Technol 14:507–518 Timko MP, Ehlers JD, Roberts PA (2007) Cowpea. In: Kole C (ed) Genome mapping and molecular breeding in plants, Pulses, sugar and tuber crops, vol 3. Springer Verlag, Berlin, pp 49–67 Tosti N, Negri V (2005) On-going on-farm micro evolutionary processes in neighbouring cowpea landraces revealed by molecular markers. Theor Appl Genet 110(7):1275–1283 Vasconcelos EV, de Andrade Fonsêca AF, Pedrosa-Harand A et al (2015) Intra- and interchromosomal rearrangements between cowpea [Vigna unguiculata (L.) Walp.] and common bean (Phaseolus vulgaris L.) revealed by BAC-FISH. Chromosom Res 23:253–266 Vavilov NI (1939) Genetics in the USSR. Chron Bot 5(1):14–15 Verdcourt B (1970) Studies in the Leguminosae-Papilionoideae for the flora of tropical East Africa, IV. Kew Bulletin 24:507–569 Wamalwa EN, Muoma J, Wekesa C (2016) Genetic diversity of cowpea (Vigna unguiculata (L.) Walp.) accession in Kenya gene bank based on simple sequence repeat markers. Int J Genomics 2016:8956412 Westphal E (1974) Pulses in Ethiopia: their taxonomy and agriculture significance, agricultural research reports 815. Centre for Agricultural Publishing and Documentation, Wageningen Willie PO, Aikpokpodion PO (2015) Mitotic activity in cowpea (Vigna unguiculata (L.) land race “Olaudi” Walp) in Nigeria. Am J Plant Sci 6:1201–1205 Xu YH, Guan JP, Zong XS (2007) Genetic diversity analysis of cowpea germplasm resources by SSR. Acta Agron Sin 33(7):1206–1209 Xu P, Wu XH, Wang BG et al (2010) Development and polymorphism of Vigna unguiculata ssp. unguiculata microsatellite markers used for phylogenetic analysis in asparagus bean (Vigna unguiculata ssp. sesquipedialis (L.) Verdc.). Mol Breed 25(4):675–684 Xu P, Wu X, Muñoz-Amatriaín M et al (2017) Genomic regions, cellular components and gene regulatory basis underlying pod length variations in cowpea (Vigna unguiculata L. Walp). Plant Biotechnol J 15(5):547–557 Zannou A, Kossou DK, Ahanchede A et al (2008) Genetic variability of cultivated cowpea in Benin assessed by random amplified polymorphic DNA. Afr J Biotechnol 7(24):4407–4414

2

Genetic Improvement and Variability

Abstract

Cowpea has substantial variability in growth habit, vegetative traits, flowering, and reproductive characteristic. The viny varieties of cowpea are generally late maturing and used as forage for animals. Significant variability for various traits, namely, plant height, number of branches, number of nodes, number of pods, days to flowering, day to maturity, pod length, pod yield, and seed yield, has been recorded. A detailed account on genetic improvement and variability in cowpea has been discussed in this chapter.

2.1

Introduction

Variation in the genetic makeup of crop is mainly responsible for morphological difference, seed quality, and yield potentials (Ajala et al. 2006; Okelola et al. 2007). Most of morphological characters traits studied in cowpea are influenced by environment conditions, and it was observed that the short flowering period cultivars of cowpea are advantageous (Stoilova and Pereira 2013). Assessment of genetic diversity and variability in cowpea has been carried out in several studies on the basis of morphological and physiological characteristics (Stoilova and Pereira 2013). Cowpea accessions had substantial variability in growth habit, vegetative traits, flowering, and reproductive characteristic (Popoola et al. 2015). Studies reveal that stem pigmentation, flower color, and the mutant characters may be potential genetic marker for breeding of cowpea (Porbeni et al. 2016). The short flowering accession showed early pod maturity and higher production prospective (Adegbite 2006; Popoola et al. 2015). Improved varieties of cowpea had more vigor and speedy germination potentials; however, it may be influenced by the type of varieties (Kamara et al. 2019). The viny varieties of cowpea generally mature late and are used for forage purposes. These varieties may be cultivated under diverse climatic # The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 R. Pathak, Genetics, Physiology and Cultivation of Moth Bean, Cowpea and Horse Gram, https://doi.org/10.1007/978-981-19-9956-7_2

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Fig. 2.1 Morphological variability in cowpea

and cultural condition. Cowpea has been reported with wide variability in terms of several morphological characters (Fig. 2.1).

2.2

Morphometric Characterization

Morphometric analysis augments the resilience and correctness of morphological classifications in the taxonomic description of cowpeas (Porbeni et al. 2016). Significant variability among morphometric characters of 20 cowpea accessions was reported (Popoola et al. 2015). The characters having low and high level of diversity may be the major factor for the morphometric analysis and portray the taxonomic similarities among Vigna species (Ambiger et al. 2019). Genetic relationship carried out through morphometric characterization grouped the cowpea varieties on the basis of their determinate and indeterminate growth habit (Pradeepkumar et al. 2017). It was also observed that morphometric analysis coupled with molecular techniques is more prominent to figure out genetic relationship among the cowpea varieties (Pradeepkumar et al. 2017).

2.3 Genetic Divergence

2.3

17

Genetic Divergence

The sub-genera, species, and subspecies classification was conventionally based on the various morphological characteristics. Identification on the basis of morphological traits takes years together to complete the work and is highly cumbersome. These traits may be unstable due to effect of the environmental conditions. However, studies on the basis of morphological and physiological markers as the crop characteristics have always been considered useful for the genetic assessment due to their simplicity, and it is preferred over molecular and biochemical markers for comparison of the results. Cowpea has been assessed for genetic diversity studies using morphological and physiological characteristics (Ehlers and Hall 1997). Various characters, namely, number of seeds per pod, number of branches, number of pods per cluster and pod length (Usha Kumari et al. 2000; Srinivas et al. 2016), plant height (Sharma and Mishra 1997; Borah and Khan 2001; Dalsaniya et al. 2009) green pod yield per plant, pod weight and plant height (Vavilapalli et al. 2014), days to maturity, 100-seed weight, and seed yield per plant (Valarmathi et al. 2007; Nagalakshmi et al. 2010), days to 50% flowering and maturity, number of pods per plant, pod length, 100-seed weight, and seed yield per plant (Rewale et al. 1996; Backiyarani et al. 2000; Sulnathi et al. 2007; Nagalakshmi et al. 2010), number of clusters per plant, number of pods per cluster, number of pods per plant and seed yield per plant (Venkatesan et al. 2003b), and protein content (Dalsaniya et al. 2009), have been recorded to contribute highest to the genetic divergence in cowpea. In a study of genetic divergence of 24 genotypes of cowpea using D2 statistics, the genotypes were grouped into three clusters, and their grouping was independent from their geographical origin (Tyagi et al. 1999). Similarly, genetic divergence study carried out using 50 genotypes and nine characters on the basis of D2 statistics; all the genotypes were grouped into four different clusters (Anbuselvam et al. 2000). Seed yield, harvest index, and earliness in flowering accounted for about 80% of the total genetic divergence, while genetic diversity was not related to the geographical boundaries (Backiyarani et al. 2000). Plant height, seeds per pod, number of branches, number of pods per cluster, and pod length have contributed maximum toward the genetic divergence (Kumari et al. 2000). Dry matter yield, green fodder yield, and plant height showed maximum contribution to the genetic divergence in a study carried out to assess genetic diversity among 60 cowpea cultivars (Borah and Khan 2001). These cultivars were grouped into ten clusters and showed no relation with their geographical origin. Number of branches per plant, test weight, dry biomass, and number of pods per plant had contributed maximum toward the total divergence (Nigude et al. 2004b). Venkatesan et al. (2004) also observed no relation between the clustering pattern and geographical origin of genotypes. Number of clusters per plant, number of pods per cluster, number of pods per plant, and seed yield per plant exhibited maximum toward the total genetic divergence. The relative contribution of various characters toward the total genetic divergence revealed that the seed yield per plant exhibited maximum contribution followed by number of seeds per pod, days to 50% flowering, plant height, and reproductive period (Kumawat and Raje 2005). The traits exhibiting maximum contribution toward the

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total genetic divergence have plays important role in the selection of parents for hybridization. Geographical origin had no influence on the genetic divergence (Naher et al. 2005) among cowpea accessions collected from different regions of India. Similarly, Narayanankutty et al. (2005) also reported no relation between geographical origin and clustering pattern in a study carried out using 63 accessions of vegetable cowpea. They grouped all the accessions into eight clusters on the basis of 12 quantitative characters. Pod yield, pod weight, number of pods per plant, and pod length exhibited maximum toward the genetic divergence. Pod length contributed maximum to the genetic divergence, while days to maturity showed least contribution (Hettiarachchi 2006). All the 81 cultivars of cowpea were grouped into 14 clusters showing the presence of wide variability in the cultivars, and the cultivars were not grouped as per their origin. Anbumalarmathi et al. (2005) grouped 26 cowpea genotypes into seven clusters on the basis of nine characters using D2 statistics. The cluster composition was not related to the genetic diversity and geographical origin. Plant yield and 100-seed weight contributed maximum toward the genetic divergence. Number of pods per plant, days to flowering, harvest index, and 100-seed weight contributed maximum toward the genetic divergence (Bhardwaj and Singh 2007) in a study carried out using 125 germplasms of cowpea on the basis of eight characters. In a genetic divergence study through multivariate analysis in 16 cowpea cultivars (Dahiya et al. 2007a), it was observed that number of pods per plant, number of seeds per pod, pod length, 100-seed weight, total yield, and yield per plant had higher values of heritability suggesting the possibility of their improvement through selection. Similarly, Bertini et al. (2009) also reported higher values of heritability for these characters, namely, number pods per plant, number of seeds per pod, pod length, 100-seed weight, total yield, and yield per plant suggesting the possibility of their improvement through selection. Days to flowering, days to maturity, and 100-seed weight contributed maximum toward the genetic divergence, and it was not related to the geographical diversity (Sulnathi et al. 2007). Days to maturity and 100-seed weight contributed maximum toward the divergence, while number of branches per plant and number of seeds per pod contributed minimum (Valarmathi et al. 2007). Dash and Mishra (2008) also revealed no relation between the geographical diversity and genetic diversity. The grouping of the genotypes did not confirm their geographical distribution (Dalsaniya et al. 2009). Plant height, green pod yield per plant, protein content, and leaf area were reported to contribute higher toward the genetic divergence in cowpea. Seed yield per plant, 100-seed weight, and days to 50% flowering contributed highest toward the total genetic divergence (Nagalakshmi et al. 2010), while number of branches per plant and petiole length showed least values. They reported existence of more diversity among the cultivars of the same geographical locations, and no parallelism could be recorded between genetic diversity and geographic diversity. Tajane (2014) and Tigga and Tandekar (2013) also reported nonoverlapping of cluster on the basis of geographical distribution.

2.3 Genetic Divergence

19

Plant height, days to 50% flowering, and biological yield had contributed maximum toward the total genetic divergence (Sandeep et al. 2014). Plant height, pod yield, and pod weight contributed maximum toward the total genetic divergence (Shivakumar and Celine 2014). Plant height, green pod yield per plant, protein content, and leaf area contributed higher to the total genetic divergence in cowpea (Dalsaniya et al. 2009). Mahalanobis’s D2 analysis for assessment of genetic diversity among 88 genotypes of cowpea (Nagalakshmi et al. 2010) revealed wider genetic diversity and grouped the genotypes into 23 clusters. Grain yield per plant was reported as the most divergent character contributing highest to the total divergence followed by 100 seed weight and days to 50% flowering, while number of branches exhibited least contribution to the genetic divergence. Similarly, 40 genotypes were grouped into six clusters on the basis of Mahalanobis’s D2 analysis (Brahmaiah et al. 2014) for 18 quantitative characters to estimate the genetic diversity and observed NSJ-161, NSJ-007, and NSJ-044 as most divergent genotypes. Number of clusters per plant followed by protein content contributed highest to toward genetic divergence suggesting that plants having higher number of clusters and protein content may be selected as diverse parents for hybridization. Contribution of various traits such as number of branches per plant (Backiyarani et al. 2000; Jindal and Gupta 1985), number of pods and pod length (Jain et al. 2006), number days to flowering (Saini et al. 2004), green pod yield per plant, plant height, days to 50% flowering, and leaf area (Kumari et al. 2000; Sharma and Mishra 1997) toward the total divergence in cowpea. The genetic divergence studies in vegetable cowpea revealed that the pod yield per plant followed by pod weight and plant height contributed maximum divergence (Vavilapalli et al. 2014). In a genetic divergence study for quality, yield, and yield components carried out in cowpea using 41 commercial genotypes on the basis of Mahalanobis distances (Rambabu et al. 2016), it was observed that pod length followed by pod ascorbic acid content, pod girth, and 100 seed weight contributed maximum towards the genetic divergence. Seed yield followed by days to 50% flowering and test weight contributed higher toward the total diversity, while days to physiological maturity, plant height, pod length, number of clusters per plant, number of pods per plant, and number of seeds per pod exhibited lower contribution toward the diversity (Viswanatha and Yogeesh 2017). Biometrical studies of yield and related traits in 66 advanced breeding lines of vegetable cowpea carried out using D2 statistics, and all the lines were grouped into 17 clusters. Number of peduncles per plant, peduncle length, and pod length exhibited maximum toward the genetic divergence (Lal et al. 2018). The cowpea genotypes in the cluster VII (VRCP-68-2, VRCP-75-3, VRCP-112-4, VRCP-167-3, VRCP-167-2, VRCP-79-4) had highest divergence with the genotypes of cluster VIII (VRCP-49-5, VRCP-52-2, VRCP-140-3, VRCP-51-5, VRCP-102-1, VRCP103-3, VRCP-53-1, VRCP-117-5, VRCP-153–1, VRCP-130-1, VRCP-155-4, VRCP-100-2) suggesting that the crossing among these genotypes may result potential genotypes having have pod yield (Lal et al. 2018). Number of pods per plant followed by leaf/stem ratio, plant height, days to maturity, leaf length, and pod length had contributed highest to the genetic diversity of 32 cowpea genotype among

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11 quantitative characters studied (Singh et al. 2018). Genetic divergence studies among 23 cowpea genotypes based on characters associated with the green pod and grain market (Filho et al. 2018) using Mahalanobis distances revealed that genotype and environment interaction influenced the genetic divergence in the grouping of genotypes and contribution of traits. The researchers also found that green grain yield and yield of green beans contributed highest toward the genetic divergence (Filho et al. 2018).

2.4

Correlation and Path Coefficient Analysis

Correlation is statistical measure to assess the magnitude and direction of association between two or more variables. Positive association between two variables indicates the changes in same direction while negative associations indicate its inverse. Path analysis is a partial regression coefficient that divides correlation coefficient into quantifiable direct and indirect effects (Dewey and Lu 1959). The analysis provides the comparative involvement of component characters directly on the main character and or indirectly through other characters resulting into enhanced efficiency in the selection program. Correlation studies in cowpea suggest that a higher plant having more number of branches, number of pods, and number of seeds and that attains earlier 50% flowering is expected to have higher seed yield. Kheradnam and Niknejad (1974) observed significant positive phenotypic correlations of seed yield with the number of pods per plant and number of seeds per pod. Seed yield had positive and significant association with number of peduncles per plant, number of branches per plant, and number of branches per peduncle (Ariyo 1995), while it was directly influenced by 100-seed weight, number of seeds per pod, number of branches per plant, and number of pods per peduncle. Interrelationship and path coefficient analysis of growth character and seed yield study (Nakawuka and Adipala 1999) revealed that seed yield had positive and significant relations with number of primary branches, number of secondary branches, days to 50% flowering, number of pods per plant, number of seeds per pod, and plant height whereas, yield per plant has maximum positive and direct effect on seed yield followed by number of pods per plant. Number of secondary branches per plant, days to flowering, days to maturity, and number of seeds per pod showed direct negative effects on the seed yield. Number of pods per plant and yield per plant can be one of the criterions for selection of potential parents during crop improvement. Highly significant and positive correlation was observed between number of clusters per plant, number of pods per plant, and pod weight in a study of crossing of two cultivars of cowpea in F2 generation (Rangaiah and Mahadevu 2000). Seed yield per plant had strong positive correlation with 100-seed weight, number of seeds per pod, plant height, crude protein, number of pods per plant, and number of branches per plant, while it had negative association with crude fiber content (Kalaiyarasi and Palanisamy 2001). Genotypic correlation coefficient was reported to be higher as compared to phenotypic correlation coefficients by several workers (Pathak and Jamwal 2002; Venkatesan et al. 2003a) suggesting lower influence of environment on these

2.4 Correlation and Path Coefficient Analysis

21

characters. Pod length had maximum direct effect on seed yield. Pod yield per plant was positively correlated with number of pods per plant, plant height, and pod weight. Number of branches per plant, number of clusters per plant, number of pods per cluster, number of pods per plant, and pod yield had positive association with seed yield both at genotypic and phenotypic level (Venkatesan et al. 2003a). Number of pods per plant, number of pickings, pod weight, and length exhibited positive and significant association with grain yield per plant, while number of days to first picking had negative correlation with total number of pickings (Kutty et al. 2003). Seed yield per plant showed positive correlation with number of pods per plant and 100-seed weight, but it was negatively associated with days to maturity (Vinieta et al. 2003). Pod length and test weight showed negative association with grain yield (Nigude et al. 2004b) suggesting that longer pods may not give more test weight. Green pod yield per plant exhibited positive association with number of primary branches per plant, pod length, pod diameter, number of pods per plant, number of seeds per pod, and 100-seed weight (Singh et al. 2004), while days to 50% flowering and days to first green pod picking had negative association with green pod yield per plant. Number of clusters per plant, number of pods per plant, pod length, number of seeds per pod, and 100-seed weight had significant positive association with the single plant yield in cowpea (Anbumalarmathi et al. 2005). Plant height and number of pods per plant had positive and significant correlation with seed yield per plant (Patil et al. 2005). Number of clusters per plant, number of pods per plant, pod length, number of seeds per pod, 100-seed weight, and harvest index were found positively correlated with seed yield (Dahiya et al. 2007b), while it was negatively correlated with plant height. Dry matter production and harvest index showed significantly high correlation with seed yield per plant (Eswaran et al. 2007). Number of peduncles per plant, number of pods per plant, pod weight, and pod length were found important characters toward the pod yield in cowpea (Lal et al. 2007). Number of pods per plant, pod length, number of seed per pod, and total soluble solids had positive association with pod yield per plant (Sharma et al. 2007). Pod length has been found positively related with the seed yield (Suganthi et al. 2007). Number of pods per plant, plant height, number of primary branches per plant, 100-seed weight, and number of clusters per plant had positive correlation with seed yield per plant and contributed maximum in this direction (Singh et al. 2011). Number of clusters per plant and number of pods per plant had positive correlation with seed yield (Cholin et al. 2012), while number of clusters per plant, pod length, and test weight exhibited direct positive effect on seed yield and days to maturity showed negative direct effect. Number of peduncles per plant, number of flowers per plant, number of pods per plant, and 100-seed weight showed positive correlation with grain yield (Manggoel et al. 2012). Various character pairs, namely, days to flowering × days to maturity, days to maturity × pod weight, days to maturity × number of beans per pod, pod weight × number of beans per pod, green pod length × pod weight, and number of pods per plant × grain yield, exhibited positive correlation in cowpea (Santos et al. 2014). In general, genotypic correlation was greater than their corresponding phenotypic

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correlation suggesting lower influence of environment on these characters. Pod length had maximum direct effect on seed yield (Santos et al. 2014). Days to 50% germination, days to flowering, pod appearance, and days to maturity have higher coefficient of diversity (Hedge and Mishra 2009; Stoilova and Pereira 2013). Days to 50% flowering, days to 50% ripe pod, pod length, number of locules per pod, and number of seeds per pod showed significant correlation suggesting importance of these traits for genetic improvement in cowpea (Popoola et al. 2015). Dry seed yield, number of pods per plant, pod weight per plant, and seed weight per plant showed positive and significant correlation in cowpea (El-Fattah et al. 2019). Pod yield per plant exhibited positive correlation with number of peduncles and pods per plant, pod weight, pod length, number of seeds per pod, and number of primary branches per plant, whereas negative association with days to 50% flowering at genotypic and phenotypic levels was recorded (Lal et al. 2018). Number of pods per plant followed by pod weight had maximum direct positive effect on pod yield per plant in vegetable cowpea (Lal et al. 2018). Days to 90% pod maturity, days to first flower initiation, days to 50% flowering, and days to first pod maturity had significant positive association (Owusu et al. 2018a) indicating their importance for selecting traits for early maturity. The study also revealed the association of higher grain yield and maturity indices for selection of progenies of cowpea. Long peduncles, high canopy width, and higher number of pods per plant were important traits for improving grain yield in cowpea due to their higher correlation with grain yield (Owusu et al. 2018b). Biological yield per plant, number of pods per plant, number of flowers per plant, test weight, number of pods per cluster, pod length, number of seeds per pod, number of clusters per plant, harvest index, and plant height exhibited significant positive association with seed yield (Sharma et al. 2016), while days to maturity showed negative effect on seed yield per plant suggesting the importance of early maturing genotypes for higher yields in cowpea. Biological yield per plant, harvest index, number of pods per plant, days to 50% flowering, number of flowers per cluster, number of primary branches per plant, number of seeds per pod, test weight, and plant height showed direct positive effect on seed yield (Sharma et al. 2016). Green pod yield per plant was highly significant and positively correlated with pod length and sugar content (Patel et al. 2016) whereas, pod length, days to 50 per cent flowering, number of pods per plant, sugar content, and plant height at final harvest had highest positive direct effect on green pod yield per plant. Pod weight had been observed an important character in having maximum direct effect on the seed yield, while number of pods per plant contributed indirectly via pod weight and 100-seed weight to the seed yield in a study of crossing of two cultivars of cowpea in F2 generation (Rangaiah and Mahadevu 2000). Plant height, number of pods per plant, and 100-seed weight has direct effect on seed yield in cowpea (Belhekar et al. 2003). Number of grains per pod, pod length, and number of pods per plant had maximum direct positive effect on pod yield per plant (Chaudhary and Sharma 2003), while number of days to 50% flowering exhibited maximum negative direct effect on seed yield. Number of pods per plant and number of grains per pod were found to be important selection indices for cowpea improvement

2.4 Correlation and Path Coefficient Analysis

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(Chaudhary and Sharma 2003). Number of pods per plant, pod length, number of clusters per plant, number of seeds per pod, and 100-seed weight had maximum direct positive effect on seed yield (Venkatesan et al. 2003a). Number of cluster per plant, number of pods per plant, number of seeds per plant, and 100-seed weight demonstrated maximum positive direct effect on seed yield, while days to maturity and days to flowering had maximum negative effect on seed yield per plant (Vinieta et al. 2003). Dry biomass at harvest and harvest index had highest direct effect on grain yield (Nigude et al. 2004b), similarly, biomass, and grain yield were significantly positively correlated. Pod length and 100-seed weight exhibited positive and significant correlation with seed yield per plant (Peksen and Artik 2004). Pod length, 100-seed weight, and number of pods per plant had maximum direct effect on seed yield per plant, while it was negatively and directly affected by pod height and number of branches per plant (Peksen and Artik 2004). The 100-seed weight had maximum direct effect on seed yield, while fresh weight of root nodules per plant, total nitrogen content, and number of pods per plant had indirect positive effect on yield via 100-seed weight (Chakraborty et al. 2005). Number of pods per plant, pod length, 100-seed weight, and days to flowering had higher direct positive effect on seed yield in cowpea (Mittal and Singh 2005). Number of pods per plant, number of seeds per pod, and 100-seed weight had high direct effect on the single plant yield in cowpea (Anbumalarmathi et al. 2005), while number of clusters per plant exhibited high indirect effect via number of pods per plant to the seed yield. Number of pods per plant and pod length exerted high direct effect on pod yield per plant (Mehta et al. 2005). Plant height at the time of first flowering, plant height at the time of 50% flowering, plant height at the time of 50% maturity, and total dry matter production had directly contributed to seed yield (Eswaran et al. 2007). Pod weight, number of peduncles per plant, and pod length exerted direct effect on pod yield (Lal et al. 2007). Number of pods per plant, plant height, and pod length has direct effect on pod yield (Sharma et al. 2007). 100-seed weight, number of pods per plant, number of seeds per pod, and days to 50% flowering had maximum direct and positive effect on green pod yield (Nawab et al. 2008). Number of pods per plant recorded highest positive direct effect on pod yield per plant (Sharma et al. 2009). Number of pods per plant had highest positive direct effect on grain yield per plant (Singh et al. 2011), while plant height and number of primary branches contributed indirectly. On the basis of correlation studies, Adeigbe et al. (2011) suggested that good height may have less number of branches supporting longer peduncles, and pods while early flowering genotypes may produce higher number of pods and its early maturation (Umar et al. 2010). Number of peduncles per plant, number of flower per plant, and 100-seed weight exhibited high positive direct effect on yield (Manggoel et al. 2012). The magnitude of genotypic and phenotypic correlations was closely related with each other. Number of pods per plant had positive and significant correlation with pod yield per plant while days to 50% flowering, and days to first pod picking were negatively but significantly correlated (Sapara and Javia 2014). Number of primary branches per plant, number of secondary branches per plant, days to 50% flowering, number of pods per plant, number of seeds per pod, and plant height had positive and

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significant correlation with seed yield, while yield per plant and number of pods per plant exerted highest direct and positive effect on seed yield. Number of secondary branches per plant, days to flowering, days to maturity, and number of seed per pod were recorded to have negative and direct effect on seed yield per plant (Shanko et al. 2014). Number of days to first flower, days to first ripe pod, pod length, and number of seeds per pod had positive correlation (Porbeni et al. 2016) with the seed yield in cowpea. Number of main branches, number of pods per peduncle, and number of seeds per pod are the important characters for improvement in cowpea (Adetiloye et al. 2017). Number of pods per plant and pod length had moderate direct effect of green pod yield. Number of branches per plant, number of nodes, pod length, number of seeds per pod, number of cluster per plant, number of pods per plant, number of pods per cluster, plant height, and protein content had significant and positive association with pod yield (Srinivas et al. 2017), while days for 50% flowering exerted negative but significant correlation with pod yield per plot. Number of branches per plant, number of nodes per plant, number of cluster per plant, number green pods per plant, number of pods per plant, number of seeds per pod, pod weight, pod yield, and protein content showed direct and positive effects on pod yield per plot (Srinivas et al. 2017). Significant positive correlation was recorded between grain yield and number of pod per plant, 100-seed weight, pod length, number of secondary branches per plant, number of seed per pod, number of primary branches per plant, and plant height, while pod per plant, 100-seed weight, number of seed per pod, number of secondary branches per plant, plant height, and pod length contributed directly to seed yield (Kwon-Ndung and Kwala 2017). Characters, namely, green pod length number of grains per green pod 100-seed weight, and dry grain yield, had maximum values for correlation. Similarly, green pod weight and number of grains per green pod had higher positive association with yield, while various character pairs, namely, main stem length × green pod weight, number of branches per plant × green pod length, number of branches per plant × green pod mass, green pod length × 100-green seeds, and green pod mass × 100-green seeds had negative and significant correlation (Lopes et al. 2017) revealing that plants with higher vegetative growth may not culminate to higher yield. Green pod weight, pod length, 100-green seeds, and number of grains per green pod are recorded to be associated one another (Lopes et al. 2017). The magnitude of genotypic correlations was higher than phenotypic correlations (Walle et al. 2018) suggesting the genetic control over the characters. Biomass and harvest index exerted maximum positive direct effect on seed yield, while pod length, seed length, seed thickness, seed width, biomass, and harvest index had positive association with seed yield (Walle et al. 2018). Pod yield exerted maximum significant and positive correlation with pod yield per plant and pod length, whereas number of clusters per plant had maximum direct effect (Diwaker et al. 2018). Highest positive direct effect toward pod yield per plant was recorded by plant height followed by number of seeds per plant, pod length, days to first pod picking, number of pods per peduncle, vitamin A content, number of primary branches per plant, pod diameter, and days to first open flower, while number of peduncle per

2.5 Hybridization

25

plant, vitamin C content, number of seeds per plant, pod weight per plant, number of pod per plant, number of branches per plant, and number of seeds per pod exhibited maximum negative effect on pod yield per plant (Patel et al. 2018). Pod width, 100-seed weight, plant height, number of pods per plant, and pod weight exerted the highest positive direct effect on pod yield in vegetable cowpea (Kalambe et al. 2019).

2.5

Hybridization

Cowpea is a self-pollinated crop having cleistogamous flower, and pollination in the crop occurs just before the anthesis (Asiwe 2009). Manual cross-pollination in the crop depends upon genetic and physiological factor along with the technical expertise for emasculation processes. The artificial cross pollination in cowpea showed good compatibility for fruit setting (Rachie et al. 1975; Doumbia et al. 2014; Rangkham and Khanna 2018). Various species, that is, V. vexillata, V. oblongifolia, and V. unguiculata, had higher phenotypic relatedness showing the close genetic relationship and give indication for crossing between these species to develop better genotypes (Adegbite 2006; Olatunde et al. 2007; Popoola et al. 2015). Study revealed that V. racemosa, V. luteola, and V. oblongifolia could be better bridging species in the hybridization between V. vexillata and V. unguiculata to create a potential progenies (Adegbite 2006; Olatunde et al. 2007; Popoola et al. 2015). Studies also suggest that wild and weedy subspecies of cowpea can be easily used for hybridization with the cultivated form to obtain viable hybrids with better vigor over the parents (Ng and Marechal 1985; Baudoin and Marechal 1985; Ng 1990; Fatokun et al. 1997; Mohammed et al. 2010). It has been suggested that the wild form may only be used as male parent (Rawal et al. 1976). In a study, wild subspecies of cowpea was crossed with the cultivated cowpea to assess their cross compatibility (Nwosu and Awa 2013), and successful hybridization was observed with the pod set ranging from 40.8 to 16.7%. The F1 hybrid plant formed viable seeds revealing that wild species may be used to transfer important genes into the cultivated varieties of cowpea. Interspecific crosses of V. unguiculata and V. sesquipedalis showed better prospect for development of hybrid vegetable bean and had enhanced genetic variability for various characters, namely, number of pods per plant, pod length, plant height, pod texture, and nutrition content, as compared to their parents (Subroto et al. 2018). Significant correlation between fruit set and percent viable pollen was observed during the study on hybridization on the basis of pollen development and fruit set in cowpea (Rangkham and Khanna 2018), and increase in pollen germination from 2 to 6 h was also reported after cross pollination. During the crossability study, selfing was found better as compared to the crosses (Nameirakpam and Khanna 2018); however, pollen germination and growth of pollen tube improved in both selfing and crossing.

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2.6

2 Genetic Improvement and Variability

Inheritance Studies

Inheritance studies give an outlook on the transfer of parent characteristics to the progenies. Phenotypic difference among parents and their progeny is essential for genetic inheritance studies (Bennet-Lartey and Ofori 2000). Pigmentation on different parts of the cowpea including stem, leaf, flower, peduncle, petiole, pod, and seeds are due to anthocyanin and a melanin-like substance, and their expression is based on several genes (Fery 1985). The complete purple pods were found dominant over green pods and were governed by a single gene (Harland 1920). Later, it was reported that three alleles at the gene locus influence green pod with purple tip, green pod with purple layers, and purple pod with green layers (Sen and Bhowal 1961). Interaction between three genes was found to be responsible for the seed coat patterns and flower color in cowpea (Saunders 1960). The brown and mottled colors of the pod are inherited in a simple manner, but purple and red colors were reported to be inherited from complementary gene action. Pod color in cowpea is influenced by one gene over two or more genes by two allelic pairs (Uguru 1995). Monogenic dominant inheritance for pod dehiscence and dry pod color in cowpea has also been reported (Aliboh et al. 1996) in F2 and backcross generations. Black pod color was partially dominant over white pod color in cowpea (Sangwan and Lodhi 1998). Pigmentation in pods of cowpea was reported to be digenic, while pod tip pigmentation exhibited both monogenicity and digenicity patterns (Mustapha and Singh 2008) along with dominance of pigmentation on the pod tip over non-pigmentation. Seed size and color of cowpea seeds are important characteristics for its marketing. Inheritance of seed size was reported to be controlled by varied number of genes, for example, five genes (Lopes et al. 2003), four pairs of genes (Bhowal 1976), and ten pairs (Aryeetey and Laing 1973) have been observed to be involved in the inheritance of seed size in cowpea. Small-sized seeds were reported to be dominant over large-sized seeds (Drabo et al. 1984), and eight loci were associated for the inheritance of seed size in cowpea. Influence of additive gene effect was observed along with significant values for dominance and additive × additive epistatic effect during the study. Influence of additive gene effect along with the association of epistatic effects was observed for seed size (Drabo et al. 1985), while additive, dominance, and epistatic effects were found to be significant for number of seeds per pod. It was observed that environmental factors are responsible for various quantitative traits including seed coat color (Chalker-Scott 1999). Two genes were found to be associated in the crosses between black or brown to cream seed coat, while one gene was reported to be associated with red and cream seed coat color crosses (Oluwatosin 2000). It was reported that several genes may be associated for the inheritance of seed coat color in cowpea (Egbadzor et al. 2014) on the basis of six different biparental crosses and segregating populations. Photoperiod is one of the important environmental factors affecting to flowering in cowpea. It has been observed that some genotypes of cowpea are photosensitive, and some are insensitive to photoperiod (Wienk 1963; Wien and Summerfield 1980; Craufurd et al. 1996). Cowpea has two phenotypic classes of photoperiod sensitivity (Wien and Summerfield 1980; Craufurd et al. 1996). Inheritance to time of sowing to flowering

2.7 Combining Ability and Diallel Analysis

27

was studied using a cross between photoperiod-sensitive photo-insensitive genotypes (Ishiyaku et al. 2005) and over insensitivity; dominance of photoperiod sensitivity was recorded. Further, seven major gene pairs were found responsible for controlling the flowering time in cowpea. Varied range of inherited earliness has been reported in cowpea by various workers for example, it varied from 10–12 days (Craufurd et al. 1996), 22–35 days (Ehlers and Hall 1997), and 36–42 days (Ishiyaku et al. 2005) among different sets of varieties. Similarly, inherited earliness has been reported to be controlled by single (Ishiyaku et al. 2005) and duplicate dominant genes (Roy and Richharia 1948; Capinpin and Irabagon 1950; Mak and Yap 1980). Flowering and pod filling of a crop within a short period is considered as earliness (Song et al. 2013). Maternal effects for inheritance of various maturity indices, namely, days to 50% flowering, days to flower initiation, days to 90% pod maturity, and days to first pod maturity in cowpea, were absent suggesting that inheritance of these traits is under the influence of nuclear gene control (Ishiyaku et al. 2005). Therefore, any maternal parent may be used during hybridization program for maturity in cowpea (Singh et al. 2007). Studies revealed that inheritance of maturity in cowpea is related to the genetic factors as compared to the environment factors (Barakat 1996; Oyiga and Uguru 2011) and is controlled by monogenic (Brittingham 1950; Hugo et al. 2014; Owusu et al. 2018b).

2.7

Combining Ability and Diallel Analysis

Ability to transmit the desirable quality to their crosses is one of the important requisites for hybridization programs. Combining ability informs about the good and poor combiners and assists in the selection of suitable parental materials. Combining ability has widely been used for the assessment of inheritance of quantitative characters for varietal improvement in various crops (Jenkins and Brunson 1932; Tysdal et al. 1942; Kempthorne 1957; Griffing 1956; Rawlings and Cockerham 1962). The theory of general combining ability (gca) and specific combining ability (sca) for quantifying nature of gene action was proposed by Spraque and Tatum (1942) in which total genetic variability is partitioned into general and specific combinig ability. Performance of a genotype in sequence of crosses for potential ability of parents and specific combining ability as a deviation of probability based on the performance of cultivars involved in the hybrid combination is considered as the general combining ability. Importance of studies of both general and combining abilities has been advocated in the expression of yield, pod length, and seed weight in cowpea (Singh and Jain 1972) including predominance of sca in the expression of number of seeds per pod. It gives indication for nonadditive gene effects. Specific combining ability gives an insight to categorize superior crosses that can be used in breeding programs to find transgressive segregants. Selection of parents having the ability to combine well and bring desirable genotypes is one of essential requirements for genetic improvement in the crops. Understanding of genetic structure of the parents contributing to yield and yield-related traits provides an insight for

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identification of potential lines and crosses. Bushy vegetable cowpea genotypes with luxuriant or semi-trailing stem having higher number of seeds per pod and protein content in its green pods are beneficial in the production of vegetable cowpea. Significant gca and sca values for various traits, namely, grain yield, number of pods per plant, number of seeds per pod, 100-seed weight, number of days to 50% flowering, number of days to 90% pod maturity, number of branches, canopy width at vegetation, canopy width at maturity, plant height suggest influence of both additive, and nonadditive gene effects over traits (Griffing 1956). Significant gca and sca have been observed for days to maturity, number of clusters per plant, number of pods per cluster, number of pods per plant, pod length, pod thickness, number of seeds per pod, 100-seed weight, and seed yield per plant (Lal et al. 1975) including the importance of additive genetic variance due to greater extent of gca variance for all these traits. Number of productive axils, number of pods per plant, pod length, pod weight, seed yield, and 100-seed weight exhibited significant gca, while number of pods per plant, number of seeds per pod, and 100-seed weight showed significant sca variance suggesting the involvement of both additive and nonadditive gene action (Bhaskaraih 1978). Bold seeded varieties of cowpea were reported to be good general combiner for seed weight (Jatasra 1980), and both additive and nonadditive gene actions are involved for inheritance of grain weight. Similarly, days to 50% flowering and days to maturity are governed by both additive and nonadditive gene action; however, nonadditive gene action was found to be more influential for the inheritance of these traits (Zaveri et al. 1980). Significant gca was observed for seed yield, number of pods per plant, number of clusters per plant, days to flowering, and days to maturity (Zaveri et al. 1983) in cowpea. Importance of both additive and nonadditive gene action was reported for yield per plant, number of pods per plant, pod length, number of seeds per pod, 100-seed weight, days to 50% flowering, and days to maturity (Patil and Shete 1986). Influence of nonadditive gene was recorded for number of pods per cluster, number of pods per plant, pod length, and seed yield (Patil and Bhapkar 1986). Days to flowering, days to maturity, number of days between flowering and maturity, plant height, number of branches per plant, number of pods per plant, number of clusters per plant, number of pods per cluster, pod length, number of seeds per pod, 100-seed weight, and grain yield per plant showed significant values for gca and sca (Patel et al. 1994); however, higher extent of gca variance for these traits indicates the influence of additive gene action in the expression of these traits in cowpea. Influence of nonadditive gene action was reported for expression of inflorescence per plant, number of pods per plant, and seed yield per plant (Sawant 1994). In another study, Sawant et al. (1995b) observed superior crosses having either high × low or low × low general combiners. Predominant role of nonadditive gene action was also reported for all the yield attributing traits. It was also advocated that selection of hybrids on the basis of sca effects and heterotic effect may be profitable (Aravindhan and Das 1996). The gca estimates were higher than sca estimates on various traits during half diallel crosses in cowpea (Rajkumar et al. 1998). Significant sca variance has been reported to number of pods per plant, number of

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secondary branches per plant, and seed yield per plant (Bhushana et al. 1998). High significant variance for gca and sca has been reported for various traits in cowpea (Shashibhushan and Chaudhari 2000b), and extent of gca was higher than sca variance indicating the dominance of additive gene action. Additive and nonadditive gene effects were reported for pod yield per plant (Hazra et al. 1996), while additive gene action was prevailing in the expression of protein content. Similarly, influence of additive gene action for days to flowering and nonadditive gene action for plant height, number of branches, and crude protein was reported in cowpea (Ponmariamma and Das 1997). In another studies, both additive and nonadditive gene effects were recorded for days to flowering, days to maturity, plant height, number of branches per plant, pod length, number of seeds per pod, 100-seed weight, yield per plant (Chaudhari et al. 1998) including dominance of non-additive effect on days to maturity, pod length, and 100-seed weight. Umaharan et al. (1997) reported additive genetic variance as the main component of genetic variance pod quality characteristics in vegetable cowpea. Influence of additive gene action was recorded for various traits in vegetable cowpea (Sawarkar et al. 1999a), and some of better genotypes (Punjab-263 and Arka Garima) were identified on the basis of gca for pod yield and its attributing traits. In another study, Sawarkar et al. (1999b) observed dominance of leaf area and number of branches per plant and overdominance of plant height and number of pods per plant in cowpea. Yadav et al. (2004) studied gene action governing the inheritance of pod yield in cowpea and found that characters like days to 50% flowering, pod length, and number of seeds per pod were governed by additive gene action. Grain yield, number of seeds per pod, and pod length (Singh et al. 2006); plant height, number of seeds per pod, and grain yield (Pandey and Singh 2010); grain yield, number of pods per plant, and 100-seed weight (Ayo-Vaughan et al. 2013); and number of days to 50% flowering, number of branches, yield, and 100-seed weight (Raut et al. 2017) have been reported to be under the influence of both nonadditive gene effects. Significant combining ability analysis has been reported for seed yield per plant and its related traits indicating the influence of both additive and nonadditive variances in the expression of these traits (Chaudhari et al. 2013). However, the extent of nonadditive variance was higher for seed yield per plant, and its contributing traits and additive gene action were higher for plant height. Combining ability study for green pod yield and its components was carried out in diverse lines of cowpea comprising of ICP-38, ICP-42, Indira Hari, and Arka Garima as general combiner for earliness and ICP-42, ICP-54, Pusa Komal, Arka Garima, and Indira Hari for green pod yield (Sharma and Khare 2015). Cross combinations of ICP-42 × Arka Garima, ICP-54 × Indira Hari, ICP-26 × Khalleshwari and ICP-49 × Khalleshwari were found best specific combiner for number of pods, while ICP-42 × Arka Garima, ICP-42 × Indira Hari, and ICP-54 × Arka Garima were observed as best specific combiner for green pod yield (Sharma and Khare 2015). gca and sca were significant for all the characters, namely, days to 50% flowering, plant height, days to maturity, number of branches per plant, number of pods per plant, seed yield per plant and protein content, seed yield per plant and harvest index, 100 seed weight, and number of seeds per pod (Badhe et al. 2016),

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while the comparison of their variance suggested dominance of nonadditive gene effects for all the traits except days to maturity, number of pods per plant, and protein content. Crosses between GC-3 × HC-08-02, GC-06-01 × JOB129, HC-0802 × PGCP-1, and GC-3 × CP-105 exhibited better specific combination for seed yield per plant, number of pods per plant, number of branches per plant, 100-seed weight, harvest index, and protein content (Badhe et al. 2016). Similarly, significant gca and sca were recorded for plant height, number of secondary branches per plant, days to first flowering, days to 50% flowering, days to maturity, number of pods per plant, seed yield per plant, green fodder yield per meter row length, stover yield per plant, and crude protein content (Satish Kumar et al. 2017) during the combining ability study of dual purpose cowpea lines. Among crosses between SWAD × UPC-9202 and UPC-8705 × BL-2 exhibited significant sca effect for yield components and maturity related traits, respectively. On the basis of gca and sca studies, it was observed that grain yield, canopy width at maturity, plant height, number of seeds per pod, pod weight, and days to 50% flowering is governed by nonadditive gene action, while days to maturity and pod length had influence of additive gene action (Owusu et al. 2018b). Cowpea parents were crossed on the basis of phenotypic and genotypic distance in half diallel to assess the combining ability (El-Fattah et al. 2019), and it was observed that both additive and nonadditive effects were involved in the inheritance of the characters.

2.8

Heterosis

Heterosis provides an insight for the selection of better parents for hybridization and simultaneously developing promising varieties. The term was first time reported by Shull (1914) working on maize referring that the F1 population found by crossing two genetically different individuals exhibited increased or decreased vigor, seed yield, etc. over its parents, and later, it was described in terms of hybridity (Shull 1948). Heterosis is a very complex phenomenon; however, dominance, overdominance, and epistasis are the major causes of heterosis (Mather and Jinks 1971; Hayes and Foster 1976). Cowpea has been subjected to heterosis analysis by various workers observing both negative and positive values for yield and yield components. Singh and Jain (1972) recorded high heterosis for grain yield over the mild and better parents and found that pod length, number of seeds per pod, and 100-seed weight were the important traits for the higher heterosis of grain yield. Seed yield per plant, number of pods per plant, and number of clusters per plant has been recorded with high average heterosis, while number of seeds per pod and number of branches per plant showed low heterosis (Kheradnam et al. 1975). Number of productive axils per plant, number of pods per plant, seed yield per plant, spread at maturity, and 100-seed weight exhibited higher range of heterosis over their mid parental values (Bhaskaraih 1978) in cowpea. In another study, they found high heterotic effect for pod yield per plant, seed yield per plant, number of pods per plant, pod length, number of seeds per pod, and lower heterotic effects for 100-seed weight (Bhaskaraih et al. 1980). Crosses of combination of low and

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medium yielding parents showed significant positive heterotic effects for grain yield per plant. Number of pods per plant, number of seeds per pod, pod length, 100-seed weight, and yield per plant exhibited significant positive heterosis in both directions while low heterosis for plant height and days to maturity (Chikkadevaiah et al. 1980). Yield, number of pods per plant, number seeds per pod, pod length, and 100-seed weight were recorded with high heterosis (Singh 1983). Grain yield, number of clusters per plant, days to 50% flowering, and days to maturity showed positive heterosis (Zaveri et al. 1983), and number of clusters per plants and number of pods per plant were the major factor contributing toward the positive heterosis for grain yield. Number of clusters per plant, number of pods per plant, 100-seed weight, seed size, and seed yield per plant showed maximum positive heterosis (Patil and Shete 1987), while number of pods per plant, number of clusters per plant, and 100-seed weight were the major contributors toward the seed yield per plant (Patil and Shete 1987). Heterosis is not always associated with widely diverse parent; it may also be associated with less diverse parents (Hazra et al. 1993), and its amount is associated with sca rank of crosses in cowpea. Estimation of heterosis values is more useful in the light of sca and genetic divergence of the parents. Number of branches per plant, number of clusters per plant, number of pods per plant, grain yield per plant, and number of pods per cluster showed high heterosis values, while days to 50% flowering and days to maturity exhibited lower heterosis (Patel et al. 2009). Number of pods per plant, 100-seed weight, and number of seeds per pod were found major contributors toward the seed yield in cowpea due to high heterosis component. Seed yield per plant, inflorescence per plant, number of pods per plant, number of branches per plant, and plant height had maximum positive heterosis (Sawant et al. 1995a). Higher number of crosses showed significant positive heterosis for seed yield per plant, number of pods per plant, pod length, number of seeds per pod, and 100-seed weigt along with positive correlation (Sangwan and Lodhi 1995) showing the importance of these traits for selecting high yielding genotypes in cowpea. Similarly, higher values of heterosis for seed yield were reported due to number of pods per plant, number of seeds per pod, number of clusters per plant, number of branches per plant, and test weight (Shashibhushan and Chaudhari 2000a). Higher heterosis over mild parents was recorded for number of secondary branches per plant and number of pods per plant (Bhushana et al. 2000). Positive heterosis for seed yield per plant, number of primary branches per plant, pod length, and test weight along with major contribution of number of pods per plant, number of primary, and secondary branches toward grain yield per plant were also reported (Bhushana et al. 2000).

2.9

Genetic Variability

Presence of variability in the genetic material is one of the pre-requisites for crop improvement program. It helps in the maximum utilization and conservation of the species. Presence of considerable amount of variability is estimated by phenotypic coefficient of variation (PCV) and genotypic coefficient variation (GCV) among

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genotypes. These are helpful in the selection of potential parents in the plant breeding program. Existence of high to low genetic variability has been reported in cowpea by various workers.

2.9.1

Genotypic and Phenotypic Coefficient of Variation

Higher fraction of GCV toward PCV is enviable during selection of traits as it illustrates the elevated genetic control than the environmental control (Kaushik et al. 2007), and the environment reliant traits may not be consistent descriptors for morphological classification (Samaee et al. 2003). Seed yield has been observed as most inconsistent trait (Ariyo 1995) and days to flowering showed least variability in terms of PCV and GCV in cowpea. Wide range of GCV and PCV among plant height, number of branches per plant, number of seed per plant, pod weight, and total seed weight has been recorded (Rangaiah and Mahadevu 2000). PCV was highest for number of pods per plant, number of clusters per plant, number of primary branches per plant, and seed yield per plant (Nehru and Manjunath 2001). High GCV was recorded for pod yield per plant, moderate to high GCV for number of days to 50% flowering, and plant height (Pathak and Jamwal 2002), while low GCV was recorded for days to first picking, pod length, and average pod weight. Considerable amount of PCV and GCV was recorded for number of pods per plant, pod weight per plant, internode length, plant height, mean pod weight, and seed weight per pod (Ramesh and Tewatia 2002). 100-seed weight and seed yield exhibited higher heritability (Rocha et al. 2003). Pod yield, number of pods per plant, and pod weight have high PCV and GCV (Narayanankutty et al. 2003). Days to flowering, days to maturity, number of clusters per plant, number of pods per plant, 100-seed weight, and seed yield per plant showed high values for PCV and GCV, and the extent of PCV was higher than that of GCV (Vinieta et al. 2003). Plant height and dry matter production recorded higher PCV and GCV, and the extent of PCV was higher than that of GCV (Venkatesan et al. 2003b). The extent of PCV was higher for various characters, namely, number of primary branches per plant, days to first harvest, days to 50% flowering, peduncle length, number of pods per plant, pod length, pod width, number of seeds per pod, 100-fresh seed weight, and fresh pod yield per plant, which were higher than their corresponding values of GCV (Prasad et al. 2004) suggesting that selection on the basis of phenotype is more effective. Plant height, seed yield, and number of pods per plant had higher values of GCV and PCV, and extent of PCV was higher than that of GCV (Nigude et al. 2004a). Plant height, 100-seed weight, and number of pods per plant had higher values of GCV and PCV, while these values were moderate for pod length and number of seeds per pod (Prasanthi 2004). Days to first flower, 100-seed weight, plant height, and harvest index had high values of GCV (Omoigui et al. 2006). Plan height, number of pods per plant, and seed yield per plant had higher value for PCV and GCV, while number of primary and secondary branches showed low values (Girish et al. 2006). Higher extent of variability for number of peduncles, number of pods per plant, pod weight, and

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pod yield per plant was observed (Lal et al. 2007). High estimates of genetic variability were observed for plant height at the time of first flowering, plant height at the time of 50% flowering, and plant height at the time of 50% maturity (Eswaran et al. 2007) indicating their dependability for effecting selection. High PCV and GCV were observed for biological yield and seed yield per plant (Mishra and Singh 2007). PCV and GCV were highest for seed yield per plant, number of pods per plant, and number of clusters per plant (Suganthi et al. 2007). Time to flowering, pod length, number of pods per plant, number of seeds per pod, 100-seed weight, total production, and per plant production of different cultivars of cowpea showed higher level of genetic variability (Bertini et al. 2009). GCV, heritability, and genetic advance study among 50 genotypes (Selvam et al. 2000) revealed that plant height number of pods, seed yield, and number of branches per plant had higher GCV and PCV, while plant height and days to 50% flowering exhibited higher GCV, heritability, and genetic advance indicating the influence of additive gene effects. Existence of significant genetic variability was recorded among 12 important character studied among 60 genotypes of fodder cowpea (Malarvizhi et al. 2005). High PCV, GCV, heritability, and genetic advance were recorded with pod yield, number of pods per plant, and pod weight (Narayanankutty et al. 2003) indicating the dominance of additive gene action. Genetic variation and correlation studies carried out for ten morphological characteristics (Kumari et al. 2003) among 50 genotypes revealed that the PCV was higher than the corresponding GCV values. Days to 50% flowering, days to maturity, number of clusters and number of pods per plant, 100-seed weight, and seed yield per plant exhibited higher GCV and PCV estimates, while seed yield per plant and number of pods and number of clusters per plan showed higher heritability and genetic advance. Number of clusters and number of pods per plant and 100-seed weight were positively correlated with the seed yield per plant, but days to maturity exerted negative impact on seed yield. PCV was higher as compared to their corresponding GCV, while number of days to first ripe pod exhibited lowest and number of branches per plant had highest values of PCV (Adeigbe et al. 2011). Higher amount of genetic contribution to the overall phenotypic expression was also observed in the study (Adeigbe et al. 2011). High phenotypic and genotypic coefficient of variation, heritability, and genetic advance were observed for days to 50% flowering, number of branches per plant, number of pods per plant, and seed yield per plant (Girish et al. 2006; Venkatesan et al. 2003a; Viswanatha and Yogeesh 2017), while days to physiological maturity (Thiyagarajan 1989), plant height exhibited low and number of seeds per pod (Chauhan et al. 2003; Kumari et al. 2003), and test weight (Neyaz and Bajpai 2002; Venkatesan et al. 2003b) had moderate PCV and GCV. Higher estimates of GCV and PCV were observed for plant height, primary branches per plant, seed yield per plant, and test weight (Sharma et al. 2017). PCV and GCV were higher for days to 50% flowering, number of peduncles per plant, number of flowers per plant, number of pods per plant, 100-seed weight, and grain yield, while it was lower for number of seeds per pod and pod length (Manggoel et al. 2012). The seed yield was highly and positively correlated with the number of peduncles per plant, number of

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flowers per plant, number of pods per plant, and 100-seed weight. These traits also have direct and positive influence on the seed yield suggesting their importance in the selection of genotypes during the crop improvement program (Manggoel et al. 2012). PCV and GCV were higher for days to 50% flowering, number of peduncles per plant, number of flowers per plant, number of pods per plant, 100-seed weight, and seed yield, while it was lower for number of seeds per pod and pod length (Manggoel et al. 2012). PCV was greater than GCV indicating that the character interacted with the environment to a lower degree (Santos et al. 2014). Pod yield per plant, number of pods per plant, peduncle length, number of primary branches per plant, pod length, pod weight, and number of seeds per pod showed higher values of genotypic and phenotypic coefficient of variations along with higher values of heritability and genetic advance for vegetable cowpea (Lal et al. 2018). The values of PCV were observed slightly higher than their corresponding GCV values indicating lower environmental influence on these characters of cowpea (Shahid et al. 2005; Tamgadge et al. 2008; Suganthi and Murugan 2008; Sharma et al. 2017; Gupta et al. 2019). Plant height (Khan et al. 2015), number of primary branches per plant (Khan et al. 2015), seed yield per plant (Resmi et al. 2004), number of pods per plant, number of pods per cluster, pod weight and pod length, and test weight (Sharma et al. 2017) exhibited higher PCV and GCV values, while harvest index (Sharma et al. 2017), number of pods per plant (Tyagi et al. 2000; Khan et al. 2015; Sharma et al. 2017), number of clusters per plant (Selvam et al. 2000; Kumari et al. 2003; Nwosu et al. 2013; Sharma et al. 2017), number of seeds per pod, days to first picking and pod diameter (Nigude et al. 2004a), and number of flowers per plant (Manggoel et al. 2012; Sharma et al. 2017) showed moderate and days to 50% flowering (Singh and Verma 2002; Venkatesan et al. 2003b; Zargar and Tahirali 2005; Manggoel et al. 2012; Chattopadhyay et al. 2014; Sharma et al. 2017) days to first flowering and plant germination percentage (Gupta et al. 2019), and days to maturity (Thiyagarajan 1989; Khan et al. 2015; Sharma et al. 2017) showed lower GCV and PCV values (Sharma et al. 2017) in cowpea. In a recent study, higher GCV was recorded for number of pods per plant, pod length, number of seeds per pod, number of aborted ovules per pod, fresh pod weight, seeds weight per pod, and seeds yield per plant (Zaki and Radwan 2022) as compared to their corresponding PCV suggesting that genotypes have interacted with the environment to influence the expression of these characters.

2.9.2

Heritability and Genetic Advance

Transfer of characters from parents to offspring is measured in the form of heritability index that provides magnitude of similarity between relatives as well as correspondence between phenotypic and breeding values. Deviation in characters of particular population over the control population is termed as genetic advance that envisage the predictable progress under the selection and assist in the evaluation of selection process. Higher values of genetic advance in the following generation give indication of good progress of transfer of characters. Therefore, estimation of

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heritability coupled with genetic advance more beneficial as compared to heritability alone (Johnson et al. 1955). Several investigations have shown that number of seeds per pod, pod length, and weight of 100-seeds were moderately to highly heritable (Singh and Mehndiratta 1969; Leleji 1975; Tikka et al. 1977; Erskine and Khan 1978). Erskine and Khan (1978) also reported moderate to low heritability for seed yield and number of seeds per pod, respectively. 100-seed weight had highest, while number of peduncles per plant exhibited lowest estimates of heritability (Ariyo 1995). High heritability along with genetic advance was observed for number of seeds per plant during the study of crossing of two cultivars of cowpea in F2 generation (Rangaiah and Mahadevu 2000), while low difference between GCV and PCV was recorded for this character. Number of branches and leaves, stem and leaf dry weight, and plant height had higher values of heritability along with genetic advance (Borah and Khan 2000), while crude protein content, days to 50% flowering, stem thickness, and leaf length and width showed high heritability but low genetic advance. Pod weight, seed yield per ha, seed yield per plant, and crude protein had higher values of heritability along with genetic advance (Belay and Fisseha 2021). High values of PCV, heritability, and genetic advance were recorded for number of pods per plant, while it was moderate for plant height, 100-seed weight, and seed yield per plant (Nehru and Manjunath 2001). Moderate to high heritability was recorded for plant height, pod length, 100-seed weight, number of branches, and number of pods per plant in cowpea (Ramesh and Tewatia 2002). Pod yield per plant exhibited high heritability and genetic advance in cowpea (Pathak and Jamwal 2002), while number of days to first picking, pod length, and pod weight showed high heritability and low genetic advance. Green pod yield, plant height, and days to 50% flowering had high genetic advance. High heritability was recorded for plant height, number of pods per plant, pod length, 100-seed weight, seed yield, and dry matter production (Venkatesan et al. 2003b). Out of these characters, plant height, dry matter production, and seed yield exhibited high heritability along with high genetic advance. High heritability with moderate to high GCV and genetic advance was recorded for plant height, peduncle length, number of primary branches per plant, number of peduncle per plant, and number of green pods per plant (Pal et al. 2003), while days to 50% flowering, days to first green pod picking, pod diameter, number of seeds per plant, and 100-seed weight exhibited high heritability and low GCV and genetic advance. Seed yield per plant, number of pods, and number of clusters per plant exhibited higher heritability and genetic advance in cowpea (Vinieta et al. 2003). High heritability and genetic advance for days to 50% flowering, plant height, number of branches per plant, number of clusters per plant, number of pods per plant, pod length, number of seeds per pod, 100-seed weight, and seed yield per plant were recorded in cowpea (Anbumalarmathi et al. 2005). High heritability and genetic advance were observed for number of branches per plant, number of leaves per plant, dry weight of leaves, and dry weight of stem in cowpea (Malarvizhi et al. 2005). High estimates of heritability along with high genetic advance were recorded for harvest index and seed yield per plant (Kumawat et al. 2005). High magnitude of PCV, GCV, heritability, and genetic advance were observed for seed yield per plant,

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number of pods per plant, and plant height in cowpea, while days to first flower opening, day to 50% flowering and days to maturity exhibited low values of genetic advance. Plant height, number of branches, number of leaves, leaf length, stem thickness, leaf weight, stem weight, leaf stem ratio, green fodder yield, dry matter yield, and crude protein exhibited higher heritability coupled with high genetic advance (Sheela and Gopalan 2006). Number of peduncles per plant, number of days to flower, number of pods per plant, and pod yield per plant had higher heritability and higher genetic advance (Lal et al. 2007). Higher genetic variability, heritability, and genetic advance were recorded for plant height at the time of first flowering, plant height at the time of 50% flowering, and plant height at the time of 50% maturity indicating their dependability for effective selective (Eswaran et al. 2007). Plant height had high, number of pods per plant, and pod yield per plant had moderate heritability and genetic advance (Sharma et al. 2007). High heritability coupled with high to moderate genetic advance was recorded for plant height, days to 50% flowering, number of leaves per plant, crude protein content, and green forage yield in cowpea (Bhandari and Verma 2008). Higher values of heritability and genetic advance were observed for seed yield per plant, number of pods per plant, and number of clusters per plant (Suganthi et al. 2007) suggesting that these characters have lower environmental influence in their expression, and genetic improvement in these traits may be carried out through selection. Pod length, number of pods per plant, number of seeds per pod, 100-seed weight, and total yield per plant showed high heritability (Bertini et al. 2009). Plant height, number of pods per plant, and green pod yield per plant had high estimates of heritability, GCV, and genetic advance (Choudhary et al. 2010). Number of pods per plant, seed yield per plant, and biological yield per plant exhibited high heritability (Singh et al. 2012), while plant height, number of pods per plant, productive branches per plant, number of seeds per pod, biological yield per plant, and seed yield per plant had high genetic advance. High heritability and genetic advance were recorded for number of clusters per plant, number of pods per plant, peduncle length, pod length, dry pod weight, 100-seed weight, seeds per pod, number of seeds per plant, and seed yield per plant indicating influence of additive gene effect in controlling these traits (Omoigui et al. 2006). High genetic variation along with high heritability coupled with high genetic advance was recorded for plant height at various stages of plant growth, namely, height at first flowering, at 50% flowering, and at the time of 50% maturity (Eswaran et al. 2007). High heritability was recorded for grain yield and its components except for pod weight (Idahosa et al. 2010), while genetic advance was comparatively higher for pod length, pod weight, number of seeds per pod, and 100-seed weight. Higher values of heritability along with genetic advance were recorded for plant height, number of pods per plant, and number of branches per plant, while the estimates of leaf area index and 50% flowering exhibited higher GCV values (Throat and Gadewar 2013). Days to flowering, pod length, number of seeds per pod, number of pods per plant, and 100-seed weight had moderate to high values of heritability estimates (Santos et al. 2014), while seed yield exhibited low value of heritability and the high value of the PCV. The highest heritability coupled

2.9 Genetic Variability

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with genetic advance was observed for 100-seed weight in cowpea accessions on high altitude (Kwon-Ndung and Kwala 2017). Studies revealed higher values for broad-sense heritability estimates for all the characters studies, while the values of narrow-sense heritability were higher for days to 50% flowering, pod length, pod weight per plant, seed weight per plant, and total dry seed yield (El-Fattah et al. 2019) indicating the importance of selection of these traits. The study also revealed non-allelic gene interactions for pod length and number of seeds per pod. The heritability estimates for days to 90% pod maturity, days to first flower initiation, days to 50% flowering and days to first pod maturity, plant height, number of seeds per pod, and 100-seed weight varied from 74 to 99% (Owusu et al. 2018a, b). High heritability coupled with high genetic advance for days to 50% flowering, number of branches, number of pods per plant, pod length, number of seeds per pod, and seed yield per plant (Girish et al. 2006; Venkatesan et al. 2003b; Kumari et al. 2003), medium heritability coupled with low genetic advance for plant height (Omoigui et al. 2006), primary branches per plant (Kumari et al. 2000), number of seeds per pod (Selvam et al. 2000), and also low heritability with low genetic advance for test weight (Selvam et al. 2000; Singh and Verma 2002) has been reported for various characters indicating the influence of gene effects in the expression of these traits. Values of high heritability are the indication of influence of environment on the characters, and direct selection would be the best strategy to improve the genotypes, while the characters having high estimates of genetic advance with significant amount of heritability may be improved in desired direction. Higher heritability coupled with higher genetic gain was found for test weight followed by plant height, primary branches per plant, seed yield per plant, and harvest index (Sharma et al. 2017) indicating the presence of additive gene action for these traits, and direct selection may be used to improve these traits. High heritability coupled with high genetic advance has been reported in various reports for plant height (Nwosu et al. 2013; Tudu et al. 2015), test weight (Venkatesan et al. 2003b; Idahosa et al. 2010), number of primary branches per plant (Malarvizhi and Rangasamy 2005; Khan et al. 2015), number of pods per plant (Girish et al. 2006; Khan et al. 2015), seed yield per plant (Khan et al. 2015), harvest index (Eswaran et al. 2007; Sharma et al. 2015), number of flowers per plant (Manggoel et al. 2012), and number of clusters per plant (Kumari et al. 2003; Nehru et al. 2009; Nwosu et al. 2013), while days to maturity (Khan et al. 2015) exhibited higher heritability and low genetic advance. Pod yield, plant height, number of pods per plant, and number of nodes on the main stem exhibited high heritability and high genetic advance in a study carried out to assess genetic variability in vegetable cowpea (Gupta et al. 2019) indicating effectiveness of direct selection for these traits. Number of primary branches per plant, number of pods per plant, pod length and test weight (Hasan Khan et al. 2015), pod yield per plant (Khanpara et al. 2015), plant height (Dinesh et al. 2017), and pod yield per hectare (Diwaker et al. 2017) had exhibited high heritability coupled with high genetic advance in cowpea. In a recent study, higher heritability was reported for number of pods per plant, pod length, number of seeds per pod, number of aborted ovules per pod, fresh pod weight, and seeds yield per plant, while it was lower for seeds weight per pod (Zaki and Radwan 2022).

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Genotype-Environmental Interaction

Yield of a genotype is generally influenced by various environmental factors, namely, moisture content, time of sowing, air temperature and photo-period length, soil characteristics, and soil fertility (Bull et al. 1992) along with the complimentary interaction between genotype and environment. A genotype may perform better in a certain environment, but its consistent performance over the varied environment is one of the most desirable characters, and it is attributed due to the interaction between genotype and environment (Ahmad et al. 1996). It is a major concern for the evaluation of genotypes across the environment as it influences the yield potential of the genotypes. The genotypes having lowest influence toward the environment are considered as the stable genotype (Becker and Leon 1988; Romagosa et al. 1996; Ojo et al. 2006). The larger sum of squares of genotype and environmental interaction as compared to the genotype suggests greater differences in genotypic response across environments. Studies suggest genotype and environmental interaction are one of the crucial factors affecting the production of cowpea (Hall et al. 2003). Development of cowpea varieties in respect to varied environmental conditions is essential to increase and sustain the yield potentials (Simion et al. 2018), and identification of genotypes for high yield and stability are considered beneficial in multi-environment trial (Waldron et al. 2002; Olayiwola and Ariyo 2013). The selection of genotype may not be based on yield only; it could be coupled with the stability parameters to obtain sustainable genotypes (Olayiwola et al. 2015). The environment manipulates the genetic performances of many quantitative traits in cowpea (Aremu et al. 2007). The genotype-environmental interaction (G × E interaction) provides an outlook of response of different genotypes into varied environment and unbiased estimates of yield and different morphometric characteristics of a crop to assess stability of the characters in varied environments (Kamdi 2001). Phenotypic characteristics especially quantitative characters of any genotype are highly influenced by different environmental conditions (Gauch et al. 2008). Various studies revealed significantly higher contribution of environment over the yield and yield attributing traits of cowpea (Stanley et al. 2005; Akande 2009; Sarvamangala et al. 2010; Nunes et al. 2014; Odeseye et al. 2018). Plant height, pod length, number of days to first flowering, number of peduncles per plant, number of days to first ripe pod, and peduncle length per plant had significant G × E interactions (Adeigbe et al. 2011). Various workers have reported different behaviors of cowpea genotypes to different environments (Ariyo and Okeleye 1998; Akande 2007). The characteristics influenced by several genes had higher environmental influence and have complex G × E interaction. Understanding of mechanisms influencing the genetic structure and environment gives an insight to develop a crop variety having enhanced capability to abide and succeed in the changing locate of environment (de Leon et al. 2016). In a study, it was observed that genotype and environment interaction influenced the genetic divergence in the grouping of genotypes according to the environmental conditions and contribution of traits (Filho et al. 2018).

2.11

2.11

Mutation

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Mutation

Induced mutations have been exploited in creating superior cultivars in cereals, fruits, and other crops (Lee et al. 2002), and several mutant varieties have been released throughout the world (Maluszynski et al. 2000). Gamma rays have been extensively applied to develop majority of mutant varieties (Ahloowalia et al. 2004). The expression of recessive genes and creation of new genetic variation can be incorporated with the mutation caused by irradiation (Schum 2003; Shin et al. 2011). Mutation has been considered as one of the important tools in breeding to create genetic changes in grain legumes for improved crop productivity, quality of protein content, disease resistance, and other useful agronomic traits (Gupta et al. 1994). Various workers have reported alterations in the morphological and reproductive characters (Adekola and Oluleye 2007; Wi et al. 2007) and protein profiling (Osanyinpeju and Odeigah 1998; Badr et al. 2014) in cowpea using irradiation. Different varieties of cowpea irradiated with 50 and 100 Gy of gamma rays exhibited increased growth parameters and yield components along with variation in the banding patterns of seed proteins, RAPD and ISSR markers (Badr et al. 2014). Increased growth attributes and yield have been observed with 50 and 100 Gy gamma radiations in different varieties of cowpea (Badr et al. 2014). The mutation-induced varieties also exhibited changes in the protein profiling as compared to the control. Seed coat color, weight, and eye pattern inheritance study carried out in cowpea using gamma ray irradiation revealed that the 50 Gy of gamma rays induced significant changes in the coat color from white to black and increased 100-seed weight in M2 and M3 generation, respectively (Gaafar et al. 2016). Mutant cowpea genotypes had been reported having more variability in terms of morphological and agronomic traits (Porbeni et al. 2016) along with level of chlorophyll concentration in the leaves (Kirchhoff et al. 1989; Fawole 1997; Porbeni and Fawole 2013). Exposure of cowpea seeds to 80 Gy gamma radiations along with zinc treatment exhibited higher variation in the genetic material of seeds (Saleh and Salama 2015). Chemical mutagen brings a wide variability among morphological and yield potential as compared to normal plants. Ethyl methane sulphonate (EMS) has been reported to induce high frequency of chromosomal changes like anaphasic bridge, anaphasic laggard, anaphasic bridge, and clumbing of chromosome (Gnanamurthy and Dhanavel 2014). Besides this, EMS has the ability to replace guanine/cytosine (G/C) pair with adenine/thymine (A/T) pairs through subsequent DNA repair, and about 92% of mutations of guanine induced by EMS has been observed as G/C to A/T transitions (Greene et al. 2003). The morphological and chromosomal variations in cowpea were mutagen sensitive that increase with increasing the concentration of EMS. Study of effect of EMS on induced morphological mutants revealed two types of viable and chlorophyll mutants (Gnanamurthy and Dhanavel 2014).

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Nitrogen-Fixing Ability

Legumes are one of the most important natural resources known for potential biological nitrogen fixation in the nature (Masson-Boivin et al. 2009) through a symbiotic association between legume plant and soil bacteria with the help of nodules. Nodules are generally formed on the roots and sometimes on the stems of legumes through molecular exchanges between the partners and morphological changes (Berrada and Fikri-Benbrahim 2014). It was assessed that legumes fixed more than double nitrogen as compared to its requirements (Peoples et al. 2009) leading to nitrogen enrichment of soil (Pule-Meulenberg et al. 2010). Various factors including availability of nitrogen in the soil affect the nitrogen fixation. Higher soil nitrogen level (Peoples and Herridge 1990; Giller and Cadisch 1995), higher soil temperature (Day et al. 1978; Giller and Wilson 1991), and hampered photosynthesis (Midmore 1993; Dakora and Keya 1997) restrict nodulation and simultaneously inhibit the nitrogen fixation activity. Plant nutrients such as phosphorus (Giller et al. 1997), potassium, calcium, manganese (Smithson et al. 1993), micronutrients, and essential elements (Giller and Wilson 1991) have been reported to be advantageous for nitrogen fixation and nodulation. New biogeographic regions can be explored to find new symbioses and microsymbionts for nitrogen fixation in support of sustainable agriculture (Chidebe et al. 2018). Significantly positive correlation was reported between nitrogenase activity, nodule weight, and number of nodules in cowpea (Miller et al. 1986). Additive gene action was more influential as compared to dominant and interallelic gene effect for number of nodules and nitrogenase activity (Miller et al. 1986). Influence of cultivar and inoculation of Bradyrhizobium strain on the nitrogen fixation and yield of cowpea was studied at the maturity level (Awonaike et al. 1990), and it was observed that the nitrogen fixation was not influenced by the inoculation with any varietal difference in the dry matter yield of pods under field conditions. Cowpea has the ability to freely nodulate with the natural bacteria (Appiah et al. 2015) and uses both biologically fixed nitrogen and mineral nitrogen to fix the atmospheric nitrogen that varies from 30 to 240 kg nitrogen per ha (Singh and Rachie 1985; Appiah et al. 2015). Inoculation of seeds with rhizobia is one of the better approaches for lowering the production cost of the crop. Cowpea shows active symbiosis with root nodule bacteria involved on the nitrogen fixation (Dakora and Keya 1997). Rhizobial isolates of cowpea are often white in color and circular in shape (Kenasa et al. 2018). Slow- and fast-growing rhizobia have been reported in the root nodules of cowpea (Mpepereki et al. 1996). Nevertheless, the slow-growing rhizobia were higher in fraction as compared to fast-growing rhizobia (Zhang et al. 2007). The cultural and physiological features of cowpea rhizobia are diverse that may be useful for assessment of identity and diversity. It was observed that the fast- and slowgrowing isolates of the rhizobia have different growth attributes (Jordan 1982), tolerance to temperature, pH, and antibiotics (Florentino et al. 2010; Abdelnaby et al. 2015). Fast-growing isolates of cowpea rhizobia show more tolerance to stresses as compared to their counterpart (Abdelnaby et al. 2015).

References

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Ndungu et al. (2018) collected root nodule symbionts and determined their association with the physicochemical soil parameters including their spread. They reported that Bradyrhizobium spp. was among the most widespread species including various types and locations. Genus Bradyrhizobium has been reported as the principal (Wade et al. 2014; Grönemeyer et al. 2015; Ndungu et al. 2018) and genus Rhizobium as the minor symbiont of cowpea by various workers (Gronemeyer et al. 2014; Ndungu et al. 2018). The cowpea plants from dry areas having low rainfall had quite distinct root nodule symbionts (Law et al. 2007; Gronemeyer et al. 2014; Ndungu et al. 2018). The rhizobial diversity and phylogeny in cowpea are little exploited. Chidebe et al. (2018) studied the distribution and phylogeny of microsymbionts associated with cowpea nodulation in three agro-ecological regions of Mozambique using PCR-based fingerprinting techniques and reported highly diverse and adapted 122 cowpea-nodulating microsymbionts, namely, Bradyrhizobium pachyrhizi, B. arachidis, and B. yuanmingense along with Bradyrhizobium sp., Rhizobium tropici, R. pusense, and Neorhizobium galegae in the soil.

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Pradeepkumar T, Mathew D, Varun RC, Veni K, Midhila KR (2017) Genetic interrelationship among cowpea varieties elucidated through morphometric, RAPD and SSR analyses. Legume Res 40:409–415 Prasad VSRK, Pan RS, Rai M (2004) Genetic variability in vegetable cowpea (Vigna unguiculata (L) Walp.). J Res Birsa Agric Univ 16(2):289–292 Prasanthi L (2004) Variability and heritability studies in cowpea. J Maharashtra Agric Univ 29(3): 362–363 Pule-Meulenberg F, Belane AK, Krasova-Wade T, Dakora FD (2010) Symbiotic functioning and bradyrhizobial biodiversity of cowpea (Vigna unguiculata L. Walp.) in Africa. BMC Microbiol 10:89 Rachie KO, Rawal KM, Franckowiak JD (1975) A rapid method of handling cowpeas. Technical bulletin no. 2, IITA, Ibadan, p 18 Rajkumar, Singh SP, Joshi AK (1998) Combining ability of quantitative characters in cowpea (Vigna unguiculata L. Walp.). Veg Sci 25(1):32–35 Rambabu E, Reddy KR, KamalaV SP, Pandravada SR (2016) Genetic divergence for quality, yield and yield components in Yardlong bean [Vigna unguiculata (L.) Walp. Ssp. Sesquipedalis Verdc.]. Legume Res 39(6):900–904 Ramesh C, Tewatia AS (2002) Character association and path analysis studies in garden pea (Pisum sativum L.). Haryana J Hort Sci 31(1/2):94–97 Rangaiah S, Mahadevu P (2000) Genetic variability, correlation and path co- efficient analysis in cowpea (Vigna unguiculata L. Walp). Madras Agric J 86:381–384 Rangkham T, Khanna VK (2018) Studies on hybridization and genetic diversity in cowpea (Vigna unguiculata L). J Oncol Med 2(1):125–134 Raut DM, Tamnar AB, Burungale SV, Badhe PL (2017) Half diallel analysis in cowpea [Vigna unguiculata (L.) Walp.]. Int J Curr Microbiol Appl Sci 6(7):1807–1819 Rawal KM, Rachie KO, Franchowaik JD (1976) Reduction in seed size in crosses between wild and cultivated cowpeas. J Hered 67:253–254 Rawlings J, Cockerham CC (1962) Triallel analysis. Crop Res 2:228–231 Resmi PS, Celine VA, Abdul Vahab M (2004) Genetic variability in yard long bean (Vigna unguiculata ssp. sesquipedalis L.). Legume Res 27:296–298 Rewale AP, Birari SP, Apte UB (1996) Genetic divergence in cowpea (Vigna unguiculata (L.) Walp.). Indian J Agric Res 30(2):73–79 Rocha MDM, Campelo JEG, Freire Filho FR, Ribeiro VQ, Lopes ACDA (2003) Estimates of genetic parameters in white coat cowpea genotypes. Rev Cientifica Rural 8(1):135–141 Romagosa I, Ullrich SE, Han F, Hayes PM (1996) Use of the additive main effects and multiplicative interactions in QTL mapping for adaptation in barley. Theor Appl Genet 93:30–37 Roy RS, Richharia RH (1948) Breeding and inheritance studies on cowpea, Vigna sinensis. J Am Soc Agron 40:479–489 Saini ML, Jain P, Arora RN (2004) Genetic divergence studies for quantitative characters in cowpea (Vigna ungiculata (L.) Walp). Forage Res 30:152–154 Saleh OI, Salama IM (2015) Effect of long period cooling storage on the nucleic acid of harvested cowpea seeds (Vigna sinensis L.) treated by gamma irradiation and micro elements. Arab J Nucl Sci Appl 48(4):195–207 Samaee SM, Shobbar ZS, Ashrafi H, Hosseini-Mazinani M (2003) Molecular characterization of olive germplasm in Iran by use of random amplified polymorphic dna (RAPD): correlation with phenotypic studies. Acta Hortic 623:169–175 Sandeep V, Hemalatha V, Bushan DS, Swarnalatha V (2014) Studies on genetic diversity in Indian cowpea (Vigna unguiculata (L.) Walp.) germplasm. Int J Plant Anim Environ Sci 4(3):177–180 Sangwan RS, Lodhi GP (1995) Heterosis for grain character in cowpea (Vigna unguiculata L. Walp.). Legume Res 18(2):75–80 Sangwan RS, Lodhi GP (1998) Inheritance of flower and pod colour in cowpea (Vigna unguiculata (L.) Walp). Euphytica 102(2):191–193

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Santos A, Ceccon G, Davide LMC, Correa AM, Alves VB (2014) Correlations and path analysis of yield components in cowpea. Crop Breed Appl Biotechnol 14:82–87 Sapara GK, Javia RM (2014) Correlation and path analysis in vegetable cowpea (Vigna unguiculata L.). Int J Plant Sci 9(1):138–141 Sarvamangala C, Uma MS, Biradar S, Salimath PM (2010) Stability analysis for yield and yield components over seasons in cowpea [Vigna unguiculata (L.) Walp]. Electron J Plant Breed 1: 1392–1395 Saunders AR (1960) Inheritance in the cowpea (Vigna sinensis) II. Seed coat colour pattern, flower, plant and pod colour. South Afr J Agric Sci 3(2):141–162 Sawant DS (1994) Gene control for yield and its attributes in cowpea. Ann Agric Res 15(2): 141–143 Sawant DS, Birari SP, Jadhav BB (1995a) Heterosis in cowpea. J Maharashtra Agric Univ 19(1): 89–91 Sawant DS, Birari SP, Jadhav BB (1995b) Genetics of yield and its attributes in cowpea. J Maharashtra Agric Univ 20(2):174–176 Sawarkar NW, Poshiya VK, Pathia MS, Dhameliya HR (1999a) Combining ability in vegetable cowpea. Gujarat Agric Univ Res J 25(1):15–20 Sawarkar NW, Poshiya VK, Dhameliya HR, Pathia MS (1999b) Gene effect of vegetable cowpea. Gujarat Agric Univ Res J 24(2):31–35 Schum A (2003) Mutation breeding in ornamentals: an efficient breeding method? Acta Hortic 612: 47–60 Selvam YA, Manivannan N, Murugan S, Thangavelu P, Ganeshan J (2000) Variability studies in cowpea (Vigna unguiculata L. Walp). Legume Res 23:279–280 Sen NK, Bhowal JG (1961) Genetics of V. sinensis (L.) Savi. Genetica 32:247–266 Shahid A, Zargar MA, Tasir A (2005) Genetic variability, heritability genetic advance for seed yield and component traits in cowpea. Natl J Plant Improv 7(2):85–87 Shanko D, Andargie M, Zelleke H (2014) Interrelationship and path coefficient analysis of some growth and yield characteristics in cowpea (Vigna unguiculata L. Walp) genotypes. J Plant Sci 2(2):97–101 Sharma D, Khare CP (2015) Combining ability for green pod yield and its components in cowpea [Vigna unguiculata (L.) Walp.]. Veg Sci 42(2):34–38 Sharma TR, Mishra SN (1997) Genetic divergence and character association studies in cowpea (Vigna unguiculata Walp). Crop Res Hisar 13(1):109–114 Sharma A, Sood M, Rana A, Singh Y (2007) Genetic variability and association studies for green pod yield and component horticultural traits in garden pea under high hill dry temperate conditions. Indian J Hort 64(4):410–414 Sharma MK, Chandel A, Kohli UK (2009) Genetic evaluation, correlations and path analysis in garden pea (Pisum sativum Var. hortense L.). Ann Hortic 2(1):33–38 Sharma SP, Sharma PP, Nehra SR, Khatik CL (2015) Variability and character association in cowpea using Bradyrhizobium strain. Int J Plant Sci 10(1):43–48 Sharma M, Sharma PP, Upadhyay B, Bairwa HL (2016) Study of correlation coefficient and path analysis in cowpea [Vigna unguiculata (L.) Walp] germplasm line. Int J Dev Res 6(8): 9011–9016 Sharma M, Sharma PP, Sharma H, Meghawal DR (2017) Genetic variability in cowpea [Vigna unguiculata (L.)Walp.] germplasm lines. J Pharmacogn Phytochem 6(4):1384–1387 Shashibhushan D, Chaudhari FP (2000a) Heterosis studies in cowpea. Ann Agric Res 21(2): 248–252 Shashibhushan D, Chaudhari FP (2000b) Selection of superior combiners in cowpea. Crop Res 20(2):268–273 Sheela MS, Gopalan A (2006) Dissection of genetic attributes among yield traits of fodder cowpea in F3 and F4. Appl Sci Res 2(10):805–808 Shin JM, Kim BK, Seo SG et al (2011) Mutation breeding of sweet potato by gamma-ray radiation. Afr J Agric Res 6(6):1447–1454

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Shivakumar V, Celine VA (2014) Assessment of genetic diversity in vegetable (Vigna unguiculata (L.) Walp). Environ Ecol 32(4):1356–1358 Shull GH (1914) Duplicate gene for capsule form in Bursa Pasteris. Z.Ver-erbungslehre 12:97–149. https://doi.org/10.1007/BF01837282 Shull GH (1948) What is heterosis. Genetics 33:439–446 Simion T, Mohammed W, Amsalu B (2018) Genotype by environment interaction and stability analysis of cowpea [Vigna unguiculata (L.) Walp] genotypes for yield in Ethiopia. J Plant Breed Crop Sci 10(9):249–257 Singh RP (1983) Heterosis in cowpea. J Res Assam Agric Univ 4(1):12–14 Singh KB, Jain RP (1972) Heterosis and combining ability in cowpea. Indian J Genet 32(1):62–66 Singh KB, Mehndiratta PD (1969) Genetic variability and correlation studies in cowpea. Indian J Genet Plant Breed 29:104–109 Singh SS, Rachie KO (1985) Cowpea research, production and utilization. Wiley, Chichester Singh MK, Verma JS (2002) Variation and character association for certain quantitative traits in cowpea [Vigna unguiculata (L.)Walp.] germplasm. Forage Res 27(4):251–253 Singh SP, Kumar R, Joshi AK, Singh B (2004) Genetic architecture of yield traits in cowpea [Vigna unguiculata (L.) Walp.]. Adv Plant Sci 17(2):495–502 Singh I, Badaya SN, Tikka SBS (2006) Combining ability for yield over environments in cowpea. Indian J Crop Sci 1(1–2):205–206 Singh BB, Olufajo OO, Ishiyaku MF et al (2007) Farmer preferences and legume intensification for low nutrient environments. J Plant Regist 1:48–49 Singh A, Singh S, Babu JDP (2011) Heritability, character association and path analysis studies in early segregating population of field pea (Pisum sativum L. var. arvense). Int J Plant Breed Genet 5(1):86–92 Singh M, Malik S, Kumar M et al (2012) Studies of variability, heritability and genetic advance in field pea (Pisum sativum L.). Progress Agric 12(1):219–222 Singh A, Shweta SSP, Tiwari A (2018) Characterization and evaluation of genetic divergence in Indian cowpea (Vigna unguiculata L. Walp.). Int J Chem Stud 6(6):2786–2789 Smithson JB, Edje OT, Giller KE (1993) Diagnosis and correction of soil nutrient problems of common bean (Phaseolus vulgaris) in the Usambara mountains of Tanzania. J Agric Sci 120: 233–240 Song YH, Ito S, Imaizumi T (2013) Flowering time regulation: photoperiod- and temperaturesensing in leaves. Trends Plant Sci 18(10):575–583 Spraque GF, Tatum LR (1942) General vs specific combining ability in single cross of corn. J Am Soc Agron 34:923–932 Srinivas J, Kale VS, Nagre PK, Meshram S (2016) Genetic divergence studies in cowpea. Int J Agric Sci Res 6(3):97–104 Srinivas J, Kale VS, Nagre PK (2017) Correlation and path analysis study in cowpea [Vigna unguiculata (L.) Walp.] genotypes. Int J Curr Microbiol App Sci 6(6):3305–3313 Stanley OPB, Samonte LT, Wilson AM, McClung JC (2005) Targeting cultivars onto rice growing environments using AMMI and SREG GGE biplot analyses. Crop Sci 45(6):2414–2424 Stoilova T, Pereira G (2013) Assessment of the geneticdiversity in a germplasm collection of cowpea (Vigna unguiculata (L.) Walp.) using morphological traits. Afr J Agric Res 82:208–215 Subroto G, Ujianto L, Idris, Yakop UM (2018) Interspecific hybridization among Vigna species to create new superior variety containing high protein and anthocyanin. Int J Agric Sci 3:34–39 Suganthi S, Murugan S (2008) Association analysis in cowpea(Vigna unguiculata L. Walp.). Legume Res 31(2):130–132 Suganthi S, Murugan S, Venkatesan M (2007) D2 analysis in cowpea (Vigna unguiculata (L.) Walp.). Legume Res 30(2):145–147 Sulnathi G, Prasanthi L, Sekhar MR (2007) Character contribution to diversity in cowpea. Legume Res 30(1):70–72 Tajane AN (2014) Genetic diversity studies for seed yield in cowpea (Vigna unguiculata (L.) Walp.). Int J Plant Sci 9(1):202–204

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Tamgadge S, Dod VN, Mahorkar VK, Peshattiwar PD (2008) Genetic variability, heritability and genetic advance in cowpea (Vigna unguiculata L. Walp.). Asian J Hortic 3(1):30–32 Thiyagarajan K (1989) Genetic variability of yield components in cowpea (Vigna unguiculata). Madras Agric J 76:564–567 Throat A, Gadewar RD (2013) Variability and correlation studies in cowpea (Vigna unguiculata (L.) Walp.). Int J Environ Rehab Conserv 4(1):44–49 Tigga K, Tandekar K (2013) Genetic divergence for yield and quality components in cowpea (Vigna unguiculata (L.) Walp.). Trends Biosci 6(5):555–557 Tikka SBS, Jaimini SN, Asawa BM, Mathur JR (1977) Genetic variability, interrelationships and discriminant function analysis in cowpea (Vigna unguiculata (L.) Walp). Indian J Hered 9:1–9 Tudu D, Mishra HN, Dishri M, Rao KM, Toppo R (2015) Variability and correlation studies in cowpea [Vigna unguiculata L. Walp.]. Trends Biosci 8(1):193–196 Tyagi PC, Kumar N, Agarwal MC (1999) Genetic divergence in early maturing cowpea (Vigna unguiculata (L.) Walp.). Agric Sci Dig Karnal 19(3):162–166 Tyagi PC, Kumar N, Agarwal MC (2000) Genetic variability and association of component characters forseed yield in cowpea (Vigna unguiculata L.). Legume Res 23:92–96 Tysdal HM, Kiesselbach TA, Westover HL (1942) Alfalfa breeding. Nebraska Agric Expt Res Stat Bull 124:1–46 Uguru MI (1995) Inheritance of color patterns in cowpea (Vigna unguiculata [L.] Walp.). Indian J Genet Plant Breed 55(4):379–383 Umaharan P, Ariyanayangani RP, Haque SQ (1997) Genetic analysis of pod quality characteristics in vegetable cowpea (Vigna unguiculata L. Walp). Sci Hortic 70:281–292 Umar ML, Sanusi MG, Lawan FD (2010) Relationships between some quantitative characters in selected cowpea germplasm Vigna unguiculata (L.) Walp. Not Sci Biol 2:125–128 Usha Kumari R, Backiyarani S, Dhanakodi (2000) Character contribution to diversity in cowpea. Legume Res 23:122–125 Valarmathi V, Surendran C, Muthiah AR (2007) Genetic divergence analysis in subspecies of cowpea (Vigna unguiculata ssp. Unguiculata and Vigna unguiculata ssp. sesquipedalis). Legume Res 30:192–196 Vavilapalli SK, Celine VA, Sreelathakumai I (2014) Genetic divergence analysis in vegetable cowpea (Vigna unguiculata subsp. unguiculata [L.]) genotypes. Legume Genom Genet 5(2): 4–6 Venkatesan M, Prakash M, Ganesan J (2003a) Correlation and path analysis in cowpea (Vigna unguiculata (L.) Walp.). Legume Res 26:105–108 Venkatesan M, Prakash M, Ganeshan J (2003b) Genetic variability, heritability and genetic advance analysis in cowpea (Vigna unguiculata (L.) Walp.). Legume Res 26(2):155–156 Venkatesan M, Veeramani N, Thangavel P, Ganesan J (2004) Genetic divergence in cowpea (Vigna unguiculata (L.) Walp.). Legume Res 27(3):223–225 Vinieta K, Arora RN, Singh JV (2003) Variability and path analysis in grain cowpea [Vigna unguiculata (L.) Walp]. Adv Arid Legumes Res 2003:59–62 Viswanatha KP, Yogeesh LN (2017) Genetic variation and morphological diversity in cowpea (Vigna unguiculata L. Walp). Arch Agric Environ Sci 2(3):176–180 Wade TK, Le Quere A, Laguerre G et al (2014) Eco-geographical diversity of cowpea bradyrhizobia inS enegal is marked by dominance of two genetic types. Syst Appl Microbiol 37:129–139 Waldron BL, Kay HA, Kevin BJ (2002) Stability and yield of cool-season pasture grass species grown at five irrigation levels. Crop Sci 42:890–896 Walle T, Mekbib F, Amsalu B, Gedil M (2018) Correlation and path coefficient analyses of cowpea (Vigna unguiculata L.) landraces in Ethiopia. Am J Plant Sci 9:2794–2812 Wi SG, Chung BY, Kim JS et al (2007) Effects of gamma irradiation on morphological changes and biological responses in plants. Micron 38(6):553–564

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Wien HC, Summerfield RJ (1980) Adaptation of cowpeas in West Africa: effects of photoperiod and temperature responses in cultivars of diverse origin. In: Summerfield RJ, Bunting AH (eds) Advances in legume science. HMSO, London, pp 405–417 Wienk JF (1963) Photoperiod effects in Vigna unguiculata (L.). Walp. Meded Land Wageningen 63:1–82 Yadav KS, Yadava HS, Naik ML (2004) Gene action governing the inheritance of pod yield in cowpea. Legume Res 27(1):66–69 Zaki HEM, Radwan KSA (2022) Estimates of genotypic and phenotypic variance, heritability, and genetic advance of horticultural traits in developed crosses of cowpea (Vigna unguiculata [L.] Walp). Front Plant Sci 13:987985 Zargar SA, Tahirali MA (2005) Genetic variability, heritabilityan genetic advance for seed yield and component traits incowpea [Vigna unguiculata (L.) Walp.]. Natl J Plant Improv 7(2):85–87 Zaveri PP, Patel PK, Yadavendra JP (1980) Diallel analysis of flowering and maturity in cowpea. Indian J Agric Sci 50(11):807–810 Zaveri PP, Patel PK, Yadavendra JP, Shah RM (1983) Heterosis and combining ability in cowpea. Indian J Agric Sci 53(9):793–796 Zhang WT, Yang JE, Yuan TY, Zhou JC (2007) Genetic diversity andphylogeny of indigenous rhizobia from cowpea [Vigna unguiculata (L.) Walp]. Biol Ferty Soils 44(1):201–210

3

Quality and Nutrition

Abstract

Cowpea is an important crop having substantial role in sustainable farming and nutritional security in developing countries. The nutritional values of the legume are comparable to other pulses and provide economic source of various nutrition. It has good therapeutic properties and has been traditionally used as astringents, laxatives, anthelmintic, aphrodisiac, diuretic, and tonic for the liver. The nutritional composition, anti-nutritional factors, and nutraceutical and medicinal properties have been summarized in this chapter.

3.1

Introduction

Plant species are major source of nutrition for human and animals. They provide very good quality of carbohydrates, protein, mineral, etc. required for wellness of human being. Cowpea is a dual-purpose crop having good quantity of protein, minerals, and vitamins for daily human diets and is equally important as nutritious fodder for livestock (Singh et al. 2003a). Its seeds are more or less similar to other legumes in quality but have low fat and high protein content. It provides both microand macronutrients (Plahar et al. 2006) and dietary protein (Devarajan 2005; Maisale et al. 2012). The seeds have high (19.5% and 27.3% w/w) protein content (Msika et al. 2012) and several essential amino acids in balanced proportions. Various workers have reported that cowpea seeds have 23–32% protein (Jose et al. 2014), 50–60% carbohydrate (Khalid and Elharadallou 2013; Kirse and Karklina 2015), and 1% fat (Kirse and Karklina 2015). Similarly, it has also been observed that the total protein content in cowpea is about two to four times higher than that of cereal and tuber crops (Sebetha et al. 2014; Trehan et al. 2015). Its protein is rich in lysine that combines with cereals to provide good food (Gonçalves et al. 2016), while its protein is deficient in methionine and cysteine as compared to animal proteins # The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 R. Pathak, Genetics, Physiology and Cultivation of Moth Bean, Cowpea and Horse Gram, https://doi.org/10.1007/978-981-19-9956-7_3

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(Vasconcelos et al. 2010; Petchiammal and Hopper 2014; Frota et al. 2017). The quantity of other essential amino acids present in cowpea is as per the recommendations of World Health Organization for the children of 2–5 years (FAO 1991). Besides this, cowpea possesses soluble and insoluble dietary fiber, phenolic compounds, minerals, vitamins and many other functional compounds (Mudryj et al. 2012; Liyanage et al. 2014), carbohydrates (Rochfort and Panozzo 2007), unsaturated fatty acids, and antioxidants (Khalid and Elharadallou 2013) proving to be beneficial source for human health. It has also been reported that cowpea gives protection against various diseases such as gastrointestinal disorders (Trehan et al. 2015), cardiovascular diseases, hypercholesterolemia, obesity (Frota et al. 2008), diabetes (Rotimi et al. 2013; Barnes et al. 2015), and several cancers (Chon 2013; Khalid and Elharadallou 2013). The presence of phytochemicals, resistant starch, dietary fiber, low-fat and unsaturated fatty acids in the crop improves digestion and blood circulation (Trehan et al. 2015) and results into weight loss (Perera et al. 2016). Preparations from cowpea seed have been reported as astringents, aperitifs, laxatives, anti-anthelmintic, aphrodisiac, diuretic, and tonic for the liver (Maisale et al. 2012). Besides, giving the cheapest sources of vegetable protein, essential amino acids, vitamins, and minerals, the legume plays an important role in the livelihood of people of developing countries toward livestock fodder during the scarcity of animal feed (Singh and Tarawali 1997). The seeds and flour of the legumes are used to prepare several nutritive rich food items for mal-nutritive population and economically miserable communities of developing country to get protein and energy in adequate quantity (Animasaun et al. 2015; Santos and Boiteux 2013; Elhardallou et al. 2015). Due to the presence of low fat, high fiber, and other health benefits, cowpea is getting more attentions in developed countries to develop new foods. Since the crop is highly adaptive to different ecological conditions, it is popular among the farmers having minimum resources. Information on the nutritive significance along with anti-nutritional factor and its dissemination will enhance the popularity and uses of the legume.

3.2

Nutrient Value

Cowpea is good source of protein, vitamins, minerals, unsaturated fatty acids, antioxidants, soluble, and insoluble fiber and carbohydrates (Meiners et al. 1976; Rochfort and Panozzo 2007; Khalid and Elharadallou 2013). The proximate compositions, that is, protein (21.2 ± 0.1%), fat (1.3 ± 0.03%), crude fiber (6.0 ± 0.1%), and carbohydrate (58.2%), in cowpea (Meiners et al. 1976) exhibit its nutritive importance. It has been observed that local cowpea in Africa had calcium (958.1–992.4 mg per kg), zinc (32.6–31.5 mg per kg), and iron (32.6–31.5 mg per kg) in good quantity (Nielsen et al. 1993; Onwuliri and Obu 2002; Mamiro et al. 2011). In another study, the calcium content was higher (5672.5 mg per kg), while zinc and iron content was at par (Liyanage et al. 2014). Various workers have reported wide range of variability in the seed protein of cowpea landraces from 15.06–38.5% (Afiukwa et al. 2013), 20.57–24.95% (Itatat et al. 2013), and

3.2 Nutrient Value

57

Table 3.1 The proximate composition of whole grain of cowpea

Whole seed Leaves

Proximate composition (%) Crude Crude fat Moisture protein 11.00 22–24 1.3–1.5

Crude fiber 5.9–7.3

Carbohydrate 55–66

85.00

2.00

8.00

4.70

0.3

Ash 3.4– 3.9 –

Source: Gondwe et al. (2019), Biama et al. (2020)

25.80–28.95% (Oke et al. 2015). A study comprising of 2000 genotypes of cowpea exhibited significant variability among seed protein content that ranged from 21 to 30.7% (Timko and Singh 2008). Studies also suggest that the improved cowpea breeding lines have more than 30% protein content (Santos and Boiteux 2013). The tender leaves of the legumes are also good source of protein and carbohydrate. The higher protein content in cowpea makes it important to the populace not getting enough protein in form of meat and fish. Cowpea seeds have better lysine content; however, it is deficient in methionine content. The proximate composition of whole grain of cowpea is given in Table 3.1. Studies revealed that cowpea has 17 amino acids (Hussain and Basahy 1998) including higher quantities of valine, leucine, phenylalanine, and lysine (Rangel et al. 2004; Elhardallou et al. 2015). The immature seeds have comparatively higher amount of amino acids than the mature seeds (Rangel et al. 2004; Elhardallou et al. 2015). It has also been observed that profile of amino acid in cowpea depends on the genotypes (Gupta et al. 2010) and its maximum and minimum content ranged from 33.43 g and 27.50 g in each 100 g of cowpea sample, respectively (Gupta et al. 2010). The total phenolic content also varied among various varieties of cowpea (Gutierrez-Uribe et al. 2011; Xu and Chang 2012; Zia-Ul-Haq et al. 2013). Ferulic acid and gallic acid have been reported in the seed coat of cowpea (Gutierrez-Uribe et al. 2011). Studies revealed that the colored seeds of cowpea varieties have higher amount of total phenolic, total flavonoid content, ferric reduction ability, and anti-lipid peroxidation activities as compared to the white colored seeds (Apea-Bah et al. 2017; Sombié et al. 2018). Cowpea has substantial amount of resistant starch along with higher proportion of slow digestible to rapid digestible starch (Thorne et al. 1983). These qualities of cowpea are beneficial for the insulin-resistant people (Yamada et al. 2005). Cowpea seeds are also good source of α-galactosides, recognized as prebiotic function (Martínez-Villaluenga et al. 2008). Cowpea has low fat content as compared to other legumes suggesting its suitability in weight restriction diets (Gonçalves et al. 2016). The fat content in cowpea is highly influenced by the environments and varies from genotype to genotype. As per Brazilian Agricultural Research Corporation, its value is about 2%. In different studies, the lipid content in cowpea ranges from 1 to 1.6% (Carvalho et al. 2012), 2.2% (Frota et al. 2008), and 4.8% (Iqbal et al. 2006). Among the total fat in cowpea, triglycerides are the most abundant lipids along with 25.1% of phospholipids, 10.6%

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of monoglycerides, 7.9% of free fatty acids, 7.8% of diglycerides, and 5.5% of sterols (Zia-Ul-Haq et al. 2010; Antova et al. 2014). Cowpea has good quantity of thiamin, riboflavin, niacin, vitamin B6, and pantothenic acid and small amount of foliate (Asare et al. 2013). Among the major vitamins, cowpea has vitamin B complex including niacin, panthothenic acid, thiamine, pyridoxine, folic acid, riboflavin, biotin, and cobalamin. It is also good source of vitamin C and E. Cowpea provides calcium, magnesium, and phosphorus in good quantity along with small amount of iron, sodium, zinc, copper, manganese, and selenium (Asare et al. 2013). The detailed analysis of mineral composition of cowpea genotypes revealed that it has 61–81 ppm iron, 27–44 ppm zinc, 84–177 ppm sodium, 9570–12,510 ppm potassium, 290–440 ppm calcium, 1310–1160 ppm magnesium, 17–29 ppm manganese, and 20–22 ppm copper (Carvalho et al. 2012).

3.3

Anti-nutritional Factors

Cowpea has been reported to contain some anti-nutritional factors, namely, protease inhibitors, antivitamins, phytase, saponins, amylase inhibitors, tannins, aflatoxins, etc., that have physiological disorders on consumption. Poor digestibility and lack of sulfur-containing amino acids are also important restrictive factors for consumption of cowpea in daily diet; however, it can be washed out using various processing methods (Elhardallou et al. 2015). Various phenolic compounds, namely, proanthocyanidins (Ojwang et al. 2013), phytic acid (Sinha and Kawatra 2003), tanins (Lattanzio et al. 2005), hemagglutinins (Aguilera et al. 2013), cyanogenic glucosides, oxalic acid (Afiukwa et al. 2011), dihydroxyphenylalanine, and saponins are considered unfavorable for human nutrition as these compounds are attached with the proteins and chelate divalent metal ions (Ojwang et al. 2013). Presence of some of the protease inhibitors in cowpea is also known as anti-nutritional factors (Monteiro Junior et al. 2017). Black-colored seeds have polyphenols and some other anti-nutritional factors. The anti-nutritional factors can be removed by heating or soaking of the seeds, but heat stable compounds such as polyphenols and phytates cannot be removed using heat or soaking treatment. It requires germination or fermentation of seeds. The processing of cowpea seeds including dehulling and roasting modifies the proximate composition and mineral element contents of the seeds (Famata et al. 2013). Seed soaking, boiling, germination, and fermentation have been used to reduce the anti-nutritional and unwanted components and to improve the nutritional quality and suitability of the legume (Kadam and Salunkhe 1985).

3.5 Medicinal Values

3.4

59

Cooking Time

Cooking time indicates the quality of cooking and is an important choice for a particular food. The longer cooking time of legumes including cowpea is a major constraint for consumers. The process of cooking includes several changes in the seeds such as denaturation of proteins, starch gelatinization, softening, and breaking of middle lamella (Vindiola et al. 1986). It also reduces the anti-nutrient substances and improves the nutritional quality (Wang et al. 2008). The process of cooking of legume seeds mainly depends upon the cotyledon parenchyma cell separation, protein denaturation, and starch gelatinization (Sefa-Dedeh et al. 1978, 1979). Minimum cooking time, lesser splitting, and soft texture are some of the most essential characters for cooking the legume seeds. The cooking time of cowpea depends upon various factors including variety, soaking of seeds, and cation content in cooking water (Akinyele et al. 1986; Taiwo et al. 1998). The seeds are generally boiled to soften the cotyledons and increase palatability (Aremu 1991). It has been observed that the pre-cooking of starch, denaturation of protein, increasing pectin solubility, and improving hydration rate of the seeds may improve the cooking time of legumes (Cenkowski and Sosulski 1998; Arntfield et al. 2001; Bellido et al. 2006). Cowpea is mainly consumed as cooked food. Cooking of seeds under limited water and under presence of low quantity of acid may help to preserve certain vitamins and minerals. Use of the legume with cereal-based food improves the nutritional quality. Cowpea leaves cooked with tomatoes, potatoes, and onions have been preferred food in many parts of the world (Matenge et al. 2012). Cowpea can be consumed in its different forms, that is, whole/green cowpea (green, roasted, boiled, fried, crushed, and cooked), dried grains (boiled, boiled, and fried cooked); dehusked splits, sprouted, and germinated (boiled and fried); puffed and roasted (spiced or salted); milled and cooked (steamed, boiled, and fried); or in form of fermented foods (Dhokla, idli, etc.). The shorter cooking time along with higher protein content has been reported to be more acceptable (Hamid et al. 2014). Water absorption capacity and cooking time in cowpea are negatively correlated (Harouna et al. 2019) suggesting that more water-absorbed seeds of cowpea may take longer time to cook.

3.5

Medicinal Values

Cowpea has been used as a medicine by various tribal communities in West Africa including the treatment of boils (Duke 1981) and is considered as one of the sacred crops. Presence of α-amylase and α-glucosidase inhibitors in cowpea is good for human health due to their ability to decrease the rate of glucose release. Polyphenols have the ability to reduce coronary heart diseases, diabetes, obesity, and certain cancers and enhance the endothelial function (Liu 2007). Cowpea has been reported to have higher soluble fiber content in its boiled and sprouted form and has been reported to adjust serum non-HDL-cholesterol level in rats (Rideout et al. 2008). The

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protein isolated from cowpea imitated the action of insulin (Barnes et al. 2015) and helped in avoiding diabetes mellitus. Its peptides have also been reported as antioxidants having cytotoxic activity against cancer cells (Dominguez-Perles et al. 2016; Cicero et al. 2017). Cowpea has been reported to have anti-inflammatory activities (Crespo et al. 2008; Lee et al. 2011; Ojwang et al. 2015) due to the presence of various phenolic compounds, anthocyanins, and different other active molecules. The phenolic extract of the crop exhibited better effect on various processes related to immunity, homeostasis, and adipogenesis (Adjei-Fremah et al. 2016a). In a study conducted on boiled, sprouted, and raw cowpea-incorporated diets modulate high fat diet-induced hypercholesterolemia in rats (Liyanage et al. 2018). It was observed that the cowpea-incorporated diets modulated the serum antioxidative capacity, cholesterol metabolism, and cecal fermentation in the rats. The researchers suggested that the boiled, sprouted, and raw cowpea may be used in the treatment of hypercholesterolemia in humans (Liyanage et al. 2018).

3.6

Nutraceutical Properties of Cowpea

Nutraceuticals are basically foods that normalize the physiological process in the human body and simultaneously maintain good health (Das et al. 2012). These are natural food sources or herbs and may be classified into dietary fiber, probiotics, prebiotics, polyunsaturated fatty acids, antioxidant vitamins, polyphenols, etc. (Kokate et al. 2002; Kalia 2005; Das et al. 2012). Several phenolic acids, flavonoids, anthocyanins, and proanthocyanidins (Ha et al. 2010) including flavonoids (Ojwang et al. 2012; Nderitu et al. 2013; Salawu et al. 2014) have been isolated and characterized from cowpea. These compounds are known as antioxidants and have health promotion properties (Apea-Bah et al. 2017). It has also been observed that varieties having darker seed coat have higher quantities of flavonoids as compared to varieties having white seed coat. Cowpea is a good source of dietary fiber that has higher water holding capacity and regulates defecation process (Iqbal et al. 2006; Campos-Vega et al. 2010); besides this, it also helps in regulating the postprandial blood glucose and insulin levels and serum cholesterol (Anderson and Chen 1986). Cowpea is also good source of oligosaccharides and provides raffinose, stachyose, and verbascose in good amount to the human foods (Sreerama et al. 2012; Gonçalves et al. 2016). Higher amount of unsaturated fatty acids is one of the important constituents in human diet (Onwuliri and Obu 2002). Cowpea has been reported to have polyunsaturated fatty acids ranging from 40.1 to 78.3% (Gonçalves et al. 2016) showing its advantage for nutritionally rich diet. Cowpea is taken as alternative of soya bean due to its characteristics of low fat and high fiber content (Timko and Singh 2008). Cowpea is a good source of vitamins A and C and possesses considerable quantity of thiamin, riboflavin, niacin, vitamin B6, and pantothenic acid along with little amount of foliate (Asare et al. 2013). It is also good source of vitamin E, and the composition of its vitamin E is different from other legumes (Kalogeropoulos et al. 2010). Potassium, calcium, magnesium, and phosphorus

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has been reported in sufficient amount, while iron, sodium, zinc, copper, manganese, and selenium have also been reported in small quantity (Asare et al. 2013).

3.7

Uses

Being a leguminous crop, cowpea has the ability of biological nitrogen fixation and provides nitrogen to the succeeding cereal crops (Singh et al. 2002; Hall 2012). Besides this, it also accumulates organic matter and carbon in the soil during crop rotation resulting into enhancement of soil fertility and its physical characteristics. Cowpea provides protein, carbohydrate, fiber, vitamins, and minerals to human food in adequate quantity along with some anti-nutritional constituents (Nassourou et al. 2016; Moreira-Araújo et al. 2017; Mtolo et al. 2017). Presence of various bioactive compounds including various phenolic compounds has immense values for human health and help human body to prevent chronic diseases (Zhao et al. 2014; Perera et al. 2016; Awika and Duodu 2017; Nassourou et al. 2016; Mtolo et al. 2017). Cowpea seeds have antioxidant, hypoglycemic, hypolipidemic, and antihypertensive properties and are beneficial for human health (Kapravelou et al. 2015). Cowpea also provides good source of protein to fodder crop in the cropping systems of tropical, subtropical, arid, and semiarid regions (Pule-Meulenberg et al. 2010; Sprent et al. 2010). It is also having importance as green manure, animal fodder, and for medicinal purposes. Its immature pods are boiled and used as vegetables in various parts of the world (Uguru 1996). The legume is usually sown as intercrop with a number of crops including cereals, root crops, and cotton along with several plantation crops under the traditional agricultural practices. The indeterminate growth habit of the crop has been observed advantageous for prevention of soil erosion and weed suppression (Singh et al. 2003b). Its haulms on harvest are used as fodder for animals (Tarawali et al. 1997), and root residues gives manure to the cultivated field on decay. It was observed that feeding of cowpea forage to goats improved body weight and their resistance to internal parasite (Adjei-Fremah et al. 2016b).

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Ojwang LO, Yang L, Dykes L, Awika J (2013) Proanthocyanidin profile of cowpea (Vigna unguiculata) reveals catechin-O-glucoside as the dominant compound. Food Chem 139:35–43 Ojwang LO, Banerjee N, Noratto GD et al (2015) Polyphenolic extracts from cowpea (Vigna unguiculata) protect colonic myofibroblasts (CCD18Co cells) from lipopolysaccharide (LPS)induced inflammation—modulation of microRNA 126. Food Funct 6:145–153 Oke DB, Tewe OO, Fetuga BL (2015) The nutrient composition of some cowpea varieties. Niger J Anim Prod 22(1):32–36 Onwuliri VA, Obu JA (2002) Lipids and other constituents of Vigna unguiculata and Phaseolus vulgaris grown in northern Nigeria. Food Chem 78:1–7 Perera O, Liyanage R, Weththasinghe P et al (2016) Modulating effects of cowpea incorporated diets on serum lipids and serum antioxidant activity in Wistar rats. J Natl Sci Found 44:69–76 Petchiammal C, Hopper W (2014) Antioxidant activity of proteins from fifteen varieties of legume seeds commonly consumed in India. Int J Pharm 6:476–479 Plahar MA, Hung YC, McWatters KH et al (2006) Effect of saponins on the physical characteristics, composition and quality of akara (fried cowpea paste) made from non-decorticated cream cowpeas. LWT Food Sci Technol 39(3):275–284 Pule-Meulenberg F, Belane AK, Krasova-Wade T, Dakora FD (2010) Symbiotic functioning and bradyrhizobial biodiversity of cowpea (Vigna unguiculata L. Walp.) in Africa. BMC Microbiol 10:89 Rangel A, Saraiva K, Narciso MS et al (2004) Biological evaluation of a protein isolate from cowpea (Vigna unguiculata) seeds. Food Chem 87:491–499 Rideout TC, Harding SV, Jones PJ, Fan MZ (2008) Guar gum and similar soluble fibers in the regulation of cholesterol metabolism: current understandings and future research priorities. Vasc Health Risk Manag 4(5):1023–1033 Rochfort S, Panozzo J (2007) Phytochemicals for health, the role of pulses. J Agric Food Chem 55: 7981–7994 Rotimi SO, Olayiwola I, Ademuyiwa O, Adamson I (2013) Improvement of diabetic dyslipidemia by legumes in experimental rats. Afr J Food Agric Nutr Dev 13:1–18 Salawu SO, Bester MJ, Duodu KG (2014) Phenolic composition and bioactive properties of cell wall preparations and whole grains of selected cereals and legumes. J Food Biochem 38:62–72 Santos CAF, Boiteux LS (2013) Breeding biofortified cowpea lines forsemi-arid tropical areas by combining higher seed protein and mineral levels. Genet Mol Res 12:6782–6789 Sebetha ET, Modi AT, Owoeye LG (2014) Cowpea crude protein as affected by cropping system, site and nitrogen fertilization. J Agric Sci 7:224–234 Sefa-Dedeh S, Stanley DW, Voisey PW (1978) Effect of soaking time and cooking conditions on texture and microstructure of cowpeas (Vigna unguiculata). J Food Sci 43:1832–1838 Sefa-Dedeh S, Stanley DW, Voisey PW (1979) Effect of storage time and conditions on the hard-tocook defect in cowpeas (Vigna unguiculata). J Food Sci 44:790–796 Singh BB, Tarawali SA (1997) Cowpea and its improvement: key to sustainable mixed crop/ livestock farming system in West Africa. In: Renard C (ed) Crop residues in sustainable mixed crop/livestock farming systems. CAB International in Association with ICRISAT and ILRI, Wallingford, pp 79–100 Singh BB, Ehlers JD, Sharma B, Freire Filho FR (2002) Recent progress in cowpea breeding. In: Fatokun CA, Tarawali SA, Singh BB, Kormawa PM, Tamò M (eds) Challenges and opportunities for enhancing sustainable cowpea production. International Institute of Tropical Agriculture, Ibadan, pp 4–8 Singh BB, Ajeigbe HA, Tarawali SA, Fernandez-Rivera S, Abubakar M (2003a) Improving the production and utilization of cowpea as food and fodder. Field Crops Res 84:169–177 Singh BB, Ajeigbe HA, Tarawali SA et al (2003b) Improving the production and utilization of cowpea as food and fodder. Field Crops Res 84:169–177 Sinha R, Kawatra A (2003) Effect of processing on phytic acid and polyphenol contents of cowpeas [Vigna unguiculata (L) Walp]. Plant Foods Hum Nutr 58:1–8

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4

Cultivation

Abstract

Cowpea is cultivated across the arid and semiarid regions of the world and is adaptable to wide range of soils and rainfall. The adaptability makes it a crop of wide geographic distribution. Cowpea is mainly cultivated in the semiarid regions of Asia, Africa, Southern Europe, Southern United States, and Central and South America. Various Asian countries, namely , India, Sri Lanka, Bangladesh, Myanmar, China, Korea, Thailand, Indonesia, Nepal, Pakistan, Malaysia, and Philippines, also contribute major role in the production of cowpea. It is drought hardy crop and does not require much attention for its cultivation. Brief account of issues associated with cultivation of cowpea and varieties of cowpea developed in India has been discussed in this chapter.

4.1

Introduction

Cowpea is cultivated across the arid and semiarid regions of the world and is adaptable to wide range of soils including sandy, sandy loam, coarse, gravel, red loam, black clay, and loamy soils. It can be grown under wide range of rainfall conditions from 400 to 700 mm per year; however, well distribution of rainfall is better for the growth of the crop. Cowpea utilizes soil moisture efficiently as compared to other crops. During moisture stress condition, cowpea reduces its vegetative and foliar growth. The adaptability makes it a crop of wide geographic distribution. Since the sowing patterns and agronomic practices differ in various climatic zones, its production also differs in different parts of the world. Besides sole cropping, cowpea is grown as mixed and inter crops. It plays various roles for food security, income generation, and soil amelioration under small-scale farming conditions (Amujoyegbe and Elemo 2013).

# The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 R. Pathak, Genetics, Physiology and Cultivation of Moth Bean, Cowpea and Horse Gram, https://doi.org/10.1007/978-981-19-9956-7_4

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It was believed that India is the major center and Africa and China as the secondary centers of origin of cowpea (Vavilov 1939) due to its prehistoric cultivation in these countries. The detailed study on the origin and evolution of cultivated forms of Vigna sinensis (Faris 1965) revealed that Vigna was ascended from the domestication of its wild form in West Africa. It is also hypothesized that the origin and domestication of cowpea is associated with sorghum and pearl millet (Vavilov 1951) in Africa, and its cultivation is about 5 to 6 thousand years old. Reports suggest that its first cultivation was in West Africa, which was associated with the farming of sorghum and pearl millet (Ng and Marechal 1985). Cowpea is mainly cultivated in the semiarid regions of Asia, Africa, Southern Europe, Southern United States, and Central and South America (Singh 2005; Timko et al. 2007). Nigeria is its major producers in the world, and International Institute for Tropical Agriculture (IITA), Ibadan, situated in Nigeria is known for wide collection of cowpea germplasm (Davis et al. 1991). The marginal and submarginal farmers of Africa produce and consume cowpea in good quantity (Pasquet and Baudoin 2001). Various Asian countries, namely, India, Sri Lanka, Bangladesh, Myanmar, China, Korea, Thailand, Indonesia, Nepal, Pakistan, Malaysia, and Philippines, also contribute major role in the production of cowpea. The vegetable varieties are trailing in nature and require proper stakes or fences for its proper growth. It has been observed that stakes at definite intervals connected by wires produced significantly higher yields (Pararajasingam 2004). The substantial cultivation of the crop is found mainly in semiarid regions of the country under rainfed conditions. India is the largest producers of cowpea in Asia, and the crop is grown in all the three cropping seasons in some states of India states including Maharashtra. The yield level of the crop is low in respect to the area under its cultivation.

4.2

Climate

Cowpea is a warm weather crop and has higher adaptability under drought conditions. However, as compared to other legumes, it has higher tolerance to heavy rainfall also, but it cannot tolerate cold and frost conditions (Mekonnen et al. 2022). The optimum temperature for the growth of the crop is 27–35°C. The response of day length varies from variety to variety due to their sensitivity. The crop generally flowers after 30 days of sowing; however, flowering in photosensitive varieties depends upon time and geographic location.

4.3

Soil

Although the crop can be grown in variety of soils (sandy, sandy loam, coarse, gravel, red loam, black clay, loam soils), but under drained loam, slightly heavy soils, light textured sandy soils, and black cotton soils, cowpea performs well. Since the crop is drought-tolerant and has the ability to fix the atmospheric nitrogen, it can

4.6 Seed Rate

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be grown on poor soil (Adeoye et al. 2011. Cowpea can be cultivated successfully in acidic to neutral soils and poor gravelly lands in the hill tracts; however, it is less adapted to alkaline soil. The cultivated varieties of cowpea are of mainly warm season and well-adapted to heat and drought condition and show good adaptation to sandy soil (Ishiyaku and Aliyu 2013).

4.4

Field Preparation

The crop requires normal field preparations, but hard soils require one deep ploughing followed by two to three harrowing and planking. Disc harrowing may be applied for large-scale production under sandy loam soils. The field should be leveled to avoid the incidence of waterlogging.

4.5

Sowing Time

Cowpea can be grown through all the seasons. The crop is sown from early June to late July under rainfed conditions, from October to November during rabi season, and in March during summer season (Kumar and Narain 2005). The sowing time varies depending upon the season, geographic location, and purpose, namely, in Karnataka, the crop is grown in the whole July, in Andhra Pradesh at the onset of monsoon, in Maharashtra from June1 to 30 , in Kerala after first week of June, and in Uttar Pradesh from March 5 to 10 (as summer crop). The crop may be grown throughout year in the kitchen garden. For green manuring, the crop is cultivated from middle June to first week of July, while for fodder purposes, it is grown in the beginning of February (Kumar and Narain 2005). Early sown crop has elongated internodes and more vegetative growth and has lower yields than the crop sown at optimum time. A study was conducted to find the effect of sowing dates on the incidences and severities of cowpea scab caused by Sphaceloma sp. on the cowpea varieties at Nigeria (Mbong et al. 2010), based on four sowing dates during late July and ending in mid-August, and it was observed that the early sown cowpeas had higher scab incidences and severities as compared to the late sown crops.

4.6

Seed Rate

Seeds should be sorted before sowing, and infested seeds should be removed. Seed rate varies and depends upon sowing time, type of soil, seed size, purpose, soil moisture, etc. If the crop is being cultivated for grain and vegetable purpose, generally 20–25 kg seed per ha is required, while for green manuring and fodder purposes, it is 30–35 kg per ha under rainfed conditions (Kumar and Narain 2005). During summer seasons, higher seed rate is required due to reduced vegetative growth and close planting. Seed rate for cultivation of bushy vegetable types,

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semi-trailing vegetable types, trailing vegetable types, and dual-purpose varieties should be 20–25, 20–25, 4–5, and 40–60 kg per ha, respectively.

4.7

Method of Sowing

Sowing of cowpea is generally done by broadcasting method, but it may depend on the purpose of cultivation and season of sowing. Cowpea seeds should essentially be inoculated with Rhizobium if the crop is introduced first time in the field. Line sowing is a better method for the crop under grain production for the Northern arid regions of India; however, broadcasting is a common practice for the crop grown for fodder and green manuring. Ridge-furrow system is better method of sowing in Maharashtra and Kerala states. Dibbing of two seeds per hole was found suitable method of sowing in Kerala state for grain and dual-purpose crop. Provision for drainage of excess water in the field is essential (Kumar and Narain 2005). Row spacing is one of the important practices for cowpea production, so care should be given during the sowing of the crop. Sowing of bushy and dwarf varieties are done with close spacing of 30 cm, while semi-spreading varieties may be sown with the row spacing of 40–45 cm. The crop for vegetable purpose may be grown at wider spacing of 40–45 cm, but the case is reverse for the crop under rainfed conditions. Inter-row spacing and varietal interaction have been found nonsignificant for the growth and phenology traits under Cameroon conditions (Lum et al. 2018), but inter-row spacing (45 cm × 25 cm) was found a significant key factor on the yield of the crop. The varieties of cowpea have been known for different types of growth habit, morphology and maturation period; therefore, they require different plant densities to express their yield potential (Ndiaga 2000). Hence, seed rate and cultivars are considered as important factors in realizing better yield and quality of legumes (Shirtliffe and Johnston 2002; Dahmardeh et al. 2010). Studies revealed that varieties with erect plant types provide higher yields with high plant population, while semi-erect plant-type varieties give optimal yield at a low population (Nangju et al. 1975). Therefore, plant spacing is a significant controlling system to maximize seed yield by increasing the amount of solar radiation captured within the canopy (Monneveux et al. 2005). Effect of plant density on the performance of cowpea in Nigerian savannas has been reported by Kamara et al. (2018a). In general, spacing for cultivation of bushy vegetable types, semi-trailing vegetable types, trailing vegetable types, and dual-purpose varieties should be 30 × 15, 45 × 30, 200 × 200 and 45 × 30 cm, respectively, under Indian conditions (Kumar and Narain 2005).

4.8

Germination

A study was conducted to test the germination ability of cowpea under acidic soil contaminated with phenanthrene and pyrene (Chouychai et al. 2007), and it was observed that cowpea was more sensitive to these polycyclic aromatic hydrocarbons.

4.10

Fertilizer

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Size of legume seed has been a matter of interest and attraction. Studies conducted to reveal the germination abilities of small and bold seeds showed no consistency as in some cases bolder seed gave more germination or emergence as compared to smaller seeds (Ambika et al. 2014), while in other case, the observation was totally reverse (Adebisi et al. 2013). Influence of seed size of cowpea varieties on the germination was studied (Baysah et al. 2018), and it was noticed that the seed size does not have any effect on the germination of cowpea seeds. It has been observed that salicylic acid increased germination ability and seedling height of cowpea by reducing the harmful effects of abiotic stress (De Araújo et al. 2018).

4.9

Irrigation

The proper soil and water management practices are the key factors for sustainable and profitable production of various crops (Murtaza et al. 2006). The quantity and frequency of irrigation depend upon the soil type and weather conditions during the growth period. Generally, cowpea requires 300–400 mm water. The vegetable crop of cowpea is generally sensitive to waterlogging, and less irrigation is required for its cultivation. The crop for seed yield requires two to three irrigations at flowering and pod development stages (Kumar and Narain 2005). Vegetable varieties need more irrigation as compared to the varieties of seed yield. Irrigation should be restricted during pre-flowering stage to avoid the excessive plant growth, but after flowering of plant, frequent light irrigation is recommended. Cowpea is drought hardy crop and has deep rooted system that can infiltrate in the soil up to depth of 150–200 cm under good soil conditions. Due to developed deeprooted system, the crop requires less irrigation. The summer crop requires five to six irrigations at the interval of 15–20 days due to high temperature and low humidity, while the crop under rainy season does not require irrigation; however, lifesaving irrigation should be given to realize good yield (Kumar and Narain 2005). The crop under intercropping system requires irrigation on the basis of requirement of both the crops. It has also been observed that varieties of the same species may respond differently to salinity in the different stages of the crop cycle (Neves et al. 2010). Application of saline (EC of 5.0 dSm-1) water throughout the life cycle of cowpea resulted into a significant decrease in the number of pods and seed yield. However, irrigation with the same water during flowering and pod formation stages has no adverse effects on the growth and crop yield (Lacerda et al. 2011).

4.10

Fertilizer

The crop is generally cultivated under poor fertile soil; therefore, nutrient management is essential. Organic fertilizers should be preferred over inorganic fertilizers for sustainable growth of the crop. Generally, 5–15 tons per ha farm yard manure (FYM) is applied in the nutrient-deficient soil for better production. Vermicomposting is better approach over FYM in reducing the cost of cultivation.

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It was observed that the combination of FYM and chemical fertilizers gave higher production of cowpea (Kumar and Narain 2005). The crop requires 15–20 kg nitrogen per ha and 30–40 kg P2O5 irrespective of region. However, the optimum dosage of nitrogen and phosphorus varies from region to region, for example, 20 kg nitrogen and 40 kg phosphorus per ha for Karnataka, Kerala, and Gujarat regions; 15–20 kg nitrogen and 30–40 kg phosphorus per ha are sufficient for arid regions of Rajasthan and Haryana (Kumar and Narain 2005). Potassium and calcium are essential fertilizers for promoting plant growth and mitigating drought effects. Therefore, a dose of 10 kg potassium and 200–300 kg gypsum/calcium carbonate per ha is applied. Sulfur is also an important fertilizer for legumes including cowpea for increasing yield and quality of the legume. Gypsum/calcium carbonate is applied as single dose the time of final ploughing before sowing, while half dose of nitrogen and full dose of phosphorus are applied at the time of sowing, and remaining dose of nitrogen is applied after 20–30 days of sowing of the crop. Foliar application of nitrogen is more useful as compared to soil application (Manjunatha et al. 2013). Application of bio-fertilizers, namely, rhizobium, vesicular arbuscular mycorrhizal fungus, and phosphate-solubilizing bacteria, plays important roles in the higher production of the crop. These bio-fertilizers provide better root growth and reduce the requirement of nitrogen. Therefore, application of bio-fertilizers coupled with FYM is beneficial in the cowpea production. Inoculation with Bradyrhizobium strains showed a difference in nitrogen fixation potential between the cowpea varieties (Fall et al. 2003). Nitrogen is helpful in the promotion of leaf, stem, and other vegetative growth of the plant, whereas phosphorus improves the activity of Rhizobium and escalates the root nodulation (Khandelwal et al. 2012). Bio-fertilizers improve the fertilizer use efficacy, and phosphorus supplies assimilate that help in the root development, proliferation, nodule formation, and nitrogen fixation (Sharma and Verma 2011; Haruna and Aliyu 2011; Singh et al. 2013). Studies revealed that higher plant growth, root proliferation, nodulation, and pod yield of cowpea may be realized with the application of nitrogen- and phosphate-solubilizing bio-fertilizers (Bohra et al. 1990; Stamford et al. 2013) along with organic and inorganic fertilizers (Abd El-Majeed et al. 2001; Madukwe et al. 2008; Singh et al. 2011; Haruna and Usman 2013). Combination of Rhizobium and phosphate-solubilizing bio-fertilizers provides synergistic effect in improved nodulation in cowpea (Singh and Prasad 2008; Ramana et al. 2010; Khandelwal et al. 2012). It was observed that cowpea gave good response with 15 kg per ha of nitrogen used at the time of sowing (Dugje et al. 2009), but the application of 40 kg nitrogen per ha suppresses flowering and reduces grain yield as well with increasing vegetative growth (Abayomi et al. 2008). The International Institute of Tropical Agriculture, Nigeria, has suggested application of 30, 14, and 12.5 kg per ha of nitrogen, phosphorus, and potassium, respectively, as optimum dosage for the cultivation of cowpea (Dugje et al. 2009). Application of 30 kg phosphorus per ha was found optimum for higher yield and yield attributing traits in cowpea in the Nasarawa state of Nigeria (Haruna and Usman 2013). The influence of 20 and 40 kg phosphorus per ha and bio-fertilizer (@10 mL per kg seed; Rhizobium, phosphate-solubilizing

4.11

Weed Management

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bio-fertilizers, and its combination) was studied over the control in cowpea (Nadeem et al. 2018). The quantity of 40 kg phosphorus per ha was found optimum for increase of plant height, leaf area index, stem girth, number of nodules per plant, number of branches per plant, total dry matter, pod yield, available soil nutrient status, similarly combined application of rhizobium, phosphate-solubilizing bio-fertilizers, and 40 kg phosphorus per ha enhanced the stem girth, total dry matter, green pod yield, soil nutrient status, organic carbon, and N, P, and K content in the North East Hill region of India (Nadeem et al. 2018). Serme et al. (2018) studied the response of nutrient application on the grain and fodder yield from 21 years of experimentation at Burkina Faso and Niger and reported increased yield with the application of phosphorus and manure. They observed that the yield of cowpea was highly responsive to phosphorus and was less affected by other nutrients. Application of manure coupled with phosphorus has synergistic effects and improves the nutrient responses in cowpea (Serme et al. 2018; Garba et al. 2018). Birla et al. (2018) studied the response of organic sources of nitrogen on the yield and quality of cowpea and reported that the application of combination of 50% nitrogen through castor cake, 50% nitrogen through vermicompost, and phosphatesolubilizing bio-fertilizers gave higher seed yield and improved the yield attributing traits along with higher nitrogen content in stover and higher phosphorus content on seeds of cowpea under Gujarat Condition of India. They also realized higher yieldand-cost benefit ratio with the application of 20 kg per ha nitrogen and 40 kg per ha phosphorus. Perez (2007) compared accumulation of cations pattern and its relationship with the legume efficiency to use phosphorus from phosphate rock among six leguminous crops, namely, cowpea, pigeon pea, soybean, Stylosanthes, crotalaria, and indigo, and observed that indigo, cowpea, and Stylosanthes exhibited comparatively higher phosphorus use efficiency. Nitrogen levels have been reported to increase the biomass yields of cowpea (Hasan et al. 2010).

4.11

Weed Management

The field having weed free conditions is essential to realize higher crop yield. Weed infestation alone is responsible for 50–62% reduction of yield of cowpea. Some of the parasitic weeds including Striga gesnerioides and Alectra spp. attack cowpea crop particularly in semiarid regions of the world (Kumar and Narain 2005). S. hermonthica, S. asiatica, and S. gesnerioides are the most common weed pests of this region. Integrated weed management comprising of optimum sowing time, plant population, and removal of weeds is the best approach of weed management. Effective weeding at 20–25 days of sowing through hoeing keeps the crop free from weeds, and if weeds develop due to repeated rainfall, one more hoeing may be done at the interval of 20–25 days. Application of pendimethalin @0.75 kg active ingredient per ha may be done along with hoeing at 35 days of sowing to reduce the weed infestation (Kumar and Narain 2005).

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Parasitic weed Striga gesnerioides is one of the major yield constraints of cowpea, and sowing of resistant cultivar is the best approach to avoid the problem. Various studies have been conducted to find molecular markers that are linked to resistance traits to cowpea parasitic. Ouedraogo et al. (2001) documented some of the AFLP markers linked to resistance of cowpea to parasitism by S. gesnerioides and reported that the dominant gene controlling resistance was located within linkage group 1 of the genetic map. AFLP and AFLP-derived sequence characterized amplified region markers associated with S. gesnerioides resistance in cowpea has also been studied (Boukar et al. 2004).

4.12

Cowpea Under Intercropping System

Intercropping of cowpea plays an important role in economizing the resource use particularly nitrogen and also increases the total productivity of the system (Ghosh et al. 2007). Intercropping of cowpea with sorghum, pearl millet, and maize is quite successful as the main source of fodder to the animals. Maize, cowpea, and oat cropping system is widely adapted in Himalayan foot hill regions. It is also intercropped with Guinea grass and Napier bajra hybrids in Western and South India, respectively. Maize-potato-wheat-cowpea is one of the most preferred sequential food cropping systems in Northern India and rice-rice-cowpea in Kerala. Besides this, dinanath grass-cowpea-rice bean-Stylosanthes system is more prevalent in the foot hill regions of West Bengal and Assam (Kumar and Narain 2005). Short during pulses such as cowpea can be grown in between two rows of sugarcane due to slow growth of sugarcane. Under the intercropping system of maize and cowpea, it was reported that with the lower application of nitrogen, its content was higher in the intercropped maize as compared to sole crop of maize (Francis 1986) revealing the allocation of good amount of nitrogen from cowpea to maize. It has been observed that sorghum intercropped with groundnut, cowpea, and green gram reduced the nitrogen requirement of subsequent wheat by 30–84 kg per ha over sole sorghum crop (Nair et al. 1979). It has been observed that by increasing the plant density of cowpea and decreasing the plant density of cereals efficacy of drought-sensitive lands can be enhanced (Katsaruware and Manyanhaire 2009). Fodder cowpea has been observed more beneficial followed by groundnut and grain cowpea in this study. A study on improving the productivity of menthol mint was conducted using cowpea intercropping system (Singh et al. 2010), and it was observed that the fresh biomass and essential oil yield of menthol mint increased by 23.4 and 25.2%, respectively, by cowpea green manure than without green manure across all the nitrogen levels. It has been observed that the biomass yield of the intercropped legumes decreases under intercropping system (Birteeb et al. 2011), but it sustains the productivity and improves the profitability and soil fertility (Aziz et al. 2015).

4.13

4.13

Cowpea Under Crop Rotation System

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Cowpea Under Crop Rotation System

Two or more crops grown in a definite order, that is, consecutive years or seasons on a similar piece of land, are considered as crop under rotation. It provides good productions and quality of crops in eco-friendly manner (El Titi et al. 1993) by conserving fertility of soil and sustaining useful biodiversity in the soil. The phases of destructive organism get discouraged due to crop rotation. Rotation of cereal crops with legumes has always been preferred by the farmers to maintain soil fertility (Baldock et al. 1981; Osunde et al. 2003). The legumes under crop rotation improve the soil organic matter and incorporate nitrogen in the soil (Eltz and Norton 1997). Cereal-legume cropping system has been successful due to various reasons including that succeeding crops have less incidence of weeds and root/leaf diseases (Smiley et al. 1994) and more availability of P, K, and S (Stone and Buttery 1989), and the field has got improved soil structure (Badruddin and Meyer 1994). Besides providing nitrogen, legume residues assist the cereal growth (Fyson and Oaks 1990). Cowpea yield significantly responds to crop rotation and significantly contributes to the yield in cereal-legume rotation (Yusuf et al. 2009). It has been observed that substantial quantity of nitrogen was left in the field by cowpea residues after harvest of sole crop of cowpea (Patra et al. 1986). Nitrogen-supplying prospective of legumes reveals that the addition of inorganic nitrogen in the bare soil was well related with the nitrogen uptake by the succeeding cereal crop (Bowen et al. 1988). The succeeding crop of maize in rotation with cowpea has been recorded with higher yields and nutrient accumulation as compared to monocropping (Horst and Ardter 1994). Improved yield of the following millet crop has been observed with cowpea plants density under arid and semiarid tropics (Bationo and Ntare 2000). Study on growth and yield of cowpea-sunflower crop rotation under different irrigation management strategies with saline water revealed that saline water had no negative impact on the crop yield, and its residual effects were also not seen on the sunflower as a succeeding crop (Neves et al. 2015) under semiarid conditions of Brazil. Therefore, crop rotation could be an important aspect to semiarid environments having problems of water salinity for better yield and sustainability. Cowpea/urdbean/mungbean-safflower is one of the preferred cropping sequences in Madhya Pradesh, Gujarat, and Maharashtra during rainfed conditions, while wheat-summer cowpea is grown as crop rotation under irrigated conditions (Kumar and Narain 2005). Cowpea-finger millets and rice-mungbean/urdbean/ cowpea are crop sequences followed in Andhra Pradesh, Tamil Nadu, Karnataka, and Kerala states under rainfed conditions, while rice-rice-mungbean/urdbean/cowpea are common under irrigated conditions. Cowpea under crop rotation with cereal crops is a choice of crops under the areas having the widest range (340–3640 mm) of annual rainfall. Under the plains and hill regions of Gujarat, having annual rainfall of about 340–1790 mm cowpea-safflower is very common cropping systems (Kumar and Narain 2005). Similarly, in the West Coast Plains and Hill Region, having annual rainfall of about 2230–3640 mm and comprising of Tamil Nadu, Kerala, Goa, Karnataka, and Maharashtra states, rice-urdbean/cowpea/chickpea is the most preferred cropping systems. Rice-rice-cowpea, sorghum-wheat-cowpea/mungbean,

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rice-mungbean/urdbean/cowpea, rice+rice-mungbean/urd bean/cowpea, and rice/ maize-cowpea are some of the common cropping systems preferred under varied agro-climatic zones of India. Cowpea has been recognized as the best rotated crop followed by sunflower, mungbean, and soybean (Kureh et al. 2006).

4.14

Seed Treatment and Inoculation with Bacterial Culture

Knowledge of rhizosphere biology has advanced the findings of different microorganisms, and it has been used for sustainable agriculture with greater pace. Plant growth-promoting effect on cowpea using coir pith aqueous extract formulation of Cyanobacterium phormidium was studied (Palaniappan et al. 2010), and it was found that its 5% aqueous extract enhanced the seed germination. Besides this, the combination of immobilized cyanobacterial formulation and foliar spray was recorded with improved seed germination, plant height, plant weight, number of flowers, root nodules, biomass, nodulation, and plant growth revealing the significance of bioactive compounds produced by the cyanobacterium in the establishment of cowpea crop. Significant increase in the growth of cowpea was observed with inoculations of bacterial species Pontibacter listensis (NII-0905) in pot experiments (Dastager et al. 2011). The inoculations also exhibited root colonization in the seedlings revealing NII-0905 as a potential plant growth-promoting rhizobacteria (PGPR) for increasing soil fertility and promoting the plant growth. Similarly, a phosphate-solubilizing bacterial strain (NII-0909) of Micrococcus sp. showing the plant growth-promoting characteristics exhibited enhanced growth and root colonization in cowpea under controlled conditions (Dastager et al. 2010). Efficacy of plant growth-promoting bacteria from non-rhizospheric soil and their effect on cowpea seedling growth was assessed (Deepa et al. 2010), and significant increase in root, shoot, and biomass and stimulation on bacterial counts in the rhizosphere was observed.

4.15

Harvesting and Threshing

The growth habit of cowpea differs from variety to variety, and therefore, their harvesting also differs. The erect type of varieties generally grown for seed purpose takes lesser time (about 100 days), while semi-erect and trailing varieties take longer (about 120 days) time to mature (Kumar and Narain 2005). The pods of the crop are harvested at its tender stage, generally at alternate days for vegetable purpose. The pods may be collected up to 45 days from the well-managed crop. The pod yield varies from variety to variety, for example, 40–50 quintal pods per ha can be realized from bushy varieties, while it may be about 70–80 and 150–180 quintal for semitrailing and erect varieties, respectively (Kumar and Narain 2005). The leaves of the crop become dry at the maturity but don’t fall completely, and about 95% pods become yellowish brown. The produce can be harvested with the help of harvester or by hand on maturity. The pods of cowpea for vegetable are picked by hand.

4.16

Photoperiodism

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The dried seeds can be separated mechanically using a combine having a platform head or row crop head or by hand. Seeds are collected, cleaned, and sun-dried for one to three days. Fully matured pods should not be left in the field to avoid field weathering or shattering of pods. Good-quality seeds are one of essential requirements; therefore, all the cares should be taken during the harvest of seeds. Sorting of seeds should be done before storage. Moisture content of the seed for storage should be lower (8–10%). The seeds should be stored at a protected place to avoid any damage due to insect pests. It may be stored in plastic boxes at 5–8°C for medium-term storage, while for long-term storage, it should be laminated in aluminum foil under vacuum to store at -20°C. Smaller and bolder seeds of cowpea do not have any difference its terms of their germination (Baysah et al. 2018); therefore, sorting of seeds are not economic; nevertheless, it may be useful for market grade.

4.16

Photoperiodism

Seed yield has always been influenced by temperature and photoperiod. Cowpea has been observed as the short day plant and respond to photoperiod (Patel and Hall 1990) in a manner that floral buds initiate at a specific cycle of short day, and its blooming requires shorter inductive period (Lush et al. 1980) having different critical photoperiods (Wien and Summerfield 1980). Earlier cowpea genotypes have been categorized into four groups on the basis of requirement of short days for flower initiation ranging from 12.50 h per day to 13.30 h per day (Wien and Summerfield 1980). Lush and Evans (1980) observed that two to four short days were required for floral initiation, and pod setting was increased with the increase in one more short day. They suggested that the synchronous flowering in cowpeas does not depend on day-length, but the cumulative photoperiodic induction of plants is mainly responsible for flower development. The number of days to first flower was delayed due to long days coupled with high temperatures, but it remained unaffected due to day length at moderate temperatures (Dow El-Madina and Hall 1986). The plants of tropical and subtropical regions had to tolerate the day length variability. A study on photoperiod and light quality effects on cowpea floral development at high temperatures (Mutters et al. 1989) revealed that the floral bud development was concealed in heat-sensitive genotype at a 14-h photoperiod under metal halide plus incandescent lamps, while a 16-h photoperiod was required to elicit a similar response under fluorescent plus incandescent lamp. The long hot days resulted even into non-production of flowering on the cowpea crop. They further observed that the bud development has the involvement of photoperiod responses, while its initiation was not much influenced to these responses. Although photoperiodism is mainly connected with reproductive changes (Salisbury and Ross 1992), various vegetative traits including rate of node development (Yourstone and Wallace 1996), branching abilities (Terao et al. 1997), growth, and yield (Ntare 1993) have also been inhibited due to short photoperiod, while higher number of leaves-and-leaf area ratio and number of internodes have been observed with longer day lengths (Rachie 1985). Positive association of yield and

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photoperiod temperature (Wallace et al. 1993) indicates that increase in photoperiod result into higher number of nods, branches, and simultaneously increase in number of pod and yields. Photoperiod has been recorded as the major issue for determining the phenology of cowpea (Shivakumar et al. 1993) in west and central African conditions having the temperature regime of 25–29°C during the crop growing season. Photoperiod has been reported as one of the important aspects affecting the appearance of leaves (Craufurd et al. 1997) and development of flowers (Ellis et al. 1994). Ohler and Mitchell (1996) identified the yield-optimizing environments for cowpea breeding lines by manipulating photoperiod and harvest scenario and found that photoperiod had no effect on the breeding lines for any harvest scenario. They further observed the photoperiod responses of breeding lines to a mixedharvest scenario and found that day length extension with higher irradiance from high pressure sodium lamps suppressed edible yield rate, shoot harvest index, and yield efficiency rate of the short day breeding line. Short photoperiod does not have any effect on the reproductive development and podding of cowpea (Singh et al. 1997). Growth and yield reduction have been observed in the photosensitive genotypes even though it got flowering and podding (Mukhtar and Singh 2005). The influence of photoperiod was studied on the vegetative growth, phenology, and yield of cowpea variety (Mukhtar and Singh 2006), and it was observed that long day lengths influenced better growth and yield except for hypocotyl length and stem circumference, while flowering and pod maturity were enhanced under short photoperiods. The effect of various intensities of photoperiod on the vegetative growth and yield of cowpea varieties revealed that short photoperiod has improved the flowering; however, photosensitive genotypes of cowpea have been recorded with higher number of pods per plant, seeds per pod, and seed weight per plant during long day length period (Mukhtar 2007).

4.17

Cowpea Varieties Developed in India

Cowpea is grown throughout arid and semiarid regions of the country with limited inputs under varying soil moisture conditions. The crop has been reported with varied range of maturity, disease resistance, grain color, and abiotic responses. With the quality of faster growth at initial stage, its wider canopy, and regeneration potential, cowpea has been considered as favored fodder crops. Development of grain type, compact, erect, non-viny varieties of cowpea, and reduction of their maturity period from 90 days to 60–65 days has been one of the most important challenges for breeders (Kumar and Narain 2005). Various vegetable-type varieties of cowpea including Kashi Shyamal, Kashi Gowari, Kashi Unnati, Kashi Kanchan, Kashi Sudha, and VRCP-06 have been recently notified. List of notified varieties of cowpea, gazette notification number, and date of notification are given in Table 4.1. The general characteristics, agronomic features, and reaction to diseases and pests of some of the cowpea varieties (www.seednet.gov.in) are described as under: Bundel Lobia-2: The variety was developed from a selection of accession number-978 by Indian Grassland and Fodder Research Institute (IGFRI), Jhansi,

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Table 4.1 Notified varieties of cowpea SN 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43

Variety name Bundel Lobia-2 Cowpea-263 (Sel-263) Narendra Lobia-1 UPC-8705 PusaSampada (V-585) UPC-9202 PusaBarsati PusaPhalguni Cowpea (kind) Pusa-152 Co-2 Cowpea-74 EC-4216 Russian Giant Type-2 Type-5269 (PusaSawni) JC-5 JC-10 RS-9 Kankamani GFC-1 GFC-2 GFC-3 GFC-4 UP-5286 V-16 UPC-5287 BirsaSweta CO-5 RC-19 PusaKomal KBC-1 TVX-cowpea (TVX-944-026) Charodi UPC-287 Shweta (no. 988) Gujarat Cowpea-3 Bundel Lobia-1 (UFC-8401) Cowpea-88 V-240 UPC-607 UPC-618 CO(CP)-7

Gazette notification no. 636(E) 115(E) 115(E) 349(E) 425(E) 425(E) 566(E) 566(E) 19(E) 1004 13 13 13 13 13 13 470 470 470 2103 2103 2103 2103 2103 19(E) 596(E) 258(E) 258(E) 867(E) 165(E) 165(E) 10(E) 10(E) 471(E) 471(E) 915(E) 386(E) 814(E) 860(E) 615(E) 283(E) 599(E) 1177(E)

Notified date 02/09/1994 02/10/1996 02/10/1996 20/05/1996 08/06/1999 08/06/1999 21/09/1974 21/09/1974 14/01/1982 23/03/1978 19/12/1978 19/12/1978 19/12/1978 19/12/1978 19/12/1978 19/12/1978 19/02/1980 19/02/1980 19/02/1980 12/08/1980 12/08/1980 12/08/1980 12/08/1980 12/08/1980 14/01/1982 13/08/1984 14/05/1986 14/05/1986 26/11/1986 06/03/1987 06/03/1987 01/01/1988 01/01/1988 05/05/1988 05/05/1988 06/11/1989 15/05/1990 04/11/1992 25/11/1992 17/08/1993 12/03/2003 25/04/2006 25/08/2005 (continued)

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Table 4.1 (continued) SN 44 45 46 47 48 49 50 51 52 53 54 55

Variety name Gomti (5286-3) Shrestha (V-37) Swarna (V-38) S-450 SwarnaHarita(IC-285143) UPC-625 KM-5 DCS-47-1 Kashi Shyamal Kashi Gowri Kashi Unnati Kashi Kanchan

Gazette notification no.

1714(E) S.O. 449(E) S.O. 211(E) S.O. 1919(E) 597(E) 597(E) 858(E) 858(E)

Notified date 01/01/1976 01/01/1983 01/01/1983 01/01/1975 18/07/2008 11/02/2009 29/01/2010 30/07/2014 25/04/2006 25/04/2006 01/06/2010 01/06/2010

Source: www.seednet.gov.in

Uttar Pradesh, and is recommended for release and cultivation in Punjab and Rajasthan with 20–25 kg per ha of seeds. The variety was released in year 1994. It is most suited to drier areas with moderate rainfall and takes 110–120 days to mature. Good response to phosphorus application and 30–45 cm row to row spacing has been observed. It yields 3070 kg seeds per ha under proper agronomic practices. The variety provides highly nutritive and palatable fodder for all kinds of livestock due to highest in vitro dry matter digestibility (IVDMD) values as compared to other varieties. The plant height of the variety ranges from 140–150 cm, and it has four to five basal and sub-basal primary branches. The leaves of the variety are mediumbroad of light green color with 15–20 cm of peduncle length. The 12–16 cm long pods containing 12–15 seeds shatter easily on drying; therefore, regular pod picking is essential for better seed recovery. The fawn white with variable pinkish shade seeds of the variety is oval in shape, medium bold, and smooth and has thin brownish hilum ring on its surface. The variety has moderate tolerance to leaf hoppers, flies beetle, and major diseases. Pusa Sampada (V-585): The variety was released in 1997 for commercial cultivation by Indian Agricultural Research Institute (IARI), New Delhi. It was developed from Pusa Phalguni with the help of induced mutation and was recommended for cultivation under North Western plain zone. It is also suitable for semiarid regions. The variety shows good response to seed rate of 25 kg per ha, row to row distance of 30–45 cm, 20–25 kg nitrogen, 50 kg phosphorus, and two irrigations. The plants of the variety are bushy and erect of about 75 cm having medium sized pubescent/glabrous leaves of green color. Plant has one to three medium-sized straight and semi-drooping type of pods on each peduncle. The crop matures within 65–110 days and shows resistance to almost all the major diseases of cowpea including Yellow Mosaic Virus (YMV), anthracnose, and bacterial blight. The average yield of the variety can be realized up to 850–1000 kg per ha under optimum agronomic conditions. It has white, bold, and oblong seeds.

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V-240: The variety was isolated as a single plant selection from Pusa Phalguni with chemical mutagens using genetic variability system by IARI, New Delhi, and was released in year 1984. It was recommended for release and cultivation for North Western plains of Central and Peninsular zones of India in 1997. It is also suitable for semiarid regions under all types of soil. However, it provides better yield potential under sandy loam soil. The variety is indeterminate and photosensitive in nature and produces few trailing branches under optimum conditions. The variety shows good response to seed rate of 20–25 kg per ha, row to row distance of 30–45 cm, 20–25 kg nitrogen, and 50 kg phosphorus. It takes 80–95 days to mature. More trailing branches have been observed under excess water supply. The plants of the variety are of 60–70 cm tall having pubescence/glabrous broad trifoliate leaves of dark green color. Plant has one to three medium-sized straight and drooping type of pods on each peduncle. The average yield of the variety may be realized to 1200–1600 kg per ha under moderate rainfed conditions. It has medium-sized dark red seeds. The variety is most susceptible to YMV diseases in North-Western and Southern parts of India, whereas it shows complete resistance to YMV in central part of India. The variety exhibited better resistance to bacterial blight, anthracnose, and macrophomia blight as compared to the checks and moderated resistance to pod borer. Swarna (V-38): The variety was developed from Pusa Phalguni by chemical treatment at IARI, New Delhi, and was released in 1981 as a mutant of Pusa Phalguni. It is a moderately trailing variety having medium height and trifoliate leaves of green color and matures within 80–100 days. The variety shows good response to seed rate of 15–20 kg per ha and row to row distance of 30–45 cm and provides a yield of 900–1400 kg per ha under moderate rainfed conditions. The variety is suitable for vegetable purpose. Pods of the variety are borne much above the plant canopy. The immature pods are of light green color, while mature pods became white. Seeds of the variety are medium small and almost round in shape having two colors, that is, fawn at hilum while reddish on remaining part of testa. It is considered to be resistant to almost major diseases, that is, bacterial blight, macrophomina, and powdery mildew of cowpea. Fewer incidences of virus diseases have been observed on the variety. RC-19: The variety was developed from Agricultural Research Station, Durgapura, Rajasthan Agricultural University, Jaipur, by crossing Virginia × New Era (single plant selection from F2 bulk) and was released in year 1993. The plants of the variety are 60–70 cm in height and have fewer tendrils. The variety having fawn-colored seeds is known for synchronous maturity. Pods are of medium size having 10–14 seeds in each pod. Optimum yields and nodulation have been observed with the seed rate of 20–25 kg per ha and row to row distance of 30–45 cm. It takes only 60–65 days to mature and yields about 1000–1100 kg seeds per ha. The variety has been found resistant to various pests, disease, and salinity under field conditions. Cowpea-88: The variety was developed from Punjab Agricultural University, Ludhiana, using the progeny obtained by irradiating the F1 seed of a cross between a high grain and forage yielding variety cowpea-74 and a virus-resistant strain. It was released in year 1990 for the humid and arid areas of the country. It is a dual-purpose

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variety and is grown both for fodder and grain production. The variety is photoinsensitive having bold seeds of ivory brown color and loose testa. Optimum yields and medium maturity have been observed with the seed rate of 20–25 kg per ha and row to row distance of 30–45 cm. The seed color of the variety changes from brown to chocolate brown with the aging of the seeds. The variety is highly resistant to yellow mosaic virus and anthracnose diseases, and comparatively less attacks of leaf miner and semi-looper have been observed on the variety as compared to the check variety. Pusa-152: The plants of the variety are tall, semi-erect, and erect having medium long pods. The pods are distributed all over branches with 11–12 seeds in each pod and are of non-shattering in nature. Seeds are medium bold and oblong shaped and are of brown in color. The variety is suitable for grain as well as fodder. The variety was developed from a selection at IARI, New Delhi, and was released in year 1985. It takes 90–100 days to mature and yields about 1200–1500 kg seeds per ha. The variety is susceptible to bacterial leaf blight disease. V-16: The variety also known as Amba is a mutant of Pusa Phalguni variety developed at IARI, New Delhi, and was released in year 1981 for cultivation during kharif season throughout India and also during rabi season in Peninsular India. The plants of the variety are of about 60–60 cm in height, non-trailing with upright growth. The trifoliate leaves of the variety are of deep green color with medium cordate leaflets. Flowers of the variety are of light violet in color. The pods are of deep green in color having eight to nine seeds in each pod, while seeds are of deep red color, glossy, and roundish and of medium large size. It matures in 90–100 days and gives a potential yield to the extent of 1000–1200 kg seeds per ha. The variety is resistant to bacterial blight, powdery mildew, root rot, and anthracnose, but it is found susceptible to pod borer. UPC-8705: The variety is a derivative of crosses and was released by G. B Pant University of Agriculture and Technology, Pant Nagar, in the year 1995 for cultivation throughout the country. The plants of the variety are of 150–175 cm tall having trailing and indeterminate habit with luxuriant growth. The leaves of the variety are of medium size and of dark green in color. The medium bold seeds are of rhomboid shape and brown color. The variety is resistant to yellow mosaic virus, stem and root rot, anthracnose, and wilt under field conditions. It also shows resistance to pod borer, pod sucking bugs, and aphids and moderate resistant to hairy caterpillar. UPC-9202: The variety is a derivative of crosses between V-260 × UPC 9805 and was developed by G.B Pant University of Agriculture and Technology, Pant Nagar, in the year 1999 for cultivation in subtropical to tropical region of Central Zone of the country comprising the states of the Madhya Pradesh, Maharashtra, Gujarat, and Uttar Pradesh. The variety is erect in its early stage but becomes trailing later on. It has indeterminate growth habit having higher number of green and broad leaves. Pods of the variety are resistant to seed shattering. The seeds are medium bold with light tan-brown color seed coat. The variety takes 140–145 days to mature and shows good response to seed rate of 20–25 kg per ha and row to row distance of 30–45 cm and phosphatic fertilizers under moderate rainfed conditions. The variety is resistant to yellow mosaic virus, stem and root rots, anthracnose, and wilt diseases

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under field conditions. Similarly, it has resistance to thrips, aphids, pod borer/bugs, foliage beetle, and semi-looper/caterpillar. CO-2: It was developed from the progenies of a cross between the grain variety C-512 and vegetable variety C-49 by Tamil Nadu Agricultural University, Coimbatore, and was released in year 1974. The plants of the variety are of 30–40 cm in height, semi-spreading bushy type having 3–4 branches. The stem is of green in color with green purple wash at the nodes. The trifoliate leaves of variety are green, broad, and long petioles. Pods are long, greenish white, and usually two pods are found in each cluster. Seeds are of kidney shaped and reddish brown in color with white irregular patches. Pods of the variety may be harvested after 60th days of sowing. The variety takes about 90 days to mature and yields about 94 quintal pods per ha and about 1300–1400 kg seeds per ha under irrigated conditions. Cowpea-74: The variety is a derivative of the cross between FS-68 × Cowpea No-102 and was released in the year 1978. The plants of the variety are erect having dark green foliage. The unripen pods of the variety are of dark green in color and of about 10–11 cm, while ripened pods become reddish brown. The seeds are round at the place of seed attachment and are of white color having dark brown spots. It takes about 90 days to mature. Type-2: The variety is a selection from a sample collected from Jhansi and was released in year 1955. It is one of the oldest varieties of cowpea that takes higher (125–130) days to mature and therefore out of the seed chain. Its plants are of spreading nature, having dark green leaves. The seeds are bold having mottled brown with black ring around hilum of the seeds. The variety is suitable only for fodder and green manuring. Type-5269 (Pusa Sawni): It is also one of the oldest varieties of cowpea released long back in year 1952 and takes about 100 days to mature. The plants of the variety are erect to semi-spreading having light green leaves. Seeds are bold with brown white color, and the average yield of green pods ranges from 50–60 quintals per ha, while its average seed yield ranges from1000–1500 kg per ha. JC-5: The variety is a selection from indigenous stock of Rajasthan state. The plant height of the variety ranges from 90–100 cm. The leaves of the variety are broad and green in color. Pods are medium sized having medium bold seeds of cream color with light brown broad hilum margin. It takes 85–90 days to mature and yields about 500–700 kg seeds per ha. JC-10: The variety is also a selection from indigenous stock of Rajasthan state. The plants of the varieties are of 100–110 cm long having light green stem, broad and green leaves, and medium-sized pods. Seeds are of medium bold size having creamy color with narrow dark brown hilum margin. It takes 80–85 days to mature and yields about 500–700 kg seeds per ha. RS-9: The plants of the variety are of 90–110 cm in height having dark green stem. Leaves of the variety are broad with purple-colored wings, while pods are smaller in size. It has buff-colored small seeds and takes about 90–100 days to mature. The average seed yield of the variety is about 600–800 kg per ha. Kankamani: The variety was developed from a pure line selection from the germplasm collected from Kunnamlulam area of Trichur district of Kerala state and

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was released in year 1981. The plant height of the variety ranges from 39–90 cm. It has dark green leaves that remain green till senescence. Pods are long (10–15 cm), dark green color at the initial stage that become light pink at maturity. Seeds are closely arranged in pods having about 12–13 seeds in each pod. The variety takes 75–80 days during kharif and 65–70 days during rabi season and yields about 1300–1400 kg seed per ha. GFC: Four varieties, namely, GFC-1, GFC-2, GFC-3, and GFC-4, were developed from various selections using the local collection from Chharodi area of Gujarat state and were released during the year 1980. GFC-1 has plant height of about 125 cm and trailing growth habit and is less prone to water lodging conditions. The pods are of dark green color and have small seeds of light brown to buff color. The average green fodder yield is about 250–300 quintal per ha. The variety GFC-2 has comparatively higher plant height of about 140 cm and shows trailing growth habit. The leaves of the variety are of dark green color with smooth surface. The pods are of dark green color and have small (5–7 mm) seeds of brown color. The average green fodder yield is about 270–350 quintal per ha. GFC-3 is again a longer (196 cm) variety having trailing growth habit. Its leaves are also of dark green color with smooth surface. The variety yields about 270–330 quintal green fodder per ha. GFC-4 is again a longer (197 cm) variety having trailing growth habit. Its leaves are also of dark green color with smooth surface. The variety yields about 290–350 quintal green fodder per ha. UP-5286: The variety was developed from a single plant selection and was released in year 1981. The plant height of the variety ranges from 195–225 cm. The variety has erect indeterminate growth habit. It has medium dark green color leaves, light green-colored stem, and pink-colored flowers. The variety is resistant to yellow mosaic virus, wilt, stem and root rot, and anthracnose. It shows moderate resistance to hairy caterpillar, pod borer, and seed borer insects. The variety yields about 300–350 quintal green fodder per ha and takes 140–150 days to mature. UPC-5287: The variety was developed from single plant selection using the line CK-74-5287 by G.B Pant University of Agriculture and Technology, Pant Nagar, in the year 1986 for cultivation throughout the cowpea-growing areas of the country. The variety has erect indeterminate growth habit, large dark green leaves, and violetcolored flowers. The ripen pods are straw color, while seeds are of light brown color and squared shape. The variety shows good response to nitrogen and phosphorus fertilizers with seed rate of 20–25 kg per ha and row to row distance of 30–45 cm and provides about 260 quintal green fodder per ha under moderate rainfed conditions. It is suitable for intercropping with maize, sorghum, or sugarcane as it takes 155 to 175 days to mature. The variety shows resistance to cowpea yellow mosaic virus, pythium-rhizactonai-fusarium complex, and pod rot. It also has resistance to hairy caterpillar, pod/seed borers, and pod-sucking bugs. Birsa Sweta: The variety was developed from single plant selection using cultivator plot of CN-73-1 by Birsa Agriculture University, Ranchi. The plant height of the variety goes up to 150–200 cm. It has dark green color leaves, whitish blue color flowers, and indeterminate growth habit with an average of seven to eight numbers of primary branches. The variety shows good response to the seed rate of

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20–25 kg per ha and row to row distance of 30–45 cm. The variety has longer pods of white color having 13–14 seeds in each pod. Pods are fleshy and soft and are suitable for vegetable purpose. A good crop can easily provide 10–12 pickings of pods in a season with about 14,500 kg pods per ha. The first and last picking of pods may be taken from 55–57 days and 90 days, respectively, after sowing. The seeds are of dark brown with light yellow color. Pusa Komal: The variety was developed by crossing (P-85-2 × P-426) × P-852 × Pusa Dofasli) at Regional Station, IARI, Karnal, and was recommended for release and cultivation during spring, summer, summer kharif, and late-kharif seasons under Northern Indian conditions. The plants of the variety are bushy and have determinate growth habit. Short vines emerge from the plant under lower temperature and higher soil moisture. It is photo-insensitive and less vegetative variety having synchronous pod bearing and flowers within 45–50 days. The variety shows good response to the seed rate of 20–25 kg per ha and row to row distance of 30–45 cm. The variety has long prominent peduncles, non-fibrous, cylindrical, and light green colored long (20–22 cm) pods. The seed is buffy with prominent brown hilum having seed rough surface. The first picking of pods may be taken from 60–65 days after sowing, and subsequently, second and third harvesting are done after 70 and 80 days of sowing. KBC-1: The variety was developed by a cross between Iran gray and pale green at AICRP (Pulses), GKVK, Bangalore. The variety has erect plant, thick green glabrous leaves, stout green stem, pink color flowers, and ovoid shape seeds. It has upright pod-bearing habit, and its peduncles are lengthy. The variety shows good response with seed rate of 20–25 kg per ha and row to row distance of 30–45 cm and provides about 1000–1200 kg seeds per ha under moderate rainfed conditions. TVX-Cowpea (TVX-944-026): The variety is an introduction from Nigeria and was developed by GKVK, Bangalore. It has narrow leaf with trifoliate structure, indeterminate growth habit with moderate plant pigmentation at the base and tips of petioles. The seeds of the variety are of light brown color, and the variety shows good response with seed rate of 20–25 kg per ha and row to row distance of 30–45 cm and provides about 800–1000 kg seeds per ha under moderate rainfed conditions. Charodi: The variety is a reselection from the seed material received from Agricultural Institute, Anand (Gujarat). It is a medium tall, erect, and well-branched variety and develops one or two tendrils during early maturing. It has non-shattering pods of brown color. The seeds are of chocolate color. The variety shows good response with seed rate of 20–25 kg per ha and row to row distance of 30–45 cm and provides about 1000–1200 kg seeds per ha under moderate rainfed conditions. UPC-287: The variety was developed from CK72–287, a single plant selection from the germplasm line 287 by G.B Pant University of Agriculture and Technology, Pant Nagar, in the year 1988 for cultivation in Gujarat, Rajasthan, Maharashtra, Madhya Pradesh, Punjab, and Bundelkhand Region of Uttar Pradesh. The variety is erect having plant height of about 200–235 cm during its early stages and becomes viny after 60–65 days of sowing. It has pink flowers and long pods having 15–20 pale brown, medium bold, square bean, or oblong-shaped seeds in each pod. It takes

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135–140 days to mature and shows good response with seed rate of 20–25 kg per ha and row to row distance of 30–45 cm. Shweta (No. 988): The variety is a selection from the introduction material received from NBPGR, New Delhi, and was developed by Mahatma Phule Agricultural University, Rahuri, for cultivation in the Western Maharashtra under both irrigated and rainfed conditions. The variety is of creeping nature and produces vines. The variety is very leafy having higher (100 to 110) number of broad leaves that remains green from flowering to late pod formation stage without deterioration in forage quality and yield. It is most suitable for kharif and summer cultivation and can be harvested from pre-flowering stage to late pod formation stage providing green forage for longer period. Since it is harvested during flowering stage, no serious problems of disease and pest are observed. The variety shows good response with seed rate of 22–25 kg per ha and row to row distance of 30–45 cm and provides about 250–350 quintal green fodder per ha under moderate rainfed conditions. Gujarat Cowpea-3 (GC-3): The variety is a cross between V-16 × Black Eye-731 and was released by Gujarat Agricultural University, Sardar Krushi Nagar, in year 1997 for cultivation in arid, semiarid, and humid regions of Southern India comprising of Andhra Pradesh, Karnataka, Tamil Nadu, and Kerala. Being an early maturing (65 to 85 days) variety, it is suitable for sole/multiple cropping systems under low fertility rainfed conditions in kharif season. It is resistant to pod shattering and pod dropping. The variety should be sown in the second half of July so that pod maturity may not coincide with late rains. It has plant height of about 50–55 cm, broad leaves with dark green foliage, and broad and long pod having white seeds with reddish hilum. The variety shows good response with seed rate of about 25 kg per ha and row to row distance of 30–45 cm and provides about 1200–1400 kg green seeds per ha under moderate rainfed conditions. It is a tall growing widely adapted variety having erect growth habit, but pods of the variety are of smaller size. UPC-4200: The variety was developed from CK76–4200, a single plant selection from the germplasm line 4200 by G.B Pant University of Agriculture and Technology, Pant Nagar, in the year 1991 for cultivation in Andhra Pradesh, Assam, Bihar, Gujarat, Karnataka, Madhya Pradesh, Maharashtra, Rajasthan, Tamil Nadu, Uttar Pradesh, and West Bengal. The variety is erect having plant height of about 140–150 cm during its early stages and becomes viny after 45–50 days of sowing. It has light violet flowers and long pods (20–22 cm) having 15–20 mottled brownish gray, bold, rhomboid-shaped seeds in each pod. It takes 145–150 days to mature and shows good response with seed rate of 20–25 kg per ha, row to row distance of 30–45 cm, and yields 275–300 quintal green fodder per ha. The variety shows resistance to yellow mosaic virus, pod and seed borer insects, and moderate resistance to pythium and rhizactonia root rot diseases and hairy caterpillar larva. Bundel Lobia-1 (UFC-8401): The variety was developed by IGFRI, Jhansi, for cultivation in entire country and is most suitable for relatively dryer areas with moderate to low rainfall. It was released in year 1992. The variety has a plant height of about 120–130 cm, five to seven numbers of basal and sub-basal branches and semi-tendril growth habit at late stages. It has medium to broad leaves of light green color. The long (25–30 cm) peduncles have two to three pods per peduncle. The long

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(16–18 cm), leathery pods having 15–18 seeds shatter when dried in the sun. Seeds are of fine brownish gray color, rectangular to round in shape. The variety is tolerant to the leaf mosaic virus disease and flea beetle and semi-looper insects. It shows good response with seed rate of 20–25 kg per ha and row to row distance of 30–45 cm and takes 90–100 days to mature. UPC-607: The variety is a crossing of L-212 × Singapore-48-2-9 and was developed by G.B Pant University of Agriculture and Technology, Pant Nagar, during the year 2002 for cultivation in Uttaranchal, Northern Utter Pradesh, Punjab, Haryana, and Rajasthan. The indeterminate and luxuriant growth with profuse branching variety is erect having plant height of about 150–160 cm during its early stages and becomes trailing at later stage. It has white flowers and long pods (18–20 cm) having 12–15 kidney shaped, medium bold size seeds with creamywhite color in each pod. The variety has abundance of lush green foliage with broad, globose, and dark green leaves. It takes 140–150 days to mature and shows good response to phosphoric fertilizers, seed rate of 35–40 kg per ha for forage production and 30–35 kg per ha for seed production, and row to row distance of 30–45 cm and yields 350–400 quintal green fodder per ha and 45–50 quintal dry matter yield per ha along with 1000–1200 kg seeds per ha under good management favorable weather condition. The drought-tolerant variety shows resistance to yellow mosaic virus, root/collar rot, anthracnose, and bacterial blight diseases along with defoliators, aphids, pod borer/bugs, flea beetle, semi-looper/caterpillar, and root knot nematode under field condition. UPC-618: The variety is a crossing of UPC-8703 × IT84E-124-2-5-1 and was developed by G.B Pant University of Agriculture and Technology, Pant Nagar, for cultivation in Uttaranchal, Uttar Pradesh, Punjab, Haryana, Rajasthan, Jharkhand, West Bengal, Orissa, Assam, Madhya Pradesh, Gujarat, and Maharashtra. It was released in year 2006. The indeterminate and luxuriant growth with profuse branching variety is erect having plant height of about 140–150 cm during its early stages and becomes trailing at later stage with non-twining tendency. It has violet flowers and long pods (13–18 cm) having 15–19 rhomboid medium size small seeds with smooth bronzy brown color in each pod. The variety has abundance of lush green foliage with broad, globose, and dark green leaves. It takes 145–150 days to mature and shows good response to phosphoric fertilizers and row to row distance of 30–45 cm and yields 350–400 quintal green fodder per ha and 45–50 quintal dry matter yield per ha along with 800–1000 kg seeds per ha under good management favorable weather condition. The drought-tolerant variety shows resistance to cowpea yellow mosaic virus, root/collar rot, anthracnose, wilt, and bacterial blight diseases along with bruchids, aphids, flea beetle/defoliators pod borer/bugs, and root knot nematode under field condition. UPC-622: The variety is a crossing of H-288 × MS 9671-1-2-1 and was developed by G.B Pant University of Agriculture and Technology, Pant Nagar, for cultivation in Uttrakhand, Uttar Pradesh, Jammu and Kashmir, Himachal Pradesh, Punjab, Haryana, Rajasthan, Madhya Pradesh, Bihar, Jharkhand, West Bengal, Orissa, and Assam. The variety was released in year 2007. The indeterminate and luxuriant growth with profuse branching variety is erect having plant height of about

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150–160 cm during its early stages and becomes trailing at later stage with non-twining tendency. The variety has abundance of lush green foliage with broad, globose and dark green leaves. The pods of the variety are tolerant to seed shattering. It has violet flowers and long pods (12–15 cm) having 14–18 ovoid medium size bold seeds with smooth, light-brown color in each pod. It shows good response tophosphoric fertilizers and row to row distance of 30–45 cm and yields 350–400 quintal green fodder per ha and 45–50 quintal dry matter yield per ha under good management and favorable weather condition. The drought-tolerant variety shows resistance to cowpea yellow mosaic virus, anthracnose, root/collar rot and bacterial leaf blight diseases along with bruchids, aphids, leaf miner, flea beetle/ defoliators, pod borer/bugs, and root know nematode under field condition. Gomti (5286-3): The variety was released in year 1974 and was developed by Rajendra Agriculture University, Ranchi, and is suitable for cultivation during summer and kharif seasons for green pods. The plants of the variety are spreading and trailing having long greenish white pods. Each pod has 14–15 black seeds. The variety takes 75–80 days to mature and yields about 1500–1800 kg green pods per ha. It shows good response to seed rate of 15–20 kg per ha, row to row distance of 30–45 cm, and 20 kg nitrogen, 60 kg phosphorus, and 40 kg potassium. Shrestha (V-37): The variety is a mutant of Pusa Phalguni and was released in year 1981. It is a trailing variety with medium height and upright growth habit. The trifoliate leaves of the variety are light green in color having medium large and cordate leaflets. It has light violate color flowers with standard and whitish wing and keel. The light green color pods of about 14 cm have about 12–14 seeds of deep red color. The variety yields about 1000–1100 kg pods per ha and shows good response to seed rate of 15–20 kg per ha, row to row distance of 30–45 cm and 20 kg nitrogen, 60 kg phosphorus, and 40 kg potassium. S-450: The variety was developed from the material obtained from Iran and was released in year 1973. The plants of the variety have about 55–70 cm height and trailing growth habit having green stem, leaves, and pods. It has bold seeds of red color and takes 90–100 days to mature. The variety yields about 800–900 kg seeds per ha and seed rate of 15–20 kg per ha and row to row distance of 30–45 cm has been found optimum for the variety. It shows tolerance to semi-looper, flee beetle, and leaf hopper, but it is susceptible to grain pests during storage. Swarna Harita (IC-285143): The variety was developed from germplasm line collected from Jamalpur of Burdwan district of West Bengal by the ICAR Research Complex for Eastern Region, Palandu, Ranchi. It was recommended for release and cultivation in West Bengal, Assam, Bihar, Jharkhand, Uttar Pradesh, Punjab, Orissa, Chhattisgarh, Andhra Pradesh, Kerala, and Tamil Nadu states. It is suitable for cultivation during spring-summer and rainy season with the spacing of 90 cm × 60 cm and seed rate of 5–6 kg per ha. The variety has a plant height of about 209 cm possessing long straight, round, and fleshy pods. The mature seeds of the variety are of light brown, elongated, and kidney shaped. The variety is resistant to rust and mosaic viral disease and pod borer insect. It takes 75–90 days to mature and yields about 60–150 quintal pods per ha.

4.17

Cowpea Varieties Developed in India

89

UPC-625: The variety was developed by G.B Pant University of Agriculture and Technology, Pant Nagar, during the year 2009 for cultivation in the entire country. It is fodder purpose variety and yields about 350–400 quintal green fodder per ha. UPC-628: The variety is a crossing of No. 1 × UPC 8706-7-4-2 and was developed by G.B Pant University of Agriculture and Technology, Pant Nagar, for cultivation in the states of Uttarakhand, Himachal Pradesh, Jammu and Kashmir, Punjab, Haryana, Rajasthan, Uttar Pradesh, Madhya Pradesh, Chhattisgarh, Bihar, Jharkhand, West Bengal, Orissa, Assam, Gujarat, and Maharashtra in irrigated summer and rainfed conditions. It was released in year 2010. The pods of the variety are tolerant to seed shattering. The indeterminate and luxuriant growth with profuse branching variety is erect having plant height of about 160–200 cm during its early stages and becomes trailing at later stage. The variety has abundance of dark green foliage with broad and sub-globose leaflets. The pods of the variety are tolerant to seed shattering. It has long pods (12–17 cm) having 14–18 rhomboid medium to small size seeds with smooth, brown coat color in each pod. It shows good response to phosphoric fertilizers and row to row distance of 30–45 cm and yields 350–400 quintal green fodder per ha under good management and favorable weather condition. The variety is resistant to major diseases, namely, cowpea yellow mosaic virus and anthracnose/leaf blight, and insect pests, namely, aphids, semi-looper, flea beetle/defoliators, pod borer/bugs, and root knot nematode and storage weevils along with drought and other edaphic/abiotic stresses. CO-71: The variety was developed from Tamil Nadu Agricultural University, Coimbatore, and was released during 2004 for commercial cultivation under rainfed and irrigated conditions in the whole country; however, it is mostly suited to Southern zones. It is an early and synchronous nature variety and takes 67–73 days to mature. The variety is moderately resistant to pod borer and tolerant to major diseases of cowpea. It provides yield of about 900–1200 kg seeds per ha and 165–190 quintal green fodder per ha under normal weather conditions. The seeds of the variety are of brownish white color. Paiyur-1: It is a selection from VM-16 developed by Tamil Nadu Agricultural University, Coimbatore, and was released in year 1985. The plants of the variety are of 60–70 cm in height with erect type of stems. The leaves of the variety possess dark green leaflets having triangular white spots. Pods are green that become brown on maturity. Seeds are of brick red in color. The variety takes about 90 days to mature and yields about 900–950 kg seeds per ha under rainfed conditions. CO-6: It is a cross between MS-9804 × C-152 developed by Tamil Nadu Agricultural University, Coimbatore, and was released in year 1993. The plants of the variety are of 30–40 cm in height having purple wash at the nodes of green stems and three to four branches on each plant. The trifoliate leaves of the variety possess purple spots at the side of leaflets. Pods are dark green in color that becomes brown on maturity having light cream color seeds. The variety matures within 65–70 days and yield about 600–700 kg seed per ha under rainfed conditions. VBN: Two varieties, namely, VBN-1 and VBN-2, were developed Tamil Nadu Agricultural University, Coimbatore, and were released in year 1997 and 1998, respectively. VBN-1 is a selection from T-85F-2020, while VBN-2 is a selection

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from IT-81-D-1228-10. VBN-1 is an early maturing variety and takes 55–65 days to mature, while VBN-2 takes 75–80 days to mature. VBN-1 is mostly grown for grain purpose and yield about 950 kg seeds per ha under rainfed conditions, while VBN-2 is mainly grown for vegetable purpose yielding about 100–110 quintal pods per ha. Both varieties are of erect nature having two to four branches, but VBN-1 is shorter (25–30 cm) as compared to VBN-2 (45–60 cm). The seed color of VBN-1 is white, and seed color of VBN-2 is ivory white having hilum with tan ring surrounded by brown band. The pods of both the varieties become creamy at maturity. CO-5: The variety is a mutant of CO-1 developed by Tamil Nadu Agricultural University, Coimbatore, using 30 Kr gamma radiations and was released in year 1986. It is a fodder-type variety and is more compatible for intercropping with fodder cereals. It gives about 20% higher yields as compared to parent. CO (CP)-7: The variety is a mutant of CO-4 developed by Tamil Nadu Agricultural University, Coimbatore, using 20 Kr gamma radiations and was released in year 2002. The variety matures within 70–75 days and yields about 1000 kg seeds per ha under rainfed and about 1500–1600 kg seeds per ha under irrigated conditions. The plants of the variety are of 40–55 cm in height and have green and purple ring at the fruiting nodes along with five to eight branches on each plant. The leaves of the variety are of ovate shape, trifoliate, entire, green, and glabrous in nature. Pods are of green color that becomes light brown on maturity, and seeds of the variety are of brownish white and square shape. CO-9: The variety is a cross of CO-5 and Bundel Lobia developed by Tamil Nadu Agricultural University, Coimbatore, and was released in year 2016 for fodder purpose. CO (FC)-8 is also a fodder variety released by the University. The variety is known for shorter maturity, higher number of branches with broader leaves, higher protein content, reduced fiber with increased digestibility, palatability, and intake. It is well suited for intercropping cultivation with sorghum and maize. It yields about 1000 kg seeds per ha under rainfed conditions and about 200–300 quintal green and 30–25 quintal dry matter yield per ha. Pant Lobia: Five varieties of cowpea, namely, Pant Lobia-1, Pant Lobia-2, Pant Lobia-3, Pant Lobia-4, and Pant Lobia-5, have been developed and released in different years by G.B Pant University of Agriculture and Technology, Pant Nagar, for cultivation in various parts the country. A brief description of all the five varieties under the group Pant Lobia is as follows: Pant Lobia-1 is a grain type variety released in 2008 showing higher adaptability for sowing during March to October months. The plants of the variety are 40–50 cm height having long (13–26 cm) pods and mature in 60–65 days in plains and 70–75 days in hills. It has erect plant type with early and synchronous maturity. Each pod contains about 14–18 white with black-eyed seeds. It is tolerant to major bacterial and viral diseases and attack of aphids and thrips. The variety requires less irrigation and yield about 2000 kg seed per ha and 2000–2500 kg dry fodder under good environmental conditions. Pant Lobia-2 is a grain type released in 2010 showing higher adaptability for sowing during March to June months. It has semi-erect plant type with early and synchronous maturity taking about 70 days to mature in plains and 75–80 days in

4.17

Cowpea Varieties Developed in India

91

hill. The plants of the variety are about 40–50 cm tall having long (15–20 cm) pods and purple color flowers. Each pod contains about 14–18 red self-colored, medium size, and slightly ovoid seeds. It is tolerant to major fungal, bacterial, and viral diseases. The variety requires less irrigation and yields about 1400–1800 kg seed per ha and 2500–3000 kg dry fodder under good environmental conditions. Pant Lobia-3 was released in 2015 showing higher adaptability for sowing during March to October months. It is grown in Madhya Pradesh, Karnataka, and Kerala. It matures in 60–65 days in plains and 75–80 days in hills. The plants of the variety are about 55–60 cm tall having long (15–20 cm) pods and purple color flowers. Each pod contains about 14–18 brown-colored, medium size, and kidney shape to oval seeds. It is tolerant to YMV, bacterial blight, and bruchids. The variety requires less irrigation and yield about 1800–2000 kg seed per ha and 2000–2500 kg dry fodder under good environmental conditions. Pant Lobia-4 has about 40–45 cm tall plants and was released in 2015. It has erect bush plant type, long (14–16 cm) pods having 12–14 white, medium size, kidney shape to oval seeds and takes about 60–65 days to mature. It is tolerant to major fungal, bacterial, and viral diseases and provides about 1400–1800 kg seed per ha and 2500–3000 kg dry fodder yield under good environmental conditions with minimum number of irrigation. Pant Lobia-5 is of about 40–55 cm tall and was released in 2015 for sowing during March to first week of September. It has erect bush plant type, long (16–18 cm) pods having 12–14 light brown, oval bold seeds and takes about 65–70 days to mature in plains and 75–80 days in hills. It is tolerant to cowpea mosaic diseases and bacterial blight and provides about 1600–2000 kg seed per ha and 1500–2000 kg dry fodder yield under good environmental conditions with minimum number of irrigation. Narendra Lobia-1: The variety was developed by Narendra Dev University of Agriculture and Technology, Faizabad, from across of Pusa Komal and Varanasi Local using the pedigree method of breeding, and was released in year 1995. It is photo-insensitive and can be grown both in summer and rainy seasons. It has determinate plant habit with plant height of 40–45 cm. The variety has broad green leaves, long (28–32 cm) pods with purple terminal end having 10–12 bold seeds with black hilum. The pods of the variety become ready to consume after 45–48 days of sowing, while its seeds takes 75–80 days to mature. The variety yields about 90 quintals green pod per ha. Pusa Phalguni: It is a selection from a promising introduction Dolique Du Tonkin and is a very old variety of cowpea. The variety has been exploited for development of several other varieties. February–March months are considered as the best time for its sowing. The plants of the variety are dwarf with bushy habit and give two flushes of dark green erect pods of 10–12 cm length with small cylindrical white seeds. The pods of the variety become ready to consume after about 60 days of sowing. The variety yields about 75 quintals green pod per ha. Pusa Barsati: The variety was developed from a selection using exotic materials from Philippines by IARI, New Delhi. It is an early maturing variety and provides first green pod picking after 45 days of sowing. The variety is suitable for growing

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during the rainy season and gives two to three flushes of light green pods. The pods are long (25–28 cm) and contain large green seeds. The variety yields about 75 quintals green pod per ha. EC-4216: The variety was developed from a selection by IARI, New Delhi, in year 1977. It is highly adapted to entire country and possesses high crude protein and shows moderate tolerance to drought conditions. The average green fodder yield obtained from the variety is about 280–300 quintal per ha. RC-101: The variety was developed from a selection by Rajasthan state in year 2001. It is an early maturing, drought-tolerant variety having determinate growth habit and non-viny stems. The variety is well suited for low rainfall areas of the country and yields about 750–950 kg seeds per ha under good environmental conditions. The variety has white seeds and takes 60–65 days to mature under arid zone conditions.

4.18

Cowpea Production in India

India is one of the most important producers of legumes and account for about 24% toward worldwide legume production and dedicates about 32% area under the legume cultivation (Kebede 2020). It has been estimated that more than 126.1 lakh ha area is under cowpea cultivation globally with an average production of about 60 lakh tons (Kamara et al. 2018b). Uganda, Kenya, and Nigeria are the largest cowpea producers, while eastern and southern Africa, north eastern Brazil, Peru, parts of India, and the south eastern and south western regions of North America are other important producers of cowpea (Ojiewo et al. 2018). Cowpea is a minor pulse in India and is mainly cultivated under arid and semiarid parts of the country. Some previous reports suggest that area under cowpea cultivation in India is about 39 lakh ha with a production of about 22 lakh tons, while its national productivity is about 680 kg per ha (Mandal et al. 2009). Karnataka, Tamil Nadu, Andhra Pradesh, Rajasthan, Kerala, Maharashtra, and Gujarat contribute major toward the area and production of cowpea; however, the crop is grown under limited areas in Punjab, Haryana, Delhi, and western part of Uttar Pradesh. In India, cowpea is generally grown as mixed crop, inter-crop, and in other agronomic systems; therefore, it is difficult to obtain the exact data on the area, production, and yield of the crop. Area, production, and yield of moth bean in India have been presented in Table 4.2. The data revealed that Karnataka dedicated about 67% of its area under cowpea cultivation during last 10 years (2010–2011 to 2019–2020) and shared about 54% to the national production. Perhaps, cowpea is the only pulse crop that is suitable for both arid and semiarid regions. It survives well under high rainfall regions, and due to its long and strong tap roots, it has acquired all the qualities to establish under drought conditions. Fast growth during its initial stage surpasses the weed competition and helps in the conservation of soil moisture.

Production 36,233 35,959 17,765 23,789 24,145 28,064 43,550 19,627 17,487 8678

Yield 13.72 14.3 9.98 10.35 14.33 11.23 20.75 5.97 10.35 8.73

Tamil Nadu area Production NA NA NA NA NA NA NA NA NA NA NA NA NA NA 47,378 34,028 44,897 35,418 47,877 37,536

Area in ha; production in tons; yield in tons/ha Source: https://eands.dacnet.nic.in a Sum of all the Indian states; data presented are sum of all the districts

Year 2010–11 2011–12 2012–13 2013–14 2014–15 2015–16 2016–17 2017–18 2018–19 2019–20

Karnataka area 70,151 68,089 64,825 63,704 54,977 67,727 56,875 86,555 46,257 30,586

Table 4.2 Area, production, and yield of cowpea in India Yield NA NA NA NA NA NA NA 17.87 20.15 18.62

Andhra Pradesh area Production 143 34 4575 1085 5000 2000 3720 1617 4459 1865 11,043 9696 3780 1966 4302 3081 13,385 1381 5816 2612 Yield 0.24 2.91 2.00 3.65 3.30 6.17 3.44 4.84 1.59 4.53

All India levela area Production 76,199 40,067 74,982 39,498 71,603 21,502 72,328 29,581 63,734 30,753 88,183 45,486 68,441 51,799 146,701 65,242 62,462 112,567 131,018 84,873

Yield 39.71 35.35 25.76 39.4 45.67 50.45 64.46 76.99 77.70 83.54

4.18 Cowpea Production in India 93

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Neves ALR, Lacerda CFD, Teixeira ADS, Costa CAG, Gheyi HR (2010) Monitoring soil coverage and yield of cowpea furrow irrigated with saline water. Rev Ciênc Agron 41:59–66 Neves ALR, de Lacerda CF, de Sousa CHC et al (2015) Growth and yield of cowpea/sunflower crop rotation under different irrigation management strategies with saline water. Ciência Rural 45(5):814–820 Ng NQ, Marechal R (1985) Cowpea taxonomy, origen and germplasm. In: Singh RS, Rachie KO (eds) Cowpea research production and utilization. Wiley, New York, pp 11–21 Ntare BR (1993) Variation in reproductive efficiency and yield of cowpea under high temperature conditions in a Sahelian environment. Euphytica 59:27–32 Ohler TA, Mitchell CA (1996) Identifying yield-optimizing environments for two cowpea breeding lines by manipulating photoperiod and harvest scenario. J Am Soc Hortic Sci 121(3):576–581 Ojiewo CO, Rubyogo JC, Wesonga JM et al (2018) Mainstreaming efficient legume seed systems in Eastern Africa: challenges, opportunities and contributions towards improved livelihoods. Food and Agriculture Organization, Rome Osunde AO, Bala A, Gwam MS et al (2003) Residual benefits of promiscuous soybean to maize (Zea mays L.) grown on farmers’ fields around Minna in the southern Guinea savanna zone of Nigeria. Agric Ecosys Env 100:209–220 Ouedraogo JT, Maheshwari V, Berner DK et al (2001) Identification of AFLP markers linked to resistance of cowpea (Vigna unguiculata L.) to parasitism by Striga gesnerioides. Theor Appl Genet 102:1029–1036 Palaniappan P, Malliga P, Manian S et al (2010) Plant growth promotory effect on cowpea (Vigna unguiculata L.) using coir pith aqueous extract formulation of cyanobacterium Phormidium. Am Eurasian J Agric Environ Sci 8(2):178–184 Pararajasingam N (2004) Effect of different training systems on pod yield of yard long bean Vigna unguiculata (L) Walp. Subsp. Sesquipedalis (L) Verde. Trop Agric 155:13–16 Pasquet RS, Baudoin JP (2001) Cowpea. In: Charrier A, Jacquot M, Hamon S, Nicolas D (eds) Tropical plant breeding. Science Publishers, Enfield, pp 177–198 Patel PN, Hall AE (1990) Genotype variation and classification of cowpeas for reproductive responses to high temperature under long photoperiods. Crop Sci 30:614–621 Patra DD, Sachdev MS, Subbiah BV (1986) 15N studies on the transfer of legume-fixed nitrogen to associated cereals in intercropping systems. Biol Fertil Soils 2:165–171 Perez MJ (2007) Efficiency of some leguminous crops to use P from phosphate rock. Rev Fac Agron Univ Zulia 24(1):113–132 Rachie KO (1985) Introduction. In: Singh SR, Rachie KO (eds) Cowpea research, production and utilization. Wiley, New York, pp 21–27 Ramana V, Ramakrishna M, Purushotham K, Reddy KB (2010) Effect of bio-fertilizers on growth, yield attributes and yield of French bean (Phaseolus vulgaris L.). Legume Res 33(3):178–183 Salisbury FB, Ross CW (1992) Photoperiod during a plant’s life cycle. In: Salisbury FB, Ross CW (eds) Plant physiology, 4th edn. Wadsworth Publication, Belmot, pp 508–512 Serme I, Maman N, Garba M et al (2018) Cowpea response to nutrient application in Burkina Faso and Niger. Afr J Agric Res 13(30):1508–1515 Sharma R, Verma ML (2011) Effect of rhizobium, FYM and chemical fertilizers on sustainable production and profitability of rajmash (Phaseolus vulgaris L.) and soil fertility in dry temperate region of North-Western Himalayas. Legume Res 34(4):251–256 Shirtliffe SJ, Johnston AM (2002) Yield-density relationships and optimum plant populations in two cultivars of solid-seeded dry bean (Phaseolus vulgaris) grown in Saskatchewan. Can J Plant Sci 82:521–529 Shivakumar MVK, Maidoukia A, Stern RD (1993) Agroclimatology of West Africa: Niger, information bulletin no. 5. ICRISAT, Patencheru Singh BB (2005) Cowpea [Vigna unguiculata (L.) Walp]. In: Singh RJ, Jauhar PP (eds) Genetic resources, chromosome engineering and crop improvement, vol 1. CRC Press, Boca Raton, FL, pp 117–162

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Singh R, Prasad K (2008) Effect of vermicompost, rhizobium and DAP on growth, yield and nutrient uptake by chickpea. J Food Leg 21:112–114 Singh BB, Chambalis OL, Sharma B (1997) Recent advances in cowpea breeding. In: Singh BB, Mohan Raj DR, Dashiel KE, Jackai LEN (eds) Advances in cowpea research. IITA and JIRCAS Publications, Ibadan, pp 30–49 Singh M, Singh A, Singh S et al (2010) Cowpea (Vigna unguiculata L. Walp.) as a green manure to improve the productivity of a menthol mint (Mentha arvensis L.) intercropping system. Indian J Crops Prod 31(2):289–293 Singh A, Baoule AL, Ahmed HG et al (2011) Influence of phosphorus on the performance of cowpea (Vigna unguiculata L. Walp) varieties in the Sudan Savana of Nigeria. Agric Sci 2:313– 317 Singh R, Malik JK, Thenua OVS, Jat HS (2013) Effect of phosphorus and bio-fertilizer on productivity, nutrient uptake and economics of pigeonpea (Cajanus cajan) + mung bean (Phaseolus radiatus) intercropping system. Legume Res 36(1):41–48 Smiley RW, Ingham RE, Uddin W, Cook GH (1994) Crop sequence for managing cereal cyst nematode and fungal pathogens of winter wheat. Plant Dis 78:1142–1149 Stamford NP, Junior SDS, Santos CE et al (2013) Cowpea nodulation, biomass yield and nutrient uptake, as affected by biofertilizers and rhizobia, in a sodic soil amended with Acidithiobacillus. Acta Sci 35(4):453–459 Stone JA, Buttery BR (1989) Nine forages and the aggregation of clay loam soil. Can J Soil Sci 69: 165–169 Terao TI, Watanabe R, Mustapha S, Hakoyama, Singh BB (1997) Agrophysiological constraints in intercropped cowpea: adaptation in crops a role for breeders, physiologists and modelers. Exp Agric 27:55–175 Timko MP, Ehlers JD, Roberts PA (2007) Cowpea. In: Kole C (ed) Genome mapping and molecular breeding in plants, Pulses, sugar and tuber crops, vol 3. Springer Verlag, Berlin, pp 49–67 Vavilov NI (1939) Genetics in the USSR. Chron Bot 5(1):14–15 Vavilov NI (1951) The origin, variation immunity and breeding of cultivated plants. Chron Bot 116: 26–38 Wallace DH, Yourstone KS, Masaya PN, Zobel I (1993) Photoperiod gene control over partitioning between reproductive and vegetative growth theory. Appl Genet 86:6–16 Wien HC, Summerfield RJ (1980) Adaptation of cowpeas in West Africa: effects of photoperiod and temperature responses in cultivars of diverse origin. In: Summerfield RJ, Bunting AH (eds) Advances in legume science. HMSO, London, pp 405–417 Yourstone KS, Wallace DH (1996) Effects of photoperiods and temperature on rate of node development in indeterminate bean. J Am Soc Hortic Sci 5:115 Yusuf AA, Iwuafor ENO, Abaidoo RC et al (2009) Grain legume rotation benefits tomaize in the northern Guinea savannah of Nigeria: fixed-nitrogen versus other rotation effects. Nutr Cycling Agroecosyst 84:129–139

5

Plant Protection

Abstract

Cowpea has been widely adapted to various regions, soil, and weather conditions and is therefore susceptible for various pathogenic organisms including viruses, bacteria, fungi, protozoa, and worms. The intensity of these diseases fluctuates under different regions, soil, and weather conditions and affects the productivity of the crop. The viral diseases of the crop are more destructive as it is transmitted from one generation to another through seed material and disseminates throughout all the cowpea-growing regions of the country. A detailed account of fungal, bacterial, and viral diseases and major insect pests of the crop has been discussed in this chapter.

5.1

Introduction

Plant protection measures help to maintain the crop health for sustainable production. It mainly depends upon the crop and associated risks. The risks may be insect-pests, diseases, or weeds. The recognition and categorization of diseases are important for application of plant protection strategies (Thomas et al. 2018). Cowpea has wide adaptation including regions, soil, and weather conditions; therefore, several pathogenic organisms including viruses, bacteria, fungi, protozoa, and worms induced plant diseases in the crop that influence the plant at all the growing stages (Anilkumar et al. 1994; Aveling and Adandonon 2000) and productivity of the crop. Aphid-borne cowpea mosaic virus, pre- and post-emergence damping-off caused by Pythium aphanidermatum (Shoyinka et al. 1978; Bankole and Adebanjo 1998), and several other diseases are found on cowpea. The intensity of these diseases fluctuates under different regions, soil, and weather conditions and affects the crop accordingly. Diseases may be of seed-borne or soil-borne in nature. The viral diseases are more destructive as it is transmitted from one generation to another # The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 R. Pathak, Genetics, Physiology and Cultivation of Moth Bean, Cowpea and Horse Gram, https://doi.org/10.1007/978-981-19-9956-7_5

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through seed material and disseminates throughout all the cowpea-growing regions of the country. Identification of genes responsible for insect pest resistance in cowpea including various inhibitors such as α-amylase, protease, and lectins has given opportunities for biotechnological interventions in cowpea (Singh et al. 2000) for development of disease resistant varieties in cowpea (Machuka 2000; Zaidi et al. 2005).

5.2

Fungal Disease

Fungal diseases are the major constraints in cowpea cultivation. Out of these, anthracnose, brown blotch, leaf spots, and web blight are prominent (LatundeDada 1990; Kormawa et al. 2000), while pathogens of the species of Rhizoctonia solani, Macrophomina, and Fusarium sp. are the most widespread and destructive in cowpea (Davis et al. 1991). An account of various fungal diseases is given below:

5.2.1

Cowpea Rust

Brown rust caused fungus Uromyces vignae (Chandrashekar et al. 1989), pink rust caused by Phakopsora pachyrhizi, and false rust caused by Synchytrium dolichiare some of the most severe diseases of cowpea throughout the world that can be seen at any part of the plant aboveground and spreads to the middle and upper parts particularly during pod formation stage (Mensah et al. 2018). The disease was first reported from India (Barclay 1891) and has been spread to many parts of world including China, Japan, and Eastern Africa (Li et al. 2007; Chung et al. 2004) causing about 50% loss (Edema and Adipala 1995). The disease interferes with usual root development and uptake of nutrients by the roots resulting into considerable yield loss (Mensah et al. 2018). Temperature from 16 to 22°C and higher humidity are the most favorable environmental conditions of the disease (Chen et al. 2016). The infection is visible in form of brown lesions on the leaf surfaces and spreads through wind by urediniospores. Cool and wet environmental conditions are highly favorable for rust development. The urediniospores germinate on the leaf surface under favorable conditions and develop hyphae that enter into the leaf through stomata (Eastburn et al. 2011; Kanade et al. 2015). The severity of the infection increases at higher humidity, plant population, and temperature (Tessmann et al. 2001; Manjesh et al. 2018). The severe infection leads to defoliation of premature leaves leading to drastic yield losses. Foliar sprays of fungicides are recommended for the management of disease. Sowing of rust-resistant varieties is the cheapest and most effective method to control cowpea rust disease. Various isolates of U. vignae have been isolated and characterized in cowpea (Chen and Heath 1990), and some accessions have been reported to be resistant to the rust (Wang et al. 2000). It was observed that the rustresistant is regulated by single dominant genes (Li et al. 2007), recessive genes (Uma and Salimath 2004), or polygenes (Uma et al. 2016). A rust-resistant gene (Ruv2)

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was mapped at chromosome 2 of cowpea having 23 expected gene models (Wu et al. 2018) that may be used in the development of rust-resistant varieties of cowpea and/or other legumes.

5.2.2

Anthracnose

The fungal diseases anthracnose and brown blotch are caused by Colletotrichum lindemuthianum and have been reported as a major cause of losses in Southern part of India. Moist and cooler weather are the most favorable conditions for the spread of disease. The fungus infects almost all the plant parts and causes leaf spot, stem blackening, pod discoloration, seed rot, seedling blight, etc., but generally, the reproductive stage is more crucial resulting into 35–50% yield loss. Tannish red spots bounded with yellow radiance that enlarges into lesions of about 2 cm in diameter are seen on the infected leaf lamina (Falade 2016). The infected pods become curly and remain stunted and empty. Infected seeds have brownish lesions. Symptoms are mostly seen on the leaves and pods along with cankers on petioles and stem resulting into defoliation and rotting of the pods (Davis et al. 1991). Age of plant at inoculation, incubation period of pathogen, and temperature are the important factors influencing anthracnose in cowpea (Pakela et al. 2002). The disease incidence was lower in the crop intercropped as compared to sole crop (Adebitan and Ikotun 1996; Falade et al. 2017), while crop sown under lesser inter- and intra-row spacing has higher chances of incidence and severity of the diseases (Adebitan and Ikotun 1996). The genetic basis for brown blotch resistance was studied (Ohlson et al. 2018), and a dominant quantitative trait locus (QTL) was identified for the resistance. Besides this, one major and three minor QTLs were recorded on the basis of allele-specific polymerase chain reaction markers and multiple interval mapping. Seed treatment with benzimidazole, dithiocarbamate, and thiram was found effective in controlling the fungus (Edema and Adipala 1994; Emechebe and Florini 1997). Spray of 0.2% active ingredient of dithiocarbamate at an interval of fortnight may provide good control. Studies conducted in the humid forest of Nigeria revealed that soil drenching or seed treatment with Trichoderma viride and foliar spray once or twice in a week has reduced the brown blotch infection (Bankole and Adebanjo 1996). Similarly, water or alcohol extract of Piper betle, Ocimum sanctum, and Citrus limon was found effective in reducing the anthracnose incidence in the field (Amadioha 1999). Intercropping of cowpea with nonhost crop of the fungus along with the spray of plant extract has reduced the incidence and severity of the disease (Falade et al. 2017). Foliar spray of Datura stramonium reduced the incidence and severity of the anthracnose disease as compared to the foliar spray of extracts of Ricinus communis and Jatropha gossypifolia (Falade et al. 2017). Increase in the dry shoot weight was recorded with the application of Trichoderma harzianum and T. Viride along with carbendazim (Nigam et al. 2018).

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Plant Protection

Blight

Stem blight, charcoal rot, seedling blight, root rot caused by Macrophomina phaseolina, and web blight caused by Rhizoctonia solani are relatively more widespread diseases in cowpea that can be seen at various growth stages of the crop. Wilt, leaf blight, and ashy stem blight (Abdon et al. 1980; Singh et al. 1990) are also caused of the pathogen. Higher temperature (32–38°C) and lower soil moisture (40–55%) regime are favorable conditions for the diseases. It is one of the most critical diseases in both tropical and subtropical regions (Chidamboram and Mathur 1975; Dhingra and Sinclair 1977; Reuveni et al. 1983). Seed, soil, and plant residue are the foundation of primary inoculum of the pathogen (Reuveni et al. 1983; Short et al. 1980). The infected seedling has stunted growth with rotting in hypocotyls and roots resulting into drying of seedling. Dry or moist grayish black sunken lesions are the major symptoms found on the lower stem of mature crop. Pelleting of cowpea seeds with T. viride either alone or in combination with carbendazim inhibited the growth of M. phaseolina under in vitro (Alagarsamy and Sivaprakasam 1988). Application of neem cake in the field was found effective in reducing the infection. Combination of carbendazim, seed treatment, and foliar spray with copper oxychloride has been found more effective in controlling the stem blight. Amendment of soil with 150 kg per ha of neem cake has reduced population of Macrophomina phaseolina in the rhizosphere and non-rhizosphere soils. Inoculation of seeds with VAM fungi also gives good results (Kumar and Narain 2005).

5.2.4

Wilt

Wilt disease caused by Fusarium oxysporum f. sp. Tracheiphilum is almost common in northern part of India and has major threat to cowpea production. Inheritance study of the resistance to F. oxysporum was carried under field conditions having disease-resistant parents (Omoigui et al. 2018), and presence of gene dominance was observed in controlling the disease. The findings were further confirmed, and it was observed that the resistance was controlled by a single dominant gene conferring the resistance in cowpea. It is both seed- and soil-transmitted disease. The pathogen penetrates through the root system and attacks the vascular tissue. Warm soil and dry weather are the optimum conditions for the disease. It is more common in the crop grown under nutrient-deficient soil. The infected plants have stunted growth, leaf chlorosis, wilting, dropping, withering, veinal necrosis of leaves, and death of the plant. Infection can be seen in the form of broad irregular patches on the affected plants (Armstrong and Armstrong 1981). The infection at the pre-fruiting stage is the most crucial stage resulting into severe yield loss (Okiror 2002). Seed treatment with thiram (0.3%) and captan (0.2%) in single or in combination is effective to control the infection. The disease may be managed properly with the application of Trichoderma harzianum, T. viride, neem cake, etc. Roguing of infected plant and sowing of resistant varieties minimize the chances of the disease (Kumar and Narain 2005).

5.2 Fungal Disease

5.2.5

103

Leaf Spot

The disease is caused worldwide by Cercospora canescens and C. cruenta. C. cruenta is more common pathogen for leaf spot disease in cowpea grown in Northern Central India. Pseudocercospora leaf spot is caused by Mycosphaerella cruenta in the form of its anamorph, Pseudocercospora cruenta (Allen and Lenne 1998). Pseudocercospora leaf spot occurs in the form of chlorotic or necrotic spots on the upper leaf surface. The masses of conidiophores and conidia are seen as downy gray to black mats on the lower leaf surface. Cercospora leaf spot is seen as circular to irregular spots of cherry red to dark red color lesions on the leaf surface of the infected plant. Several spots combined resulting into yellowing and dropping of leave. The injury from the disease generally occurs at the full broom of the crop including vegetative and reproductive stage. The disease not only affects the seed yield but also reduces the fodder quality. Inheritance study of the disease was carried under field conditions having disease-resistant parents (Omoigui et al. 2019), and presence of gene dominance was observed in controlling the disease. The findings were further confirmed, and it was observed that the resistance was controlled by a single dominant gene (Omoigui et al. 2019). The pathogens persist during the lien period on infected crop residue and in infected seed (Williams 1975; Scheneider et al. 1976) and result about 40% yield loss (Scheneider et al. 1976). Rainy season of relatively hot and high humid conditions are more favorable for the disease incidence in legumes (Poehlman 1991). Septoria leaf spot caused by Septoria vignae and S. vignicola, Ascochyta blight leaf spot caused by Ascochyta phaseolorum, A. boltshauseri, and web blight caused by Rhizoctonia solani are the major foliar diseases reported in cowpea. Ascochyta blight leaf spot and web blight are the major foliar diseases of cowpea causing severe loss to the crop, while Septoria leaf spot is also widespread but is more prevalent in the savannahs of Africa. Alternaria cassiae is one of the causal agents for destructive foliar diseases of cowpea (Berg et al. 2003). The debris of infected parts of the crop should be destroyed properly to evade perpetuation of the pathogens. Seed treatment with thiram or captan (2.5 g per kg seed) can be used to avoid the disease. Foliar application of Mancozeb 75% WP (0.2% active ingredient) can be used to control the spread and severity of pathogens. Weekly spray of benomyl starting from third week of sowing exhibited good control of disease and higher seed yield (Amadi 1995).

5.2.6

Powdery Mildew

It is a major disease of the crop caused by Erysiphe polygoni, Sphaerotheca fuliginea, and Oidium sp. The fungus is an obligate parasite that produces whitish to dirty whitish mycelium (Yardwood 1957). Ascospores are the primary source of infection found in the soil (Rangaswami and Mahadevan 1988) that attack the lower leaves near the soil; secondarily, it spreads through conidia. The pathogen is ectoparasitic and gets nutrition from the host tissues through haustoria. The disease

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appears in form of small white patches on the upper surface of the leaves, petioles, branches, stem, and pods. Initially, it appears on the older leaves at the bottom of the plant in form of irregular white powdery spots on the upper part of the leaves. The infected plant has stunted growth and curly and yellowish leaves. The severely infected plants have talcum powder-like appearance. The white powder changes to grayish brown at later stages. In severe conditions of infection, the leave wither and dropped down. The disease is more common in the crop grown under shadow and favored by higher day and lower night temperatures. The disease also affects the fodder cowpea, and 18–46% reduction in seeds per pod has recorded with along reduction in the plant growth and yield (Saxena et al. 1992). Sowing of disease-resistant varieties is the best approach to get rid of the disease. Foliar spray of wettable sulfur can be used to manage the disease. Sulfur fungicides have been considered as superior fungicides earlier for controlling powdery mildew in general (Butler 1918). Application of benomyl (0.2%), or tridemorph (0.1%), or dinocap (0.05%), or 0.05% Kerthane immediately on appearance of disease twice at the interval of 15 days can effectively reduce the intensity of disease. Application of benomyl @2.3 g of active ingredients 7 days after the sowing was found effective in controlling the powdery mildew in cowpea (Arif and Goode 1970). Similarly, spray of cosan (0.2%) or benomyl (0.2%) at the interval of 15 days was found effective on cowpea (Sohi and Sokhi 1974). Foliar spray of chlorothalonil, mancozeb, dinocap, benomyl, and macuprax resulted into better control of cowpea powdery mildew (Rodriguez and Melendez 1984). Dinocap showed effective control over E. Polygoni under dry seasons, but its effect was comparatively lower under rainy season (Rodriguez and Melendez 1984). Biloxazol, carbendazim, and triadimefon used as seed dressings, foliar spray, or soil drenches exhibited efficient control over powdery mildew of cowpea (Singh et al. 1986). Partially resistant cultivars to E. polygoni were screened under Indian conditions, and V-105, V-269, V276, V-282, and V-385 were obtained to be moderate resistant to the disease (Raju et al. 1991).

5.2.7

Root Rot

Various fungal pathogens such as Rhizoctonia solani and R. bataticola (Kalim et al. 2003); species of Pythium including P. ultimum, P. debaryanum, P. mytiotylum, P. helicoids, P. aphanidermatum, P. oligandrum, P. rostratum, P. pulchrum, P. vexans, P. anandrum, and P. acanthicum (Zaumeyer and Thomas 1957; Gale 2002; Agrios 2005; Dutta 2005); Fusarium oxysporum (Shrestha et al. 2016); and Macrophomina phaseolina (Sendhilvel et al. 2005; Mohanapriya et al. 2017) are responsible for root rot in cowpea. These are commonly soil pathogenic fungus and attack the cowpea seedlings at the base of stem and root (Dutta 2005). It was observed that cowpea grown under rainfed conditions had more prevalence of root rot caused by M. phaseolina as compared to the irrigated cowpea (Mohanapriya et al. 2017) suggesting the growth of fungus under dry conditions. Generally, overcrowding of plant population and over-watering are favorable conditions for the fungus. Root rot is observed as rapid death of young plants, discoloration of

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taproots, longitudinal cracks, stunting, and wilting of the stems. Continuous humid weather prior to the emergence of first true leaf and dense population of seedlings deteriorates the condition (Kumar and Narain 2005). Crop rotation, deep ploughing of fields, weeding, and sowing of disease-resistant varieties are the best approach to get rid of the disease. Application of manganese sulfate was found beneficial in controlling the root rot of cowpea caused by Rhizoctonia solani and R. bataticola (Kalim et al. 2003). Application of plant growthpromoting rhizobacteria such as Pseudomonas fluorescens is efficient in inhibiting the cowpea root rot (Sendhilvel et al. 2005). Various plant extracts, namely, ginger, aloe, and neem, have also been found efficient in controlling the root rot disease of cowpea caused by P. aphanidermatum (Suleiman and Emua 2009); however, their effects were of short duration.

5.2.8

Basal Stem Rot

It is also a major disease of cowpea caused by fungal pathogen Sclerotium rolfsii. The fungus was reported on tomato (Rolfs 1892) and named as Sclerotium rolfsii (Saccardo (1911); later, its physiology and parasitism were studied in detailed (Higgiens 1927). S. rolfsii is found in soil and is widely spread in warm humid climatic conditions (Adandonon et al. 2004). Its sclerotia survived on organic matter from few weeks to several years (Punja 1985). The fungus propagates, survives, and infects the plant from the soil surface. It secretes an enzyme that helps it to penetrate in the host tissues and consequently decay of cell and development of mycelium and sclerotium (Billah et al. 2017) within 2 to 10 days. The symptom is observed as the yellowing and wilting of the leaves along with decaying of stem at the ground level. Encircling of lesions on the stem near the soil line is the critical symptom of the diseases. The economic impact studies of the disease were carried out by various workers, and it was observed that it has reduced the plant vigor and yield loss from one (Toler et al. 1963) to about 53% (Fery and Dukes 2002). Studies revealed up to 20% mortality and leaf blight within 10 days old seedlings of cowpea (Langyintuo et al. 2003). Various cowpea lines were evaluated to find their susceptibility (Muquit et al. 1996; Karat et al. 1985; Nwakpa and Ikotun 1988), and resistance to highly susceptible reactions was observed along with significant variability among the cowpea germplasm (Fery and Dukes 2002). In India, variety GC-4 was found moderate resistant to S. rolfsii, while Pusa falguni, Pusa komal, GC-5, and Anand-1 were recorded as moderate to susceptible (Kachhadia 2013). Pythiurn stem rot caused by Pythium aphanidermatum is also an important disease of cowpea and is principally soil-borne disease. It is observed in the form of gray-green watersoaked girdles on the stem parts rising from the soil level. During the high humidity period, white cottony mycelia is seen on the base of the stem. The infected plants wilt rapidly and die. Application of castor cake followed by neem cake and vermi-compost is efficient in preventing the growth of mycelia and sclerotial production. Carbendazim, thiram, carboxin, thiophanate methyl, and fosetyl AL 80% wp were found to be highly toxic

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to S. Rolfsii (Khodke and Raut 2010; Kachhadia 2013). Influence of Pseudomonas fluorescence was studied on the development and growth parameters in cowpea seedlings (Nandi et al. 2013), and about 70% growth of S. rolfsii was recorded under in vitro conditions. In a study of influence of different crop rhizosphere and microbial community on the dynamics of S. rolfsii (Ray et al. 2017), it was observed that the sclerotial number was reduced in the napier, maize, and sorghum plots suggesting the usefulness of crop rotation for declining the sclerotial population in the field.

5.2.9

Seedling Mortality

Various fungi such as Pythium aphanidermatum, Rhizoctonia solani, Thanatephorus cucumeris, etc. are responsible for seedling mortality in cowpea. About 75% seedling mortality is generally found within 21 days after sowing of the crop. The disease is favored during cool, wet, and overcasted weather conditions. However, overcasted weather is most favorable, and generally, pre- and postemergence of the mortality is observed during this stage. Reddish brown lesions are observed with the hypocotyl regions that may spread to the entire seedling leading to watery collapse. Seed dressing with chloroneb (2 g per kg) is effective in controlling the disease (Singh and Allen 1979).

5.3

Bacterial Diseases

5.3.1

Blight

The disease caused by Xanthomonas axonopodis pv. Vignicola is widely distributed in Africa, the United States, and India resulting into 3–92% yield loss depending upon the genotype and stage of infection. The disease was reported first time from Tanzania in Africa during 1964 (Allen 1981), in the United States during mid of twentieth century (Nandini and Kulkarni 2016), and in Nigeria during the year 1975 (Williams 1975), and presently, it has been recorded from the entire cowpeagrowing regions (Bastas and Sahin 2017; Moretti et al. 2007; Nandini and Kulkarni 2016; Shi et al. 2016). It appears as water-soaked dots having yellow radiance and chlorotic borders (Okechukwu et al. 2010) on the lower surface of the leaf and several dots combined with each other during severe infection resulting into defoliation of plant. These dots are also seen on the pods ,which turn into dark green spots. The infected stem becomes cankerous near the ground and crackdown in later stage. Under severe conditions, the plant is badly affected becoming stunted and bushy and may die. The main effect of the infection is observed on the leaves followed by pods, seeds, and stems and depends on the susceptibility of the genotype (Claudius-Cole et al. 2014). Higher intensity of the disease has been observed with higher plant population. Seeds are the primary source of the disease, and sowing of infected seeds results into infected seedlings followed by mortality (Ganiyu et al. 2017). Besides

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the seeds, crop residues, perennial grasses, cereals, insect transmission, and contact from plant to plant may also be the source of inoculum (Moretti et al. 2007; Sikirou and Wydra 2004; Zandjanakou-Tachin et al. 2007). It has been observed that the landraces or the wild relatives of the crop have the sources of resistance for various diseases (Hegde and Mishra 2009), and both durable and multiple-disease resistance are available in it (Tanksley and McCouch 1997; Wiesner-Hanks and Nelson 2016). Therefore, landraces should be exploited for various purposes including search of disease or insect pest resistance or challenges for biotic and abiotic stresses (Dwivedi et al. 2016). The seed-borne pathogen may be destroyed by treating the seed with hot water (52°C) for 15 min. Seed treatment with bactericides, intercropping, and sowing of disease-resistant varieties are the best approaches to combat the disease (Sikirou and Wydra 2004). Seed treatment with mercuric chloride, antibiotic, and solar treatment have been useful for surface sterilization of infected seeds. Use of healthy seeds and sowing of resistant varieties are best approach to prevent and control the disease (Emechebe and Lagoke 2002) as chemical is very expensive and is also away from reach of smallholder farmers (Shi et al. 2016). Evaluation and development of bacterial blight-resistant varieties has been carried out regularly throughout the world (Deo-Donne et al. 2018; Durojaye et al. 2019).

5.3.2

Bacterial Spot

Bacterial spot caused by Xanthomonas sp. is widespread diseases of cowpea that occur in both wild and cultivated form. The infection is observed in form of tiny dark water-soaked lesions on the dorsal surface of the leaves. In the later stage, the lesions enlarge and become circular and cover the entire surface of the leaves. The highly infected leaves become yellowish and fell down. The disease spreads very fast during the rainy weather conditions or under heavily irrigated crop. It is a seedborne disease; therefore, sowing of resistant varieties is the best options to avoid the disease (Singh and Allen 1979).

5.4

Viral Diseases

Viral diseases have been the major constraints for large-scale cowpea production in tropical and subtropical countries (Mali and Thottappilly 1986) and impose severe effect on the crop. Various workers have reported about 40 viruses on cowpea worldwide (Lamptey and Hamilton 1974; Thottappilly and Rossel 1985; Jeyanandarajah and Brunt 1993; Hughes and Shoyinka 2003). Mottling of the leaves, yellow mosaic on the leaves, chlorotic and necrotic spots, and stunting are some of the typical symptoms of viral diseases in cowpea (Thottappilly and Rossel 1985), and losses due to the disease are estimated from 10–100 per cent (Rachie and Rawal 1976). Sowing of disease-resistant varieties is the best approach to manage the viral diseases (Fraser 1992), and identification of source of resistant is another

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best approach in the breeding of cowpea (Singh et al. 2003). A brief account of various viral diseases of cowpea is described below:

5.4.1

Cowpea Mosaic

This is one of the most common viral diseases of cowpea and is widely distributed in various parts of the world causing 40–90% yield losses. Various insect vectors including beetles have been associated in transmitting the cowpea mosaic viruses. Aphids of various species, that is, Myzus persicae, Aphis gossypii, and A. craccivora, were associated with the transmission of cowpea mosaic virus (Surekha et al. 2018). The infected plants have light yellow color leaves having necrotic or chlorotic local lesions. The severely infected may die, and 100% yield loss has been observed in the field. Sowing of disease-resistant varieties and healthy seeds, roguing, and destroying the infected plants are the best practice to avoid the disease. The disease may be avoided by removing the susceptible weeds from the field. Infected plant and insect vector should be removed to reduce the spread the disease. Foliar spray of monocrotophos or methyl parathion helps to control the horizontal spread of disease by checking the insect vector (Kumar and Narain 2005).

5.4.2

Cowpea Yellow Mosaic

The disease is caused by Alfalfa mosaic virus (AMV), but its incidence is limited to only 10%. It is transmitted through aphids, while the golden mosaic virus is spread through white flies. The infected plants have yellow mosaic leaves, and at later stage, it becomes stunted and deformed. Pods appearing on the plant also become yellow. The disease may cause up to 50% loss at severe conditions. Cowpea yellow mosaic virus may be control with similar cultural and chemical practices as described in cowpea mosaic virus.

5.5

Insect Pests of Cowpea and Their Management

Infestation of certain insect pests is responsible for poor yield and productivity of the crop, and it has been observed that about 85 insect and pests cause loss to cowpea (Oladejo et al. 2017). Pod-filling stage in cowpea can be reduced to protect the crop from insects without affecting seed yield and seed size (Singh and Allen 1979). Some insect pests are found at the certain growth stage of the crop, while others are found almost entire growth cycle. For example, the hairy caterpillar normally appears in the second and third week of July, while jassids come in the second and third week of August (Kumar and Narain 2005). Weevils are generally seen in the middle of August but went away in the first and second week of September. Grasshoppers are seen on the crop during the entire plant growth period. Dry spells

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of 20–35 are very crucial for the crop for termite attack; similarly, variable extent of humidity, sunshine, and cloudy weather are responsible for aphid attack. The extent of severity mainly depends upon the favorable conditions for the insect pest. It has been observed that the crop sown during 8–15 July has minimum infestation of jassids, white fly, and weevils (Kumar and Narain 2005). Delayed sowing has got higher chances of insect infestation; therefore, early sowing up to July 15–20 is recommended in the climatic conditions of Rajasthan (Kumar and Narain 2005). Several insect pests infest the crop during various plant stages, and aphids, flower thrips, cowpea pod borer, pod-sucking bugs, the cowpea weevil, and the leaf beetle are the important pre-harvest pests causing 20–60% yield losses (Kumar and Narain 2005). A brief account of some major insect pests associated with the crop is given below:

5.5.1

Pod Borer

Pod borer of Helicoverpa armigera species is widely distributed insect and is one of the serious pests of cowpea. Besides this, pod borers of the species Maruca testulalis and Cydia ptychor have also been reported on cowpea (Singh and Allen 1979; Bhat et al. 1988). The polyphagous caterpillars of pod borer target the young pods and foliage and penetrate and feed on the developing seeds in the pods or foliage. Single larvae may destroy 30–40 young pods before its growth to adult stage. In absence of pod and flower, the larvae may attack on the leaflets. Almost half portion of the caterpillar stuck into the pod and results into severe loss. Severely infested crop may have degraded quality of seeds with poor production (Dialoke 2017). Highest incidence of pod borer was observed during rainy season (Sharma et al. 2021) that attained peak positive within 2 weeks of its first appearance. The population of the insect may be control with the foliar spray of carbaryl (0.01%) or phosphamidon (0.04%). Spray of monocrotophos (0.04%) or quinalphos (0.05%) at flowering and pod filling stage gives good control against pod borer. Neem seed extract and monocrotophos have been found efficient in controlling the M. testulalis and C. ptychora (Bhat et al. 1988).

5.5.2

Leaf Hopper and Foliage Beetles

Leaf hoppers of Empoasca species such as E. kerri, E. dolichi, and E. kraerneri are found on cowpea in the tropical and subtropical regions of the world. All the species have almost similar appearance in general and infect the crop during the seedling stage. Yellow discoloration on the leaf vein and margins and twisting of leaves are some of the common symptoms of the infestation. Its infestation some time resembles with the viral infection as the severe infestation of the insect may lead to stunted plants (Singh and Allen 1979). Eggs are laid underneath the leaves that hatch within 7–10 days to start nymphal stage. Some of the leaf hopper-resistant cultivars have been identified (Singh and Allen 1979).

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Species of Ootheca mutabilis, O. bennigseni, Medythia quaterna, Lagria villosa, and Chlysolagria nairobana are some of the important foliage beetles found on cowpea crops. These are 4–6 mm long beetles and lay egg on the soil. The adult beetles feed on leaves, while larvae feed on the roots of the crop. Adult beetles are the carrier of viruses, while higher population of the beetles may lead to defoliation of the plants (Kumar and Narain 2005).

5.5.3

Thrips

Thrips of different species are one of the important insect pests of cowpea reported globally attacking the flowers or leaves (Jackai and Daoust 1986; Singh and van Emden 1979). Thrips of Megalurothrips sjostedti and Sericothrips occipitalis species attack on the crop during entire growing stages (Ezueh 1981). The nymphs and adults graze the epidermis and sap of the leaves resulting into spots of light brown on the leaf surface. The infested leaves become curly and dry. The insect also feeds on the flower buds and flowers leading to necrosis and abscissions and causes about 20–70% of yield loss (Singh and Allen 1980; Edema and Adipala 1996). Studies also revealed that the infestation of the thrips is related to the flowering cycle of cowpea (Ngakou et al. 2008). Thrip populations are generally higher during the dry periods as compared to humid period. Tobacco thrips, Frankliniella fusca, has also been reported on cowpea during the seedling stage (Sweeden and McLeod 1993; McLeod and Rashid 2012) that feeds on the young leaves of the crop. The effect of thrips can be seen within 2 to 3 weeks of planting (Chalfant 1976; Nilakhe and Chalfant 1982). The mouth parts of the thrips are designed in such a way so that it can puncture and mine the plant sap from the leaves. Although the damage from thrips is mostly seen at the seedling stage, but its effect becomes normal after 3 weeks of plant growth (Jones et al. 2010; McLeod and Rashid 2012). Cowpea intercropped with maize or sorghum has lower population of thrips. Early sowing of crop having early maturity period has also lesser infestation. Foliar spray of neem extract or chlorpyrifos during morning or evening hours is beneficial to reduce the thrip population (Kumar and Narain 2005). Biological treatments comprising of Metarhizium, mycorrhiza/rhizobia, and mycorrhiza/rhizobia/ Metarhizium have been found beneficial in controlling the attack of the insect (Ngakou et al. 2008).

5.5.4

Weevil

Weevil of the species of Callosobruchus maculatus has been reported one of the important insect pests on cowpea. It is also a cosmopolitan pest of stored leguminous seeds and is widespread throughout temperate and tropical parts. These insect chew the leaflets of cowpea and make holes on it. Its grubs feed on soil and crop roots, while adults feed on leaves, buds, flowers and young pods. Various species of

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weevils have been reported to have detrimental effect on cowpea but C. maculatus has been found to cause more damage (Baoua et al. 2012) infesting the seeds at field as well as stored conditions (Cheng et al. 2013) resulting into reduction of the quality and yield (Vales et al. 2014). It is small elongated beetle of reddish brown color having a whitish C-shaped larva. The insect damages the seeds and its quality by eating and enter into it by making holes. Therefore, storage of cowpea seeds is not preferred and is sold just after the harvest. The insect may be controlled by mixing the grains with 5% ash. It can be controlled by the application of phosphine, pyrethroid, and organophosphate insecticides (Gbaye et al. 2012; Lopes et al. 2016). Spray of malathion dust (20–25 kg per ha) may control the weevil population.

5.5.5

Aphids

Cowpea aphid, Aphis craccivora, is considered as the major crop pest (Huynh et al. 2015). It causes damage to plant by sucking sap and through virus transmission. It has been observed that A. craccivora is responsible to transmit about 14 legume viruses (Thottapilly et al. 1990). Small aphids of black color having glossy black legs white to pale yellow antennae are one of the common insect pests in cowpea found on pods or underside of leaves (Kumar and Narain 2005). Its adults are often wingless and are serious pest during kharif season. Aphid attack during the early growth of the crop and is dangerous resulting into reduction into yield due to reduced seed setting. The heavily infested leaves become yellow, wrinkled, and distorted and about 45–80% yield losses may occur. The salivary secretion of the insect provides platform for fungal development that affects the photosynthesis in the plant and other plant diseases (Kumar and Narain 2005). Insect feeds on the plant sap and badly affects the growth of the plant. Abnormality in flower, leaf, and buds has also been reported due to aphid invasion (Singh and Allen 1980). Cowpea varieties resistant to A. craccivora have been developed (Singh 1977), and responsible genes have been identified on the basis of quantitative studies (Pathak 1988) and confirmed by the quantitative trait loci (QTL) analysis (Huynh et al. 2015). An aphid resistance gene has been identified using RFLP marker (Myers et al. 1996) that may be used to combat the aphid problem in cowpea. Genetic studies on aphid resistance have also been done (Bata et al. 1987; Pathak and Krishna 1991; Huynh et al. 2015) to address the inheritance in cowpea aphids. Ouédraogo et al. (2018) reported that aphid multiplication is genotype-dependent; therefore, development of aphidresistant varieties has the immense value. Heavily infested plants should be pulled out from the field and destroyed to control the further spread of other diseases. Dimethoate at the rate of 0.04% has been effective in controlling aphid population in cowpea (Kumar and Narain 2005).

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Pod-Sucking Bugs

The insect also known as green vegetable bug belongs to the Nezara, Anoplocnemis curvipes, Riptortus, and Acanthomia species that is one of the important insect pests of cowpea (Singh and Allen 1979). A. curvipes is about 3 cm long bugs of black color and lays gray to black colored eggs in chain. Eggs are laid on the weeds and never on the cowpea crop. The adult of the bugs are very good fliers and feed on the sap of the green pods. Several species of Riptortus including R. fuscus, R. pedestris, R. linearis, and R. pilosus are found in Asia (Singh and Allen 1979). The adult bugs are of light brown color having white or yellow lines on the body and are of cylindrical in shape. Species of Acanthomia including A. tomentosicollis and A. horrid are important bugs causing damage to cowpea (Singh and Allen 1979). A. tomentosicollis is of brown in color and cylindrical in shape, while A. horrid is of gray colored and compact shaped having furry body. Both adults and nymphs of the bugs feed on the green pod sap. Large number of bugs can be seen feeding on a single flower. Nezara viridula is commonly known as green sting bug and is found in tropical and subtropical regions of the world. Although it is an important pest of soybean, but it has been found causing damage on cowpea (Singh and Allen 1979). The bugs lay eggs underneath the leaves in batches of 25–75 eggs. Its nymphs are glossy having bright spots, while adults are of green in color and triangular in shape. Both adults and nymphs of the bug cause damage and suck sap from the developing pods. The bugs are active during the morning hours. Infestation can be seen in form of pod shrivelling and pre-matured drying that can be confirmed by sign of feeding punctures on the pods. The bug may also be seen on the pods and beneath the leaves. The bugs are mobile and therefore difficult to manage. Early sowing intercropped with sorghum and green gram has been found to reduce the bug population in the field (Kumar and Narain 2005). Bugs can be collected manually or with the help of insect net during the flowering and pod formation stage from the field and killed to control the population. The foliar spray of plant extracts of cashew nut, garlic bulb, and bitter leaf has been found beneficial.

5.5.7

Blister Beetle

Various species of the genus Mylabris are responsible to damage the cowpea throughout world. Generally, M. farquharsoni is found in Africa and M. pustulata in Asia (Singh and Allen 1979). The insect secrets a chemical that causes itching upon its touch results into large blister within few hours. It is a small elongated insect and narrow in shape. Bright elytra having broad black, yellow, or red bands on its back are the common characteristic of the insect. The beetle feeds on the flowers of cowpea and damage the flower. Higher population may lead to severe damage in the field. The adults are harmful and feed on buds and flowers of the crop, while its larvae are nondestructive (Singh and Allen 1979).

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It is a minor pest, and its control is difficult. The beetles may be collected manually or through insect net and killed. The foliar spray of aqueous extracts of Zanthoxylum zanthoxyloides, Allium sativum, Datura metel, and Annona senegalensis has been found effective in managing the beetles (Degri et al. 2010).

5.5.8

Bean Fly

Bean fly (Ophiomyia phaseoli) is a small (2 mm) unobtrusive insect of black color and is difficult to notice. The adults and larvae of the fly cause damage to the seedlings of the crop during the first 2–3 weeks of seedling emergence. The fly feed on the young leaves and lays white and oval shaped eggs by making a hole and completes its life cycle (Kumar and Narain 2005). The plants have weak growth and may dry and fell in later stage. Its infestation is difficult to identify on the basis of leaf symptoms; however, dark streaks can be seen on the petiole. Its infestation is specific on the stems causing swelling on the stem at ground level. The larvae of the fly enter from this place making a hole. The pupae come out by cracking the stem of the plant. The field should be free from debris to avoid the fly. Application of granular insecticides is found effective in the management of bean flies (Kumar and Narain 2005).

5.5.9

White Fly

The fly is common in the pulse-growing state and feeds on the plants. It is a major carrier of yellow mosaic virus. The symptoms are seen form of yellowing of leaves and stunting growth of the plant. Various insecticides, namely, monocrotophos, dimethoate, disulfoton, and phorate, may be used to control the population of the fly. Monocrotophos has been found more effective in controlling the white fly. It may be applied (at the rate of 0.25 kg active ingredient per ha) thrice at the interval of 15 days from 15 days of sowing (Kumar and Narain 2005).

5.5.10 Jassids Its Empoasca kerri species is the most common species of jassids that are found in almost all the kharif pulses grown in India. It is a sucking pest that sucks the leaf sap and deteriorates the shape of the leaflets. The leaves become brown and dried upon heavy infestation. Quinolphos, carboryl, and dimethoate are some of the insecticides that can be applied to control the population. Application of aldicarb during the sowing of crop and foliar spray of monocrotophos has been found more effective in controlling jassids in cowpea (Kumar and Narain 2005).

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5.5.11 Cut Worm It is polyphagous insect and cuts the seedlings from the ground level resulting into heavy loss to the plant population. It may be controlled by mixing chlorpyrifos during the planting of crop, or methyl parathion dust may be applied as foliar spray during the evening (Kumar and Narain 2005).

5.5.12 White Grub The insect is generally found in loose soils having rich decaying organic matter and active root feeders. In the presence of unrotten organic matter, its population rises. The young grub of the insect start damaging the root regions of the crop soon after the hatching. The young plant suddenly dried up and can be easily pulled out from the soil, while older plant has got yellow foliage. The beetle may be attracted through light during the night and trapped. The trapped insects may be destroyed (Kumar and Narain 2005).

5.6

Striga Gesnerioides

It is a parasitic weed commonly known as witch weed having many species, but S. hermonthica, S. asiatica, and S. gesnerioides are the common species occurring in the leguminous field. S. gesnerioides is commonly found with cowpea and is considered as the most common parasitic angiosperm weed (Emechebe et al. 1991; Lagoke et al. 1994). The weed is of about 15 cm high; however, some taller plants have also been reported. The bushy pale to dark green plants have pink flowers and small leaves. The tiny brown seeds of the weed remain viable in the soil and take 6 months to break the dormancy. It germinates in the contact of roots of young plants of cowpea. The germination of the weed seed is triggered with chemicals released by the roots of host plant. The plant does not take much time to flower and produces more than 20,000 seeds. The yield loss due to the parasitic weed is reported to the tune of about 44% (Muleba et al. 1997). Its control is very difficult and cumbersome. Reduction of Striga seeds in the soil is the best approach to control the weed. It may be possible by crop rotation with nonhost striga cultivars (Berner and Williams 1998; Berner et al. 1999) such as Cajanus cajan, Lablab purpureus, Sphenostylis stenocarpa, and Sorghum bicolor. The field having enhanced soil fertility has been observed with lesser attach of the weed. Hand weeding is also recommended to control the weed (Kumar and Narain 2005).

5.8 Storage Grain Pest

5.7

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Nematodes

Cowpea is susceptible to various nematodes, and reports revealed that nine species (Florini 1997) to 51 species (Caveness and Ogunfowora 1985) of different genera of parasitic nematodes are associated with cowpea; therefore, the crop should not be planted repeatedly on the same land (Kumar and Narain 2005). Various species of Meloidogyne, namely, M. javanica, M. areneria, and M. incognita (Sarmah and Sinha 1995; Khan et al. 1996; Adegbite et al. 2005), are the important root knot causing pathogens. Due to root-knot nematodes, root of the plant becomes knotted and galled, and its symptoms appear as nutrient deficiencies with stunting and wilting of the plants. The infected plants die prematurely due to extensive damage to the root. The root becomes unable to absorb nutrient and water from the soil. Yield reduction from 20 to 60% has been recorded due to nematode infestation at various conditions (Caveness 1979; Ogunfowora 1976; Babatola and Omotade 1991; Adegbite et al. 2005). Crop rotation, fallowing, sanitation, weed control, and sowing of resistant varieties are the best approach to control the nematodes. Significant reduction in the hatching of larvae of Meloidogyne javanica and its increased mortality have been observed with the application of Bacillus species (Dawar et al. 2008). Bacillus subtilis exhibited higher inhibition of knots and showed increased growth parameters, namely, shoot length, root length, shoot weight, and root weight. Studies revealed that several plant derived extracts, that is, Anacardium occidentale, Gmelina arborea, Azadirachta indica, and Chromolaena odorata, are effective in controlling the species of Meloidogyne (Onifade and Fawole 1996; Olabiyi et al. 2007).

5.8

Storage Grain Pest

Bruchids of the species of Callosobruchus has been reported as the major insect pests on cowpea and is widespread throughout temperate and tropical parts. These insects feed in the field and stored seeds as well. Callosobruchus maculatus has been reported one of the important insect pests on cowpea, while C. chinensis and C. analis have been observed lesser on cowpea (Johri et al. 2010). During the fecundity and host preference of C. chinensis (Qazi 2007), it was observed that the host preference for cowpea was lower as compared to pea, green mung, black gram , and black bean. It attacks the matured and dry pods and makes round holes. Eggs can be seen on the pods and stored seeds. Cowpea is one of the preferred legumes of C. maculatus. Selection of cowpea varieties against bruchids has been done, and some of the resistant varieties have been identified (Kumar and Narain 2005). Seeds treated with different oils, namely, coconut, groundnut, safflower, and mustard, have exhibited mortality of eggs at the surface, but it has no effect on the eggs that have entered into seeds. Similarly, neem leaf powder and malathion dust have been found effective. However, malathion dust has prevented the infection for 8 months. The grain should be dried properly before storage. It may be stored in

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earthen containers sealed with earthen lids or covered with sand or ash. The grains should also be treated with neem oil or linseed oil before storage in a sealed bag (Kumar and Narain 2005).

5.9

Disease and Pest Linked Resistance Markers

Marker-assisted selection is a choice of molecular markers to detect the target trait linked to resistance. Identification of disease and pest linked markers is the best strategy to combat the problems of disease and insect pest in cowpea. Various studies have been conducted to find molecular markers that are linked to resistance traits to cowpea parasitic weed Striga gesnerioides (Ouedraogo et al. 2001; Boukar et al. 2004) and aphid infestation (Singh and Allen 1980; Myers et al. 1996). Some QTL of resistance to disease and insects have also been identified. Agbicodo et al. (2010) identified three QTLs, namely, CoBB-1, CoBB-2, and CoBB-3 on LG-3, LG-5, and LG-9 linkage groups, respectively, associated with bacterial blight resistance (CoBB) loci in cowpea using single nucleotide polymorphism (SNP) with 282 SNP markers. Similarly, QTL for resistance to Thrips tabaci and Frankliniella schultzei have been identified on linkage groups 5 and 7 on the basis of AFLP genetic linkage map (Muchero et al. 2010). In another study, Muchero et al. (2011) reported QTL for Macrophomina phaseolina resistance and maturity in cowpea.

5.10

Termites

Termites are the common problem in arid and semiarid regions. Drought or dry spell worsens the situation. Soil amendment with chlorpyrifos before sowing is one the best approaches to control the termite population in the field (Kumar and Narain 2005).

5.11

Integrated Pest Management

Integration of various components, that is, early sowing, appropriate agronomic practices, application of insecticides, plant extracts, and sowing of disease-resistant varieties, may lead to effective control of insects and pest of cowpea with minimum inputs. A brief outline of integrated pest management for the crop is given below: • Deep summer ploughing and soil solarization in the month of May are effective to eradicate latent stages of pests and soil-borne nematodes. • Sowing of crop in the first or second week of July to avoid pest population. • Sowing of recommended and short duration varieties to avoid disease incidence. • Row sowing at proper depth is effective for better establishment of the crop and simultaneously for performing better against the pathogens.

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• Crop rotation, field sanitation, and proper drainage are the best approaches to avoid the disease incidence including seedling blight. • Application of neem cake, neem aqueous, and neem seed powder is useful in preventing the insects and pests. • Application of neem seed pellets (200 kg per ha) in the furrows at the time of sowing and spray of neem extract at the initial stage of crop growth is effective against various insect pests including termite, white grub, red hairy caterpillar, etc. • Roguing of diseased plants, destruction of egg mass, larvae, infected leaves, and removal of crop residues are the best approach to avoid the spread of the diseases. • Seed treatment with Trichoderma viride to prevent the crop from soil-borne fungal infection. • Spray of streptocycline and mancozeb may be done to at the appearance of bacterial leaf blight and Alternaria blight, respectively. • Fertilizer and approved labeled pesticides/insecticides should be used in balanced doses. • Spray of monocrotophos (0.03%), dimethoate (0.03%), or demtonmethyl (0.05%) may be done at the first appearance of the symptoms to control the nymphs and adults of jassids, thrips, aphids, and white fly.

References Abdon YA, Hassan SA, Abbas HK (1980) Seed transmission and pycnidial formation in sesame wilt disease cause by M. phaseolina Maubi. Agric Res Rev 52:63–69 Adandonon A, Aveling TA, Tamo M (2004) Occurrence and distribution of cowpea damping-off and stem rot associated fungi in Benin. J Agric Sci 142(5):561–566 Adebitan SA, Ikotun T (1996) Effect of plant spacing and cropping pattern on anthracnose (Colletotrichum lindemuthianum) of cowpea. Fitopatol Bras 21:5–12 Adegbite AA, Amusa NA, Agbaje GO, Taiwo LB (2005) Screening of cowpea varieties for resistance to Meloidogyne incognita under field conditions. Nematropica 35:155–159 Agbicodo EM, Fatokun CA, Bandyopadhyay R et al (2010) Identification of markers associated with bacterial blight resistance loci in cowpea [Vigna unguiculata (L.) Walp.]. Euphytica 175: 215–226 Agrios GN (2005) Plant pathology, 5th edn. Academic Press, London Alagarsamy G, Sivaprakasam K (1988) Effect of antagonists in combination with carbendazim against Macrophomina phaseolina infection in cowpea. J Biol Control 2:123–125 Allen D (1981) Two bacterial diseases of cowpea in East Africa: a reply. Int J Pest Manag 27:144 Allen DJ, Lenne JM (1998) Diseases as constraints to production of legumes in agriculture. In: Allen DJ, Lenne JM (eds) Pathology of food and pasture legumes. CAB International, Wallingford, pp 1–61 Amadi JE (1995) Chemical control of Cercospora leaf spot disease of cowpea (Vigna unguiculata [L.] Walp.). Agrosearch 1:101–107 Amadioha AC (1999) Evaluation of some plant leaf extracts against Colletotrichum lindemuthianum in cowpea. Arch Phytopathol Plant Prot 32:141–149 Anilkumar TB, Chandrashekar M, Saifulla M, Veerappa KB (1994) Assessment of partial resistance in cowpea cultivars to leaf spot (Septoria vignicola Rao). Trop Agric 71:36–40 Arif A, Goode MJ (1970) Systemic chemical control at cowpea powdery mildew. Plant Dis Rep 54(4):340

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6

Physiology and Abiotic Stresses

Abstract

Cowpea is a crop of the arid and semiarid regions of the world and has tolerant capacity toward various physiological and abiotic stresses. However, better seed production can be realized by addressing various issues related to physiological and abiotic stresses. Physiological aspects associated with seed color, germination and seedling growth, seed yield, and storage along with effect of heavy metal, water stress, drought condition, and salinity on seed yield have been discussed in this chapter.

6.1

Introduction

Several physical and/or chemical factors such as temperature (higher and lower), water (deficiency or excess), salinity, and heavy metals impose negative impact on the plants. These factors are collectively known as abiotic stresses and have negative impact on the crop yield and its performance (Wania et al. 2016). Plant species have developed various mechanisms to cope up with these stresses. Abiotic stresses are becoming major concern under the changing climatic conditions, increasing pollutions, and salinity (He et al. 2018). Soil salinity, drought, and water stress are major factors influencing the crop production (Guo et al. 2018). It has been observed that abiotic stresses have varied response on different plant parts; therefore, its effect is screened on leaves, shoot, and root of the plants (Singh et al. 1999). Since cowpea is commonly cultivated in the semiarid regions under water scarce conditions, its potential against various abiotic stresses makes it a choice of crop of the farmers of arid and semiarid regions. Drought-tolerant capability and comparatively small (estimated at ~620 Mb) nuclear genome size (Arumuganathan and Earle 1991) of cowpea make it model crop to look into the molecular mechanisms for drought tolerance in other crops. Cowpea is comparatively well adapted to high temperatures # The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 R. Pathak, Genetics, Physiology and Cultivation of Moth Bean, Cowpea and Horse Gram, https://doi.org/10.1007/978-981-19-9956-7_6

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and drought conditions (Hall 2004), but inconsistent rainfall is the major constraint in better yield. Several studies have identified the effect of abiotic stresses on the morphological, biochemical, and physiological traits in cowpea (Matsui and Singh 2003; Slabbert et al. 2004; Souza et al. 2004; Hamidou et al. 2007).

6.2

Seed Coat Colour

Environmental factors affect various quantitative traits including seed coat color in plants (Chalker-Scott 1999). Seed coat color has been related to the leakage of substances during seed imbibition (Asiedu and Powell 1998). The color of seed coat also plays important role on the germination (Debeaujon and Koorneef 2000). White-colored seeds have been observed to imbibe more water as compared to dark seeds (Mabhaudhi and Modi 2010) and exhibit low emergence rate. Cowpea has varied seed coat colors that have relevance in germination and longevity capacities. Cowpea may be classified on the basis of color of its seed coat. Molecular studies revealed that the accessions of cowpea having similar seed coat color were grouped in similar clusters (Adetiloye et al. 2013; Zannou et al. 2008). Black, red, and brown seed coat color in cowpea were dominant over the cream seed coat color (Oluwatosin 2000), and it was also observed that cowpea cultivars having cream seed coat color when crossed with black, red, and brown seed coat color cultivars behave differently. Several genes are reported to be associated with the inheritance of seed coat color in cowpea (Mustapha 2009; Egbadzor et al. 2014). Seed coat color has been reported to affect germination (Debeaujon and Koorneef 2000) and water absorption. Lower water uptake has been reported in dark colored seeds of legumes due to the presence of phenolic compounds (Chachalis and Smith 2000). The significant association among various seed yield attributes and seed coat color has been reported in cowpea revealing the importance of trait in the breeding program (Egbadzor et al. 2014).

6.3

Germination and Seedling Growth

Seed germination, early seedling emergence (Ahmaed and Suliman 2010), seed development, and maturation (Alqudah et al. 2011) are very crucial stages, and occurrence of drought during the stage may badly affect the seed quality. Therefore, it was suggested that seeds should be of good quality so that it may quickly and uniformly germinate even under adverse conditions (Fischer and Turner 1978). Germination ability and vigor are the inherent property and major quality of a seed. These qualities are governed by various factors occurring during the seed developmental stage, harvest stage, and during storage time (Tekrony 2003; Powell et al. 2005). Various abiotic conditions such as temperature, water deficit, photoperiod, soil fertility, etc. may influence the seed properties (Wulf 1995). Various workers have also reported that water stress during reproductive stage had detrimental effect on seed vigor and germination (Younesi and Moradi 2009; Drummond et al. 1983). Higher temperatures during the stage of seed development lead to early

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pod ripening and fast seed maturation resulting into small, poor quality seeds, lower germination, and vigor in legumes (Siddique and Goodwin 1980). The physiological quality of the seeds indirectly controls the crop production (Shaibu and Ibrahim 2016) through fast seedling emergence, plant vigor, and plant stand revealing the importance of seeds having high physiological quality to improve crop production (Adebisi et al. 2013). Plant growth regulators play important role in promoting the growth of plant including germination, vigor, seeding growth, etc. Gibberellic acid (GA3) has been widely used to evaluate germination and vigor of plant seeds, and enhanced growth and yield have been observed. Cowpea seeds treated with 20 ppm of GA3 showed better performance for germination percent, germination index, shoot length, root length, seedling length, seedling fresh weight, seedling dry weight, and vigor index (Thorat et al. 2017). Studies on germination and initial growth of cowpea cultivars under osmotic stress and salicylic acid (De Araújo et al. 2018) to assess morphophysiological changes revealed that salicylic acid reduced the detrimental effects of abiotic stress and enhanced the germination percentage, seedling height, chlorophyll, proline, and carotenoid content under induced water stress conditions.

6.4

Storage

Storage of seeds is essential to maintain steady supply throughout the year, availability of seeds during scarcity, and next cropping season simultaneously to get profit from the stored seeds (Vitis et al. 2020). The potential storage of cowpea mainly depends on moisture content in the seeds before its storage. The seeds having lower moisture content are good for storage. Cold storage is the best ways to store the seed for future use. The seeds are stored in air tight polyethylene bags to avoid the infestation of Callosobruchus maculatus (Freitas et al. 2016). Polyethylene terephthalate bottles may also be used for small-scale storage of grain. Storage in these containers improves the quality of preserved grains as it prevents the gas exchange with the environment (Freitas et al. 2016). Silva et al. (2018a) observed that storage of cowpeas in polyethylene bags and polyethylene terephthalate bottles effectively controls the C. maculatus and retains the quality of cowpeas for at least 120 days of storage. Although cold storage is considered as one of the best technologies for storage of postharvest produce including cowpea (Carvajal et al. 2015), but low temperatures may cause chilling injury to the pods of cowpea and make it susceptible to rusty spots and diseases (Fan et al. 2016). Studies showed that the immature seeds and pods of cowpea may be stored for 7 and 14 days, respectively, at 4 and 8°C (Collado et al. 2019). Although microwaving slightly affects the phenolic content and antioxidant capacity of cowpea seeds, but it was found that it is useful in the degradation of non-nutritional factors such as raffinose (Collado et al. 2019).

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6 Physiology and Abiotic Stresses

Water Stress and Drought Tolerance

Drought stress is mainly caused by disparity between requirements of water supply and demand, which is the major characteristics of arid or semiarid regions. Besides this, irregular distribution of rainfall also leads to adverse conditions for plant growth and yield. Out of several abiotic factors including drought, flood, low and high temperatures (Lawlor 2002), salinity, excess radiation, toxic heavy metals, and excessive macro- or micronutrients (Cramer et al. 2011), drought has been considered as the most significant abiotic factor restraining the crop production (Kramer and Boyer 1995; Reddy et al. 2004). Similarly, scarce water availability leads to nutrient deficiency and reduction in the photosynthesis resulting into energy starvation in the plant. Drought conditions lead to drying of soil and result into decreased plant water uptake and affect the plant tissues, photosynthesis (Xu et al. 2010), damage of root system, and disturbance within the integrity of cell membrane. The severe conditions may also lead to suppression of rhizobia. Sustained drought period disturbs and weakens the plant growth, decreases its capacity, and makes the plant more vulnerable to insect and pest attack. Plants under drought conditions had higher level of antioxidant metabolites and enzymatic activities to cope up with the stress. Studies found that the leaflet position in cowpea changed to paraheliotropic and orientated parallel to the sun rays under drought conditions to make the plant cooler and lessen the transpiration (Shackel and Hall 1979) for minimizing water loss. Drought stress results in low pod density and small seeds leading to reduced seed yield in cowpea (Turk et al. 1980). It may be due to the changes in the seed compositions caused by drought stress that affect the seed vigor. Delayed leaf senescence also plays important role in drought tolerance during reproductive stage (Gwathmey et al. 1992), recovers the plant after drought stress, and develops second flush of pods (Gwathmey and Hall 1992) in cowpea. Cowpea has been reported to evade both atmospheric and soil drought (Turk and Hall 1980). The early maturing varieties of cowpea are more advantageous and useful for dry areas due to their ability to escape the drought period (Hall and Patel 1985) and insect pest infestations (Ehlers and Hall 1997). The effect of carbon isotope discrimination on cowpea revealed that genotypes having more photosynthesis rate result in more absorption of internal carbon dioxide in their leaves (Hall et al. 1997; Condon and Hall 1997), and these genotypes showed more productivity. Although the crop has deep rooted system, but roots develop vertically leading to the water stress. The water uptake of the crop is lower; therefore, it is suitable for water scarce situations. Flowering stage and pod-filling stages of cowpea are more sensitive to water stress (Figueiredo et al. 1999). Cowpea has been reported to drought susceptible during pod set stage, and lower night temperature may cause damage to heat-susceptible cultivars. Studies suggest that cowpea is a dehydration escaper and exhibit robust stomatal compassion (Lawan 1983). Several dehydration avoidance strategies (Ludlow and Muchow 1990; Petrie and Hall 1992; Singh and Matsui 2002) have also been reported in cowpea to survive under drought stress. The dehydration avoidance strategy, namely, stomatal closure, reduced leaf growth, and leaf senescence, reduces water loss and increases roots to maintain the water

6.5 Water Stress and Drought Tolerance

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requirements of the plant (Blum 2005). Significant genetic variation has been observed at seedling stage in response to drought stress in cowpea (Muchero et al. 2008). Accumulation of proline has been reported during biotic and abiotic stresses (Szabados and Savoure 2009). The cowpea plants under drought stress elongate their roots in search of water and retard the other vegetative growth (Onuhm and Donald 2009). Several morphological characters, namely, plant height, number of leave and leaf expansion, stem elongation, and leaf area index, are also affected due to drought stress (Loka et al. 2011). Severity of water stress and developmental stage of cowpea are the important factor in the growth of the crop (Hsiao and Acevedo 1974). The water deficiency in the field disturbs the respiration and affects the plant development that can be observed as stomatal closure, withering of leaves, and poor photosynthesis process (Sutcliffe 1980; Santiago et al. 2001). Water stress imposes negative effect on every stage of plant growth and development (Kramer 1983) leading to low productivity. The extent of effect may vary from species, degree of tolerance, and magnitude of stress (Figueiredo et al. 1999). Water deficiency is one of the important limitations in crop production that has considerable effect on the growth, yield, and quality of cultivated crops (Sousa et al. 2015; Ramachandiran and Pazhanivelan 2016). Various plant species develop different mechanism to cope up with the water-deficit conditions including reduction of leaf size, number of stomata, and stomatal conductance (Afzal and Kumar 2015). Biological nitrogen fixation in cowpea (da Gomes et al. 2001) and reduction in leaf chlorophyll content (Sanchez et al. 1983) have been reported to be affected due to water stress. Nodulation in cowpea has also been found associated with the soil water content along with other components (Onuhm and Donald 2009) and affects the nitrogen fixation. Considerable water-deficit tolerance has been observed at various growth stages of cowpea, namely, vegetative, flowering, and pod filling stage (Ahmed and Suliman 2010). Leaves of the crop are highly affected due to water deficiency, and senescence and abscission have been reported (Ram et al. 2016). The vegetative, flowering, and pod-filling stages are the most sensitive stage to water stress in the production of cowpea (Ong 1984; Mousa and Qurashi 2018). It was observed that number of seeds per pod reduced up to 72% due to water stress during vegetative and reproductive stage of the crop (Ahmed and Suliman 2010). Reduction in seed yield has also been observed in the range of 35–69% due to imposed water stress during various growth stages of cowpea (Warrag and Hall 1984; Aboamera 2010). Mousa and Qurashi (2018) observed highly negative effect of water stress on growth and yield of cowpea during vegetative, flowering, and pod-filling stages. Guimaraes et al. (2018) studied the structural and productive characteristics of cowpea under different water availabilities. The water availability on the range of 78.5–84.5% offers the optimum soil water retentions for better growth and development of the crop. Plant acquires various resources of the soil through its root system. Abiotic stresses particularly drought stress have direct impact on the root systems or patterns of the plants (Matsui and Singh 2003). The alteration in the root architecture provides an understanding for the performance of genotypes; however, impact studies based on root system architecture (RSA) on the performance of cowpea are

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limited (Burridge et al. 2016, 2017). Studies based on RSA may help in the development of crop production under the changing climatic scenario (OrmanLigeza et al. 2014). Assessment of genetic diversity in cowpea for RSA characteristics associated to growth of the crop in poor soil and arid conditions has been described (Krasilnikoff et al. 2002, 2003; Matsui and Singh 2003). The root traits related to the soil phosphorus and its use efficiency have been categorized (Kugblenu et al. 2014). Deep root systems have been found advantageous under drought conditions (Matsui and Singh 2003; Agbicodo et al. 2009). Adu et al. (2019) identified some key contributing root system traits, namely, soil and root tissue angle-related traits, shoot and root diameter-related traits, root biomass, hypocotyl root length, root count, and lateral root density-related traits for the genetic diversity in cowpea, and suggested that identification of root traits may help in the quick screening of populations in the field.

6.6

Salt Tolerance

Salinity is one of the major constraints in semiarid and arid regions due to erratic and lower rainfall conditions. The seedling stage of the crop is more susceptible for salinity and affects the growth and development of the plant. However, it was observed that sodium chloride has no general detrimental effect on the growth of cowpea due to reduction in the total chlorophyll content and photosynthesis rate (Kannan and Ramani 1988). Cowpea genotypes may be categorized into salt tolerance during the early seedling stages on the basis of germination percentage (Murillo-Amador et al. 2001). Substantial variations have been reported for various parameters in the cowpea cultivars, namely, leaf area, leaf dry weight, steam dry weight, and root dry weight on the basis of salt tolerance (Wilson et al. 2006). Salinity-tolerant genotypes of cowpea avoid the sodium ions to accumulate in the leaves (Praxedes et al. 2009). Cowpea genotypes varied in response to salt tolerance showing their competence toward the stress (Win and Oo 2015; da Silva et al. 2016; Tsague et al. 2017; Ravelombola et al. 2018; Islam et al. 2019) and revealed the presence of genetic differences with respect to salt stress. Salinity has direct impact on the plant height and fresh shoot biomass (Ravelombola et al. 2017; Dong et al. 2019) and increases the chlorophyll content. Reduction of seedling growth and relative water content was recorded with the 75 mM NaCl concentration; however, its effect was different on different cultivars (Win and Oo 2015). Cowpea has been observed salt tolerant at germination and maturity stages, but it is sensitive during early seedling and vegetative growth stage of the crop (Ashraf 1994; Win and Oo 2015). Salinity has adverse effect on the germination of cowpea and simultaneously reduces the crop production (Ravelombola et al. 2017). Contrarily, it has also been observed that the genotypes of different crops including cowpea performing better under salt stress conditions have yielded higher biomass and yield (Krishnamurthy et al. 2007; Ilori 2017). Development of salt-tolerant varieties of cowpea may be the best approach to reduce the influence of salinity stresses. Further, the molecular studies revealed that

6.7 Other Abiotic Stress

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salt tolerance in the cowpea genotypes is controlled by QTLs, and single nucleotide polymorphisms may be used as one of important techniques during marker-assisted selection for development of salt-tolerant varieties of cowpea (Ravelombola et al. 2018). Salt stress has imposed negative impact on seed germination and its process along with reduction in the radicle length, plumule length, plant height, and biomass yield of the cowpea genotypes (Islam et al. 2019).

6.7

Other Abiotic Stress

Crops are the main target of several pollutants, chemical fertilizers, industrial effluents, and several other human activities. These toxic elements enter in the plant through soil or environment (Arshad et al. 2008). Irrigation with contaminated water, industrial emissions, and transportation may lead to heavy metal contamination that is dangerous not only to the plants but also to food chain (Arora et al. 2008; Srivastava and Chopra 2014). Some of the heavy metals, namely, iron, zinc, copper, and nickel, have immense values in the effective action of biological systems, but their shortage and excess quantity may be harmful for the functioning of the system (Singh et al. 2012). Copper is essential metal for protein components (Marschner 1995), but its higher concentration in the soil causes toxicity and inhibits plant growth including cowpea (Kopittke and Menzies 2006). Irrigation of crop with effluent water having unwanted metals adversely affects the soil and food quality and causes serious concern to the safety (Muchuweti et al. 2006; Srivastava and Chopra 2014). Cowpea has also been reported to have lower accumulation of heavy metals as compared to other vegetables (Itanna 2002; Muchuweti et al. 2006). Effect of different concentration of mercury exposure on seed germination, early seedling growth, metabolite level, enzyme activities, and on uptake of heavy metal of cowpea seeds was studied under controlled environment (Umadevi et al. 2009), and it was observed that mercury had adverse effect on projection of radical, delayed the germination process, and hampered the plant growth. Mercury was found more toxic to the root and shoot of cowpea. The influence of silicon concentration was observed on the plant growth and nutritional quality of cowpea (Mali and Aery 2009), and it was reported that lower concentration of silicon has better effect on the yield, leaf area, chlorophyll, and iron content; however, proline content was reduced. Plants show defense to accumulation of heavy metal in the reproductive organs (Silva et al. 2013). Accumulation of chromium, nickel, cadmium, and lead has been reported in the plants including cowpea (Silva et al. 2013), but these are not translocated to the grains (Mortvedt 2001; Silva et al. 2013). Influence of selenium on crop yield is disputed. Its positive effect has been reported on the yield of cowpea (Manaf 2016). However, application of more than 50 g ha-1 selenium concentration has decreased the phloem diameter and palisade parenchyma thickness, and brown necrotic lesions were also observed subsequent to the trichomes (Silva et al. 2018b). Lead is an important toxic metal found in the soil and affects the crop yield. Lead tolerance was induced in cowpea through exogenous application of nitric oxide (Sadeghipour 2017), and it was observed that the lead toxicity has decreased the

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hormones such as auxin and gibberellic acid; however, it increased the abscisic acid in the plant cell. Lead has detrimental effects on stomatal conductance, leaf area, and reduced the seed yield in cowpea. Cowpea accessions were tested against iron toxicity in a ferruginous ultisol for growth and yield responses (Ifie et al. 2019), and significantly lower (up to 35%) yields were recorded with several accessions grown under the soil having higher iron concentrations. Besides this, plant growth was also suppressed by the iron toxicity. A study was conducted in Nigeria to assess the transfer of heavy metals from the contaminated soil of dumpsite to the plants of cowpea (Musa and Ikhajiagbe 2019), and it was observed that zinc concentration was below the World Health Organization (WHO) and National Agency for Food and Drug Administration and Control, Nigeria (NAFDAC), standards, while chromium, lead, and nickel concentration was higher than the WHO and NAFDAC standards. The transfer factor of heavy metals from soil to plant was higher within 45 days old plants of cowpea (Musa and Ikhajiagbe 2019). Cadmium is a soil pollutant and retards the plant growth. Cadmium toxicity tolerance in cowpea was studied, and the study revealed that the cadmium stress has detrimental effect on the cowpea plants (Sadeghipour 2020). Cadmium-stressed plants have reduced shoot length, leaf area, chlorophyll content, and relative water contents. The study also suggests that seeds treated with proline and glycine betaine have improved potential to diminish the cadmium toxicity (Sadeghipour 2020). The effect of foliarintervention of nano-TiO2 on Cd toxicity in cowpea plants was investigated, and enhancement in the chlorophyll was reported. The foliar application of nano-TiO2 has reduced the concentration of cadmium in the root, shoot, and grains of cowpea, but its concentration was higher than the recommended concentrations in the leaves (Ogunkunle et al. 2020). The stress enzyme activity, zinc, manganese, and cobalt level was also enhanced due to the foliar application of nano-TiO2 (Ogunkunle et al. 2020).

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Ram H, Singh G, Aggarwal N (2016) Effect of irrigation, straw mulching and weed control on growth, water use efficiency and productivity of summer mung bean. Legume Res 39:284–288 Ramachandiran K, Pazhanivelan S (2016) Abiotic factors (nitrogen and water) in maize: a review. Agric Rev 37:317–324 Ravelombola WS, Shi A, Weng Y et al (2017) Evaluation of salt tolerance at germination stage in cowpea [Vigna unguiculata (L.) Walp]. HortSci 52(9):1168–1176 Ravelombola W, Shi A, Weng Y et al (2018) Association analysis of salt tolerance in cowpea (Vigna unguiculata (L.) Walp) at germination and seedling stages. Theor Appl Genet 131:79–91 Reddy AR, Chaitanya KV, Vivekanandan M (2004) Drought-induced responses of photosynthesis and antioxidant metabolism in higher plants. J Plant Physiol 161(11):1189–1202 Sadeghipour O (2017) Nitric oxide increases Pb tolerance by lowering Pb uptake and translocation as well as phytohormonal changes in cowpea (Vigna unguiculata (L.) Walp.). Sains Malaysiana 46(2):189–195 Sadeghipour O (2020) Cadmium toxicity alleviates by seed priming with proline or glycine betaine in cowpea (Vigna unguiculata (L.) Walp.). Egypt J Agron 42(2):163–170 Sanchez RA, Hall AJ, Tripani Cohen DE, Hunau R (1983) Effects of water stress on the chlorophyll content, nitrogen level, and photosynthesis of leaves of two maize genotypes. Photosynth Res 4: 35–47 Santiago AMP, Nogueira RJC, Lopes EC (2001) Growth in young plants of mimosa caesalpiniifolia Benth. Grown under hydrical stress. Revista Ecossistema 26:23–30 Shackel KA, Hall AE (1979) Reversible leaflet movements in relation to drought adaptation of cowpeas, Vigna unguiculata (L.) Walp. Aust J Plant Physiol 6:265–276 Shaibu AS, Ibrahim SI (2016) Genetic variability and heritability of seedling vigor in common beans (Phaseolus vulgaris L.) in Sudan savanna. Int J Agric Policy Res 4(4):62–66 Siddique MA, Goodwin PB (1980) Seed vigour in bean (Phaseolus vulgaris L. cv. Apollo) as influenced by temperature and water regime during development and maturation. J Exp Bot 31: 313–323 Silva MDM, Araújo ASF, Nunes LAP et al (2013) Heavy metals in cowpea (Vigna unguiculata L.) after tannery sludge compost amendment. Chilean J Agric Res 73(3):282–287 Silva MGC, Silva GN, Sousa AH et al (2018a) Hermetic storage as an alternative for controlling Callosobruchus maculatus (Coleoptera: Chrysomelidae) and preserving the quality of cowpeas. J Stored Prod Res 78:27–31 Silva VM, Boletaa EHM, Lanzab MGDB et al (2018b) Physiological, biochemical, and ultrastructural characterization of selenium toxicity in cowpea plants. Environ Exp Bot 150:172–182 Singh BB, Matsui T (2002) Cowpea varieties for drought tolerance. In: Fatokum CA, Tawarali SA, Singh BB, Kormawa PM, Tamo M (eds) Challenges and opportunities for enhancing sustainable cowpea production. World Cowpea Conference III Proceedings, 4–8 September, International Institute of Tropical Agriculture, Ibadan, pp 287–300 Singh BB, Mai-Kodomi Y, Terao T (1999) A simple screening method for drought tolerance in cowpea. Indian J Genet 59:211–220 Singh R, Gautam N, Mishra A, Gupta R (2012) Heavy metals and living systems: an overview. Indian J Pharmacol 43(3):246–253 Slabbert R, Spreeth M, Kruger GHJ (2004) Drought tolerance, traditional crops and biotechnology: breeding towards sustainable development. S Afr J Bot 70:116–123 Sousa CC, Damasceno-Silva KJ, Bastos EA, Rocha MM (2015) Selection of cowpea progenies with enhanced drought tolerance traits using principal component analysis. Genet Mol Res 14: 15981–15987 Souza RP, Machado EC, Silva JAB, Lagoa AMMA, Silveira JAG (2004) Photosynhtetic gas exchange, chlorophyll fluorescence and some associated metabolic changes in cowpea (Vigna unguiculata) during water stress and recovery. Environ Exp Bot 51:45–56 Srivastava S, Chopra AK (2014) Irrigational impact of distillery effluent on Abelmoschus esculentus L. okra with special reference to heavy metals. Environ Monit Assess 186(7):4169–4179

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Genetic Markers and Biotechnology

Abstract

Genetic diversity studies have immense importance as it provides information for selection of suitable genotype for hybridization. Cowpea is a self-pollinated crop, and pollination in the flower usually occurs before the opening of flowers. Therefore, variation in the DNA polymorphism is not much expected. The crop has been widely exploited for genetic assessment using various molecular markers. A brief account of various marker techniques, namely, random amplified polymorphic DNA (RAPD), simple sequence repeats (SSR), inter simple sequence repeats (IRRs), DNA amplification fingerprinting (DAF), start codon targeted (SCoT), sequence-related amplified polymorphism (SRAP), restriction fragment length polymorphism (RFLP), along with biochemical markers used for different analyses in cowpea, has been described. Besides, these genetic linkage and genetic map studies carried out in cowpea have also been described in this chapter.

7.1

Introduction

Assemblage of germplasms from varied origin and environment, their characterization, and evaluation are the basic key to crop improvement programs. Various morphological characteristics including photosensitivity and adaptation are the major aspects of assessment of genetic diversity in any crop species. These characters are highly influenced by the environment and can be taken as total genetic diversity rather the insight of variability. Therefore, classification of germplasm of a species on the basis of morphological characteristics may not offer precise information of genetic divergence. Although very good information has been generated using the morphological characterization for various crop improvement programs, namely, crossing, hybridization, introduction, selection, and recombination # The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 R. Pathak, Genetics, Physiology and Cultivation of Moth Bean, Cowpea and Horse Gram, https://doi.org/10.1007/978-981-19-9956-7_7

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following pedigree, but these characters are found insufficient in the development of varieties having higher variability. Therefore, assessment of genetic diversity was moved from morphological to biochemical and molecular characterization. Genetic variability depends on inherited characteristics resulting into differentiation between plant materials (Van Hintum 1995). Genetic diversity studies have immense importance as it provides information for selection of suitable genotype for hybridization. Various studies have been conducted to assess the genetic diversity in cowpea using qualitative and quantitative, agronomic, and morphological traits but could not reveal tangible genetic relationships (Patil et al. 2013) as environmental conditions have more influence on the expression of these traits restraining the understanding of genotypic structure for specific ecological adaptations. Cowpea has been classified on the basis of protein variants, and various studies stating isozymes are carried out and found suitable for assessment of genetic diversity. DNA-based molecular markers including PCR-based markers, namely, RAPD (Prasanthi et al. 2012; Udensi et al. 2016), ISSR (Tantasawat et al. 2010), SSR (Badiane et al. 2012; Adetiloye et al. 2013), DAF (Simon et al. 2007; Spiaggia et al. 2009), and SRAP (Alghamdi et al. 2019), have been successfully carried out in cowpea. Besides, these genetic linkage (Saunders 1960a, b; Sen and Bhowal 1961) and genetic map (Andargie et al. 2011; Kongjaimun et al. 2012) studies have also been conducted in cowpea.

7.2

Biochemical Markers

Biochemical markers are mainly based on the protein markers and enzymatic studies. Various enzymes have been tagged with the genes resistant for diseases. Isoenzymes have been widely used in cowpea for different studies including populations, taxonomy, genetic relationship, and diversity studies. Isozymes have been considered a choice of biochemical markers for assessment of genetic similarity in various crops (Brown 1979) and have been widely used for population, taxonomic, genetic relationship, and variability studies. Cowpea seeds have good amount of lipoxygenase isoenzyme (Truong et al. 1979; Truong and Mendoza 1982). These enzymes were stable at wide range of pH ranging from 4–9 and under acidic solution for longer time. The activities of superoxide dismutase were increased in resistant cultivars of cowpea on inoculation with root knot nematode, and the number of isozymes remained similar upon electrophoretic analysis (Ganguly and Dasgupta 1988). Two protein pattern types (A and B) having different polypeptide bands and globulins have been reported in cowpea using seed protein profiling (Pedalino et al. 1990). Similarly, variability at polypeptide bands in the albumins has also been detected (Oghiake et al. 1993), but the total protein content remained unchanged. Genetic relationship on the basis of isozyme analyses was assessed within cowpea genotypes (Panella and Gepts 1992), and the observation revealed a key factor for taxonomic classification of cowpea. Isoenzymic variability has been assessed among cultivated and wild accessions of cowpea (Vaillancourt et al. 1993). The study

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revealed low magnitude (23.1%) of variation among cultivated accessions, while higher (73.1%) variability was recorded with the wild accessions. Cowpea has been reported to possess different isozymes as compared to other species of Vigna (Vaillancourt et al. 1993). Isoenzyme studies on identification of cowpea cultivars exhibited presence of adequate variability and allow isozyme electrophoresis as an important tool for cultivar identification in cowpea (Eeswara and Peiris 1994). Isozyme variability between various species of subgenus Vigna exhibited that V. unguiculata was more related to V. vexillata as compared to other species (Sonnante et al. 1996). The finding was also supported the belief that V. vexillata is the intermediate species between African and Asian Vigna species. Close relationship between V. unguiculata and V. vexillata has also been advocated by other workers (Vaillancourt and Weeden 1996). Presence of different patterns of enzymes and genotype-specific zymogram suggests that isozyme studies can be used to differentiate cultivars to complement morphological markers. Grouping of various Vigna species including cowpea on the basis of isozyme variability suggested that cowpea is the most divergent species. Isozymic diversity among Vigna vexillata studied on the basis of electrophoretic comparison suggested that it has some similarities with the gene pool of cowpea (Garba and Pasquet 1998). Isozymic variation among cowpea accessions of various countries was assessed, and eight enzymes were identified (Reis and Frederico 2001). The esterase zymograms helped in the identification of some accessions. Selvi et al. (2003) also suggested that the extent of genetic variability and relationship among accessions of Vigna species can be better understood on the basis of their isozyme variability. The morphological groupings were unable to differentiate the accessions into truer taxonomic manner. Salicylic acid has been observed to have negative effect on germination and seedling growth of cowpea (Chandra et al. 2007a). It has also been observed that salicylic acid has increased the peroxidase activities in cowpea. In another study, Chandra et al. (2007b) determined phenylalanine ammonia lyase (PAL) activities leading to reduce disease development caused by Rhizoctonia solani in cowpea after application of salicylic acid and observed increase in PAL activities with two application of salicylic acid, while total soluble protein was not affected. Foliar spray of brassinolide has been found effective to encourage antioxidant enzymes such as superoxide dismutase, peroxidase, and polyphenol oxidase resulting into mitigation of salt stress in cowpea (Aziz and Mohamed 2011). Cowpea seed protein types have been recorded with different variants, for example, glutelins had 21, albumins had 20, and globulins had 16 protein variants (Tchiagam et al. 2011), and these protein fractions had varied molecular weight (Gupta et al. 2014).

7.3

Molecular Markers

The studies on genetic diversity of cowpea have been carried out on the basis of different morphological and physiological traits (Ehlers and Hall 1997), allozymes (Panella and Gepts 1992; Pasquet 2000), seed storage proteins (Fotso et al. 1994),

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chloroplast DNA polymorphisms (Vaillancourt and Weeden 1992), random amplified polymorphic DNA (Nkongolo 2003; Diouf and Hilu 2005; Prasanthi et al. 2012; Udensi et al. 2016), restriction fragment length polymorphisms (Fatokun et al. 1993a; Ouedraogo et al. 2002a), amplified fragment length polymorphisms (Tosti and Negri 2002; Fang et al. 2007; Kolade et al. 2016), inter simple sequence repeat (Ghalmi et al. 2010), ISSR and SCoT (Igwe et al. 2017), simple sequence repeats (Lee et al. 2009; Asare et al. 2010; Adetiloye et al. 2013; Wamalwa et al. 2016; Chen et al. 2017a), and single nucleotide polymorphisms (SNP) (Muchero et al. 2009a; Carvalho et al. 2017). A brief account of these markers has been summarized below:

7.4

PCR-Based Markers

7.4.1

Random Amplified Polymorphic DNA (RAPD)

Various workers have employed RAPD to study the genetic relationships among cowpea genotypes (Samarajeewa et al. 2002; Diouf and Hilu 2005; Karuppanapandian et al. 2006; Chen et al. 2008; Prasanthi et al. 2012; Motagi et al. 2013). Combination of different markers, namely, RAPD, AFLP, and SAMPL, was used to assess genetic diversity among cowpea landraces (Tosti and Negri 2002), and the markers were found efficient revealing the wide range of genetic diversity. Study of genetic association between wild and cultivated Vigna spp. (Samarajeewa et al. 2002) and cowpea (Sharawy and Fiky 2003; Badiane et al. 2004) was carried out using RAPD markers, and higher level of genetic distances among accessions was observed. It was suggested that RAPD markers could provide better estimates of genetic relationships in cowpea. Sharawy and Fiky (2003) characterized six cowpea genotypes based on yield traits and RAPD markers and reported about 65% polymorphism. RAPD markers were found useful in eliminating the duplicate varieties and identifying the better varieties (Fall et al. 2003). The genetic characterization of Malawian cowpea landraces was carried out to assess the diversity and gene flow among accessions (Nkongolo 2003) on the basis of RAPD markers, and no relation between morphological and clustering pattern was observed. A set of 26 cultivated 30 wild accessions of cowpea from west, eastern, and southern Africa was subjected to RAPD analysis (Ba et al. 2004). The wild species collected from eastern Africa had more polymorphisms. Genetic diversity study in mutants of cowpea having diverse morphological characteristics was carried out using RAPD (Pandeay et al. 2004), and mutant-specific polymorphic markers were detected with high range of genetic diversity confirming the usefulness of mutants in cowpea. The cultivated cowpea and its wild progenitors were studied for genetic diversity individually and in combinations (Ba et al. 2004) using RAPD markers, and it was observed that wild accessions of cowpea have higher diversity as compared to cultivated accessions. Genetic diversity among local Senegal cowpea varieties and breeding lines was evaluated using RAPD and SSR makers (Diouf and

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Khidir 2005). Genetic diversity and genetic relationships among cowpea landraces from different geographical locations of Tamil Nadu were studied (Karuppanapandian et al. 2006) using RAPD, and about 25–100% polymorphism was recorded showing wider genetic diversity among the landraces. Though RAPD gave information on the genetic diversity, but SSRs were found effective in determining the relationship among cowpea. The genetic diversity in 70 cowpea accessions of cultivated cowpea collected from Benin was assessed using RAPD markers (Zannou et al. 2008), and wide genetic diversity was observed among the accession. Ghalmi et al. (2009) studied the morphological and molecular diversity within Algerian cowpea using RAPD markers and recorded a wide range (3–34%) genetic diversity. Similarly, genetic diversity among ten Indian cowpea cultivars was estimated (Malviya et al. 2012), and the genetic diversity ranged from 17 to 40% with the identification of some distinct cultivars. Prasanthi et al. (2012) evaluated genetic diversity in cowpea genotypes collected from different geographical regions of India using RAPD and recorded about 90% of polymorphic fragments indicating that the Indian genotypes of cowpea have broad genetic base. Khan et al. (2015) assessed genetic diversity of Bangladeshi landraces of cowpea using RAPD markers and observed that the genetic distances between landraces were interrelated with their source of origin with 55% polymorphism.

7.4.2

Simple Sequence Repeat (SSR)

SSR markers have been widely exploited for the assessment of genetic diversity in cowpea. Li et al. (2001) constructed microsatellite libraries of cowpea and isolated more than 100 microsatellite sequences. The sequences were used in the differentiation and estimation of genetic diversity of 90 cowpea breeding lines of International Institute of Tropical Agriculture (IITA), Nigeria. The Polymorphic Information Content (PIC) values ranged from 0.02 to 0.73 with a mean of 0.47 among cultivated cowpea. They observed that the markers are polymorphic and can be applied to differentiate the accessions of cowpea because the grouping of cowpea lines was on the basis of pedigree records. Kuruma et al. (2002) determined variation among and within cowpea populations on the basis of SSR markers and reported PIC in the range from 0.09 to 0.82 with a mean value of 0.34. The genetic diversity of 316 cultivated cowpea germplasms collected from China, Africa, and other Asian countries was assessed using SSR markers (Xu et al. 2007), and it was observed that the genetic diversity of Africa and other Asian countries was comparatively higher. Ogunkanmi et al. (2008) estimated the genetic diversity in 48 lines of wild cowpea collected from varied geographical locations in Africa using SSR markers and found that the accessions collected from Southern Africa had higher diversity suggesting that Southern Africa may be the core location of wild cowpea. Fatokun et al. (2008) assessed genetic diversity in cowpea and found PIC values from 0.29 to 0.87 with a mean value of 0.68 among 48 wild cowpea lines. Analysis of genetic diversity of 492 Korean landraces of cowpea was carried out using six SSR markers, and a core collection was established (Lee et al. 2009). In a genetic diversity and phylogenetic

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relationship study conducted using SSR markers (Asare et al. 2010) among 141 cowpea accessions of nine geographical areas of Ghana, the influence of geographical location was lower. Differentiation of Striga-resistant genotypes from susceptible cultivars is possible with the help of SSR markers (Sawadogo et al. 2010). In a study carried out for the development and polymorphism in asparagus bean (Vigna unguiculata ssp. sesquipedalis) using microsatellite markers (Xu et al. 2010), it was suggested that landrace germplasm may be utilized to improve genetic variability and long-term gains and decrease genetic vulnerability to pathogen or pest epidemics. Gioi et al. (2010) categorized 40 lines of cowpea into two major groups on the basis of microsatellite markers to study the genetic relationship among yellow mosaic virus (CYMV)-resistant cowpea lines and observed that the CYMV resistance group comprised of 18 cowpea lines with 77–100% similarity. The PIC values in their study ranged from 0.30 to 0.72 with a mean value of 0.34. The genetic diversity and phylogenetic relationships study among 22 local and inbred lines collected from Senegal carried out using SSR markers (Badiane et al. 2012) revealed that the clustering of accession was in conformity with the pedigree information of local as well as inbred lines. Adetiloye et al. (2013) studied the genetic diversity among 20 accessions of Nigerian cowpea using SSR marker and reported sufficient genetic variability. The genetic diversity in 19 cowpea accessions from Kenya National Gene Bank was assessed using SSR markers (Wamalwa et al. 2016), and high divergence was observed between accessions from Ethiopia and Australia as compared to the accession from Western Kenya, while lower variability was observed between accessions from Eastern and Rift Valley. SSR markers along with morphological characters were used to characterize 32 genotypes of cowpea under irrigated and drought conditions (Mafakheri et al. 2017), and about 76% of genetic similarity was observed among the genotypes.

7.4.3

Amplified Fragment Length Polymorphism (AFLP)

The technique has been considered as one of the most effective molecular markers in the study of genetic relationship (Vos et al. 1995). AFLP and bulked segregant analysis were used to identify genes linked to resistance of cowpea by Striga (Ouedraogo et al. 2001), and it was observed that resistance to S. gesnerioides race-1 was controlled by a single dominant gene. Three codominant AFLP markers linked to Rsg2–1 and six markers linked to Rsg4–3 were also identified. Similarly, seven AFLP markers were identified linked to Rsg3, which was found located on linkage group-6 on mapping of the resistance loci (Ouedraogo et al. 2002b). AFLP and AFLP-derived SCAR markers associated with Striga gesnerioides resistance in cowpea were also identified by Boukar et al. (2004) and were validated in second F2 population developed from crossing the same resistant parents. The technique was used for the study of genetic relationship among 117 cowpea accession (Coulibaly et al. 2002), and it was observed that the wild cowpea (var. spontanea) was more diverse than domesticated cowpea. Genetic association between breeding lines from West Africa and the United States and landraces

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from Africa, Asia, and South America was studied using AFLP markers (Fang et al. 2007), and it was observed that the cowpea grown in Asia and Americas had common origin that had no relation with the germplasms of West Africa. Tosti and Negri (2002) assessed the genetic variability among three landraces of cowpea and observed that the landraces showed distinctness from one another. The combination of AFLP and SSR markers utilized in the study of genetic diversity of cowpea showed the presence of heterogeneity in some accessions (Gillaspie et al. 2005). Similarly, combination of AFLP and SSR was used to find the genes linked to the resistance to Alectra vogelii in the cowpea (Kouakou et al. 2009), and a single dominant gene conditioning A. vogelii resistance was found with a probability of 30–50%. AFLP markers coupled with the bulk segregant analysis technique was used to identify cowpea golden mosaic virus (CGMV) resistance gene in cowpea (Rodrigues et al. 2012), and it was observed that tolerance to CGMV was controlled by a single dominant gene. They also identified three markers linked to the CGMV resistance gene. Kolade et al. (2016) studied phylogenetic relationship and polymorphism in the mutant of cowpea using RAPD and AFLP markers and recorded a genetic diversity of 47 and 31%, respectively. AFLP was observed as more discriminatory in grouping the plant samples and was found more powerful over RAPD (Kolade et al. 2016). Cowpea germplasms collected from six geographical locations of Oman were evaluated using AFLP, and morphological traits (Al-Hinai et al. 2018) and moderate to low level of genetic differences were observed among the populations.

7.4.4

Inter Simple Sequence Repeats (ISSR)

The technique has been considered ideal for genetic diversity and phylogenetic studies due to its variable, reproducible, and cost-effective nature (Wang et al. 2009). Genetic relationship among Vigna species was assessed using ISSR markers (Ajibade et al. 2000), and it was observed that the closely related species were grouped together. The cultivated cowpea was grouped with the wild subspecies of V. unguiculata. ISSR was found more efficient in determining genetic relationship at the species level, but it was not effective for the assessment of genetic distance relationships at the subgeneric level suggesting that subgeneric classification should be done carefully (Ajibade et al. 2000). ISSR and SSR markers have been exploited to assess the genetic diversity and relatedness among various cowpea accessions (Tantasawat et al. 2010) along with morphological characters, and it was observed that ISSR markers have higher efficiency for assessment of genetic diversity in the crop. In another study comprising of combination of RAPD and ISSR markers (Ghalmi et al. 2010), it was noticed that ISSR markers had better link to morphological variation as compared to RAPD markers. ISSR markers have been reported more efficient as compared to RAPD in respect to detection of polymorphism (Gajera et al. 2014); however, resolution power and number of polymorphic loci of RAPD were comparatively better. Molecular diversity among ten cowpea genotypes was determined using 50 ISSR and

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14 RAPD primers (Anatala et al. 2014a), and higher number of polymorphic band and polymorphism with RAPD was recorded as compared to ISSR. Anatala et al. (2014b) compared ISSR and SSR markers for characterization of cowpea genotypes and observed that combination of ISSR and SSR markers was more efficient to categorize the genotypes. The ISSRs are generally distributed across the genome and produce genetic information consistently in good quantity (Mahfouz 2015). Higher polymorphism was recorded by ISSR primers, and 19 unique bands out of 32 polymorphic bands were identified (Mahfouz 2015). Genetic variability among 60 genotypes was studied using ISSR markers (Mendes et al. 2015), and higher intra-population diversity was observed; however, there was no relationship between the genetic and geographical distances. ISSR marker was used to screen the cowpea genotypes for salinity tolerance, and some ISSR primers were identified producing salinity specific bands (Bashandy and El-Shaieny 2016). A comparative study of ISSR and start codon-targeted (SCoT) markers was undertaken to assess the genetic diversity among 18 cowpea accessions of different regions in Nigeria (Igwe et al. 2017), and it was observed that SCoT markers were more efficient than ISSR due to higher number of alleles, polymorphic information content (PIC) values, and polymorphic loci. Chaubey et al. (2017) assessed genetic diversity in cowpea using 52 ISSR primers and identified some useful primers for identification of elite lines in cowpea. Joshi et al. (2018) studied intraspecific genetic diversity in different cowpea germplasm using 25 ISSR markers and reported four unique polymorphic bands that may be useful for the study of intraspecific diversity in cowpea. Araujo et al. (2019) studied genetic diversity among 52 landraces of cowpea using 25 ISSR markers and reported 76% polymorphism. They observed that the markers were efficient in revealing the genetic variability, but the genetic base among the landraces was narrow. Salt-tolerant cowpea genotypes were also identified using ISSR and proteome analysis (Mini et al. 2019), and it was observed that ISSR markers discriminated salt-tolerant genotypes of cowpea.

7.4.5

DNA Amplification Fingerprinting (DAF)

DAF is a low-priced, highly reproducible simple, and powerful method for generating molecular markers (Winter et al. 2000; Simon et al. 2007). The technology was used to study the relatedness between two parental inbred lines and four varieties of cowpea (Spencer et al. 2000), and the profile had some specific bands that showed intra-varietal variability suggesting inheritance of agronomical and botanical traits. Similarly, DAF was applied to estimate the genetic diversity and phylogenetic relationships among 16 accessions from six Vigna species (Simon et al. 2007), and it was observed that the Brazilian genotypes of V. unguiculata were quite different from African genotypes. The DAF markers were found to be most informative at the intraspecific level for detecting a large diversity among cowpea genotypes. Spiaggia et al. (2009) characterized 30 accessions of cowpea and one accession each of Vigna angularis and V. umbellata using DAF and distinguished

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cowpea accessions from the remaining species revealing the diversity at the intraspecific level.

7.4.6

Sequence-Related Amplified Polymorphism (SRAP)

It is PCR-based molecular marker tool used to the genetic assessment and is highly acceptable due to its simple and consistent nature (Li and Quiros 2001). This technique is meagerly exploited in cowpea for evaluation of genetic variability. Alghamdi et al. (2019) characterized cowpea landraces using seed storage proteins and SRAP marker patterns and found that the cowpea seeds have mainly globulin (45–50%) and albumin (31–35%) proteins of about 15–110 and 15–150 kDa, respectively. SRAP markers in their study exhibited 100% polymorphism with an average PIC value of 0.93. The landraces were delineated according to their growth habit in the principal clusters, while the sub-clusters had the landraces of similar to their geographic origin. The genetic diversity and relationships among six cowpea genotypes were evaluated (El-Fattah et al. 2019) using morphological traits along with ISSR and SRAP markers. It was observed that ISSR markers were more competent with respect to detection of polymorphism, average number of polymorphic bands, resolving power, marker index, and polymorphism-information content. Genetic variability for protein fractions and glutelins was evaluated among seven landraces of cowpea using SDS-polyacrylamide gel electrophoresis and 34 SRAP markers (Salem et al. 2019). The study showed 100% polymorphism with an average of 93% of PIC values revealing high genetic diversity among landraces corresponding to their growth habit and geographical origin.

7.5

Genetic Linkage Studies and Inheritance

Various genes in cowpea have been reported to be linked qualitatively and quantitatively. The seed eye pattern and seed coat color in cowpea have been reported as independently inherited characteristics, and both characters have close linkages (Harland 1919). Various characters, that is, branching peduncle, non-petiolate leaf, crinkled leaf and septa foliolate leaf number (Fawole and Afolabi 1983; Fawole 1988), nodal pigmentation (Harland 1919), hastate leaf shape (Ojomo 1977), flower color (Hanchimal and Goud 1978), dehiscent pod (Aliboh et al. 1996), narrow eye pattern (Spillman 1913), dry pod color (Saunders 1960a), seed coat color (Spillman 1913; Saunders 1959), and smooth seed coat (Rajendra et al. 1979), have been reported under control of single gene inheritance with the dominance of various traits such as dominance of non-branching peduncle over the branching peduncle, petiolate leaf over non-petiolate leaf, non-crinkled leaf over crinkled leaf, trifoliolate leaf number over septafoliolate leaf, nodal pigmentation over non-pigmentation, hastate leaf shape over subglobose leaf shape, purple flower over white flower, shattering of dry pod over non-shattering, narrow eye pattern over the solid eye pattern, brown

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color of the dry pod over the white seed coat color, and smooth seed coat over the rough seed coat texture. Genes controlling black seed coat and purple pod were found to be closely associated (Harland 1920). Likewise, purple seed coat, brown seed coat, dense speckling of the seed coat, blue seed coat, and spotting pattern were also found linked (Spillman 1913). It was also observed that purple-tipped pod was linked to the loci controlling purple petiole base and purple branch base (Sen and Bhowal 1961). Genes governing vining tendency of cowpea and the genes responsible for early maturity, general color factor, and the genes associated for pod length, buff seed coat, and seed size were also strongly linked (Brittingham 1950). Nevertheless, it was also stated that the association between genes responsible for pod length and seed size is due to multiple effect of these genes (Saunders 1960a). The genes related to seed coat color and date of maturity were also found associated in a quantitativequantitative linkage (Saunders 1960b). Color of immature pod and flower bud are found to be governed by the genes of same set and show pleiotropic gene action in controlling the inheritance of color in flower bud as well as in immature pods (Hanchimal and Goud 1978). The inheritance of flower is also governed by single gene, whereas color of seed coat is governed by two genes (Hanchimal and Goud 1978). Genetic linkage has been analyzed in the cowpea using backcross and F2 joint segregation data (Kehinde et al. 1997), and it was observed that the locus for branching peduncle (Bpd) was linked to the locus for brown dry pod (Bp) and locus for pod dehiscence (Dhp) with a probable order of Bpd ~ Bp-Dhp. Similarly, crinkled leaf and sessile leaf, hastate leaf shape, and septafoliolate leaf number were also exhibited close linkages. The inheritance study of flower and pod color revealed that black pod color is somewhat dominant to white pod color (Sangwan and Lodhi 1998). Studies in the pattern of inheritance of pod and pod tip pigmentation in cowpea (Mustapha and Singh 2008) revealed that pod pigmentation in the crop is controlled by two genes, while coloration of pod tip exhibited patterns of both inheritance, that is, monogenicity and digenicity. Dominance of pigmentation was observed over non-pigmentation (Mustapha and Singh 2008).

7.6

Genetic Map Studies

The study is based on the exchange frequency of chromosome recombinant and provides an outlook to locate the target gene. The observations are utilized in the preparation of a map that can be a significant device for marker assisted selection during breeding or cloning of a crop. Studies on genetic linkage maps offer an insight about the genomic framework pertaining to identification of quantitative trait loci, cloning, estimation of genetic diversity, marker-assisted selection, etc. Several efforts have been made for the development of genetic map of cowpea using various approaches (Thottappilly et al. 1992; Fatokun et al. 1993b; Menendez et al. 1997; Ubi et al. 2000; Ouedraogo et al. 2002a, b; Lucas et al. 2011). The first genetic linkage map in cowpea was constructed by crossing between an improved cultivar

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and a wild progenitor (Thottappilly et al. 1992) on the basis of segregation of RFLP markers. Another genetic map was developed using mapping population of 58 F2 plants obtained from crosses between IT84S-2246-4 and TVNu-1963 (Fatokun et al. 1993b) with the help of 79 RFLP, five RAPD, four cDNA markers, and one inherited morphological trait, which were dispersed on ten linkage groups of the cowpea genome. Later, a map was developed using 94 F8 recombinant inbred lines derived from a cross between two cultivated genotypes IT84S-2049 and 524B with the help of 133 RAPD,19 RFLP, 25 AFLP, and three each of morphological and biochemical markers, which were dispersed on 12 linkage groups. This map was later upgraded by adding 242 another AFLP marker that generated 11 linkage groups (Ouedraogo et al. 2002a). The map was developed on the basis of the maps developed by Thottappilly et al. (1992) and Menendez et al. (1997), but it has a large contiguous portion of linkage group that was not detected in earlier maps. Another genetic map was developed using 98 recombinant inbred lines derived from the cross between a cultivated, IT84S-2246-4 and a wild relative TVNu110-3A of cowpea (Ubi et al. 2000) with the help of 77 RAPD and three morphological markers. A genetic map based on the genotyping of 741 members of six biparental recombinant inbred lines derived from the crosses of 524B × IT84S-2049, CB27 × 24-125B-1, CB46 × IT93K-503-1, DanIla × TVu-7778, TVu-14,676 × IT84S-2246-4, and Yacine×58–77 (Muchero et al. 2009a) was developed using 928 SNP markers dispersed over 11 linkage groups of the cowpea genome. This consensus map was further improved by genotyping 579 individuals of five recombinant inbred lines obtained from UCR–US, IITA–Nigeria, ISRA–Senegal, ZAAS–China, and two F4 populations (Lucas et al. 2011). Comparative mapping between the genome of cowpea and mungbean exhibited high level of conservation and collinearity (Menancio-Hautea et al. 1993), while comparison between linkage map of azuki bean and cowpea showed significant blocks of synteny (Kaga et al. 1996). Various maps have also been developed to identify QTLs for important traits in cowpea. Genetic linkage maps have been developed to recognize QTLs for resistance to flower bud thrips (Omo-Ikerodah et al. 2008), resistance to foliar thrips (Muchero et al. 2009b), bacterial blight resistance (Agbicodo et al. 2010), Macrophomina resistance (Muchero et al. 2010), cowpea yellow mosaic virus resistance (Gioi et al. 2012), aphid resistance (Huynh et al. 2015), and resistance to root-knot nematodes (Huynh et al. 2016) in cowpea. Similarly, markers linked with S. gesnerioides race-specific resistance genes in cowpea were reported in different studies (Ouedraogo et al. 2001, 2002a, b; Boukar et al. 2004; Menendez et al. 1997). QTLs for days to flower, days to maturity, pod length, number of seeds per pod, leaf length, leaf width, primary leaf length, primary leaf width, and derived traits such as leaf area and primary leaf area have also been identified (Ubi et al. 2000). QTLs responsible for leaf shape and drought tolerance (Pottorff et al. 2012) and heat-induced browning of seed coats (Pottorff et al. 2014) in cowpea have also been identified. SSR-based genetic linkage maps and QTL analyses for various traits in Vigna unguiculata have been carried out (Andargie et al. 2011; Kongjaimun et al. 2012). Besides these, genetic maps on the basis of SNP and SSR markers (Xu et al. 2011)

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and EST-derived SNPs (Muchero et al. 2009a) have also been constructed. Development and validation of EST-derived SNP was reported in cowpea for construction of map and determination of synteny to reference genomes using 183,118 ESTs sequenced from 17 cDNA libraries (Muchero et al. 2009a). About 10,000 SNPs were obtained out of which almost 90% of the SNPs were successful. Genetic diversity and population structure study was carried out among 768 cultivated genotypes of cowpea collected from 56 countries (Xiong et al. 2016). Genotyping by sequencing was applied to detect SNPs. The study revealed West and East of Africa as the first domestication regions and India as a sub-domestication region of cultivated cowpea. A genetic linkage map of cowpea was constructed using 135 SNP markers (Adetumbi et al. 2016), and 12 linkage maps with an average of ten markers to a chromosome were obtained. The information for QTLs obtained from genetic map may be used for the development of brown blotch-resistant cowpea varieties. Genetic analysis and inheritance of resistance to cowpea mosaic virus were studied in cowpea (Dinesh et al. 2018) to recognize DNA markers linked to genomic regions for resistance to cowpea mosaic virus. It was observed that the resistance was governed by single recessive gene.

7.7

Restriction Fragment Length Polymorphism (RFLP)

RFLP technique has been widely used in the study of genetic linkage mapping (Thottappilly et al. 1992; Fatokun et al. 1993b) and taxonomic relationship (Fatokun et al. 1993a) related studies in cowpea. The studies revealed higher genetic variations within the genus. RFLP markers have been used to develop first genetic map in cowpea. These maps have been helpful in the detection of genomic regions containing useful QTLs including genes responsible for seed weight (Fatokun et al. 1992), pod length (Young et al. 1992), etc. Owing to the development of RFLP map studies associated with genes of interest and RFLP markers has been started. Myers et al. (1996) screened a cross between an aphid-resistant cultivated and an aphid susceptible wild cowpea genotype using aphid phenotype and RFLP marker segregation. They reported a RFLP marker that was closely associated with an aphid resistance gene and different flanking markers in the same linkage group.

7.8

Transcriptomic Studies

Development of deep-sequencing techniques has offered ways to identify gaps between a model and crop species. Cowpea has been widely exploited for the development of genetic maps and transformation capabilities as described above. Owing to the presence of the information, identification of transcript sequences, and their expression will have immense value for genomic studies and genetic improvement of the crop. A gene expression atlas was developed, and 27 cDNA libraries were generated using leaf, root, stem, flower, pod, and seed along with a time series for pods and seeds (Yao et al. 2016) resulting into 36,529 transcript sequences. Out

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of these sequences, 24,866 unigenes were identified. The expression atlas can give information on the molecular mechanisms takes place during the seed development including some of the drought-related mechanisms. Chen et al. (2017b) analyzed cowpea transcriptome and developed genic molecular markers using 54 million high-quality cDNA sequence reads and generated 47,899 unigenes. Genomic data and genic SSR markers obtained in the study may be used in characterization of genes linked with the major agronomic traits in cowpea. QTL mapping and transcriptome analysis of cowpea (Santos et al. 2018) revealed a major QTL (designated as QRk-vu9.1) associated with resistance against root-knot nematode. Supporting genomic and transcriptomic data including tissue-specific datasets for transformable cowpea varieties has been released (Spriggs et al. 2018). A transcript set of 35,000–74,000 transcript contigs was assembled, and leaf transcriptomers were reported to be the largest in terms of de novo assembled contig.

7.9

Callus Induction and Regeneration Protocol

Genotype-dependent artificial recalcitrance has been one of problems in the tissue culture of legumes; nevertheless, optimization of tissue culture factors can solve the problem. Application of different regeneration protocols including shoot and root apices (Kartha et al. 1981; Kulothungan et al. 1995), primary leaf (Muthukumar et al. 1995), and zygotic embryos (Amitha and Reddy 1996) as explants have been successfully applied in cowpea to resolve the problem. Significant works have been carried out for genetic transformation and development of in vitro plant regeneration protocols for cowpea (Pandey and Bansal 1989; Premanand et al. 2000; Anand et al. 2001; Van Le et al. 2002; Machuka et al. 2002; Ikea et al. 2003; Avenido et al. 2004). Highest callus induction has been obtained in Murashige and Skoog (MS) medium having different concentrations of 2,4-dichlorophenoxyacetic acid (2,4-D) including 2 mg per L (Li et al. 1993, 1995) and 0.5–4 mg per L (Cheema and Bawa 1992). Embryogenic callus induction study was carried out (Kulothungan et al. 1995) from leaf explants of cowpea on MS medium, and highest somatic embryogenesis was observed with the medium supplemented with 2 mg per L 2, 4-D. Induction of shoot multiplication was performed from shoot tip explants in cowpea (Brar et al. 1997) on MS medium having N6-benzyladenine, 6-furfurylaminopurine (kinetin) combined with 2,4-D or naphthalene acetic acid. Treatments with benzyladenine induced greater shoot proliferation as compared to kinetin, whereas maximum shoots were obtained on 5 mg benzyladenine per L in combination with naphthalene acetic acid (NAA) or 2,4-D at 0.01 mg per L. Increased span of calli was recorded on MS medium containing 0.5 mg per L BAP and 0.5 mg per L NAA (Brar et al. 1997; Aasim et al. 2008), while highest shoot frequency was obtained on the MS medium having 0.5 mg per L 6-benzylaminopurime (BAP) but no NAA. Significant decrease in the frequency of shoot was recorded on the addition of NAA (Brar et al. 1997; Aasim et al. 2008) to the MS medium. Presence of indole butyric acid (IBA) in the medium has been reported to have positive effect (Aasim et al. 2008) and no effect (Mao et al.

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2006) on root induction and on secondary shoot formation. Multiple shoot induction from embryo derived callus cultures of cowpea was carried out (Odutayo et al. 2005), and it was observed that the root development was promoted by the action of auxin, NAA at low concentration of cytokinin. Simultaneously, shoots (2–4) were also developed on the sub-culturing with media having higher concentration of cytokinin and BAP. In vitro somatic embryogenesis from cell suspension cultures of cowpea was developed (Ramakrishnan et al. 2005) using primary leaf derived embryogenic calli grown on MS medium with B5 medium having 2, 4-D, casein hydrolysate, and l-glutamic acid-5-amide. The embryo development was highly influenced by the concentration of 2, 4-D. Higher level of somatic embryo induction and maturation with reduced abnormalities was recorded by reducing the 2,4-D level in suspensions. Various factors, namely, medium constitution, hormonal ratios, temperature, age of the explant, and genotypes along with concentration and combination of hormones, play important role in the callusing of cowpea (Saxena et al. 2010). The effect of pulse treatment duration, concentration of NAA, and presence of NAA in the culture medium on shoot regeneration from plumular leaf explant of cowpea was studied (Aasim 2010), and it was observed that pulse treatment of mature embryos with 20 mg per L NAA for 1 and 3 weeks followed by culturing of plumular leaf explant on MS medium containing 0.25, 0.50 and 1.0 BAP with 1.0, 2.0, and 4.0 mg per L of NAA enhanced somatic embryogenesis in cowpea. Longer period of pulse treatment showed negative effect on the embryo including death. Primary leaves of cowpea were used to induce embryogenic callus in MS medium having 2, 4-D (Premanand et al. 2000), and with the callus, suspension culture was established resulting into globular, heart-shaped, and torpedo-shaped embryos. The highest induction of globular embryos was reported followed by heart-shaped and torpedo-shaped somatic embryos in the suspension. These embryos have 22% germination and 8–10% of plant survival. In their study, cytokinin has potential role in the conversion of embryos into plantlets, while benzyladenine and kinetin have inhibited the conversion (Premanand et al. 2000). Successful plant regeneration from embryonic axis explants of cowpea has reported (Yusuf et al. 2008) using MS medium and B5 medium supplemented with low concentration (0.5 mg per L) of BAP. The explants of primary leaves, epicotyls, hypocotyls, cotyledons, cotyledonary node, shoot meristem, shoot tip, and plumular apices have been used for plant regeneration through organogenesis in cowpea (Amitha and Reddy 1996; Pellegrineschi 1997; Raveendar et al. 2009; Aasim et al. 2009a, b). Higher number of shoots could be realized with 5–6 days old seedling on B5 medium having 1 mg per L of BAP. Tang et al. (2012) reported the culture factors accountable for regeneration of plants from the cotyledons of cowpea. They found a regeneration system through organogenesis using cotyledonary node explants of the crop. A concentration of 1.25 mg per L of BAP was found optimum for shoot induction, while combination of BAP with IBA had no significant effect on shoots proliferation. The concentration of 2–3 mg per L of BAP enhanced the number of adventitious buds, while its higher (5 to 15 mg/L) concentration was observed suppressive. Higher concentrations of cytokinins were found appropriate for later shoot induction (Brar et al. 1999; Van Le et al. 2002; Raveendar et al. 2009).

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Association of genotype, explants, and 2,4-D concentration plays an important role in callus induction from cowpea (Dadmal and Navhale 2011). The mean genotypic response for callus induction in genotype × explant × 2, 4-D concentrations interaction ranged from 12.50 to 91.67%. A comparative study on the competence of axillary shoot regeneration on unsliced and longitudinally sliced cotyledon nodes of cowpea was carried out (Aasim et al. 2012), and it was observed that shoot regeneration frequency of longitudinally sliced cotyledon node explants was higher than that of unsliced cotyledon node explants. Embryo axes with single cotyledon and leaf disc explants of ten cowpea genotypes were cultured (Sawardekar et al. 2013) on MS medium supplemented with different growth regulators to study the genotypic differences with respect to explants and growth regulators for callus induction. It was observed that days to callusing were independent of genotype and explants. Highest regeneration response was obtained with 2 mg per L of BAP. The effect of moisture content on in vitro regeneration of embryonic axis explants of cowpea was studied (Jain et al. 2017) to observe the effect of drought on seed survival. In vitro effect of different hormones was studied on the growth of embryonic axis. Combination of MS basal salts and vitamins of Gamborgs’ (B5) medium having 0.2 mg per L of BAP has been found essential for the growth of embryonic axis explants in cowpea plants. The in vitro culture of embryonic axis explants can be utilized to rescue the cowpea accession having poor seed viability (Jain et al. 2017) due to lower moisture content. The genetic transformation studies conducted to obtain kanamycin-resistant callus in cowpea failed to get plant regeneration (Garcia et al. 1986, 1987). The earlier studies were unable to describe better genetic transformation and regeneration systems (Penza et al. 1991; Muthukumar et al. 1995; Ikea et al. 2003). However, later studies could develop reliable protocols for recovery of transgenic cowpea plants (Popelka et al. 2006), and successful transformation of cowpea with the Bt gene could be attained. Identification of explants and culture media was the crucial character in the transformation system. Cotyledonary node explants have been found more receptive for induction of multiple shoots and agrobacterium-mediated transformation (Chaudhury et al. 2007; Raji et al. 2008; Adesoye et al. 2010), and its shoot multiplication was influenced by the presence/absence of explants (Diallo et al. 2008). A study was conducted to find factors influencing Agrobacteriummediated genetic transformation in cowpea (Vinchurkar et al. 2017) having kanamycin-resistant gene, and it was observed that leaf disc was the better explants as compared to embryonic axes, while higher sucrose concentration exhibited better callus induction. Various techniques, that is, sonication and vacuum infiltrationassisted Agrobacterium-mediated transformation (Bakshi et al. 2011) and sonication and a kanamycin-geneticin selection regime (Bett et al. 2019), have been used to increase the transformation efficiency in cowpea.

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Saunders AR (1960b) Inheritance in the cowpea III: mutations and linkages. South Afr J Agric Sci 3:327–348 Sawadogo M, Ouedraogo JT, Gowda BS, Timko MP (2010) Genetic diversity of cowpea (Vigna unguiculata L. Walp.) cultivars in Burkina Faso resistant to Striga gesnerioides. Afr J Biotechnol 9(48):8146–8153 Sawardekar SV, Jagdale VR, Bhave SG et al (2013) Genotypic differences for callus induction and plantlet regeneration in cowpea [Vigna unguiculata (L.) Walp]. Int J Appl Biosci 1(1):1–8 Saxena AK, Saxena KK, Roy S (2010) Induction of callus in cowpea. J Phytol Res 23(2):381–382 Selvi R, Muthiah AR, Maheswaran M, Shanmugasundaram P (2003) Genetic diversity analysis in the genus Vigna based on morphological traits and isozyme markers. Sabrao J Breed Genet 35(2):103–112 Sen NK, Bhowal JG (1961) Genetics of Vigna sinensis (L.) Savi. Genetica 32:247–266 Sharawy WM, Fiky ZA (2003) Characterization of cowpea (Vigna unguiculata L.) genotypes based on yield traits and RAPD–PCR analysis. Arab J Biotechnol 6(1):67–78 Simon MV, Benko-Iseppon AM, Resende LV, Winter P, Kahl G (2007) Genetic diversity and phylogenetic relationships in Vigna savi germplasm revealed by DNA amplification fingerprinting (DAF). Genome 50:538–547 Sonnante G, Piergiovanni AR, Ng NQ, Perrino P (1996) Relationships of Vigna unguiculata (L.) Walp., V. vexillata (L.) A. rich., and species of section Vigna based on isozyme variation. Genet Resour Crop Evol 43:157–165 Spencer M, Ndiaye M, Gueye M et al (2000) DNA-based relatedness of cowpea [Vigna unguiculata (L.) Walp.] genotypes using DNA amplification fingerprinting. Physiol Mol Biol Plants 6(1): 81–88 Spiaggia F, De Carvalhoand R, Benko-Iseppon AM (2009) Preliminary molecular characterization of cowpea (Vigna unguiculata (L.) Walp.) accessions by DNA amplification fingerprinting (DAF). www.geneconserve.pro.br/artigo075.pdf Spillman WJ (1913) Colour correlation in cowpea. Science 38:302 Spriggs A, Henderson ST, Hand ML, Johnson SD, Taylor JM, Koltunow A (2018) Assembled genomic and tissue-specific transcriptomic data resources for two genetically distinct lines of cowpea (Vigna unguiculata (L.) Walp). Gates Open Res 2:7. https://doi.org/10.12688/ gatesopenres.12777.2 Tang Y, Chen L, Li XM et al (2012) Effect of culture conditions on the plant regeneration via organogenesis from cotyledonary node of cowpea (Vigna unguiculata L. Walp). Afr J Biotechnol 11(14):3270–3275 Tantasawat P, Trongchuen J, Prajongjai T, Seehalak W, Jittayasothorn Y (2010) Variety identification and comparativeanalysis of genetic diversity in yardlong bean (Vigna unguiculata spp. sesquipedalis) using morphological characters, SSR and ISSR analysis. Sci Hort 124(2): 204–216 Tchiagam JBN, Bell JM, Nassourou AM, Njintang NY, Youmbi E (2011) Genetic analysis of seed proteins contents in cowpea (Vigna unguiculata L. Walp.). Afr J Biotechnol 10(16):3077–3086 Thottappilly G, Monti LM, Mohan-Raj DR, Moore AW (1992) Biotechnology: enhancing research on tropical crops in Africa. IITA, Ibadan Tosti N, Negri V (2002) Efficiency of three PCR-based markers in assessing genetic variation among cowpea (Vigna unguiculata subsp. unguiculata) landraces. Genome 45:268–275 Truong VD, Mendoza EMT (1982) Purification and characterization of two lipoxygenase isoenzymes from cowpea [Vigna unguiculata (L.) Walp.]. J Agric Food Chem 30:54–60 Truong VD, Raymundo LC, Mendoza EMT (1979) Cowpea lipoxygenase: part 1. Physiochemical characterization. Bull Philipp Biochem Soc 2:1–12 Ubi BE, Mignouna H, Thottappilly G (2000) Construction of a genetic linkage map and QTL analysis using a recombinant inbred population derived from an inter-subspecific cross of a cowpea [Vina unguiculata (L.) Walp.]. Breed Sci 50:161–173

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Udensi OU, Okon EA, Ikpeme EV, Onung OO, Ogban FU (2016) Assessing the genetic diversity in cowpea (Vigna unguiculata L. Walp) accessions obtained from IITA, Nigeria using random amplified polymorphic DNA (RAPD). Int J Plant Breed Genet 10(1):12–22 Vaillancourt R, Weeden NF (1992) Chloroplast DNA polymorphism suggests a Nigerian center of domestication for the cowpea, Vigna unguiculata, Leguminosae. Am J Bot 79:1194–1199 Vaillancourt RE, Weeden NF (1996) Vigna unguiculata and its position within the genus Vigna. In: Pickersgill B, Lock JM (eds) Advances in legume systematics, legumes of economic importance. Royal Botanic Gardens, Kew, pp 89–93 Vaillancourt RE, Weeden NF, Barnard J (1993) Isozyme diversity in the cowpea species complex. Crop Sci 33:606–613 Van Hintum TJL (1995) Hierarchical approaches to the analysis of genetic diversity in crop plants. In: Hodgkin T, AHD B, van Hintum TJL, Morales EAV (eds) Core collection of plant genetic resources. Wiley Sayce, Rome, pp 23–34 Van Le B, de Carvalho MHC, Zully-Fodil Y, Thi ATP, Van KTT (2002) Direct whole plant regenerationof cowpea [Vigna unguiculata (L.) Walp] from cotyledonary node thin layer explants. J Plant Physiol 159:1255–1258 Vinchurkar AS, Sonawane SR, Mane PP, Dama LB (2017) Study of factors influencing agrobacterium mediated genetic transformation in Vigna unguiculata. Trends Biotechnol Res 6(1):9–12 Vos P, Hogers R, Bleeker M et al (1995) AFLP a new technique for DNA-fingerprinting. Nucleic Acids Res 23:4407–4414 Wamalwa EN, Muoma J, Wekesa C (2016) Genetic diversity of cowpea (Vigna unguiculata (L.) Walp.) accession in Kenya gene bank based on simple sequence repeat markers. Int J Genom 2016:8956412. https://doi.org/10.1155/2016/8956412 Wang HZ, Wu ZX, Lu JJ et al (2009) Molecular diversity and relationships among cymbidium goeringii cultivars based on inter-simple sequence repeat (ISSR) markers. Genetica 136(3): 391–399 Winter P, Benko-Iseppon AM, Hüttel B et al (2000) A linkage map of the chickpea (Cicer arietinum L.) genome based on recombinant inbred lines from a C. arietinum x C. reticulatum cross: localization of resistance genes for Fusarium wilt races 4 and 5. Theor Appl Genet 101:1155– 1163 Xiong H, Shi A, Mou B et al (2016) Genetic diversity and population structure of cowpea (Vigna unguiculata L. Walp). PLoS One 11(8):e0160941 Xu YH, Guan JP, Zong XS (2007) Genetic diversity analysis of cowpea germplasm resources by SSR. Acta Agron Sin 33(7):1206–1209 Xu P, Wu XH, Wang BG et al (2010) Development and polymorphism of Vigna unguiculata ssp. unguiculata microsatellite markers used for phylogenetic analysis in asparagus bean (Vigna unguiculata ssp. Sesquipedialis (L.) Verdc.). Mol Breed 25(4):675–684 Xu P, Wu XH, Wang BG et al (2011) A SNP and SSR based genetic map of asparagus bean (Vigna unguiculata ssp. sesquipedialis) and comparison with the broader species. PLoS One 6(1):1–8 Yao S, Jiang C, Huang Z et al (2016) The Vigna unguiculata gene expression atlas (VuGEA) from de novo assembly and quantification of RNA-seq data provides insights into seed maturation mechanisms. Plant J 88:318–327 Young ND, Fatokun CA, Danesh D, Menancio-Hautea D (1992) RFLP mapping in cowpea. In: Thottappilly D, Monti LM, Mohan Raj DR, Moore AW (eds) Biotechnology: enhancing research on tropical crops in Africa. CTA/IITA, Ibadan, pp 237–246 Yusuf M, Raji A, Ingelbrecht-UGent I, Katung MD (2008) Regeneration efficiency of cowpea (Vigna unguiculata (L.) Walp.) via embryonic axis explants. African J Plant Sci 2:105–108 Zannou A, Kossou DK, Ahanchédé A et al (2008) Genetic variability of cultivated cowpea in Benin assessed by random amplified polymorphic DNA. Afr J Biotechnol 7(24):4407–4414

Part II Horsegram

8

Introduction

Abstract

Horsegram is one of the important underutilized and unexplored legumes. It has a sub-erect, bushy annual herb with trifoliate leaves, slender and branching stem, and pale yellow flowers having deep rooted system. This drought-resilient, hardy, highly adaptive to poor soils and adverse climatic condition legume is native to India. It is an excellent source of protein, carbohydrates, dietary fiber, micronutrients, and feed and fodder for animals. Presence of medicinal and nutraceutical properties in its grains has attracted the attentions of researchers and commercial food manufacturers for cultivation.

8.1

Introduction

Horsegram (Macrotyloma uniflorum Lam. verdc, Dolichos biflorus Linn.) of the family Fabaceae is one of the important underutilized (Aiyer 1990) and unexplored (Reddy et al. 2008) food legumes. It is usually grown under late rainy season or with the rains after a prolonged drought conditions or under aberrant weather conditions by poor farmer in tribal localities and drought-prone areas. This tropical grain legume is well known for its hardiness, adaptability to poor soils and adverse climatic condition (Oram 1990), drought (Bhardwaj and Yadav 2012a), salinity (Reddy et al. 1998), and heavy metal stresses areas (Reddy et al. 2005). It is a good and economic source of protein, vitamins, calcium, carbohydrates, iron, and energy (Katiyar 1984; Bravo et al. 1998). It provides high-quality inexpensive proteins to cereal or starchy food-based diets and is consumed both in boiled and fried form by poorest section of the society in general. Besides this, the crop improves the soil fertility if incorporated as green manure into the soil at the time of flowering (Gohokar 1983).

# The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 R. Pathak, Genetics, Physiology and Cultivation of Moth Bean, Cowpea and Horse Gram, https://doi.org/10.1007/978-981-19-9956-7_8

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Due to shorter height of the crop, it is often grown as intercrop with other crop species, namely, sorghum, pearl millet, or pigeon pea (Nezamuddin 1970; Krishna 2014) to retain the soil ability. It is also grown as a preparatory crop in newly reclaimed lands to improve the soil fertility by fixing nitrogen and increasing organic matter status (Sen and Bhowal 1959). Besides the nitrogen fixing ability, the crop is comparatively less prone to various pests and diseases. All these advantageous traits have placed the crop as a unique potential future crop species (Smartt 1990; Reddy et al. 2008). The plant of crop is sub-erect, annual herbs with trifoliate leaves, slender and branching stem, and pale yellow flowers. Pod is flattened and linear containing five to seven small seeds. Seeds are 3–6 mm in diameter and flattened with shining surface. Seed color varies from light red, brown, black, or mottled (Purseglove 1974). Horsegram is native to Southeast Asia and tropical Africa, but the center of its origin as a cultivated crop is considered to be India due to a long history of its cultivation (Vavilov 1951; Verdcourt 1971; Blumenthal and Staples 1993; Nene 2006). The old world tropics, especially India and Himalayas regions, are considered to have maximum genetic diversity of the crop (Zeven and de Wet 1982). It is widely spread in India and also cultivated in Pakistan, Bangladesh, Sri Lanka, Nepal, West Africa (Jansen 1989; Blumenthal and Staples 1993), Australia, Burma, Malaysia, Mauritius, and West Indies (Jeswani and Baldev 1990) under low soil fertility status with limited inputs (Witcombe et al. 2008). In India, it is known as kulthior, kalath, and kulthi. Horsegram accounts for approximately 5–10% of India’s pulses, with annual production of about 590 kg (Kiranmai et al. 2016). Presently, the crop ranked fifth among the grown pulse species in India (Fuller and Murphy 2018) and is considered as one of the important legume crops. It is extensively grown in peninsular India and is cultivated up to 5000 feet elevation in Himachal Pradesh and Nepal both in kharif and rabi seasons. The crop is extensively grown in Tamil Nadu, Karnataka, and Andhra Pradesh of South India for grain legume and fodder purposes and is consumed as an important supplement for the cereal-based balanced diet of small income populaces (Edulamudi et al. 2015; Virk et al. 2006). It covers an area of 17.02 lakh hectare with an annual production of 7.19 lakh tons with the national average productivity of 494 kg per ha (Suthar et al. 2017). The annual yield of the crop is low may be due to its cultivation in poor agronomic condition, lesser research attentions, and declining importance from south to north part of India (Lokeshwar 1997). Horsegram provides the excellent source of protein, carbohydrates, dietary fiber, micronutrients (Yadav et al. 2004), and feed and fodder for animals (Gohokar 1983). Being rich in proteins, its fodder is widely used as a feed to milch animals and horses (Prakash et al. 2008) from ancient time; therefore, it was named as horsegram (Watt 1889–1893). The protein content in wild species of the horsegram has been recorded higher (38.32%) as compared to cultivated species (16.9–30.4%). The lysine content in these proteins is higher as compared to pigeon pea and chickpea making horsegram better in the cereal-based diet (Gopalan et al. 1999; Prasad and Singh 2015). Along with its usage as dry fodder, cattle feed, and cover crop, it is also used for water conservation in the semiarid region. The husks of horsegram have excellent

8.2 Origin and Distribution

167

water retaining capacities (Nezamuddin 1970; Zaman and Mallick 1991). The crop contains various alkaloid, namely, dolichin and pyroglutaminyl glutamine along with some flavonoids (Incham et al. 1981; Handa et al. 1990). Isolation of kaempferol-3-O-β-D-glucoside, β-sitosterol and stigmasterol (Kawsar et al. 2003) and phenolic compounds (Kawsar et al. 2008a) was carried out from horsegram. Presence of anti-nutritional factors in the crop is a matter of major concern (Sudha et al. 1995). Moreover, the plant parts have antimicrobial activities and are effective in dissolution and dislocation of kidney stones (Narayanan and Balasubramanian 1991; Reddy et al. 2005; Chahota et al. 2005; Kawsar et al. 2008b). The insoluble dietary fibers of its seeds are required in normal functioning of lower intestine (Anderson et al. 1994; Kawale et al. 2005; Kang et al. 2006). Certain anti-nutrients such as phytate, tannins, and trypsin inhibitors limit the nutritional values of its grains (Sreerama et al. 2012), but these anti-nutrients are believed to have medicinal and nutraceutical properties (Prasad and Singh 2015) and therefore attracted the attentions of researchers and commercial food manufacturers (Khatum et al. 2013). Horsegram has got lesser research as compared to other important legumes, namely, Vigna radiata, V. mungo, or Cajanus cajan (Fuller and Murphy 2018), for agronomic research although some genetic researches have been conducted on the crop (Sharma et al. 2015). Various researchers have assessed the genetic variability for the improvement of the crop (Bolbhat and Dhumal 2009, 2012; Dikshit et al. 2014;Bhardwaj and Yadav 2012b; Bhardwaj et al. 2013; Prakash et al. 2010; Varma et al. 2013; Sharma et al. 2015), with respect to the genetic and biochemical properties of drought-tolerant variants (Bhardwaj et al. 2013; Bhardwaj and Yadav 2012b; Morris et al. 2013; Reddy et al. 1998, 2008).

8.2

Origin and Distribution

It is believed that India is the primary center of origin of horsegram due to its cultivation in the country since pre-historic times (Vavilov 1951; Nene 2006). The plains and hills of the southern part of India are assumed as the domestication regions and geographical limits of the crop (Mehra 2000). On the contrary, Dana (1976) speculated that since out of 240 species of horsegram, 217 are found in Africa, therefore Africa may be the main center of its origin. On the basis of various archeological and botanical evidences, it was reported that the crop was domesticated in ancient India, and it may be one of earliest cultivars of Neolithic of peninsular India (Fuller et al. 2004; Asouti and Fuller 2008; Fuller and Murphy 2018). The archeological reports suggest the presence of seed of the crop in the villages of Neolithic period situated on the banks of Tungabhadra River of South India, revealing the cultivation of horsegram since ancient in south states of India, namely, Tamil Nadu, Karnataka, and Andhra Pradesh (Nezamuddin 1970; Sundararaj and Thulasidas 1993; Fuller and Harvey 2006). The presence of grains and cotyledons of crop has also been sketched in Neolithic settlements through Indo-Gangetic belt (Fuller and Harvey 2006). It has also been reported that horsegram has been one of

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the main sources of protein during Neolithic period (Boivin et al. 2007). Archeological investigations have revealed the use of horsegram as food especially in India around 2000 BC (Mehra 2000). Horsegram grows wild in the eucalyptus forests of Queensland and is distributed throughout the tropics. It is reported to be cultivated across tropical Africa, South Asia, Southeast Asia, China, the Americas, and Australia (Kingwell-Banham and Fuller 2014) including India, Myanmar, Nepal, Malaya, Mauritius, Sierra Leone, Transval and West Indies (Sundararaj and Thulasidas 1986), Pakistan, Bangladesh (Spate and Learmonth 1967), Taiwan, and the Philippines to a lesser extent. Reports suggest that horsegram was grown as a fodder crop in colonial Southeast Asia (Burkill 1966), but archeological surveys specify its introduction in peninsular Thailand (Castillo et al. 2016). The information about the progenitors of horsegram is not available, and Macrotyloma uniflorum is the only known domesticated species of the crop. Horsegram may be grown from 0 to 1500 m above sea level in soil of low fertility level and can survive at 35–40°C temperatures. It is widely distributed in the African (Sudan, Ethiopia, Zaire, Kenya, Tanzania, Zimbabwe, South Africa, Mozambique, and Angola) and Asian (China, Philippines, Bhutan, Pakistan, Sri Lanka, India) countries. India is the major producers of horsegram, and its cultivation in India is spread in all over the country from North (Uttarakhand) to South (Tamil Nadu) and West (Gujarat) to East (West Bengal). The southern states of India, namely, Tamil Nadu, Karnataka, and Andhra Pradesh, contribute nearly 90% of total Indian acreage (Fuller and Murphy 2018) of horsegram cultivation.

8.3

Descriptive Botany and Taxonomy

Horsegram belongs to the family Fabaceae and subfamily Faboideae. The taxonomic classification of horsegram has a chaos. The botanical name of horsegram been widely used as Dolichos biflorus (L.) in the literatures, namely, Joseph Dalton Hooker’s Flora of British India (1879), India floristics, and archaeobotanical literature (Watt 1908; Gamble 1935; Kajale 1991; Saraswat 1992; Vishnu 1989). Smartt (1985) reported that the material studied for classification of horsegram by Linnaeus in 1753 was catjang-type cowpea, which is presently known as Vigna unguiculata (L.) Walp. Therefore, D. biflorus has been revised as Macrotyloma uniflorum (Lam.) Verdc. (Kingwell-Banham and Fuller 2014); besides this, after transfer of the heterogenous genus from Dolichos to Macrotyloma (Verdcourt 1970, 1982; Smartt 1985), D. biflorus has been named as M. uniflorum. The genus Macrotyloma also includes M. uniflorum, M. axillare (Meyer) Verdcourt and M. geocarpum (Harms) Marechal & Baudet (Isely 1983). One more species, namely, M. axillare, has also been identified for fodder purpose. Besides this, three forage species, namely, M. axillare, M. africanum, and M. daltonii, have been reported from Australia. M. axillare is reported as resistant to yellow mosaic disease and has been used to transfer the character to M. uniflorum (Dikshit et al. 2014). Horsegram is an annual herb of 30–40 cm long (Nezamuddin 1970; Smartt 1985; Sundararaj and Thulasidas 1993). Wide phenotypic variability has been recorded in

8.4 Taxonomic Classification

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the germplasm of horsegram (Neelam et al. 2014). The crop is well adapted under varied soil and climatic conditions, and its tolerance can be imagined due to its presence in the harsh conditioned soil of eucalyptus forests of Queensland (Nezamuddin 1970). In southern India, the crop is usually grown without any irrigation in lateritic soils (Kingwell-Banham and Fuller 2014; Nezamuddin 1970) during August to October months. Macrotyloma axillare: It is a wild relative of cultivated horsegram and generally grown for fodder purpose. M. axillare, M. africanum, and M. daltonii are three related species reported from Australia and are forage types. It is an annual herb of climbing nature having a length up to 3.5 meters. Its stems are glabrous or pubescence, and leaves are tri-foliolate, pubescent to glabrous on both surfaces. Flowers are axillary and are found in pairs. It has glabrous to pubescent pods having three to eight seeds. The seeds are fawn to deep red spotted black (Dikshit et al. 2014). Macrotyloma ciliatum: Macrotyloma ciliatum (Willd.) Verdc. is an herbaceous species found in Tamil Nadu (Nair and Henry 1983; Matthew 1983) and Andhra Pradesh (Pullaiah and Chennaiah 1997), and its distribution has been extended up to Orissa. It acts as a sand binder in the seaside areas. Usually, it grows in sandy place and has more sprawling nature. It has comparatively higher number of pods in the cluster and ciliated margin of leaves. Pods and seeds are similar to the cultivated species of horsegram. Macrotyloma sar-garhwalensis: It is a wild relative of horsegram found in the Garhwal Himalayas (Gaur and Dangwal 1997) and is cultivated in the entire sub-Himalayan tracts up to 1800 m. This drought-resistant species adapted to a wide range of soils and cannot withstand waterlogged condition. It is known to tolerate a pH range of 6.0–7.5. The species have high protein content (38.37%) in its seeds (Yadav et al. 2004) and have much variation as compared to cultivated species of horsegram (Chahota et al. 2017).

8.4

Taxonomic Classification

Domain: Eukaryota Kingdom: Plantae Subkingdom: Viridiplantae Phylum: Magnoliophyta Subphylum: Euphyllophyte Class: Magnoliopsida Subclass: Rosidae Order: Fabales Family: Fabaceae Subfamily: Faboideae Tribe: Phaseolaceae Genus: Macrotyloma Specific epithet: uniflorum(L.) Verdc.

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8 Introduction

Botany

Horsegram belongs to the family Fabaceae or Leguminaceae and subfamily Faboideae. Several synonyms of the crop are known including Macrotyloma uniflorum var. benadiri anum, Macrotyloma uniflorum var. steno carpum, Macrotyloma uniflorum var. uniflorum, and Macrotyloma uniflorum var. verrucosum. In English, it is known as horsegram, in French dolicbiflore, in German Pferdebohne, in Portuguese Faveira, and in Spanish Frijol Verde. Horsegram is also known by various names in Indian language, namely, Kulatha in Sanskrit, Gahat in Hindi, Huruli in Kannada, Kollu in Tamil, Vulavu in Telugu, and Parippu in Malayalam. The genus Macrotyloma comprises 25 species (Verdcourt 1980). It is a selfpollinated crop with 2n = 20 chromosomes. It is believed that the chromosomal evolution of M. uniflorum has evolved in two directions, that is, one (M. uniflorum, M. baumannii, and M. axillare) with 20 small chromosomes and another (M. glabrescens, M. lignosus, and M. argentinus) with 22 large chromosomes. The length of chromosomes has sub-median primary constrictions (Sen and Vidyabhushan 1959). It has diploid chromosome numbers of 2n = 20, 22, 24 (Cook et al. 2005). Horsegram is horizontal or partly erect, annual, or perennial herb of about 30–50 cm and normally has long runners. The leaves are alternate, stipulate, petiolate, and trifoliate and 2.5–5 cm in length, and leaflets are membranous entire, pilose, ovate, and acute. The stipules are ovate, lanceolate, and minute. It produces one to three greenish yellow-colored flowers in the leaf axis. The flowers are bisexuals, bracteates, bractealate, pedicellate, hypogynous, zygomorphic, complete, and pentamerous. The downy calyx has lanceolate teeth type, and the papilionaceous corolla has five petals with cream, yellow, or greenish yellow color (Kumar 2007). The peduncles are short. The standard is longer than the wings, while the keel petals are obtuse, scarcely, reflexed, and narrow. Stamens are short, diadelphous, and filamentous and have long dithecous, introse, uniform, and dorsified anthers. The ovary is monocarpellary, unilocular having five to seven marginal placentas. Style is curved and terminal, while stigma is capitate glabrous and flat. The pods are linear, dehiscent, and curved toward apex having five to eight seeds. Seeds are small (3–6 mm), non-endospermous, and flattened having shiny testa. The seeds are oblong or round, and its color varies from pale to dark reddish brown or reddish black and orange-brown. The crop takes 3 to 4½ months to mature depending upon the variety (Cook et al. 2005). The seed has three fraction, namely, cotyledon, seed coat, and embryonic axe, that represents about 89, 10, and 1% of the total seed weight, respectively (Neelam 2007).

References

8.6

171

Constraints

The improved varieties of horsegram under cultivation have been developed from the local germplasm. The conventional breeding methodology needs to be taken up for the improvement in yield, quality, and shorter growth duration of the crop. The long maturity and non- synchronous pod maturity of crop expose it to moisture stress during grain filling stage resulting in low yield. Pod shattering habit is also a major constraint for the higher yields. The crop is always given second or even third priority, and generally sub-marginal and poor quality soil is chosen for its cultivation. The photosensitive and thermosensitive nature of the crop does not permit its expansion in nontraditional and remote regions. The dissemination technology for increasing the yield of this crop is also a constraint of cultivation. The role of this legume in various farming systems needs to understand and worked out.

8.7

Prospects

The ability of surviving of horsegram in prolonged droughts, lesser incidence of attack of insects, pests and diseases, and higher adaptability toward wide range of soil and climatic conditions can be exploited for the improvement of other crops. The seeds of the crop can be stored for a long time as its seeds are not much damaged by grain pests. Horsegram is considered as the wealth house of therapeutic, bioactive compounds, and phytochemicals along with excellent nutritional quality. The legume may be investigated for its chemo-profile, pharmacology, biological evaluation, toxicological consequences, and health-promoting aspects. The nutritional quality and antioxidant potential of the crop can be used to address food and nutritional security issues.

References Aiyer YN (1990) Horse gram. In: Aiyer YN (ed) Field crops of India, 7th edn. Bangalore Press, Banglore, pp 115–117 Anderson JW, Smith BM, Gustafson NJ (1994) Health benefits and practical aspects of high-fiber diets. Am J Clin Nutr 59:1242S–1247S Asouti E, Fuller DQ (2008) Trees and woodlands of South India. Walnut creek, California: archaeological perspectives. Left Coast Press, San Francisco Bhardwaj J, Yadav SK (2012a) Genetic mechanisms of drought stress tolerance, implications of transgenic crops for agriculture. In: Lichtfouse E (ed) Agro-ecology and strategies for climate change, Sustainable agriculture reviews. Springer, Cham, pp 213–235 Bhardwaj J, Yadav SK (2012b) Comparative study on biochemical andantioxidant enzymes in a drought tolerant and sensitive variety of horsegram (Macrotyloma uniflorum) under drought stress. Am J Plant Physiol 7:17–29 Bhardwaj J, Chauhan R, Swarnkar MK et al (2013) Comprehensive transcriptomic study on horse gram (Macrotyloma uniflorum): De novo assembly, functional characterization and comparative analysis in relation to drought stress. BMC Genomics 14:647

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9

Genetic Improvement and Variability

Abstract

Horsegram has wide genetic variability including variability in the seed colour. Significant variability for various morphological traits, namely, plant height, number of branches, number of nodes, number of pods, days to flowering, day to maturity, pod length, pod yield and seed yield, has been recorded. The genetic variability in the crop has been assessed using different methods. A detailed account on genetic improvement and genetic variability in horsegram has been discussed in this chapter.

9.1

Introduction

The genetic improvement is an important area of any research programmes in order to increase productivity of the crop, and the knowledge of genetic variability is one of the prime requirements for improvement of a crop variety. The cultivated crops have been interest of subject for human and have resulted into collection of enormous germplasms, land races and wild species of various crops throughout the world using natural selection. The legume needs to be improved not only as the source of pulses but also as forage plant (Hanet 2001) during its breeding. Horsegram generally gets its place under poor fertility soil and receives less attention after its sowing. The crop has great medicinal potential and is a very good source of vegetable protein, but it has not got due attentions for its genetic improvement. Kulkarni and Mogle (2011) evaluated horsegram genotypes for quantitative and qualitative traits and observed wide variability in terms of several morphological characters. Wide variation in seed colour from brown grey to brown pink with both shattering and non-shattering abilities was also reported. Genotypes IC-268213, IC-341283, IC-282590, IC-259326 and IC-341308 are the top ranking, in terms of yields per plant, and it has been found that the local selection # The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 R. Pathak, Genetics, Physiology and Cultivation of Moth Bean, Cowpea and Horse Gram, https://doi.org/10.1007/978-981-19-9956-7_9

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178 Table 9.1 Morphological variability in horsegram

9 Genetic Improvement and Variability

Morphological characters Days to 50% flowering Plant height Number of primary branches Number of pods per plant Number of seeds per pod Pod length Seed yield per plant 1000-seed weight Seed colour

Range 36.58–76.76 days 47.13–112.13 cm 3.61–7.01 27.41–48.00 3.61–6.48 4.02–5.36 cm 2.09–7.57 g 24.94–34.10 g Brown grey to brown pink

Source: Kulkarni and Mogle (2011)

Fig. 9.1 Morphological variability in horsegram

had fewer yields and attained delayed 50% flowering. Horsegram has several genetic defects including longer maturity, poor harvest index, thermosensitive nature, susceptibility to some of the diseases, etc. that demands the genetic upliftment of the crop to increase its production and productivity (Kulkarni and Mogle 2011). Horsegram bean has been reported with wide variability in terms of several morphological characters (Table 9.1; Fig. 9.1).

9.3 Genetic Divergence

9.2

179

Morphometric Characterization

Seed production is a crucial aspect of breeding programme. Its every stage requires care for maintenance for obtaining authentic and quality seed material. Varietal description on the basis of morphometric characters is the most integral part for its identification. The stable characters are used for classification of varieties at field and laboratories. Uma Rani et al. (2013) characterized 22 genotypes of horsegram on the basis of morphometric traits. They identified some important characters, namely, seed colour, seed shape, hilum colour at seed stage, anthocyanin pigmentation, leaf shape, leaf colour at seedling stage and flower colour, petal pigmentation at plant stage for varietal identification and maintenance of genetic purity. The seedling and plant characters, namely, anthocyanin pigmentation, growth habitat and leaflet shape, can be detected only at the specific stage of plant growth; in the later stages of plant development, these characters disappeared. Flower and pod characters were also important for breeders (Uma Rani et al. 2013). Seed coat colour in horsegram is governed by dominant genes. Mikhailov and Travyanko (2008) reported that black colour is governed by two dominant genes. So seed coat colour may be an important character for broad classification of horsegram genotypes. Although it is a heritable character, environmental impacts are also seen during ripening of seeds (Uma Rani et al. 2013).

9.3

Genetic Divergence

Genetic divergence is a process in which the deviation of the gene pool takes place from one population to the others. It can be due to mutation, genetic drift and selection. The genetic differences among divergent populations may have silent mutations or significant morphological and/or physiological changes. Assessment of genetic divergence is an essential component in the genotype characterization and conservation. Generally, it is believed that the genotypes originating from different geographic regions may have different genetic backgrounds. With this presumption, genotypes are included in the hybridization programme to obtain promising genetic recombinants (Lee and Kaltsikes 1973), but it is not always true. Besides this, sometimes the analysis of variance is also not a consistent basis for measuring the presence of extent of genetic diversity. To overcome this problem and to quantify genetic divergence between any two genotypes or group of genotypes, the numerical measures of diversity is obtained with the help of D2 statistics and constellations of genotypes. A large number of divergent lines should be used in the hybridization for creating variability and developing the best selection criteria (Gohil and Pandya 2008; Bhatt 1970). D2 statistics has been described as an important tool for quantitative estimation of genetic divergence among the populations (Mahalanobis 1936). Later, a more flexible method was suggested that replaced the quantification of characters contributing to the some degree towards the discrimination by relatively little measurement (Rao 1948). The technique has been widely used for assessment of genetic divergence in breeding materials.

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Various reports on genetic divergence suggested no association between geographic and genetic diversity. A 100-seed weight and dry weight of nodular tissues (Ramakrishna et al. 1979), plant maturity (Ganeshian 1980), pod weight (Balan et al. 1992), number of pods, days to flowering, seed yield per plant, pod length and number of branches (Dobhal and Rana 1994), days to flowering, maturity, plant height, number of branches and number of pods per plant (Patil et al. 1994), days to maturity, days to flowering and number of seeds per pod (Patel et al. 2010a; Sahoo et al. 2014) have been found to be the major contributors to the total divergence in horsegram. In a genetic divergence study comprising of seed yield and yieldattributing traits, Balan et al. (1992) could group the horsegram genotypes into nine different clusters and reported that none of them were related to their geographic origin. Test weight was the main contributor towards the total divergence while seed yield per plant, number of seeds per pod, pod length, days to maturity, plant height, days to 50% flowering and number of pods per plant had moderate contribution towards total divergence (Patel et al. 2010a). Study carried out for the assessment of genetic divergence among 50 accessions of horsegram using Mahalanobis D2 technique revealed no relationship between geographical origin and genetic divergence in the cluster formation (Dasgupta et al. 2005). The major divergence was contributed by the flowering duration, seed yield per plant, 100-seed weight, soluble protein percentage and days to flowering (Dasgupta et al. 2005). Chahota et al. (2005) assessed the presence of variability among 63 landraces of horsegram and reported adequate genetic diversity for days to maturity, plant height, number of pods per plant and leaf colour. They found HPKC-1, HPKC-6, HPKC-7, HPKC-9, HPKM-51 and DMK-12 as the most potential lines. Similarly, Sunil et al. (2009) could not find any relation between genetic diversity and their eco-geographical distribution on the basis of genetic divergence studies using D2 technique. Prakash et al. (2010) assessed the genetic diversity among germplasm lines of horsegram using D2 statistics and suggested that genotypes GPM-12 and GPM-29 had higher inter-cluster distances and may be crossed with other genotypes to get more transgressive segregants. Geetha et al. (2011) studied genetic divergence among 100 germplasm accessions of horsegram for seed yield and yield-attributing traits and grouped all the germplasms into 16 clusters. Cluster I comprises KK-30-kr, HA-871-5-67/2, Bangalore-208, 12-EB, HYD-90-20-kr, KK-20-kr, KPT-20-kr, Bangalore-302, Bangalore-96, 10-EB, 14-EC, 13-EB, Bellary Buff and Paiyur-7, and cluster XIII has Kambainallur; Hebbal-1 germplasm lines showed maximum inter-cluster distances indicating the choice of hybridization for improvement of traits through pedigree breeding. Varma et al. (2013) studied 23 accessions of horsegram to assess the presence of genetic diversity and reported sufficient genetic variation. They observed that test weight (8.70%) followed by seed yield per plant (5.53%), pod length (2.37%) and seedling dry weight (50.99%) contributed maximum inter-cluster distance towards the divergence. On the basis of the maximum inter-cluster distance, they reported HG-18 and AK-38 as the most divergent genotypes and may be used as promising parents in the hybridization programme to obtain better segregants. These accessions have also been reported as the most

9.4 Correlation and Path Coefficient Analysis

181

promising accession by other workers (Lal et al. 2001; Jayalakshmi and Ronald 2011). Combination of genotypes KCM-110, PDP-1, OHG-64, OHG-95, OHG-58-1, AK-21, AK-42, Bastav-2, Birsa and DLP-38, OHG-11, DLP-22, DLP-42, DLP-21, DLP-64, DLP-35, DLP-19, DLP-41, DLP-145, DLP-5, OHG-51, OHG-35, OHG-58-2, OHG-42, OHG-5-1, OHG-20, OHG-16, OHG-76, OHG-3, OHG-53, OHG-117, SK-2001, KCM-181, BGM-1, VZM-1, PHG-9, Urmi and Bastav-1 may produce superior segregants through biparental mating (Sahoo et al. 2014). Viswanath et al. (2016) studied the morphological diversity in 500 accessions of horsegram using principal coordinate analysis and grouped all the accessions in seven clusters. They reported that the accessions PHG-9, BGM-1 and DPI-2278 showed better performance for plant height, number of branches per plant, number of seeds per pod and 100-seed weight. Vijayakumar et al. (2016) studied the genetic diversity among germplasm of horsegram and reported that the genetic diversity is not related to the geographic diversity. They found PHG-21 as the most promising parent to obtain potential hybrid.

9.4

Correlation and Path Coefficient Analysis

The genotypic correlation provides the insight, degree of relatedness and genotypic association between two characters. The coefficient does not partition direct and indirect influences of a character to be quantified (Cruz et al. 2012). Path analysis, proposed by Wright (1921), informs about the causes involved in associations between the traits. With the help of path analysis, the information of direct and indirect influences of different traits on the principal variable can be assessed accurately because the improvement of one character affects the other character simultaneously. Correlation and path analysis have been used to categorize the characters that can be used indirectly for the selection of superior genotypes in various crops including horsegram (Pathak et al. 2011a; Prakash and Khanure 2000; Silva et al. 2015). Various researchers have recorded high positive correlation of seed yield with number of pods per plant, seed size, pod length, plant height and number of branches per plant (Agarwal and Kang 1976), number of seeds per pod and number of nodes per plant (Shivashankar et al. 1977), number of pods, number of secondary branches and 100-seed weight (Patil and Deshmukh 1983). A negative association of days to flowering and maturity with seed yield, number of seeds per pod and nodes per plant (Shivashankar et al. 1977; Ghorpade 1985) has been recorded. Ghorpade (1985) classified 216 genotypes of horsegram into three groups on the basis of days to 50% flowering and seed yield and observed that the seed yield had a positive association with days to the first pod maturity, number of pods per plant and seeds per pod, while seed yield had negative correlation with that of number of pods per plant. Similarly, strong positive correlation of seed yield with number of days to the first pod maturity, number of pods per plant and number of seeds per pod has also been observed with negative correlation between 100-seed weight and all other characters

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(Birari et al. 1987). The four cultivars of horsegram, namely, CO-1, CODB-2, CODB-5 and CODB-6, subjected to various photoperiods showed positive correlation between the flowering nodes and the leaves (Manian et al. 1987). The seed yield, plot yield and number of clusters were found to be positively correlated with each other (Dabas et al. 1990). Higher correlation of seed yield recorded with pod length, number of pods per plant, number of seeds per pod and dry weight of number of pods per plant (Lad et al. 1999; Nagarajan et al. 1999) revealed that a plant having more number of primary branches, pod-bearing nods and number of pods may be the desirable plant type for the improvement in horsegram. The varieties having early maturity, higher number of branches, pods and higher seed weight may be a good choice for cultivation of horsegram (Tripathi 1999). The seed yield was positively and significantly correlated with number of pods per plant, number of seeds per pod, pod length, 1000-seed weight plant height, number of leaves, number of branches, nodule number and leaf area index (Roopdevi et al. 2002). Pandya et al. (2003) reported significant correlation of grain yield with 100-seed weight, number of seeds per pod, number of branches per plant and plant height. Bhadait (2005) observed significant positive correlation of seed yield with plant spread, number of pods per plant, number of seeds per pod, number of branches per plant and 100-grain weight. The plant height, number of branches and number of seeds per pod had high positive direct effects on grain yield, whereas negative direct impact of pod length was observed on the grain yield (Khan and Ahmed 1989). While Singh (1990) observed that the grain yield was positively and significantly associated with number of pods per plant, number of grains per pod and pod length, number of pods per plant had highest direct effect followed by test weight (Prakash and Khanure 2000) in horsegram. Similarly, Asha et al. (2006) also observed maximum direct effect of number of pods per plant on yield followed by pod length. The researchers also found direct negative impact of number of primary branches, pod width and seed length on the seed yield of the crop suggesting that these parameters are less important for the selection. The plant height and number of primary branches also exerted positive indirect effect via number of pods per plant on seed yield of the crop. The increase in the height of the plant will lead to more number of branches and pod-bearing nodes. Therefore, the cumulative effect of increase in plant height may enhance the seed yield. Prakash and Khanure (2000) reported positive association of seed yield with the number of pods per plant, number of branches per plant and plant height. They suggested that plant height, number of branches and pods per plant may be the important components of seed yield in horsegram. The maximum correlation has been recorded between number of pods per plant and seed yield followed by pod length and width, plant height and number of pods per plant and number of primary branches and number of pods per plant, while negative association between pod length and seed width and pod width and seed length has been recorded (Asha et al. 2006). Number of pods per plant had maximum direct effect on the seed yield followed by number of secondary branches (Agarwal and Kang 1976; Patil and Deshmukh 1982). It was observed that the pod weight and 100-seed weight contributed more towards seed yield as compared to number of seeds per pod (Ganeshian 1980).

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Similarly, number of pods and number of nodes on the plant were the major yieldcontributing traits (Kallesh 1987). Number of clusters per plant followed by days to flowering and number of pods per plant had highest direct effect on seed yield (Dobhal and Rana 1994). It was reported that the pod length, number of pods per plant, number of seeds per pod and 100-seed weight are the important traits for the improvement of seed yield in horsegram (Sharma 1995). The positive correlation of number of pods per plant with seed yield was partitioned into direct and indirect effects (Lad et al. 1999), and it was observed that days to the first flower, bud appearance, pod length, number of seeds per pod, test weight, number of compound leaves, days to maturity and dry weight of plant had indirectly influenced to increase the seed yield. Nagarajan et al. (1999) worked out path coefficient and selection indices on 20 genotypes of horsegram for seed yield and reported that the correlations of number of primary branches, pod-bearing nodes per plant and pod yield with seed yield were mainly due to their direct effects. They suggested that the desirable plant type in horsegram should have high number of primary branches, pod-bearing nodes and pods to realize high seed yield (Nagarajan et al. 1999). The partitioning of correlation data revealed that days to 50% flowering and number of pods per plants had maximum direct effect while number of pods per plant exhibited indirect influence on seed yield via days to 50% flowering, plant height and number of branches per plant indicating that number of pods per plant, days to 50% flowering and plant height may be considered for increasing seed yield in horsegram (Chakrabarty and Singh 2002). Correlation and path analysis revealed that the number of pods on main branches and 100-seed weight are the important traits to be considered in selecting for higher seed yield per plant. The direct and indirect effects of yield-related traits on grain yield of horsegram investigated using 18 genotypes revealed that number of branches per plant, 100-seed weight, days to maturity, plant height and number of seeds per pod had the highest direct impact on grain yield suggesting that selection for yield would be successful using these characters (Pandya et al. 2003). The plant spread had the highest and positive direct effect on grain yield followed by number of branches per plant suggesting the importance of these traits during the improvement of grain yield (Bhadait 2005). Mahajan et al. (2007) assessed contribution of different characters towards yield to identify phenotypically stable genotypes of horsegram and observed that seed yield was associated with pod length, plant height, seed filling period, days to flowering and days to maturity. They reported that the days to maturity and pod length were the most important characters for genetic improvement in horsegram. Nandi and Tah (2014) studied growth variability and correlation studies in horsegram and reported positive association among plant height and leaf area, pod length, number of pods per plant, number of grains per pod and seed yield per plant. Neelam et al. (2014) recorded significant correlation between number of pods per plant and yield per plant. The correlation coefficient suggests that the seed yield of horsegram can be improved with the selection of plants having higher number of branches per plant, seeds per plant, pods per plant, higher 100-seed weight and seed length-breadth ratio (Neelam et al. 2014).

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Seed yield had a significant positive correlation with several characters such as biological yield, number of pods and number of branches suggesting that seed yield is a dependable character on various yield-attributing traits (Singh et al. 2020). Biological yield, 100-seed weight, number of pods, days to 50% flowering and number of seed per pod had highly positive and direct influence on seed yield revealing their importance to get higher yield in horsegram (Singh et al. 2020).

9.5

Hybridization

Hybridization is a process of interbreeding. It may happen between the individuals of different species or same species. The hybridization between different species or genetically different individuals is known as interspecies, and hybridization between same species is known as intraspecific hybridization. The process is more common in plants as the pollen from flowering plants scatters extensively and may land on flowers of other species resulting into hybridization. Therefore, hybridization in nature is a very common phenomenon. It is employed in breeding programmes to acquire desirable variation among lineages for development of novel phenotypes. Plant hybridization was studied long back in 1760 by Josef Kolreuter who reported that interspecific hybridization in nature is rare unless humans disturb the habitat. Since then, many studies on hybridization have been documented for identifying gene flow and growth (Payseur and Rieseberg 2016). Hybridization studies in horsegram are limited. Horsegram is a self-pollinated crop and has cleistogamous nature of flowers (Sundararaj and Thulasidas 1976). The anther of flower dehisces longitudinally on the previous day of flower opening. Pollen grains are bigger in size and fully cover the stigma. The flowers of the crop open in the night and petals fold back after 24 h. All these conditions make difficult to distinguish from mature unopened buds and affect the studies on anthesis and techniques for selfing and crossing. The hybridization studies between photosensitive and day-neutral varieties having black and brown coloured seeds suggest that the photoperiodic response is controlled by complementary or inhibitory gene action. The black colour was found to be dominant colour over the brown colour (Sreenivasan 2003). Long back in 1959, Sen and Bhowal observed dominance of black seed and purple plant colour over brown seeds and green pods and also suggested that these characters are dependent on a single gene or two closely linked genes. The black seeded parents have early flowering which is a dominating character over the late flowering of brown seeded parents. The gene governing the pigmentation and time of flowering inherited independently in horsegram. It was also reported that the relations between two duplicate genes and non-dominance of either of these two genes by an inhibitory gene were responsible for pigmentation in calyx (Kulkarni et al. 1978). Besides this, the inhibitory action of other common genes has also influenced the pigmentation. The studies on inheritance patterns and gene action controlling the quantitative traits are meagre in horsegram. Horsegram is autogamous in nature. Attempts for induction of polyploidy have been carried out but it was not successful. The seeds and apical buds of one-week-

9.7 Diallel Analysis

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old seedlings were subjected to Colchicines treatment to induce polyploidy (Sen and Vidyabhushan 1960). The Colchicine-treated apical buds developed tetraploids in the young plants. The germination of treated seeds was similar or lower as compared to diploid seeds. The treated seedlings and seedling of treated seeds have slow initial growth and produced less number of thicker stems having larger flowers as compared to diploid one. The number of pods was higher in tetraploid plant but had fewer seeds as compared to diploid plant. Although the pollen fertility of tetraploid was higher but due to zygotic sterility, it had lesser seeds (Sen and Vidyabhushan 1960).

9.6

Inheritance Studies

The genetic inheritance studies provide insight about the transfer of information from one progeny to another. The inheritance occurs due to the transfer of genetic material from parents to their offspring, and various characteristics including colour encoded on the DNA are passed down to the generation. Long back it was reported that a single factor was liable for the presence and absence of pigmentation in horsegram (Ayyangar et al. 1934). The studies on the mode of inheritance of purple pigmentation in various plant parts revealed that the purple spot on petal is independent of these genes (Ayyangar et al. 1934). Later, it was observed that the black seed colour and colouring on various plant parts of the horsegram are due to a single or a pair of closely linked genes (Sen and Bhowal 1959). The black seed colour and earliness of flowering were found to be dominant over brown seed colour and late flowering of brown seeded plants, respectively, but the factors for pigmentation and flowering were inherited individually (Sen and Bhowal 1959). The horsegram varieties have also been described on the basis of seed coat colour (Sundararaj and Thulasidas 1976). The environmental vagaries during the ripening process have also influenced the seed coat colour in horsegram resulting into different colours of seeds on a same plant. Kulkarni et al. (1977) suggested that standard petal can be used as a marker gene expression of black seed coat colour and purple pigmentation on different parts of plant.

9.7

Diallel Analysis

Selection of superior parents and selection method are the prime strategies for any plant breeding programme. Knowledge about the type of gene action, heterosis and combining ability prevailing the inheritance of the important traits have immense importance for planning of a successful plant breeding. The diallel analysis deals with the study of combining ability and gene action, and its method was initially proposed by Jinks and Hayman (1953) in form of graphical analysis which was later expanded by Jinks (1954) and Hayman (1954a, b). Estimation of combining ability in diallel crosses (Griffing 1956a, b) was reported to be better as compared to the graphical analysis in expecting the superiority of genotypes (Tandon et al. 1970) and

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give more reliable information as it is not regulated to one gene model and have flexible assumptions (Arunachalam 1976). The combining ability is further classified into general combining ability (GCA) and specific combining ability (SCA). The GCA is an average performance of a strain in a series of crosses while SCA is the deviation of specific crosses from the predicated GCA (Allard 1960). Diallel analysis was carried out in horsegram for estimation of combining ability using pod yield and yield-attributing traits (Kabir and Sen 1990). They observed that the repeated selection on the basis of biparental mating from selected recombinants was useful for exploiting additive and dominant characteristics. In their study, additive genetic variance was found to be important for days to flowering and pod length (Kabir and Sen 1990).

9.8

Heterosis

The information of performance of parents with respect to their hybrids is very useful for plant breeders. The assessment of heterosis magnitude helps in the preparation of breeding methodology and finding the best crosses. Heterosis studies give an insight towards the extent of heterosis and help in the isolation of crosses having high heterotic potential. Various yield-attributing traits have significant role in the magnitude of heterosis. The studies on heterosis in horsegram are limited. Alle et al. (2014) studied heterosis for yield and yield contributing characters using nine lines, namely, PDM-1, HGP-80, VZM-1, HGP-43, TLR-646, HGP-44, HGP-67, TLR-811 and HGP-40, and three testers, namely, Palem-1, Palem-2 and AK-42 of horsegram. They obtained 27 F1 crosses through line × tester mating system. The crosses HGP-67 × Palem-2, HGP-40 × AK-42, HGP-67 × AK-42, HGP-44 × Palem2 and HGP-80 × AK-42 based on the mean performance and heterosis had higher seed yield and yield contributing characters.

9.9

Genetic Variability

The genetic variability is an important prerequisite for beginning of any crop improvement programme. The higher genetic diversity will lead to more probabilities of developing desirable plant types. A crop has two types of variability, that is, genotypic and phenotypic. The genotypic variability is the reflection of presence of diversity in the population, while phenotypic variability is a combined expression of genotype, environment and their interaction. Horsegram has wide genetic variability that can be utilized to improve the economic traits including seed yield. Various workers have recorded significant variability for different traits, namely, plant height, number of branches, number of nodes, number of pods, days to flowering, days to maturity, pod length, pod yield and seed yield in horsegram (Ramkrishnan et al. 1978; Ganeshian et al. 1982; Suraiya et al. 1988; Singh 1990; Balan et al. 1992; Dobhal and Rana 1994; Rao and Nanda 1994; Sood et al. 1994;

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Savithramma et al. 1996; Nagarajanet al. 1997; Samal and Senapati 1997; Lad et al. 1998). Little information on the genetic improvement of this crop particularly for grain yield and yield-attributing traits is available. The varietal improvement in this crop is mainly carried out through single plant selection; therefore few improved varieties could be developed that are suited to local climatic conditions. In addition to single plant selection, other types of breeding programme including hybridization followed by selection for several important characters are required to speed up (Kumar 2006). Varieties with trypsin and growth inhibitors may get priority to combat the problem. There is an essential requirement to develop economical control measures and good packages of practices to reduce the pest infestation in the field and storage.

9.9.1

Genotypic and Phenotypic Coefficient of Variation

The information on genotypic coefficient of variation (GCV), phenotypic coefficient of variation (PCV), genetic advance and heritability is essential for development or advancement of genotypes and desired improvement in the existing varieties. The increase in the seed yield has always been one of the major intentions of a plant breeder. Seed yield is a complex trait and is influenced by both gene and environmental conditions; therefore, direct selection or evaluation of this trait is very difficult. So, indirect selection, that is, assessment of characters associated with seed yield should be carried out and the traits closely associated with the seed yield may be exploited. Adequate information on the magnitude and type of genetic variability and their corresponding heritability is necessary to improve grain yield potential of crops because selection of superior genotypes is relative to the amount of genetic variability present along with the extent to which the characters are inherited. The genotypic variability was used in terms of GCV first time by Fisher (1930) wherein he suggested a method for separation of genotypic effects on the basis of phenotypic and environmental factors. The GCV has been used as a relative magnitude of genetic diversity present in the crop and provides an insight to compare the presence of genetic variability for different traits (Hutchinson 1940). Later various statistical methods have been developed for the calculation of genetic component of variance (Frankel 1947; Burton 1952; Panse and Sukhatme 1967). Highest GCV has been observed for number of nodes followed by number of branches and number of pods, whereas it was moderate for seed yield and plant height and low for seeds per pod and pod length in horsegram (Sreekantradheya et al. 1975). Similar results were reported by other workers during the study of 100 genotypes of horsegram (Shivashankar et al. 1977; Ganeshian 1980). The higher variability for number of nodes, number of pods and plant height is due to genetic factors and suggest good scope for selection in the crop improvement. Patil and Deshmukh (1982) recorded significant variability for plant height, days to flowering, days to maturity, number of primary, number of secondary branches, number of pods and seed yield per plant. The variability was narrow for 100-seed weight and number of seeds per plant. Ganeshian et al. (1982) also found similar GCV and PCV for

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these traits. They observed lower values of GCV and PCV for number of seeds per pod, days to flowering, 100-seed weight and number of pods per plant. Low GCV for days to maturity has been recorded in this crop (Varma et al. 2013). Highest GCV was observed for pods per plant, plant height, days to 50% flowering and days to maturity while it was lowest for 100-seed weight (Suraiya et al. 1988). The magnitude of GCV and PCV was similar for seed yield, days to flowering, maturity and 100-seed weight (Sood et al. 1994). Dobhal and Rana (1994) reported high heritability for number of clusters per plant, number of pods per plant and seed yield per plot in horsegram. Savithramma et al. (1996) also reported narrow values of PCV and GCV for days to flowering, days to maturity, number of seeds per pod, 100-seed weight, threshing percentage and protein percentage indicating lesser control of environment on the expression of these traits. Maximum variation for plant height, number of pods per plant, days to 50% flowering, number of branches per plant and yield per plant has been recorded (Samal and Senapati 1997), while it was minimum for 100-seed weight. Lad et al. (1998) reported larger genetic variability for yield and yield-attributing components in horsegram. They observed that the PCV was higher for almost all the traits as compared to GCV. Pathak et al. (2011b) also observed higher PCV in comparison to GCV in clusterbean. Lower estimates of PCV and GCV have been reported for days to flowering and days to maturity, but these were higher for primary branches (Nagarajan et al. 1997). Lower variability for pod length and number of seeds per pod (Sreekantradheya et al. 1975; Balan et al. 1991; Savithramma et al. 1996; Rao and Nanda 1994), days to flowering, days to maturity and 100-seed weight (Samal and Senapati 1997; Sood et al. 1994; Rao and Nanda 1994) has been observed. Prakash and Khanure (2000) reported a wide range of phenotypic variabilities among days to 50% flowering, plant height, number of branches, number of pods, test weight and seed yield. The PCV was higher with their corresponding GCV and ranged from 2.33 (days to 50% flowering) to 42.24 (yield per plant). The GCV was lower for days to 50% flowering (1.73) and higher for seed yield per plant (42.04). The difference between PCV and GCV was less for number of pods per plant and maximum for seed yield per plant suggesting that number of pods per plant was least influenced, whereas seed yield per plant was highly influenced by the environments. The heritability coupled with genetic advance was higher for number of pods per plant indicating the presence of additive gene effects. High heritability and low genetic gain for test weight and seed yield per plant indicated that these traits were controlled by non-additive gene action (Prakash and Khanure 2000). Nehru et al. (2000) evaluated 21 genotypes of horsegram under dryland conditions to study different variability parameters for yield and associated components and reported high heritability for grain and biomass yield. They noticed moderated heritability for nodes on main stem, plant height, nodes on primary branches and pods on primary branches, while low heritability was observed for number of primary branches, pod length and number of seeds per pod. The maximum GCV were estimated in plant height, number of seeds per pod, pod length, 100-seed weight, fresh weight and vigour index. Higher and moderated GCV indicated that improvement could be achieved for such characters through simple

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selection (Shukla et al. 2010). Further, they observed that the local germplasm collection had wide variability for different traits coupled with high heritability and genetic advance and early vigour may be used as one of the selection criteria in breeding programme for yield improvement. The PCV was higher than GCV and found to be high to moderate for all traits except for days to 50% flowering (Singhal et al. 2010). They also reported existence of wide diversity among the genotypes studied on the basis of genetic divergence. High coefficient of variation both at phenotypic and genotypic levels was found for number of pods per cluster, number of clusters per plant, pod yield per plant, biological yield per plant, number of branches per plant, seed yield per day, biological yield per day, number of pods per plant and plant height (Sahoo et al. 2010). High heritability coupled with high genetic advance for number of pods per cluster, number of clusters per plant, number of branches per plant, number of pods per plant, seed yield, pod yield and biological yield per plant and plant height indicated a positive response of selection for these characters (Sahoo et al. 2010). The highest GCV was observed for number of pods per plant followed by seed yield per plant, whereas very low GCV estimates were observed for pod length and number of primary branches per plant. High heritability coupled with high GCV and high genetic advance as per cent mean for seed yield indicated low environmental influence and high transmission index (Varma et al. 2013). PCV was higher than the GCV for all the characters studied for horsegram. The maximum difference between PCV and GCV for number of primary branches per plant was a clear indication of maximum influence of environment, while it has minimum influence on test weight (Samal and Senapati 1997; Varma et al. 2013; Priyanka et al. 2019). Higher PCV and GCV was reported for number of pods per plant and seed yield in horsegram (Singh et al. 2019). A study conducted under moisture stress conditions on 30-horsegram genotypes explained that PCV was higher to the corresponding GCV for all the traits studied (Visakh and Bindu 2022) which indicated greater option of their improvement through simple selection under the environment of study.

9.9.2

Heritability and Genetic Advances

The presence of higher magnitude of genetic variability is main source for planning and execution of a breeding programme. The GCV and PCV help in exploring the occurrence of variability in breeding population, while heritability is the index of transmissibility of characters. The GCV alone does not indicate the proportion of total heritable variations, while heritability indicates as better indicator with this respect. Similarly, heritability values as well as estimates of genetic advance are more useful than heritability alone under a selection programme. The estimates of heritability and genetic advance help in the development of suitable selection strategy for higher yields in the agriculture crops. The heritability is controlled by environment; therefore; the knowledge on heritability alone will not provide reliable information (Johanson et al. 1955). Hence, heritability estimates in conjunction with the predicted genetic advance will be more reliable for providing consistent

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information (Shukla et al. 2006). In general, higher heritability estimates accompanied with higher genetic advance for a trait suggest that the genes governing the trait may have additive effect, thereby indicating the importance of these characters for selection. Higher estimates of heritability and genetic advance were reported for seed yield per plant; 100-seed weight and number of pods per plant have been reported in horsegram (Sreekantradheya et al. 1975; Agarwal and Kang 1976). Higher genetic advance for number of secondary branches and number of nodes per plant and higher heritability values for number of primary/secondary branches, number of nodes per plant, days to 50% flowering and 100-seed weight has also been reported (Shivashankar et al. 1977). Similarly, Ganeshian (1980) observed maximum heritability values for days to flowering and maturity. Higher estimates of heritability and genetic advance have been recorded for various traits, namely, seed yield, number of primary/secondary branches and number of pods per plant (Patil and Deshmukh 1982, 1983). Maximum estimates of heritability for test weight, maturity, leaf area, yield per plant, number of pods per plant and dry weight and its relatively lower magnitude have been observed for plant height and number of seeds per pod. High estimates of genetic advance and heritability have been recorded with yield per hectare (Birari et al. 1987), number of primary branches, number of seeds per plant and number of pods per plant (Kallesh 1987), days to 50% flowering, days to maturity, plant height and number of branches per plant (Suraiya et al. 1988), number of nodes, clusters per plant and days to flowering (Dobhal and Rana 1994), number of pods per plant, number of seeds per pod and yield per plant (Samal and Senapati 1997), number of pods and number of clusters per plant (Venkateswarlu 2000a). High heritability coupled with moderate genetic advance has been observed for the number of seeds per pod (Senapati et al. 1998), days to maturity and 100-seed weight (Chakrabarty and Singh 2002) indicating that the gene governing the traits may have additive effect. High heritability was reported for number of pods per plant, while seed yield had higher heritability coupled with the genetic advance (Singh et al. 2019). Higher heritability coupled with higher genetic advance was reported for days to 50% flowering, primary branches, plant height, number of pods, harvest index, days to maturity, leaf area index, root dry weight and seed yield per plant (Visakh and Bindu 2022) suggesting that these traits are under the control of additive gene action and their improvement is possible through selection.

9.10

Genotype-Environmental Interaction

The genotype-environmental interaction (G × E interaction) is an assessment of response of two different genotypes to the varied environments. The expression of a phenotype is a combined reflection of genotype, environment and differential phenotypic response of genotypes to different environments. The detailed knowledge of type of genetic structure and mechanisms controlling genotype and environment will present an insight to develop a crop variety having enhanced capability to

9.11

Mutation

191

abide and succeed in the changing location of environment (de Leon et al. 2016). The stable performance of horsegram varieties under varied environments is of great significance for its varietal improvement. Various workers have worked out the information on G × E interactions and stability of horsegram varieties (Deshmukh et al. 1986; Henry and Daulay 1988; Birari et al. 1990; Savithramma et al. 1996). Birari et al. (1990) observed that DPLK-111, DPLK-77, DPLK-292, DPLK-35 and DPLK-11 were the most suitable genotypes for favourable environmental conditions. The genotypes B-5-12-2 and BGM-2 were found promising from the stability point of view (Savithramma et al. 1996). The G × E interaction studies for protein content were carried out (Tah and Dasgupta 1997) under two different sets of environment, and significant difference in protein content was recorded with breeding lines of cross combination of horsegram having significant G × E interactions. Venkateswarlu (2000b) reported genotypes PHML-42 and Palem-2 as the most stable genotypes under different environmental conditions out of 20 genotypes during the stability studies. The seed yield and yield-attributing components of 18 genotypes evaluated under 2 rainfall environments (400 and 615 mm) revealed significant variations for days to flowering, days to maturity, plant height, number of branches per plant, number of pods per plant, number of seeds per pod, 100-seed weight, plant stand at maturity and grain yield (Ram et al. 2003). In a study comprising of 60 genotypes of horsegram (Bhadait 2005), PCV were found slightly higher as compared to GCV estimates, and high heritability coupled with high genetic advance was observed for number of branches per plant, yield per plant, yield per plot, number of seeds per pod and plant spread suggesting the additive gene control in the inheritance of characters. Shukla et al. (2010) studied genetic and seed quality parameters in horsegram genotypes under mid hills of Northwestern Himalaya to identify stable genotypes with better seed quality parameters and reported that the genotypes PRH-01, PRH-10 and VLG-1 can be used in future crossing programme to develop superior high-yielding genotypes in the mid hill conditions of Northwestern Himalaya.

9.11

Mutation

Mutation creates appropriate genetic variability in the plant type as well as in its performance in terms of productivity and nutritional alterations. The beauty of mutation breeding lies in creating the variability without harmful effects in plant type and its performance. For this, selection of appropriate mutagens and their doses is important to create desirable variability without deleterious effects. Sen and Vidyabhushan (1960) attempted induction of polyploidy in the seeds and apical buds of horsegram using colchicine. The seed treatment was not successful, but the apical buds showed development of polyploid in young plants. They obtained pure tetraploids from these plants in the next generations. The tetraploid had comparatively more growth, thicker stem and higher number of flowers and pods, but the number of seeds in the pod was less.

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Various workers have induced mutation using gamma radiations in horsegram (Gupta and Sharma 1996; Shirsat et al. 2010; Raghu Ram Reddy et al. 2010) for desirable traits. The frequency of chlorophyll mutation increased with increasing ethyl methane sulphonate (EMS) concentration and decreased thereafter in M2 generation, while there was an increase in the mutation frequency with increasing dosage of gamma rays from 5 to 15 kR, and it decreased thereafter in M2 generation (Kulkarni et al. 1978). It was observed that EMS induced more mutation, that is, dwarfness and testa colour as compared to gamma rays (Kulkarni and Shivashankar 1978). Sinha and Himansu (1984) reported an increase in the chlorophyll content in horsegram with gamma radiation (1.25–15 kR). Rudraswamy (1987) reported induction of chlorophyll mutants in varieties of horsegram. In this study, he found that the gamma rays induced wider spectrum of chlorophyll mutants as compared to EMS. Variability for grain yield and dry matter production has been induced with 10–80 kR gamma rays into the M3 progeny of horsegram varieties. The local horsegram lines were subjected to 20, 40 and 60 kR gamma rays (Samal and Senapati 1997), and 15 mutants were evaluated with three standard checks in M4 progeny. They observed that KHG-60-5 was the higher yielder followed by KHG-40-8 and KHG-20-3 mutants. The effect of gamma rays (5–80 kR), EMS and diethyl sulphonate (DES) was studied and found that the lower dosages of gamma rays showed stimulatory effect while all the concentrations of EMS inhibited germination percentage except the case of pre-soaked EMS treatment (Bakle and Poci 1991). Micro-mutations are more effective and induce higher amount of desirable mutations and may provide future base for selection through induction of vast polygenic variability (Solanki and Sharma 1999). The increased dosage of gamma rays, EMS and DES caused abnormalities in plant height, leaf numbers, leaf size, shape, induction of chlorophyll chimeras and chromosomal abnormalities. The lower dosage of gamma rays and concentration of EMS influenced the number of pods, seed yield and protein content. Vishwanath et al. (2002) studied the effect of gamma rays and EMS on seed fertility and chlorophyll content in horsegram varieties, namely, HPK-4, HH-2 and BGM-1, and reported that the mutagens have inhibited the growth and food accumulation in the developing seeds. Datir et al. (2007) irradiated seeds of horsegram with different doses (200, 300, 400, 500, 600, 700 and 800 Gy) of gamma rays and treated with varying concentrations (0.4%, 0.6%, 0.8%, 1.0%, 1.2%, 1.4% and 1.6%) of EMS to determine their effects on seed germination and plant survival. The gamma radiation doses of 400 Gy or below were considered suitable for inducing mutations, whereas EMS concentrations below 1.4% with 6 h soaking were suitable for mutational experiments in horsegram (Datir et al. 2007). Bolbhat and Dhumal (2009) studied the effect of gamma radiation (100–600 Gy) and EMS (0.2–0.6%) separately and in combination of both on seed germination and recorded gradual reduction in seed germination, root length, shoot length and seedling height with increasing doses of mutagenic treatment in M1 generation, while in M2 generation, the mutagenic treatments with lower doses were stimulative. Higher doses of gamma radiation and EMS had inhibitory effect on chlorophyll and morphological mutations (Bolbhat

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Mutation

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and Dhumal 2009). Sanjeev-Kumar et al. (2009) treated dry and healthy seeds of horsegram with gamma rays (25, 30, 35, 40 and 45 Kr) and EMS (0.1%, 0.2%, 0.3%, 0.4% and 0.5%) to study the biological damage by both the mutagens separately and with their combinations. They recorded reduction in all the traits with increasing doses of gamma rays and EMS and with their combinations in both the treatments. Gamma rays and their combinations with EMS were found highly effective for modifying majority of the traits. EMS was found more efficient than gamma rays on the basis of reduction in plant survival, seedling height, seedling leaf reduction, root length, shoot length and seed sterility (Sanjeev-Kumar et al. 2009). Bolbhat and Dhumal (2010) studied on the desirable mutants for pod and maturity characteristics in M2 generation of horsegram and found that the lower doses/concentrations of gamma radiation and EMS induced greater viable macro-mutations than higher doses/concentrations. Patel et al. (2010b) studied the effect of different doses of gamma rays (5, 10, 15, 20, 25, 30, 35 and 40 kR) on three varieties of horsegram, namely, AK-21, AK-42 and MK-1, and reported that the germination percentage decreased with increasing gamma rays doses in all three varieties in M1 generation under field conditions, while with higher doses, chlorophyll-deficient chimeras and morphological abnormalities increased. With the increase in gamma ray doses, fresh and dry weight of seedling was reduced in all the varieties. The maximum reduction in survival was reported with 40 kR, while it was lowest with 5 kR in all the varieties. They reported MK-1 as most sensitive genotype while AK-42 and AK-21 as least sensitive genotypes to gamma ray irradiation in M1 generation. The higher number of seeds per pod with 5 and 10 kR radiation in AK-42 and MK-1 revealed the efficacy of mutagenic treatment (Patel et al. 2010b). Bolbhat and Dhumal (2012) subjected the seed of horsegram to gamma radiation (100, 200, 300 and 400 Gy), EMS (0.2%, 0.3%, 0.4% and 0.5%) and combination treatments and reported that both the mutagens proved to be very effective to induce variability in quantitative traits like plant height, number of primary branches per plant, days required for first flowering and first pod maturity, number of pods per plant, pod length, number of seeds per pod, 1000-seed weight and seed yield per plant in M2 and M3 generations. A horsegram variety (CRIDA-18R) developed with the help of mutation breeding matures within 87 days and gives higher seed and pod yields (Raghu Ram Reddy et al. 2010). The variety having brown seeds is resistant to yellow mosaic virus, powdery mildew and mites, and its pods do not shatter. Chahota et al. (2013) irradiated two varieties of horsegram, namely, HPKC-2 and VLG-1, with three dosages, that is, 150, 250 and 350 Gy, of gamma rays to create variation and to modify the plant type. They observed that the M2 generation was morphologically different from the parental lines for one or the other traits and suggested that gamma radiation is one of the suitable mutagens for creation of mutation in horsegram. Horsegram variety Paiyur-2 was subjected to irradiation with gamma rays, electron beam and its combinations to assess their effect on the genetic variability, and considerable transgressive variation was observed in M2 progeny (Priyanka et al. 2021). The study revealed encouraging shift towards higher yields and yieldattributing traits suggesting that selection made on early generation may be more

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effective (Priyanka et al. 2021). Genetic variability among horsegram genotypes was induced using gamma rays and EMS irradiation, and the morphological data recorded from mutants were subjected to genetic analysis (Pushpayazhini et al. 2022). All the mutants were grouped into ten groups with the significant intra- and inter-group variation exhibiting wide induced variability. The mutants showed high genotypic and phenotypic coefficient of variation for seed yield and yield-attributing traits (Pushpayazhini et al. 2022).

9.12

Nitrogen Fixing Ability

Rhizobia belonging to Proteobacteria subdivision are soil bacteria and are responsible for the symbiosis with leguminous plants (Allen and Allen 1981). The beneficial interaction between legume and rhizobia provides nitrogen to soil without any hazard to the environment. Rhizobia are generally dispersed in the agro-ecosystem and play an important role in yield/growth improvement of various crops. Legumes support the ecosystem, agriculture and agro-forestry efficiently due to their ability to fix the atmospheric nitrogen in symbiosis mode (Graham and Vanace 2003). Nitrogen fixation is an interesting natural incidence involving some legumes that fix the atmospheric nitrogen under favourable conditions and supply it to the plant under its vicinity (Hungria and Vargas 2000; Chen et al. 2002). It is considered as the most environment-friendly approach for obtaining nitrogen in the ecosystem (Jensen and Hauggaard 2003) and is getting attention as an alternative source of supply of nitrogen. Horsegram rhizobia are phylogenetically distinct and produce bacteriocin (Edulamudi et al. 2011) playing an important role in interspecific competition. Prabhavati and Mallaiah (2009a) examined the production of indole acetic acid (IAA) by 32 salt-tolerant strains of rhizobium from horsegram and observed that eight strains were efficient for IAA production at 0.2 and 0.4 M salt concentrations. They suggested that the horsegram rhizobium strains can be exploited for IAA production under salt stress conditions. The effect of different carbon, nitrogen and cell wall affecting agents on phosphate solubilization by Rhizobium sp. nodulating horsegram was studied (Prabhavati and Mallaiah 2009b), and it was observed that genotypes HGR-19 and HGR-22 were efficient phosphate solubilizers under various cultural conditions. They also noticed glucose and sucrose as best carbon and ammonium sulphate as best nitrogen source. Enhanced plant growth and yield (Keshava et al. 2007), seeding growth and shoot length (Kala et al. 2011) have been reported with rhizobial inoculants/nitrogen fixing bacteria as compared to that of seedling raised by non-bacterized seeds. The increase in the root length may be due to the secretion of IAA by the bacteria that facilitate root initiation, cell division, cell enlargement and absorption of more nutrients from the soil (Mantelin and Touraine 2004). The increase in root dimensions is directly related to the colonization by desired beneficial rhizobia. The direct effect of root dimensions and rhizobial colonies may induce the plant productivity and phosphate solubilization process (Bashan et al. 2004). The overproduction of ethylene leads to

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abnormal root growth and restricts the plant growth. Rhizobia inhibit the overproduction of ethylene, possibly due to low level of ethylene; root and vegetative parameters increase (Saraf et al. 2010). Seed inoculation with rhizobium had positively influenced the shoot growth, root length, number of nodules, yield and protein content of horsegram and has been considered as one of the promising fertilizers (Kala et al. 2011). Horsegram cultivation has extended from semiarid to sub-humid regions of India where salinity, pH and temperature conditions are not favourable to the crop due to hampered nitrogen fixation (Mishra et al. 2017). Rhizobial inoculations are the best solution to improve the nitrogen fixing ability in these areas. Mishra et al. (2017) isolated some rhizobium isolates that showed tolerance towards temperature, pH and salinity. These isolates may be utilized for seed bacterization of the crop in humid and semiarid regions of India.

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Quality and Nutrition

10

Abstract

Horsegram is an important crop that has significant role in sustainable farming and nutritional security in developing countries. The nutritional values of the legume are comparable to other pulses and provide cheap source of various nutrition. It has good therapeutic properties and has been traditionally used to cure kidney stones, asthma, inflammation, pain, bronchitis, leucoderma, urinary discharges, heart diseases, piles, etc. The nutritional composition, anti-nutritional factor and nutraceutical and medicinal properties of horsegram have been summarized in this chapter.

10.1

Introduction

Legumes are one of the most important agricultural produces that offer a wide range of vital nutrients, namely, protein, carbohydrates, dietary fibre, minerals and vitamins. Their consumption is highly recommended since ancient times (Erbersdobler et al. 2017). Legumes have been considered as the most potential source of proteins in human diet during the Ancient and Middle Ages of the human developments. Legumes possess higher protein as compared to other plant produces. They contain low fat and are free from saturated fat with some exceptions. Gluten free, presence of phytonutrients (isoflavones, lignans, protease inhibitors), low sodium content and presence of higher fibres make legumes a choice of food for healthy and sick persons. Horsegram has been identified as a potential food source for the future (Anonymous 1979). The nutritional quality of the legume is affected by various factors, namely, genotype, soil, fertilizer application, cultural practices, weather and climatic factors, postharvest handling and storage (Hornick 1992). The nutritious composition, medicinal properties and pest resistance nature make horsegram a rich source of # The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 R. Pathak, Genetics, Physiology and Cultivation of Moth Bean, Cowpea and Horse Gram, https://doi.org/10.1007/978-981-19-9956-7_10

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Quality and Nutrition

food, fodder, fuel supplement and green manure (Bhardwaj et al. 2013). The seeds of horsegram are generally utilized as cattle feed and are given to the cattle after boiling (Reddy et al. 2008; Kadam and Salunkhe 1985). Horsegram grains are good source of protein, carbohydrates, fat, minerals (Begum et al. 1977), essential amino acids, energy, lipid, iron (Bravo et al. 1999), molybdenum (Bravo et al. 1999), phosphorus, iron, vitamins and lower quantities of cysteine and methionine. It has been identified as possible future food source by the US National Academy of Sciences (Kadam and Salunkhe 1985; Sosulski and Young 1979). The boiled beans are used to prepare protein- and mineral rich-soups along with various other preparations such as curry, papad, etc. in South India. Nevertheless, the presence of oligosaccharides such as raffinose, stachyose, verbascose, etc. causes flatulence on its consumption and reduces the bioavailability of nutrients in the pulses (Jain et al. 2009). Nowadays, the anti-nutritional factors such as phytic acid, phenols and tannins found in horsegram have been exploited as antioxidants that show positive effect on human health (Bhatt and Karim 2009). The ancient Indian literatures Charak and Sushruta Samhita mention the application of horsegram seeds for treatments of piles, hiccup, abdominal lump and bronchial asthma and in regulating sweat (Pati and Bhattacharjee 2013). Studies revealed its application in curing kidney stones, asthma, bronchitis, leucoderma, urinary discharges, heart diseases and piles (Ghani 1998; Yadava and Vyas 1994), eradicating worms (Philip et al. 2009), hypolipidaemic and hypoglycaemic actions (Senthil 2009), inflammation and pain (Ramalingam et al. 2020). Horsegram seeds are rich source of dietary antioxidants (Siddhuraju and Manian 2007) and have antidiabetic effect (Gupta et al. 2011). Several functional ingredients of the crop work against hypercholesterolemia and obesity (Kumar et al. 2013).

10.2

Nutrient Value

Horsegram is one of the cheapest sources of protein, vitamins, calcium, iron and urease (Katiyar 1984). The grain contains 22–24% protein, 57.2% carbohydrates, 0.5% fat and 3.2% minerals (Begum et al. 1977), essential amino acids, energy, lipid (0.58–2.06%), iron (Bravo et al. 1999), molybdenum (Bravo et al. 1999), phosphorus, iron and vitamins. Bravo et al. (1999) also reported horsegram as a potential source of protein (25%), carbohydrates (60%), essential amino acids, energy and low content of lipid (0.58%), iron and molybdenum. Gopalan et al. (1999) reported 57.2% of carbohydrate, 22% protein, 5.3% dietary fibre, 0.50% fat, 287 mg calcium, 311 mg phosphorous, 6.77 mg iron and 321 Kcal energy in horsegram seeds. Horsegram is a rich source of iron, molybdenum and various vitamins. Its seeds contain comparatively higher quantities of polyphenols and haemagglutinins and scarce amount of methionine and tryptophan-like amino acids. A comparative study on the presence of polyphenols and tannins suggests that horsegram has higher polyphenol and tannin content as compared to other common legumes (Mishra and Pathan 2019).

10.2

Nutrient Value

205

Table 10.1 The proximate composition of whole and dehulled grains of horsegram

Grain Whole Dehulled Cotyledon Embryonic axe Seed coat

Proximate composition (%) Crude Moisture protein 11.5 23 9.7 22 5.8 22.6 8.4 18.6 3.9

9.1

Crude fat 1.5 1.6 1.8 2.6

Crude fibre 5.07 1.9 1.6 11.2

Carbohydrate 58 61 66.9 68.2

Ash 3.3 2.9 2.9 2.2

0.6

21.8

82.6

3.8

Source: Fuller et al. (2004), Krishna (2010), Subba Rao and Sampath (1979), Sudha et al. (1995); Verdcourt (1982); Prasad and Singh (2015)

The albumin-globulin protein and glutelin are the major fraction of its protein (Yadav et al. 2004). Horsegram seed also has high lysine content as compared to blackgram and pigeon pea (Gopalan et al. 1989). Arginine, histidine, lysine, valine, leucine, etc. are the major amino acids found in horsegram, while methionine and tryptophan are found in limited amount (Thirumaran and Kanchana 2000). Various other reports also revealed the legume as potential source of protein, dietary fibre, micronutrients and phytochemicals (Sreerama et al. 2012) including iron, molybdenum and calcium (Prasad et al. 2010; Bhokre et al. 2012). Horsegram also contains carbohydrate in rich quantity. Starch, oligosaccharides and dietary fibres are the major carbohydrates found in horsegram (Bravo et al. 1998). Sucrose, maltose, glucose, galactose, arabinose, fructose and inositol are the soluble sugars found in horsegram. The seeds of horsegram have higher insoluble dietary fibre as compared to kidney bean (Kawale et al. 2005), and its values are higher in seed coat and embryonic axe fractions. Various vitamins, namely, thiamine (0.4 mg), riboflavin (0.2 mg) and niacin (1.5 mg) per 100 g of dry matter (Bolbhat and Dhumal 2012), have also been reported in the seeds of horsegram. The dietary fibre content in seeds and flour of horsegram was worked out, and it was found that the seeds contain 27.82% insoluble dietary fibre and 1.13% soluble dietary fibre with its ratio of 24.6 (Khatoon and Prakash 2004) while its flour has 14.9 and 1.4% insoluble and soluble dietary fibre, respectively (Sreerama et al. 2012), revealing that the seeds of horsegram had higher dietary fibre (Kawale et al. 2005) than the requisite amount for normal function of lower intestine (Anderson et al. 1994). The proximate composition of whole and dehulled grains of horsegram is given in Table 10.1. The carbohydrate content in whole and dehulled horsegram seeds varied from 51.9–60.9 to 56.8–66.4%, respectively (Sudha et al. 1995); similarly it has 6.38% of total soluble sugar (Bravo et al. 1999). The dehulled horsegram seeds have higher protein (18.4–25.5%), crude fat (0.81–2.11%), moisture (11.55%), ash (3.0–3.8%) and calcium (238 mg) content as compared to the whole seeds (Sudha et al. 1995); however, changes in protein content have been observed with the varietal differences (Murthy 1980). The legume has poor cooking quality, but its sprouted seeds can be easily cooked. Moisture content in the seeds of horsegram

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depends on stage of its harvesting which remains generally higher (18–25%), but its storage should be done at the moisture level of 9–12% (Mohan et al. 2011). The estimation of mineral content in the leaves of the crop reveals that it had higher (4.5%) mineral content as compared to the leaves of other vegetable (1.5–2.4%) crops (Mandle et al. 2012). Calcium and iron contents in the seeds of horsegram varied from 244–312 mg to 5.89–7.44 mg per 100 g of seed, respectively, and its in-vitro bio-accessibility can be increased by germination, cooking and roasting of seeds (Khatun et al. 2013). Due to the presence of higher values of nutrition, the crop is in demand for its application in addressing the malnutrition and various diseases in developing countries (Chel-Guerrero et al. 2002; Arinathan et al. 2003). Horsegram has slow digestibility due to the presence of trypsin inhibitor. The level of oligosaccharides changes due to soaking, cooking and sprouting. Some antinutritional factors, namely, oxalic acid and tannins, have also been reported in the seeds of horsegram (Subba Rao and Sampath 1979; Sudha et al. 1995). Sreerama et al. (2010a) evaluated milled fractions of horsegram for various nutritional and anti-nutritional characteristics and reported wide variability in the nutrient and antinutrient composition. They suggested that the variability can be exploited in the development of functional food product. Jain et al. (2012) assessed physicochemical and nutritional properties of horsegram and reported that the hydration capacity of horsegram varieties was 0.03–0.04 g per seed. They suggested that the nutritional values and its consumption can be improved by its proper processing and making new products. It may be included in daily diet as a source of nutrient due to its medicinal properties. Bhokre et al. (2015) studied the physicochemical and functional properties of different genotypes of horsegram to assess their application in the food products. They observed that the genotype AK-21 had better swelling capacity (0.041 mL/seed), water absorption capacity (1.53 g/g), oil absorption capacity (1.21 g/g), foaming capacity (48.18%), foaming stability (40.13%), emulsifying activity (59.53%), emulsifying stability (55.16%), in vitro protein digestibility (81.80%) and required less cooking time (55 min) as compared to other genotypes. Sharma and Bhatnagar (2017) studied the effect of processing on phytic acid, iron and its bioavailability in horsegram and reported that the in vitro iron bioavailability can be increased by germinating and roasting of the seeds. The process has also reduced the phytate content. It has also been reported that horsegram supplementation has increased the activities of antioxidant enzymes (Rajagopal et al. 2017). Due to the high protein digestibility and available lysine content, horsegram was advocated to be an important protein constituent of food industry (Lalitha and Singh 2020). Horsegram proteins were isolated from its germinated seeds using alkali treatment and acid precipitation method (Banerjee et al. 2022), and about 72.7% protein could be isolated. The study suggests that horsegram proteins may be a perfect match for food fortification and it can provide good nutrition.

10.3

10.3

Anti-nutritional Factors

207

Anti-nutritional Factors

Anti-nutritional factors are the substances produced in the natural food materials by the plant species that have harmful effects contrary to ideal nutrition. These factors include trypsin inhibitor, phytic acid, cyanogen, etc. Anti-nutritional factors reduce the bioavailability of nutrients in the pulses (Jain et al. 2009). Legumes are known to have some anti-nutritional compounds including various enzymes, protease inhibitors and lectins (Thompson 1993). They can be grouped into protein and non-protein anti-nutritional compounds (Duranti and Gius 1997). Alkaloids (Markievicz et al. 1988), phytic acid, phenolic compounds (Davis 1981) and saponins (Hudson and El-Difrawi 1979) are considered as non-protein antinutritional compounds. Some of the compounds, namely, phenols, tannins (Cardador-Martinez et al. 2002), phytic acid (Urbano et al. 2000) and oligosaccharides (Udensi et al. 2007), are found as antioxidants and help to reduce the threat of gall stones, diverticulosis, constipation, colon cancer and coronary heart disease, prevent dental caries and treat diabetes (Asp et al. 1996; Oku 1996). Saponins have been reported as hypocholesterolemic and anticarcinogenic agents (Koratkar and Rao 1997). The cotyledon fractions of horsegram seed have significant concentration of phytic acid. Davis (1981) reported phytic acid as an anti-nutritional compound because it slows down the digestibility of proteins (Stanley and Aguilera 1985) and availability of minerals (Sandberg 2002). Findings also revealed that phytic acid has great potential to be antioxidant (Graf and Eaton 1990) and anticarcinogenic (Turner et al. 2002; Shamsuddin et al. 1997) agents, and it also diminishes the speed of cell proliferation and enhances the immune responses (Reddy 1999) and hypoglycaemic (Rickard and Thompson 1997) activities. Horsegram has been grouped under high phenolic compound (Marathe et al. 2011) including quercetin, kaempferol and myricetin, vanillic, ρ-hydroxybenzoic and ferulic acids (Sreerama et al. 2010b). The phenolic acids have various beneficial effects in different diseases (Soobrattee et al. 2005). Tannins have also been reported in horsegram seed (Sundaram et al. 2013). The cotyledon fractions of the horsegram seeds have higher concentrations of raffinose, stachyose and verbascose (Sreerama et al. 2010b). These oligosaccharides have been reported to cause flatulence in human beings (Reddy et al. 1984). However, it has been observed that the galactooligosaccharides assist the bifidobacterium (Alles et al. 1999) and energize the human body. The horsegram seeds have higher proteinase inhibitors (Sreerama et al. 2010b). The higher trypsin inhibitor activity of the legume can be used as a major ingredient of functional foods (Blanca et al. 2009). The trypsin inhibitors reduce the serine proteases (Kumar and Gowda 2013) associated with the carcinogenesis (Chen et al. 2005; Clemente and Domoney 2006). Management of obesity, several degenerative and autoimmune diseases and potential anti-inflammatory activities (Duranti 2006) have also been reported with the legumes. It has been reported to treat ulcerative colitis (Gary et al. 2008) and multiple sclerosis (Gran et al. 2006).

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Various oligosaccharides such as raffinose, stachyose, verbascose, etc. are present in the seed of horsegram and cause flatulence on its consumption. Besides these, trypsin inhibitor, lectins, haemagglutinins, phytic acid and α-amylase inhibitor are also present as anti-nutritional factors in its grains (Liener and Kakade 1980; Sreerama et al. 2012). The presence of these factors is the major constraint for the utilization of horsegram as human food, but various traditional processing techniques, namely, dehusking, germination, cooking and roasting, have been reported to decrease these factors and enhance nutritional quality of horsegram grains for human consumption (Kadam and Salunkhe 1985; Dhumal and Bolbhat 2012). Diwakar et al. (2000) studied the level of anti-nutritional principles and in vitro protein digestibility of raw, heat processed and germinated horsegram on the basis of their seed coat colour. They observed that autoclaving and roasting decreased the level of trypsin inhibitor, haemagglutinin, and induced the stimulation of polyphenol content in the varieties having red and brown seed coats. Significant reduction in the anti-nutritional factors has been reported by soaking and cooking of the seeds (Kumar 2006). The dehusking of the seeds improves protein efficiency ratio and digestibility and reduces cooking time from 2 h to 30 min; besides this, dehusking, germination, cooking and roasting have been found to have beneficial effects on the nutritional quality of horsegram (Kadam and Salunkhe 1985). The influence of seed soaking and seed germination on anti-nutritional factors and nutritional properties of horsegram was carried out, and significant physicochemical and functional characteristics were observed (Handa et al. 2017). The study revealed that 18 h seed soaking and 48 h germination are advantageous to obtain higher nutrient content from horsegram seeds and the obtained flour may be utilized in the development of value-added products (Handa et al. 2017). Similarly, the antinutritional factors such as phytic acid, trypsin inhibitor and tannin in the seeds after 72 h of germination reduced, while considerable increase in the mineral contents was observed after seed soaking (Rizvi et al. 2022).

10.4

Medicinal Values

The anti-nutritional factors such as phytic acid, phenols and tannins found in horsegram are now considered as antioxidants showing positive effect on human health (Bhatt and Karim 2009). The crop has enormous potential as human health, but meagre information is known on this aspect. The decoction of horsegram has several medicinal properties for treating cough, bronchitis, kidney trouble and irregular periodicity of menstrual cycle. Dolichos biflorus agglutinin-agarose was found appropriate for isolation and characterization of glycoproteins from teratocarcinoma cells (Muramatsu et al. 1981). These cells have high differentiation potential with a variety of differentiated tissues in addition to stem cells. The seeds of horsegram are used for treatment of urinary stones (Yadava and Vyas 1994; Ravishankar and Vishnu Priya 2012), urinary diseases and piles (Yadava and Vyas 1994), regulate the abnormal menstrual cycle, act as astringent, are tonic (Brink 2006) and are also used to treat calculus afflictions, corpulence, hiccups

10.5

Nutraceutical Properties of Horsegram

209

and worms (Chunekar and Pandey 1998). Horsegram is known for diuretic properties (Watt 1972) and is said to be good for patients suffering from urinary and kidney problem (Thakur 1979). It helps in dissolving and dislocation of kidney stones in human beings (Upadhyay et al. 2015; Gautam et al. 2020). The soup prepared from sprouted seeds help in better sleep. Grains are useful in curing whooping cough and reducing acidity and constipation. Biotechnological interventions may be carried out to manufacture medicine for urinary problems through understanding the chemical nature of the grains. Peshin and Singla (1995) reported anti-calcifying inhibitors of crystallization in the seed extract of horsegram, which is water soluble, heat stable, polar, non-tannin and non-protein in nature showing its efficiency in the treatment of kidney stones. The cooked liquor of its seeds mixed with spices is used as the remedy of common cold, throat infection and fever (Perumal and Sellamuthu 2007). The lipids of horsegram are used as protective and promoting healing of acute gastric ulceration caused due to excessive alcohol consumption (Jayraj et al. 2000). It has been reported that horsegram has polyphenols having antioxidant properties (Ramesh et al. 2011) and therefore is used to cure oedema, piles and renal stones (Bhatt and Karim 2009). The anti-urolithiatic activity has been proved in horsegram seeds (Chaitanya et al. 2010; Atodariya et al. 2013). Pramod et al. (2006) studied the effect of horsegram on the degranulation of mast cells and basophils of atopic subjects and identified food allergy due to consumption of horsegram on the basis of the presence of D. biflorus agglutinin-specific IgE with a positive correlation to basophil histamine release.

10.5

Nutraceutical Properties of Horsegram

Nutraceuticals are foods or food parts that provide health and/or medical benefits. They have the ability to prevent, protect and treat the disease (Brower 1998; Belem 1999). Besides the proteins and dietary fibre, pulses are the major sources of micronutrients and phytochemicals (Messina 1999) and provide many bioactive substances of metabolic and/or physiological significance. Phenolic acids, flavonoids, alkaloids, carotenoids, prebiotics, phytosterols, tannins, fatty acids, terpenoids, saponins and soluble and insoluble dietary fibres are the bioactive substances (Patwardhan et al. 2005; Siddhuraju and Becker 2007) that have the potential to inhibit various diseases like coronary heart diseases, diabetes and obesity (Bazzano et al. 2001). The plant-derived nutraceuticals are getting much attention due to no side effect (Raskin et al. 2002). Reports suggest that the grain legumes not only provide a balanced diet but also prevent widely diffused diseases, including type II diabetes and cardiovascular diseases (Leterme 2002). The beginning of nutraceutical conception and health consciousness has enhanced the utilization of potential antioxidants from legumes as it has the ability to reduce the risk of intestinal diseases, diabetes, coronary heart disease, prevention of dental caries, etc. due to the presence of bioactive compounds (Prasad and Singh 2015). The seed coat of horsegram has higher antioxidant activities; therefore, consumption of

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unprocessed seeds may be more useful for the persons having hyperglycaemia (Tiwari et al. 2013). Various flavonoids, that is, Dolichin A and B and pyroglutamylglutamine, have been isolated from horsegram (Handa et al. 1990; Kawsar et al. 2009). Besides these, kaempferol-3-O-β-D glucoside, β-sitosterol, stigmasterol (Kawsar et al. 2003) and phenolic compounds (Kawsar et al. 2008a) were isolated from horsegram that have cytotoxic and antimicrobial activities (Kawsar et al. 2008b). The seed extract of horsegram acts against Bacillus subtilis, Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa (Gupta et al. 2005; Kawsar et al. 2008c). The ethanolic seed extract of horsegram had potential antioxidant (Ravishankar and Vishnu Priya 2012). The advantage of free radical scavenging capacities of horsegram seed protein can be exploited as natural antioxidant and may be used as therapeutics for health benefits of mankind (Petchiammal and Hopper 2014). The seeds and sprouts of horsegram play an important role in lowering the risk of various diseases and promoting human health (Ramesh et al. 2011). The aerial parts of horsegram have nontoxic extract showing its ethnobotanical applications (Kawsar et al. 2008b). Plants’ leaves possess anthocyanins that act as free radical scavengers and show anti-inflammatory activities (Morris 2008). Quantification of bioactive compounds was carried out in horsegram seeds, and it was observed that the seeds possessed epicatechin (158.1 μg/g) and daidzein (6.51 μg/g) in considerable amount (Ramalingam et al. 2020). The study also revealed that these bioactive compounds are effective inhibitors of cyclooxygenase; thus, horsegram seeds may be useful in the treatment of inflammation and pain (Ramalingam et al. 2020). Metabolite profiling and protein quantification horsegram germplasm revealed the presence of 45 metabolites including 17 amino acids, 7 flavonoids, 7 carbohydrades and 4 vitamins (Gautam and Chahota 2022) suggesting the importance of horsegram as nutraceuticals and management of several human health ailments. The good functional properties of horsegram flour, namely, swelling capacity, water solubility index, oil absorption capacity, water absorption capacity, swelling index, etc., reveal that it can be used for food formulation for nutrition purposes (Sreerama et al. 2012; Marimuthul and Krishnamoorthi 2013; Thirukkumar and Sindumathi 2014). Horsegram has great potential in terms of realizing various phytochemicals, therapeutic applications and development of low-cost functional foods for nutrition and medicine that can be utilized under malnourished and drought-prone areas of the world (Morris 2008).

10.6

Chemical Compound

Phenolic compounds are bioactive secondary plant metabolites which act as powerful antioxidants. The major phenolic compounds are flavonoids, phenolic acids and tannins and are widely present in the foods of plant origin. Various chemical compounds, namely, kaempferol-3-O-β-D-glucoside, β-sitosterol and stigmasterol (Kawsar et al. 2003; Sarkar et al. 2009), and phenolic compounds (Kawsar et al.

10.7

Uses

211

2008a) have been isolated from horsegram. Keen and Ingham (1980) have isolated and identified eight isoflavonoids, namely, genistein, 2‫׳‬-hydroxygenistein, dalbergioidin, kievitone, phaseollidin, isoferreirin, coumestrol and psoralidin from horsegram. Several bioactive compounds such as methyl ester of hexadecanoic acid and ethyl ester of hexadecanoic acid mixture and n-hexadecanoic acid were recognized in horsegram UV, IR, 1H NMR, 13C NMR and mass spectroscopy techniques (Kawsar et al. 2009). Furthermore, the 1-butanol extract exhibited considerable hemolytic action against mice erythrocytes. Sreerama et al. (2010a) evaluated seed coat, cotyledon and embryonic axe fractions of horsegram for phenolic composition in relation to antioxidant activities and revealed a wide variation in the distribution of flavonols, isoflavones, phenolic acids and anthocyanins. The cotyledon fractions were rich in phenolic acids, namely, ferulic, chlorogenic, caffeic and vanillic acids, but the concentrations of flavonols, namely, quercetin, kaempferol and myricetin, were lower than the embryonic axe and seed coat fractions. The isoflavone genistein was detected at levels greater than daidzein in the embryonic axe fraction of horsegram. Horsegram possessed reducing power and ferrous ion-chelating potency proving its multiple antioxidant activity. The relationships between major phenolic compounds and antioxidant activities provide useful information for effective utilization of legume-milled fractions as functional food ingredients (Sreerama et al. 2010a).

10.7

Uses

The green or dry crop is mostly used as animal feed. The seeds, sprouts or whole meal is used along with cereal flour by the rural population. The boiled beans are used to prepare protein- and mineral-rich soups. Various tasty preparations such as curry, papad, etc. are prepared from their seeds in South India. The crushed husks, pods, grains, haulms and residues of horsegram are mixed with water to prepare nutritious animal feed. The green and dry stem of the crop is used as pastures and forages. The crop has the advantage of biological nitrogen fixation and adds nitrogen to the soil; therefore, it is considered as the best cover crop during fallows (Krishna 2014). The higher biomass production in horsegram makes the crop of choice for pasture production (Bhartiya et al. 2015). The nitrogen fixation ability of the crop helps to improve the soil fertility. It is believed that the soup of the horsegram seed is consumed from the Sutra (1500–800 BC) period (Achaya 1998). The rural populace of South India consumes its seeds after drying followed by boiling or roasting with rice, sorghum or pearl millet (Purseglove 1974). Its sprouted seeds have high nutritional quality and are choice of snack of tribal people (Bravo et al. 1999). It has been reported that the sprouted seeds have the potential to reduce the chances of diseases and promote the human health (Pasko et al. 2009). Horsegram has been considered as an important food legume, and flour of horsegram seed can be utilized in several food items. Horsegram flour was mixed with wheat flour to prepare biscuits, and physical property was tested (Joshi and

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Awasthi 2020). The physical property of biscuit such as weight, diameter and thickness declined with the increasing of horsegram flour in the blend suggesting that horsegram flour may be used for the development of good quality nutritive biscuits. A translucent and water-resistant film was developed with horsegram protein cross-linked with citric acid, and its physical, chemical and biological potential was estimated (Sakkara et al. 2020). The findings revealed that horsegram protein-based films cross-linked with citric acid had better physicochemical as well as biological potential and could be better packaging material (Sakkara et al. 2020).

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Cultivation

11

Abstract

Horsegram is one of the important pulses of arid and semi-arid areas cultivated mainly in Karnataka, Odisha, Andhra Pradesh, Maharashtra and Tamil Nadu with small extent at Rajasthan, Maharashtra and Madhya Pradesh. It is a drought hardy crop and does not require much attention for its cultivation. The area, production and productivity of the crop, brief account of varieties developed in India and their characteristics along with various associated issues of its cultivation has been discussed at length in this chapter.

11.1

Introduction

Horsegram is grown in majority of Indian states, but 90–95% area of the crop is confined to five major states, namely, Karnataka, Odisha, Andhra Pradesh, Maharashtra and Tamil Nadu, while it has been reported in small extent at Rajasthan, Maharashtra and Madhya Pradesh. The area and its production under the crop during 2012–2015 were 2.32 lakh ha and 1.05 lakh tonnes, respectively (Tiwari and Shivhare 2016). Karnataka ranked the top in terms of contribution of area and production (26.72% and 25.71%) followed by Odisha (19.46% and 15.48%) and Chhattisgarh (19.29% and 13.29%) at the national level. The yield of the crop was highest in Bihar (959 kg/ha) followed by West Bengal (796 kg/ha) and Jharkhand (603 kg/ha) (Tiwari and Shivhare 2016). Significantly decreasing trends at national level were reported in terms of the area and production from 2002 to 2015 (Tiwari and Shivhare 2016), and the crop is not given more importance in the northern part of India. Horsegram offers good quality of feed and fodder for cattle and horses and makes excellent hay and is suitable as a green manure. It is a rich source of grain protein, calcium, iron, phosphorus and vitamins. Horsegram has been widely grown under # The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 R. Pathak, Genetics, Physiology and Cultivation of Moth Bean, Cowpea and Horse Gram, https://doi.org/10.1007/978-981-19-9956-7_11

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varied rainfall (300–500 mm), altitude (0–3°N), temperature (20–35 °C), soils (deep red, loam, sandy, stony, gravelly) and cropping systems (Kumar 2007). The crop is also sown under wider duration from July to October at different part of the country. Horsegram can be easily grown under number of cropping systems including crops, grasses and trees under early and late sown situations of rainfed areas. Long maturity, photo and thermal sensitivity, higher biomass production, etc. are the major defects of the crop (Kumar 2007).

11.2

Soil and Climate

The crop is grown mostly under the soil having poor fertility as a general practice of farmers in which other crops are not able to germinate. Horsegram is adapted to a wide range of soils, namely, deep red, loam, black, clayey, sandy shallow, stony, gravelly, upland, rough jungle, etc. However, light sandy soils are better for the crop. In West Bengal, it is grown on acid lateritic soils (pH 5.5). Its cultivation has been reported on red loams, black cotton soils and stony and gravely upland soils of Deccan having pH 5.5–8 without much preparatory tillage (Bolbhat and Dhumal 2010). The crop can be easily grown on the soils having low nitrogen and organic matter to reclaim the poor soil fertility (Krishna 2014). It was observed that the use of field soil increased the germination and growth of horsegram; therefore, growing of horsegram has been recommended near Chir pine forest (Singh and Verma 1988). Horsegram can be grown under sub-humid and semiarid climatic conditions. It requires average temperature of 18–32 °C to grow, but in drought-prone areas, it can tolerate temperature up to 40 °C (Smartt 1985). Horsegram is a short-day plant and requires 12 h sunlight to flower. The crop is successfully cultivated during both kharif and rabi seasons in the South Indian states, namely, Tamil Nadu, Karnataka, Andhra Pradesh and Odisha (Edulamudi et al. 2015). The medicinal properties, nutritious composition and pest resistance ability, source of food, fodder and green manure make the crop immense important for its cultivation (Bolbhat and Dhumal 2009; Reddy and Reddy 2005; Ghani 2003; Sudha et al. 1995; Edulamudi et al. 2015; Virk et al. 2006). It is cultivated in the areas with annual rainfall range of 300–600 mm but does not tolerate water logging. The seeds sown in the first fortnight of August and September had higher grain and straw yields as compared to the crop sown in the first fortnight of October (Naik 2001). The delayed (beyond August 28th) sowing had significant reduction in the crop yield (Bajpai et al. 1990).

11.3

Horsegram Under Intercropping System

The intercropping system, that is, growing of two or more crop species in the same field during a cropping season, is the best approach to get profit in case of even crop failure due to biotic or abiotic hindrance with limited inputs. Besides this, the system facilitates yield advantage of the companion crop and improves the soil fertility and efficient use of resources, reducing damage caused by pests, diseases and weeds

11.4

Horsegram Under Crop Rotation System

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(Banik et al. 2006). The intercropping systems comprising of cereals and pulses have been found as profitable systems (Sharma et al. 2008; Pathak 2015). Horsegram has been grown under number of intercropping systems. It is a short duration crop; hence, it can be rotated with number of crops. The crop can be intercropped with various cereals, namely, sorghum, maize, pearl millet, etc., depending upon the season, soil fertility and genotypes. It can also be grown as under-story crop within tree plantations to add nitrogen and organic matter to the soil. Intercropping of groundnut (two rows) and hybrid sorghum (two rows) with horsegram has been reported profitable without affecting the total income per unit area. Horsegram variety Kulthi Birsa exhibited better performance with two rows of Niger intercropping (Bajpai et al. 1990). In a study of intercropping of Niger under rainfed condition with horsegram at 2:1 row ratio, seed yield of Niger is at the tune of 107–131 kg per ha while the yield of horsegram was highest (351 kg per ha) among sesame, soy bean and groundnut. Mishra et al. (1997) studied intercropping of cowpea and horsegram with sorghum and observed that the performance of cowpea was better as compared to horsegram. Patil et al. (1987) observed highest yield (2800 kg per ha) of finger millet when grown alone followed by intercropping with horsegram under three cropping systems, namely, finger millet alone, intercropped with horsegram and soybean. The intercropping of horsegram with maize was not found profitable (Singh et al. 1990). This may be due to the sustainability of maize fodder component. Under an intercropping system having amaranth-horsegram, the yield of amaranth was highest (Arya et al. 1996). The yield of horsegram was decreased in agroforestry system, but its yield was highest under the trees spaced in 15 m rows (Basavaraju and Rao 1997). The system productivity, profitability and competition indices of horsegram intercropping under rainfed condition were evaluated on the basis of intercropping systems, namely, horsegram + maize (2:1), horsegram + finger millet (1:1), horsegram + pigeon pea (1:1) and horsegram + barnyard millet (1:1) under replacement series in comparison to sole horsegram (Kumar et al. 2010a). Higher plant height, number of pods per plant, number of grains per plant, grain weight per plant and horsegram equivalent yield were recorded during intercropping as compared to sole horsegram. They suggested that intercropping of horsegram + finger millet (1:1) is beneficial under hilly agro-ecosystem in India. Further, ridge sowing, zero-tillage, growth retardant and intercropping were found beneficial in enhancing the productivity of horsegram (Kumar et al. 2010b).

11.4

Horsegram Under Crop Rotation System

Since the nutrient requirement of each crop is not in similar proportion, therefore sowing of crops in rotation can be utilized to improve the soil fertility and depletion of nutrients. Horsegram has been widely used as the crop of rotation in various parts of the country. Significantly higher yield of finger millet was recorded with the field after harvesting of horsegram (Singh and Venkateswarlu 1985). Horsegram has been considered as the most preferred crop on the uplands of Odisha after harvesting

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paddy, maize, sorghum and ragi crops (Patra 1991). It has been observed that the available soil moisture and nutrients after the harvest of horsegram are utilized efficiently by the non-leguminous crops (Jena and Mishra 1990). In a study, maize-horsegram combination gave the highest economic returns (Tharmarajah and Herath 1988). In another study, higher net return was recorded when maize, sorghum or finger millet was sown after the harvest of horsegram (Nayak 1993).

11.5

Sowing Method

The proper and timely preparation of land for growing of the crop not only conserves the available moisture but also reduces the growth of weeds in the field (Kumar 2007). The surface of red loam, black cotton and acid laterite soils hardened after a long dry spell; therefore, deep ploughing is very essential during kharif season, but in light sandy soils, about 15 cm deep ploughing is sufficient. The land where horsegram is sown after the harvest of rice or ragi, disc plough may be done prior to the sowing of the crop. Hoeing should also be done after rain to conserve the moisture in the field (Kumar 2007).

11.6

Seed Rate

The seed rate generally depends on the variety, time of sowing, availability of soil moisture and spacing of rows. An average seed rate for the sowing of horsegram is about 20–50 kg per ha. It has been observed that the seed rate of 40–50 kg per ha gave significantly higher yields over 20 kg per ha of seed rate, while no significant difference was observed with the seed rate of 30–10 kg per ha (Rafey and Srivastava 1989).

11.7

Spacing

The spacing between plant to plant and row to row provides proper utilization of nutrition, moisture and sunlight and minimizes the plant competition for growth and is considered as the most important non-monetary input affecting the yield. The spacing depends on the optimum plant stand and varies for different regions having varied rainfall intensities. The influence of spacing has been studied in horsegram. Generally, the photosensitive varieties of the crop need wider spacing for early sowing and closer spacing for late sowing. Higher seed yield was recorded with 30 cm row spacing and seed rate of 40 kg seeds per ha. Higher seed yield was realized with 30 or 37.5 cm row spacing at Bangalore and at Dharwad for long- and short-duration varieties (Chandranath and Hosmani 1995), while closer row spacing gave higher yields but reduced some of yield attributing parameters. Prakash et al. (2007) studied the effect of four different row spacings on yield and its components on horsegram cultivars and recorded highest yield and yield components with

11.9

Fertilizer Management

223

45 × 6.5 cm of row-to-row spacing as compared to 30 × 10, 45 × 6.5, 60 × 5 and 60 × 10 cm spacing. Purushottam et al. (2017) suggested that the seed should be sown at the depth of 1.5–2 cm with a plant-to-plant distance of 10 cm and row-torow distance of 30 cm. Similarly, Suthar et al. (2017) also found 30 cm inter-row spacing as optimum for getting higher yield and net profit in kharif season on loamy sand soil under North Gujarat agro-climatic conditions for the cultivation of horsegram varieties.

11.8

Sowing Time

The time of sowing plays a crucial role in the growth and production of the crop. The sowing of horsegram is generally done in the first fortnight of June during the kharif season to October–November during winter season. Significant decrease (10.6–4.6 q/ha) in the yield of horsegram was observed with the delayed sowing of crop from 15th June to 30th July in Himachal Pradesh (Thakur and Sharma 1992). Poor yields have also been observed in Rajasthan (Henry and Daulay 1988), Bihar and Madhya Pradesh (Bajpai et al. 1990; Rafey et al. 1988) due to delayed sowing of horsegram. In a long-term study conducted to assess the optimum sowing time at Bangalore, it was recorded that horsegram sown up to middle of August may give higher yields but delayed sowing resulted into significant reduction in the seed yield. The sowing of horsegram during second fortnight of October at Tamil Nadu gave better yield and performances. The dry sowing of the crop done on July 11th resulted into higher (120%) seed yield as compared to the sowing done after the onset of monsoon rains (Patil et al. 1981). Tayade (2018) assessed the performance of tractoroperated seed cum fertilizer drill for line sowing of horsegram and reported increased yield (24.24%) and saving of seeds (44.89%) with line sowing as compared to traditional practice of broadcasting method of sowing. Sowing of horsegram during the 40th meteorological standard week (MSW) was beneficial under rainfed conditions of northwestern zone of Tamil Nadu (Ramani et al. 2020), and higher dry matter and yield of haulm were realized; however, the crop sown during the 41st MSW had higher pods, seeds and consequently higher grain yield (Ramani et al. 2020). The researchers also reported that the horsegram variety Paiyur-2 cultivated during the 41st MSW gave higher grain yield under rainfed conditions of northwestern zone of Tamil Nadu (Ramani et al. 2020).

11.9

Fertilizer Management

Horsegram is a leguminous crop, so it requires lesser amount of nitrogen but the modest dose of nitrogen stimulates plant growth in its early stage and improves nodulation, growth and nitrogen fixation. Phosphorus plays an important role on the growth of horsegram. In general, if soil is deficient in nitrogen, phosphorus and potassium (NPK) content, 5–6 tonnes of well-rotten farm yard manure or compost should be added at the rate of 1 ha area along with basal application of 20–25 kg of

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nitrogen and 25–30 kg of phosphorus. Phosphorus deficiency decreased the biomass and growth of plant particularly leaves. Its deficiency also inhibited tertiary root production. The application of phosphorus in optimum dosages has increased the plant growth and uptake of other nutrients, namely, nitrogen, potassium, calcium and sodium, by the plant (Marwaha 1982; Henry et al. 2006). The application of 40 kg P2O5 per ha seeded with the early crop gave higher seed yield in Himachal Pradesh (Sharma 1987; Thakur and Sharma 1992). The application of 20 kg nitrogen per ha and 60 kg P2O5 per ha was found beneficial for increasing seed and straw yields in horsegram. In another study, it was suggested that 20 kg nitrogen per ha and 60 kg P2O5 per ha may be more beneficial as compared to either of the nutrients (Henry et al. 2006). The lower dosage of nitrogen and phosphorus has also been suggested for some part of the country. Mahapatra et al. (1973) reported that 15 kg nitrogen per ha and 30 kg P2O5 per ha may result better profit. Patra (1991) assessed the impact of different dosages of nitrogen and phosphorus under rainfed conditions in Odisha and reported that 10 kg nitrogen per ha and 20 kg P2O5 per ha were the optimum dosages. The application of 20 kg nitrogen per ha and 40 kg P2O5 per ha was found to be optimum for the late sown crop. In Rajasthan, 8.8–17.6 kg phosphorus per ha was found to be sufficient for better seed yield (Singh and Singh 1992; Choudhary and Singh 1994). The fertilizer level of NPK in the ratio of 20:40:40 kg per ha increased the yield of horsegram (Dwivedi et al. 1996). Under Bihar plateau region 20 kg nitrogen and 10–30 kg phosphorus (Rafey and Srivastava 1989), in Konkan region 60 kg P2O5 per ha (Verenkar and Thorat 1988), in Dharwad region 30 kg P2O5 per ha (Chandranath and Hosmani 1995), in Karnataka 25 kg nitrogen per ha and 40 kg P2O5 per ha (Nagaraju et al. 1998) gave higher yields of horsegram. Horsegram sown on the marginal lands of Rajasthan under rainfed conditions required 10 kg N per ha and 8.8 kg P per ha whereas no zinc is required (Choudhary and Singh 1994). Application of N and P increased the number of pods per plant, number of seeds per pod, pod length and 1000-seed weight resulting into increased seed yield (Choudhary and Singh 1994). Phosphorus is the most important nutrient for arid and semi-arid regions (Arnon 1972) and the areas having acid soils (Kurtz 1953; Taylor and Gurney 1964) for cultivation of legumes and other crops, and it improves the uptake of NPK and calcium to the plant (Kashirad et al. 1978), but its higher quantity may cause iron stress (Kashirad and Marschner 1974; Brown 1975). Marwaha (1982) studied the effect of four phosphatic fertilizers on the horsegram grown under acid hill soil and observed that the increase in the supply of phosphorus increased the growth and uptake of NPK, calcium and sodium by the plants. The crop shows deficiency symptoms of various nutrients, and application of micronutrient has been beneficial for horsegram production. Zinc-, iron-, copperand manganese-deficient soil resulted to chlorotic leaves in the horsegram plant (Pradhan and Sarkar 1985). Foliar spray of 600 ppm FeSO4 partially reduced the symptoms and increased about 20% seed yield. Application of 30 kg sulphur per ha influenced the number of branches, number of pods per plant, seed and straw yield of horsegram (Pradhan and Sarkar 1985). The micronutrients increase the rate of metabolic processes in the plant and subsequently enhance the meristematic

11.10

Seed Treatment and Inoculation with Bacterial Culture

225

activities resulting into higher apical growth. The response of the crop to 100 g molybdenum per ha increases the dry weight of stem, leaves and nodules, number of pods per plant and seed yield in the lateritic acid soil of West Bengal (Pradhan and Sarkar 1985). Prasad et al. (1990) studied the response of horsegram to fertilizers in cultivators’ fields of Bangalore District and recorded highest seed yield (740 kg/ha) with 40 kg N, 80 kg P2O5 and 40 kg K2O per ha as compared to the seed yield (270 kg/ha) without fertilizers. The plant inoculated with vesicular arbuscular mycorrhiza (VAM) had improved plant growth (Mosse 1973). Horsegram treated with VAM exhibited significant improvement in the shoot height, fresh and dry weights of plant, nodule number, fresh and dry weights of nodules and dry weight of seeds as compared to the control (Pattanaik et al. 1995). The VAM treatment can be used to improve the productivity of the crop grown near iron mine area. If the nitrogen, phosphorus and potassium are deficient in the soil, basal dosage of 12.5 t FYM (farm yard manure), 12.5 kg nitrogen, 25 kg phosphorus and 12.5 kg potassium per ha should be applied. Seed treatment with 600 g per ha of rhizobial culture and phosphobacteria was found beneficial. In case of non-treated seeds, 2 kg per ha of rhizobial culture and phosphobacteria may be applied with 25 kg of each FYM and soil before the sowing of seeds. Patra and Nayak (2000) studied the response of horsegram to different agronomic management practices in Odisha state of India. They reported higher seed yield, number of pods per plants and number of seeds per pod with 20 kg nitrogen and 17.5 kg phosphorus per ha, seed rate of 30 kg per ha, line sowing and weeding at 25 days after sowing over control. Omokanye et al. (2000) studied the effect of phosphorus application (0, 40, 80 and 120 kg/ha) on seed production of horsegram in Northern Nigeria and observed that the days to flowering and 100-weight increased. The seed yield, days to pod maturity, number of seeds per pod and residual herbage yield increased up to phosphorus level of 80 kg per ha. Raut et al. (2016, 2017) studied the effect of tillage and methods of fertilizer application on yield and economics of horsegram and reported that the crop may be grown under conventional tillage condition using dibbling method with soil application of 100% recommended dose of fertilizer at sowing time to obtain higher grain and straw yield, net returns and B:C ratio.

11.10 Seed Treatment and Inoculation with Bacterial Culture Since horsegram is a leguminous crop and rhizobia are associated with its root nodules for nitrogen fixation, it is always recommended to inoculate the seeds before sowing for the success of crop grown under disease-prone areas. The crop sown by the inoculated seeds coupled with phosphorus application gave 44.3% increase in seed yield over the un-inoculated seeds (Sahu 1973).

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11.11 Irrigation Management Horsegram is sensitive to water logging throughout its all development stages. So accumulation of water should be avoided in the field, and proper drainage of water should be ensured during rainy seasons. The monitoring of crop is essential for any stress conditions to obtain quality seeds. Proper soil moisture should be maintained in the field because water stress may lead to flower shedding and subsequently affect the seed yield (Kumar 2007). The flowering, pod formation and seed development are very crucial stages; therefore, proper irrigation is essential during these stages.

11.12 Weed Management The horsegram crop sown during kharif season has to compete for moisture; nutrients and space with a large number of weeds come up during the rainy season. This leads to considerable reduction in crop yield. Manual weeding is the best practice to remove the weeds and should be carried out after 2 weeks of sowing of the crop (Kumar 2007). The manual weeding also maintains the aeration and conserves moisture in the field. However, chemical weeding can also be done. The early growth of weeds may be reduced with the spray of 2 mL of fluchloralin dissolved in 1 L of water (Kumar 2007).

11.13 Harvesting and Threshing The crop may be harvested when the pods become straw in colour. The rain during the pod maturation stage may shrivel, discolour the seeds and also affect its germination (Rangaswamy et al. 1991). Therefore, harvesting should be done in clear sky conditions. The crop is harvested by sickles. The harvested crop plants should be spread for one or two days for proper drying. The seeds are separated from pods by beating with sticks. Harvested seeds are dried to reduce the moisture content and finally stored. On an average, about 700–900 kg per ha seeds can be realized from improved varieties, and about 1000 kg per ha green fodder may be obtained from the crop (Kumar 2007).

11.14 Photoperiodism Photoperiodism is an important factor in determining the growth and progression of development of plants (Stiles 1969). The rate of vegetative growth and duration of flowering is highly affected by photoperiod (Garner and Allard 1920). Studies also revealed that the flowering time is influenced by temperature, day span and illumination intensity (Stiles 1969). The long dark period followed by the light period having high intensity provides effective photo-induction in short-day plants, but long light period is harmful to the photo-induction of flowering in these plants.

11.15

Horsegram Production in India

227

Horsegram cultivars are adapted to specific day lengths according to different seasons and places of growing (Balasubramanian 1985). The cultivars grown in rainy season are day neutral while the cultivars grown during post-rainy seasons are short-day plants (Balasubramanian 1985). Most of the local genotypes and few varieties of horsegram are photosensitive and flower only during October– November (Sreekantradheya et al. 1975). The photosensitive genotypes are late maturing (~140 days), highly indeterminate and limit the production of crop (Balasubramanian 1985). Such cultivars should be sown during the month of September–October. The crops grown before September take more time to mature while crops grown after December have poor seed set (Balasubramanian 1985).

11.15 Horsegram Production in India Drought has always been considered as the major abiotic stress not only for the flora but also for the fauna (Bhardwaj and Yadav 2012a). The antioxidant and osmolyte biosynthesis in various plant parts of the crop makes horsegram capable to survive for longer periods under drought conditions with least management (Bhardwaj and Yadav 2012b; Prakash et al. 2010). Horsegram is mainly grown as a mixed crop or a subsistence crop during drought spells, and meagre inputs are applied for its cultivation. It can succeed on the fertility and moisture remained after the rabi crop. Horsegram has got tough competition from other legumes in the recent years, even in dry lands, and its cropping zones have shrunk in last past 41 years with the sharp decline in cropping area. The area and its production of the crop showed significant decrease during the recent years (Tiwari and Shivhare 2016). Horsegram cultivation is limited to mainly six states, namely, Andhra Pradesh, Karnataka, Madhya Pradesh, Maharashtra, Odisha and Tamil Nadu of India, and occupies about 90–95% of the total area. Horsegram contributes only 2% area, 1% production and 469 kg per ha of productivity in the country, and the major contribution is made by Karnataka followed by Odisha and Chhattisgarh at the national level (Tiwari and Shivhare 2016). Horsegram contributes about 0.33% of the total food grain production in India (http://www.apdes.ap.gov.in). Area under horsegram cultivation in the major states of India is given in Table 11.1. The data clearly indicate that the area of the crop reduced from 1976–77 to 2016–2017. Karnataka is the only state having highest area for horsegram cultivation. Out of national area (46,802 thousand ha) comprising of 16 states, namely, Andhra Pradesh, Bihar, Chhattisgarh, Haryana, Himachal Pradesh, Jammu and Kashmir, Jharkhand, Karnataka, Kerala, Madhya Pradesh, Maharashtra, Odisha, Tamil Nadu, Telangana, Uttarakhand and West Bengal of the crop, Karnataka contributed 15,315 thousand ha of area during last 41 years followed by Odisha and Andhra Pradesh. Almost consistent area was devoted to the crop in states of Bihar, Madhya Pradesh, Chhattisgarh and Jharkhand during last 41 years. The area of the crop in Maharashtra reduced drastically from 325 thousand ha to about only 12 thousand ha during the last 10 decades due to higher competition with other crops and legumes. After the formation of Chhattisgarh and Jharkhand by

Year 1976–1977 1977–1978 1978–1979 1979–1980 1980–1981 1981–1982 1982–1983 1983–1984 1984–1985 1985–1986 1986–1987 1987–1988 1988–1989 1989–1990 1990–1991 1991–1992 1992–1993 1993–1994 1994–1995 1995–1996 1996–1997 1997–1998 1998–1999 1999–2000 2000–2001

Karnataka 384 551 688 559 685 681 683 627 566 504 464 513 395 414 353 365 391 390 403 314 321 342 325 356 295

Andhra Pradesh 319 346 358 346 320 294 308 282 237 216 186 196 155 136 130 131 133 139 133 127 121 110 111 102 79

Maharashtra 300 273 265 290 314 292 238 302 271 272 325 288 219 263 188 188 243 187 176 139 124 112 104 104 91

Odisha 204 310 340 363 343 332 274 262 345 341 368 431 394 390 406 410 111 8 120 108 103 116 97 90 76

Madhya Pradesh 205 197 200 187 180 181 189 188 183 179 174 169 159 161 160 157 147 149 146 140 136 128 124 115 37

Table 11.1 Area (‘000 ha) under horsegram cultivation in selected states of India Tamil Nadu 197 193 207 195 161 149 176 153 156 166 126 163 121 134 123 120 121 128 128 91 77 84 84 133 102

Bihar 106 120 106 221 93 89 80 90 82 83 81 75 76 74 72 63 62 11 58 62 60 60 57 54 18

Chhattisgarh – – – – – – – – – – – – – – – – – – – – – – – – 65

Jharkhand – – – – – – – – – – – – – – – – – – – – – – – – 38

228 11 Cultivation

343 335 274 283 270 329 227 216 228 221 180 206 163 181 166 124

80 82 79 67 57 64 50 38 59 32.0 28.0 28.1 28.0 36.0 57.0 12.00

53 54 63 73 65 72 78 43 35 34.0 11.7 13.3 NA 12.0 NA NA

91 76 88 84 75 73 72 59 64 69.4 44.3 48.4 42.1 38.3 33.4 34.09

36 33 31 32 30 30 26 24 23 0.4 20.3 16.0 11.7 25.0 14.0 20.45

Source: Ministry of Agriculture and Farmers Welfare, Govt. of India (https://agricoop.nic.in)

2001–2002 2002–2003 2003–2004 2004–2005 2005–2006 2006–2007 2007–2008 2008–2009 2009–2010 2010–2011 2011–2012 2012–2013 2013–2014 2014–2015 2015–2016 2016–2017

132 86 69 103 61 55 48 45 47 47.3 69.0 62.5 88.7 92.0 75.9 38.60

14 13 15 15 11 14 14 11 11 9.9 8.6 8.0 8.2 8.3 7.8 8.30

62 58 55 56 54 53 51 54 49 49.2 50.2 44.8 51.2 54.6 47.8 44.8

11 14 18 17 18 16 16 14 14 20.9 16.2 12.2 24.7 32.3 26.5 25.1

11.15 Horsegram Production in India 229

230

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partitioning the states of Madhya Pradesh and Bihar, respectively, in November 2000, the area of horsegram cultivation in Madhya Pradesh and Bihar reduced due to transfer of location of the crop. Production of the crop in Karnataka was quite higher as compared to the other states ranging from 16,000 tonnes to 276,000 tonnes, but its productivity reduced over the years may be due to less care and attention of the crop (Table 11.2). Out of national production comprising of 16 states, namely, Andhra Pradesh, Bihar, Chhattisgarh, Haryana, Himachal Pradesh, Jammu and Kashmir, Jharkhand, Karnataka, Kerala, Madhya Pradesh, Maharashtra, Odisha, Tamil Nadu, Telangana, Uttarakhand and West Bengal (17,342 thousand tonnes), Karnataka produced 5778, 000 tonnes of horsegram during last 41 years followed by Odisha (3091.7,000 tonnes) and Maharashtra (1883.4 thousand tonnes). However, production of the crop reduced over the years in Karnataka due to shifting of area to other crops. There was high fluctuation in the production of the crop at Odisha and Maharashtra. Drastic decrease in production of the crop was observed in Maharashtra from about 100,000 tonnes to only 3.4,000 tonnes. It may be due to reduction of area and shifting of farmers’ to another legumes or crop. Andhra Pradesh, Bihar and Tamil Nadu maintained the production of horsegram over the years and exhibited second to fifth rank in terms of production (Table 11.2). Crop productivity is the quantitative values of crop yield in the given area of crop cultivation. The productivity of horsegram during 1976–1977 to 2016–2017 in the major crop growing states is given in Table 11.3. Out of national productivity comprising of 16 states, namely, Andhra Pradesh, Bihar, Chhattisgarh, Haryana, Himachal Pradesh, Jammu and Kashmir, Jharkhand, Karnataka, Kerala, Madhya Pradesh, Maharashtra, Odisha, Tamil Nadu, Telangana, Uttarakhand and West Bengal of (282,299 kg per ha), Karnataka had highest productivity of 30,891 kg per ha followed by Andhra Pradesh (30,147 kg per ha), Tamil Nadu (27,552 kg per ha) and Bihar (26,338 kg per ha). Karnataka experienced low productivity over the years ranging from 363 to 1204 kg per ha; however, the productivity in Karnataka was better and consistent as compared to other states. There was a drastic decrease in the productivity of the crop in Odisha from 1994–1995 to 2015–2016; nevertheless, it was higher during 2010–2011. The productivity trends in Bihar were consistent during the last two decades; the similar trends were observed in Chhattisgarh and Jharkhand. Tamil Nadu is performing better in terms of productivity of the crop, while Odisha showed decreasing trends over the years due to the decrease in area and production of the crop. The season-wise area, production and productivity of horsegram from 1976–1977 to 2016–2017 in India is presented in Table 11.4. Area, production and productivity of the crop were highest during kharif season as compared to rabi season showing that horsegram is a choice crop of the farmers in kharif. Farmers dedicate more area during kharif than rabi season. The production and productivity of the crop were comparable during the rabi season indicating that the productivity of the crop may be increased with the increase in the area during rabi season.

Year 1976–1977 1977–1978 1978–1979 1979–1980 1980–1981 1981–1982 1982–1983 1983–1984 1984–1985 1985–1986 1986–1987 1987–1988 1988–1989 1989–1990 1990–1991 1991–1992 1992–1993 1993–1994 1994–1995 1995–1996 1996–1997 1997–1998 1998–1999 1999–2000 2000–2001 2001–2002

Karnataka 13 233 259 201 203 276 183 251 170 123 186 203 93 140 120 170 182 172 149 141 151 123 153 155 158 149

Andhra Pradesh 42 85 89 74 61 78 96 82 61 64 62 53 35 42 51 53 52 40 45 44 48 44 36 36 21 39

Maharashtra 93 81 75 82 57 63 51 95 84 78 93 70 76 100 67 38 87 81 59 50 46 35 44 35 31 16

Odisha 75 143 156 111 161 156 138 155 147 170 162 208 205 209 198 203 31 3 42 39 22 33 24 23 15 28

Table 11.2 Production (‘000 tonnes) of horsegram in selected states of India Madhya Pradesh 1 58 56 40 48 54 46 58 47 43 44 39 46 46 47 40 42 45 44 42 41 36 34 31 7 9

Tamil Nadu 46 46 49 46 38 36 77 61 61 64 54 72 54 61 51 48 56 63 59 29 30 43 42 58 47 61

Bihar 37 49 51 100 36 45 35 41 43 46 43 30 34 34 39 32 27 4 27 28 32 35 36 43 14 12

Chhattisgarh – – – – – – – – – – – – – – – – – – – – – – – – 19 21

Horsegram Production in India (continued)

Jharkhand – – – – – – – – – – – – – – – – – – – – – – – – 31 6

11.15 231

Karnataka 109 77 119 131 107 120 88 111 134 92 80 87 87 79 16

Andhra Pradesh 29 39 26 20 30 25 16 36 13.1 14 17 15 16 22 6

Maharashtra 14 17 24 22 25 35 18 15 14.5 4.2 4.3 NA 3.4 NA NA

Odisha 14 25 21 21 21 21 16 20 22.5 10.7 4.9 15.0 13.2 9.4 14.85

Madhya Pradesh 8 10 8 8 9 8 8 7 0.1 5.0 17.5 5.8 10.0 5.0 9.42

Source: Ministry of Agriculture and Farmers Welfare, Govt. of India (https://agricoop.nic.in)

Year 2002–2003 2003–2004 2004–2005 2005–2006 2006–2007 2007–2008 2008–2009 2009–2010 2010–2011 2011–2012 2012–2013 2013–2014 2014–2015 2015–2016 2016–2017

Table 11.2 (continued) Tamil Nadu 24 18 40 22 38 23 21 22 21.7 37.2 24.9 56.9 68.3 42.2 12.36

Bihar 10 11 12 10 12 13 10 10 9.7 8.2 7.8 7.8 8.0 7.2 7.60

Chhattisgarh 14 19 17 17 17 16 16 14 14 14.9 14 15.5 17.6 16.2 16.8

Jharkhand 6 6 8 7 7 7 6 6 17.2 9.8 7.2 15 22.3 18.8 19.5

232 11 Cultivation

Year 1976–1977 1977–1978 1978–1979 1979–1980 1980–1981 1981–1982 1982–1983 1983–1984 1984–1985 1985–1986 1986–1987 1987–1988 1988–1989 1989–1990 1990–1991 1991–1992 1992–1993 1993–1994 1994–1995 1995–1996 1996–1997 1997–1998 1998–1999 1999–2000 2000–2001 2001–2002

Karnataka 471 638 573 360 582 692 521 812 565 543 838 801 484 668 635 918 913 869 766 868 920 709 940 875 1057 434

Andhra Pradesh 388 490 480 415 356 501 622 584 493 580 668 527 446 654 798 883 793 604 604 719 781 763 725 701 708 893

Maharashtra 512 462 482 523 180 218 382 559 563 563 531 508 741 805 747 437 628 862 717 884 908 698 820 764 345 717

Odisha 720 939 897 661 901 906 987 592 937 1124 899 907 521 1137 1070 1013 279 712 352 358 214 286 247 254 191 308

Table 11.3 Productivity (kg per ha) of horsegram in selected states of India Madhya Pradesh 418 585 572 437 539 569 522 601 536 524 524 513 556 570 585 550 589 619 615 626 629 495 535 567 176 250

Tamil Nadu 232 236 238 233 233 242 436 398 392 387 429 438 447 452 412 396 464 497 927 637 774 1016 1012 876 863 915

Bihar 352 412 479 914 387 505 435 454 522 546 527 399 448 458 537 515 436 381 466 455 538 584 627 810 771 804

Chhattisgarh – – – – – – – – – – – – – – – – – – – – – – – – 295 618

Horsegram Production in India (continued)

Jharkhand – – – – – – – – – – – – – – – – – – – – – – – – 835 573

11.15 233

Karnataka 673 586 843 984 676 1060 821 974 1204 530 786 1040 954 945 363

Andhra Pradesh 743 879 873 754 963 1059 912 1240 813 1078 1305 1081 895 831 545

Maharashtra 665 645 609 770 777 986 916 856 847 355 323 NA 284 NA NA

Odisha 188 615 248 279 288 292 274 309 1370 575 362 691 677 283 936

Madhya Pradesh 237 645 665 285 298 329 317 303 310 744 804 496 400 357 960

Source: Ministry of Agriculture and Farmers Welfare, Govt. of India (https://agricoop.nic.in)

Year 2002–2003 2003–2004 2004–2005 2005–2006 2006–2007 2007–2008 2008–2009 2009–2010 2010–2011 2011–2012 2012–2013 2013–2014 2014–2015 2015–2016 2016–2017

Table 11.3 (continued) Tamil Nadu 602 537 718 948 1226 926 943 846 981 1077 801 1267 1499 966 633

Bihar 794 740 807 858 864 894 920 962 984 951 968 951 957 926 916

Chhattisgarh 573 623 548 602 613 636 607 549 548 796 607 539 694 624 670

Jharkhand 443 335 456 410 405 405 436 436 822 606 590 609 691 710 780

234 11 Cultivation

Year 1976–1977 1977–1978 1978–1979 1979–1980 1980–1981 1981–1982 1982–1983 1983–1984 1984–1985 1985–1986 1986–1987 1987–1988 1988–1989 1989–1990 1990–1991 1991–1992 1992–1993 1993–1994 1994–1995 1995–1996 1996–1997 1997–1998 1998–1999 1999–2000 2000–2001

Area (in ‘000 ha) Kharif Rabi 1232 499 1350 653 1465 714 1445 744 1400 720 1329 716 1343 631 1308 623 1130 744 1132 668 1084 671 1103 767 897 643 943 660 820 644 784 680 924 312 582 456 752 439 755 306 660 307 641 336 617 305 512 464 541 274 Total 1731 2003 2179 2189 2120 2045 1974 1931 1874 1800 1755 1870 1540 1603 1464 1464 1236 1038 1191 1061 967 977 922 976 815

Production (in ‘000 tonnes) Kharif Rabi 346 136 486 214 504 237 436 231 356 262 439 282 397 245 478 281 377 254 329 283 375 287 360 333 277 278 353 296 312 278 285 316 365 132 244 183 292 152 282 115 255 131 242 124 253 129 198 196 231 120 Total 482 700 741 667 618 721 642 759 631 612 662 693 555 649 590 601 497 427 444 397 386 366 382 394 351

Table 11.4 Season-wise area, production and productivity of horsegram in India from 1976–1977 to 2016–2017 Productivity (in kg/ha) Kharif Rabi 2640 1731 3193 1786 3028 1797 2634 2361 2643 2445 2865 2462 2728 2724 2769 2997 3031 2673 3091 2987 3109 2977 2442 2980 2036 2435 3431 3088 3519 3014 3480 3065 3372 2339 2941 3557 3272 3247 3412 3141 3311 3311 3423 3084 3621 3175 3582 3295 4799 2812

Horsegram Production in India (continued)

Total 4371 4979 4825 4995 5088 5327 5452 5766 5704 6078 6086 5422 4471 6519 6533 6545 5711 6498 6519 6553 6622 6507 6796 6877 7611

11.15 235

Area (in ‘000 ha) Kharif Rabi 453 382 409 358 410 299 441 297 381 269 390 327 367 225 312 203 335 206 291 217 247 201 229 235 234 207 253 249 238 208 178 148 29,382 17,419 Total 835 767 709 738 650 717 592 515 541 508 448 464 441 502 446 326 46,802

Production (in ‘000 tonnes) Kharif Rabi 188 162 128 109 134 96 173 108 161 102 140 132 152 122 120 85 138 109 145 118 109 99 98 95 113 121 124 137 106 108 88 29 10,327 7015

Source: Ministry of Agriculture and Farmers Welfare, Govt. of India (https://agricoop.nic.in)

Year 2001–2002 2002–2003 2003–2004 2004–2005 2005–2006 2006–2007 2007–2008 2008–2009 2009–2010 2010–2011 2011–2012 2012–2013 2013–2014 2014–2015 2015–2016 2016–2017 Total

Table 11.4 (continued) Total 350 237 230 281 263 272 274 205 247 263 208 193 234 261 213 117 17,342

Productivity (in kg/ha) Kharif Rabi 4563 3755 3758 2952 3941 3683 4325 3363 4489 3107 4472 3725 4696 3990 4719 3476 4642 3767 7043 4433 5548 2706 5762 3646 5915 7415 6295 3662 5283 2895 5862 3740 155,697 126,602

Total 8318 6710 7624 7688 7596 8197 8686 8195 8409 11,476 8254 9408 13,330 9957 8178 9602 282,299

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11.16

Horsegram Varieties Developed in India

237

11.16 Horsegram Varieties Developed in India Horsegram is mainly cultivated for grain and fodder. It has wide variability in the shape and size of plant and seeds. Prakash et al. (2008) evaluated horsegram varieties to identify the best suitable variety for Northern Dry Zone of Karnataka and reported BJPL-1 as high-yielding nature due to high number of pods per plant, maximum number of seeds per pod, 100-seed weight, high fodder yield, resistant to iron chlorosis, fairly good protein percentage and multiple disease resistance for cultivation under Northern Dry Zone of Karnataka. The selection BGM-1 was found stable and released as KBH-1 by the University of Agricultural Sciences, Bangalore, for general cultivation. Similarly, the selection of PHG-9 has been released by CVRC (Central Variety Release Committee) from Himachal Pradesh. List of notified varieties of horsegram, gazette notification number and date of notification is given in Table 11.5. The general characteristics, agronomic features and reaction to diseases and pests of some of the horsegram varieties are described as follows: CO-1: The variety is a selection from Munduka Lathur area and was released in 1953 for Tamil Nadu state. It is suitable for rainfed areas of Tamil Nadu. The maturity period of the variety ranges from 110 to 115 days. It yields about 600–700 kg seeds per ha. Paiyur: Two varieties Paiyur-1 and Paiyur-2 are available for Tamil Nadu state with different characteristics. Paiyur-1 is suitable for rainfed areas, matures within 110–115 days after sowing and yields 650–700 kg seeds per ha. Paiyur-2 is suited for sesame-groundnut-ginger-horsegram crop sequence in rainfed region of Tamil Nadu, matures in 105–110 days and yields 700–800 kg seeds per ha. Hebbel Hurali: Two varieties, namely, Hebbel Hurali-1 and Hebbel Hurali-2, have been identified for the state of Karnataka. These varieties mature within 90–100 days, and their yield ranges between 1800 and 2000 kg per ha. Hebbel Hurali-1 was developed from a PLKU-32 whereas Hebbel Hurali-2 was developed from EC-1. Both varieties are photo-insensitive. HPK: HPK-2, HPK-4 and HPK-6 are the varieties well adapted to Himachal Pradesh. HPK-2 was a selection from local germplasm of Himachal Pradesh. It is a semi-spreading variety having light yellow colour seeds. HPK-4 also known as Baiju is similar to HPK-2 but has dark grey seeds of mottle shape. HPK-6 is also known as Deepali and is a selection from Himachal Pradesh developed by the Agricultural Research Station, Badnapur. The varieties mature within 120–130 days after sowing and yield 1000–1200 kg seeds per ha. MAN: The variety is a selection from early erect-type bulk sample collected from stock available at the Pulse Research Station, Badnapur, and the All India Coordinated Research Project (AICRP) for Dryland Agriculture, Solapur. The variety was released in 1989. The average yield of the variety is 650–700 kg seeds per kg. Madhu: The variety was developed from the selection of local germplasm and suitable for the Bihar state. It has bushy habit and its seeds are of dark cream colour having red spot. It matures within 105–110 days and yields 850–1000 kg seeds per ha.

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Table 11.5 Notified varieties of horsegram SN 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31

Variety name Arjia Kulthi-21 (AK-21) Baizhu Kulthi (HPK-4) BGM-1 Birsa Kulthi-1 (Strain-43) CO-1 CRIDA-1-18R CRIDA Harsha (CRHG-19) CRIDA Latha (CRHG-4) Dapoli-1 Deepali (HPK-6) GPM-6 Gujarat Dantiwada Horsegram-1 (GHG-5) Hebbal Hurali-1 Hebbal Hurali-2 Indira Kulthi-1 (IKGH-01-01) KS-2 Madhu MAN Maru Kulthi-1 Paiyur-2 Palem-1 Palem-2 PHG-9 Pratap Kulthi-1 (AK-42) VLGahat-1(VLG-3) VL Gahat-10 VL Gahat-8 VL Gahat-10 VL Gahat-15 (VLG-15) VL Gahat-19 (VLG-19) VL Gahat-8

Gazette notification no. 425(E)

S.O. 454(E) S.O.1146 (E) S.O. 733(E) 867(E) 471(E) O.S. 2187(E) S.O.1708(E)

S.O. 2326(E) 793(E) 13 599(E) 915(E) 425(E) 401(E) 401(E) 92(E) 122(E)

122(E) S.O. 454(E) S.O. 211(E) 599(E)

Notified date 08/06/1999 01/01/1982 1990 01/01/1987 01/01/1955 11/02/2009 24/04/2014 01/04/2010 26/11/1986 05/05/1988 27/08/2009 26/07/2012 01/01/1978 01/01/1978 10/10/2011 22/11/1991 19/12/1978 31/07/1989 06/11/1989 08/06/1999 15/05/1998 15/05/1998 02/02/2001 02/02/2005 01/01/1985 01/01/2008 01/01/2007 06/02/2007 11/02/2009 29/01/2010 25/04/2006

Source: www.seednet.gov.in

PDM-1: The variety is a selection from Bhimali Patnam and is suitable for sowing during kharif at Andhra Pradesh state. It has light colour flowers with light purple wash and its seeds are of manila colour. It takes 100–105 days for maturity and yields about 1400–1600 kg seeds per ha. VZM-1: The variety is a selection from local germplasm Vizianagaram and is suitable for sowing during kharif at Andhra Pradesh state. Its plants are tall, semierect having light yellow flowers with purple wash and seeds are of black colour. The variety matures within 100–105 days and yields 1200–1500 kg seeds per ha. Birsa Kulthi-1: It is a selection from local germplasm and was released in 1985 for Bihar state. The variety has trailing growth habit with light yellow colour flowers.

11.16

Horsegram Varieties Developed in India

239

It is moderately resistant to Macrophomina leaf blight, matures within three months and yields about 800–1000 kg seeds per ha. VLG-1: The variety is a selection from local material collected from hilly areas of Uttar Pradesh and was released in 1983 for hilly areas of Uttar Pradesh (now Uttarakhand). Its plants are semi-erect with spreading branches and are tolerant to blight diseases. The seeds of the variety are medium size having brownish yellow colour. The variety matures within 120–130 days and yields about 800–1000 kg seed per ha. Maru-Kulthi: The variety was released in 1989 for cultivation in dryland of Western Rajasthan and its adjoining districts and Maharashtra state. It is a selection of plants from germplasm entry collected from Pali-Marwar region of Rajasthan which was developed by the Central Arid Zone Research Institute, Jodhpur. The variety is semi-spreading type having light brown seeds and takes about 69–161 days to mature. It yields 700–900 kg seeds per ha. The variety is drought resistant and gives higher yield as compared to other varieties and local germplasms. No serious diseases/insect-pest attack is observed on the variety under field condition, and also it is not attacked by any storage pest during storage. BGM-1: The variety is well adapted for the state of Karnataka and is a selection from a local germplasm Bailhongal. It was released for the state of Karnataka in 1990. It has bushy appearance and is tolerant to yellow mosaic virus. This photosensitive variety takes 100–110 days to mature and yields 900–1000 kg seeds per ha. PHG-9: The variety is a selection from Palampur local and was released in 1997 for South India state. It is well adapted for the state of Karnataka. It takes 100–105 days to mature and yields about 1000–1200 kg seeds per ha. AK-21: The variety is also known as Arjia Kulthi-21. The variety was developed from a selection, a locally adapted variety of village Karoi by the AICRP for Dryland Agriculture, ARS Arjia, Bhilwara, Rajasthan. The variety has lush green colour and attains plant height up to 35–80 cm. It is an early maturing variety taking about 60–105 days to mature and well suited for Northern India. It is well adapted for the state of Rajasthan and has been recommended for all the areas of horsegram growing states during kharif season. It yields about 800–1000 kg seeds per ha and no major disease/pest has been reported. Dapoli-1: The variety is a selection from the local bulk of Konkan region and was developed from the Department of Agriculture Botany, College of Agriculture, Konkan Krishi Vidyapeeth, Dapoli, in 1984. It has semi spreading tendrilar growth habit with 45–55 cm tall plants. It takes 90–110 days to mature and yields 9000–10,000 kg seeds per ha. KS-2: The variety is a selection of plants from local germplasm collected from village Virwara of district Sirohi, Rajasthan, and was developed by the Agricultural Research Station, Mandor, Jodhpur, for dryland farming zone II b of the state. It is an early maturing variety and takes 80–85 days to mature. The plants of the variety are semi-spreading in nature and have 60–80 cm height. No serious diseases/insect-pest attack is observed on the variety under field condition, and also it is not attacked by any storage pest during storage. The variety yields 600–700 kg seeds under 1 ha of area.

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AK-42: The variety is also known as Pratap Kulthi-1 and was developed by Maharana Pratap University of Agriculture and Technology, Udaipur, Rajasthan. The variety was released in 2005 and is well adapted for the state of Rajasthan. It is recommended for the states of Rajasthan, Gujarat, Madhya Pradesh and Haryana during kharif seasons for grains as well as fodder purpose in marginal lands. It is highly drought tolerant and can be grown where the rainfall is uncertain and erratic. It takes 62–120 days to mature and yields 850–1100 kg seeds per ha. No serious incidence of diseases/insect-pest attack is observed on the variety under field condition. VLG-8: The variety takes 92–106 days to mature and was released in 2007. The average yield of the variety is about 1200 kg per ha. It is resistant to anthracnose and stem rot. VLG-19: The variety is a selection from VH-61 and was developed by the Vivekananda Parvatiya Krishi Anusandhan Sansthan, Almora, Uttarakhand. It is recommended for cultivation in timely sown rainfed conditions of North Zone and was released in 2010. The variety exhibited multiple disease resistant to important diseases of North India. The plant of the variety has indeterminate, semi erect growth habit, and the plant has 41.0–56.88 cm height. The variety matures within 88–94 days and yields about 500 kg seeds per ha. CRHG-4: The variety is also known as CRIDA Latha. It is a derivative from Hyderabad Local, evolved by physically induced mutation through gamma ray irradiation by the Central Research Institute for Dryland Agriculture (CRIDA), Hyderabad. It has medium maturity of 72–110 days and has been recommended for cultivation in South India under rainfed conditions. It yields 750–800 kg seeds per ha and is tolerant to major diseases, namely, yellow mosaic virus, powdery mildew, leaf blight, root rot, etc. GHG-5: The variety is also known as Gujarat Dantiwada horsegram-1. It is a selection from AK-42 and was developed by the Sardarkrushinagar Dantiwada Agricultural University, Sardarkrushinagar. It is recommended for cultivation in northern states of India comprising Gujarat, Rajasthan, Uttarakhand, Jharkhand, Uttar Pradesh and Maharashtra under rainfed condition during kharif season. The variety takes 89–100 days to mature. The variety has been found resistant to root rot disease and moderately resistant to various diseases including powdery mildew, collar rot, cercospora leaf spot, leaf blight and anthracnose. It was found free from the attack of feeder and leaf minor pests, while the population of aphids, jassids and mites were at par with checks. The variety yields 550–600 kg seeds per ha. Palem-1: The variety matures within 80–85 days from the date of sowing and yields 1000–1200 kg seeds per ha. It was released in 1998. CRIDA-18R: The variety is a derivative from K-42 evolved by physically induced mutation through gamma rays irradiation by CRIDA, Hyderabad. The variety was released in year 2009. It has medium maturity of 72–102 days and has been recommended for cultivation in the states of Andhra Pradesh, Tamil Nadu and Karnataka under rainfed conditions. It is well tolerant to powdery mildew, yellow mosaic virus and root rot diseases. It yields about 800–850 kg seeds per ha.

References

241

References Arnon I (1972) Crop production in dry regions, vol 2. Leonard Hill, London Arya MPS, Singh R, Singh R (1996) Effect of NPK on the nodulation, growth and yield characters in horsegram. Legume Res 19:65–69 Bajpai RP, Dwivedi RK, Singh VK (1990) Performance of horsegram on different dates of sowing, phosphorus levels and intercropping. Indian J Pulses Res 3(2):159–162 Balasubramanian V (1985) Horsegram. Central Research Institute for Dry Land Agriculture, Hyderabad Banik P, Midya A, Sarkar BK, Ghose SS (2006) Wheat and chickpea intercropping systems in an additive series experiment: advantages and weed smothering. Eur J Agron 24(4):325–332 Basavaraju TB, Rao MRG (1997) Effect of Acacia nilotica and Azadirachta indica on the yield of horsegram in agri-silvi culture system. Karnataka J Agric Sci 10:1210–1212 Bhardwaj J, Yadav SK (2012a) Genetic mechanisms of drought stress tolerance, implications of transgenic crops for agriculture. In: Lichtfouse E (ed) Agroecology and strategies for climate change, Sustainable agriculture reviews. Dordrecht, Springer, pp 213–235 Bhardwaj J, Yadav SK (2012b) Comparative study on biochemical and antioxidant enzymes in a drought tolerant and sensitive variety of horsegram (Macrotyloma uniflorum) under drought stress. Am J Plant Physiol 7:17–29 Bolbhat SN, Dhumal KN (2009) Induced macromutations in horsegram [Macrotyloma uniflorum (lam.) Verdc]. Legume Res 32:278–281 Bolbhat SN, Dhumal KN (2010) Desirable mutants for pod and maturity characteristics in M2 generation of horsegram (Macrotyloma uniflorum (lam.) Verdc). Res Crops 11(2):437–440 Brown JC (1975) Competition between phosphate and plant for Fe and Fe+2 ferrozine. Agron J 64: 240–243 Chandranath HT, Hosmani MM (1995) Effect of row spacing and phosphorus levels on phosphorus uptake by horsegram. Karnataka J Agric Sci 8(1):83–86 Choudhary LS, Singh I (1994) Effect of nitrogen, phosphorus and zinc on growth and yield attributes of rainfed horsegram. Indian J Agri Sci 64(4):257–258 Dwivedi DK, Kumar A, Pandey SS, Kumar A (1996) Response of horsegram cultivars on different fertility lands under rainfed conditions. J Appl Biol 6:70–72 Edulamudi P, Masilamani AJA, Divi VRSG, Zakkula V, Konada VM (2015) Genetic characterization of rhizobia associated with horsegram [Macrotyloma uniflorum (lam.) Verdc.] based on RAPD and RFLP. Br Microbiol Res J 5(4):339–350 Garner WW, Allard HA (1920) Effect of the relative length of day and night and other factors of the environment on growth and reproduction in plants. J Agric Res 18:553–606 Ghani A (2003) Medicinal plants of Bangladesh: chemical constituents and uses, 2nd edn. Asiatic Society of Bangladesh, Dhaka Henry A, Daulay HS (1988) Genotype and environment interaction for seed yield in horsegram. Indian J Agric Sci 58:794–795 Henry A, Sodani SN, Tikka SBS (2006) Crop production. In: Kumar D (ed) Horsegram in India. Indian Arid Legumes Society, Scientific Publishers (India), Jodhpur, pp 53–70 Jena D, Mishra C (1990) Symbiotic nitrogen fixation and fertilizer nitrogen use efficiency in legume-cereal intercropping system. J Indian Soc Soil Sci 38:667–673 Kashirad A, Marschner M (1974) Iron nutrition of sunflower and corn plants in mono and mixed cultures. Plant Soil 41:91–101 Kashirad A, Bassiri A, Kharadnam M (1978) Responses of cowpeas to application P and Fe in calcareous soils. Agron J 70:67–70 Krishna KR (2014) Horsegram farming zones Asia and Africa. In: Krishna KR (ed) Agroecosystems: soils, climate, crops, nutrient dynamics and productivity. CRC Press, Boca Raton, pp 170–174 Kumar D (2007) Production technology for horsegram in India. Central Arid Zone Research Institute, Jodhpur

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Kumar N, Srinivas K, Mina BL, Kumar M, Srivastva AK (2010a) System productivity, profitability and competition indices of horsegram intercropping under rainfed condition. J Food Legumes 23(3&4):196–200 Kumar N, Prakash V, Srinivas K et al (2010b) Effect of sowing method, growth retardant and intercropping on horsegram (Macrotyloma uniflorum) productivity. Indian J Agric Sci 80(4): 335–337 Kurtz LT (1953) Inorganic P in acid and neutral soils: soils and fertilizer phosphorus in crop rotation. Agron Monogr 4:59–80 Mahapatra IC, Bapat SR, Sardana MG, Bhendia NL (1973) Fertilizer response of wheat, gram and horsegram under rainfed conditions. Fert News 18:57–63 Marwaha BC (1982) Efficiency of phosphatic fertilizers differing in water solubility, their effect on growth and nutrients uptake by horsegram [Macrotyloma uniflorum (lam.) Verde.] on acid alfisols. Proc Indian Nat Sci Acad B48(3):434–439 Mishra RK, Choudhary SK, Tripathi AK (1997) Intercropping of cowpea (Vigna unguiculata) and horsegram (Macrotyloma uniflorum) with sorghum for fodder under rainfed conditions. Indian J Agron 42(3):405–408 Mosse B (1973) Advances in the study of vesicular-arbuscular mycorrhiza. Annu Rev Phytopathol 11:171–196 Nagaraju AP, Chalapathi MY, Khalal A, Vishwanatha KP, Khalak A (1998) Response of horsegram to phosphorus and sulphur fertilization. Crop Res 15:140–145 Naik RG (2001) Effect of date of sowing on disease incidence and yieldsof horsegram (Macrotyloma uniflorum) lam verdec. Legume Res 24(3):182–185 Nayak BL (1993) Performance of horsegram grown as winter crop wider double cropping systems in rainfed upland laterite soil. Odisha J Agric Res 6:107–112 Omokanye AT, Onifade OS, Amodu JT, Balogun RO (2000) Effect of phosphorus application on seed production of horsegram (Macrotyloma uniflorum) in Northern Nigeria. Seed Res 28(2): 145–148 Pathak R (2015) Cultivation. In: Clusterbean: physiology, genetics and cultivation. Springer Science, Singapore Patil ND, Koregave BA, Salunke SS et al (1981) Dry sowing of rainfed crops according to rainfall probabilities. J Maharashtra Agric Univ 6:76–77 Patil VC, Nanjappa HV, Ramachandrappa BK, Muniyappa TV (1987) Effect of weed competition in drill sown finger millet intercropping system. Curr Res Univ Agric Sci 16:162–164 Patra SS (1991) Response of horsegram to dates of sowing and fertilizer under rainfed conditions. Indian J Agron 36:296–297 Patra AK, Nayak BC (2000) Response of horsegram (Macrotyloma uniflorum) to agronomic management practices. Indian J Agron 45(2):357–360 Pattanaik R, Sahu S, Padhi GS, Mishra AK (1995) Effect of inoculation of vesicular arbuscular mycorrhiza on horsegram (Macrotyloma uniflorum) grown in soil in iron-mine area. Indian J Agric Sci 65(3):186–190 Pradhan AC, Sarkar AK (1985) Effect of micronutrients on horsegram in lateritic acid soils of West Bengal. Seeds Farm 11:17–22 Prakash BG, Halaswamy KM, Guled MB (2007) Influence of different spacings on yield and its components in horsegram (Macrotyloma uniflorum lam.). J Arid Legumes 4(2):92–94 Prakash BG, Guled MB, Bhosale AM (2008) Identification of suitable horsegram varieties for northern dry zone of Karnataka. Karnataka J Agric Sci 21:343–345 Prakash BG, Hiremath CP, Devarnavdgi SB, Salimath PM (2010) Assessment of genetic diversity among germplasm lines of horsegram (Macrotyloma uniflorum) at Bijapur. Electron J Plant Breed 1(4):414–419 Prasad TVR, Hosmani MM, Sharma KMS (1990) Response of horsegram (Dolichos biflorus L.) to fertilizers in cultivators fields of Bangalore District. Karnataka J Agric Sci 3(1–2):119–120 Purushottam RK, Barman R, Saren BK (2017) Improvement of neglected horsegram production for benefit of mankind. Int J Bioresou Environ Agric Sci 3(2):521–527

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Rafey A, Srivastava VC (1989) Agronomic management of late sown horsegram. Indian J Agron 34:461–463 Rafey A, Prasad RB, Srivastava VC (1988) Studies on seeding time of horsegram. Indian J Agron 33:335–336 Ramani K, Latha KR, Tamilselvan N, Sivakumar R (2020) Influence of sowing time and varieties on growth and yield of horsegram (Macrotyloma uniflorum lam.) under rainfed condition. Int J Curr Microbiol App Sci 9(11):2214–2221 Rangaswamy KT, Anil Kumar TB, Yadahally YH (1991) Seed health of horsegram in relation to dates of sowing. Plant Prot Bull 43:45 Raut SD, Mahadkar UV, Nitave SS, Rajemahadik VA, Shendage GB (2016) Effect of tillage and methods of fertilizer application on yield and economics of horsegram. J Res ANGRAU 44(3&4):1–5 Raut SD, Mahadkar UV, Nitave SS, Rajemahadik VA (2017) Effect of different methods of fertilizer application and varying tillage conditions on nutrient content, uptake, quality and soil fertility of horsegram. Environ Ecol 35(2D):1429–1433 Reddy LVA, Reddy OVS (2005) Improvement of ethanol production in very high gravity fermentation by horsegram (Dolichos biflorus) flour supplementation. Lett Appl Microbiol 41:440–444 Sahu SS (1973) Effect of rhizobium inoculation and phosphate application on black gram and horsegram. Madras Agri J 60:989–993 Sharma SK (1987) Grown attributes and macro-chemical constituents as indices of dates and graded phosphorus levels in hors gram. J Plant Nutr 10:2031 Sharma RP, Singh AK, Poddar BK, Raman KR (2008) Forage production potential and economics of maize (Zea mays) with legumes intercropping under various row proportions. Indian J Agron 53(2):121–124 Singh I, Singh G (1992) Response of horsegram varieties to phosphorus levels and sowing spacing. Indian J Agric Sci 62:400–401 Singh RP, Venkateswarlu J (1985) Role of AICRPDA in research development. Fert News 30:46 Singh SK, Verma KR (1988) Allelopathic effects of leachates and extracts of Pinus roxburghii on four legumes in Kumaun Himalayas. Indian J Agric Sci 58:412–413 Singh RP, Das SK, Bhaskara UN, Reddy MN (1990) Towards sustainable agricultural practices. CRIDA, Hyderabad Smartt J (1985) Evolution of grain legumes II. Old and new world pulses of lesser economic importance. Exp Agric 21:1–18 Sreekantradheya R, Shetter BI, Chadrappa HM (1975) Genetic variability on horsegram. Mysore J Agric Sci 9:361–363 Stiles W (1969) An introduction to the principles of plant physiology. Methuen, London Sudha N, Mushtari-Begum J, Shambulingappa KG, Babu CK (1995) Nutrients and some antinutrients in horsegram (Macrotyloma uniflorum (lam.) Verdc.). Food Nutr Bull 16:81–83 Suthar R, Patel PH, Kumar A, Urmila (2017) Effect of horsegram (Macrotyloma uniflorum lam Verdec) varieties and different row spacing on yield attributes and yield. Life Sci Int Res J 4:1–6 Tayade NH (2018) Assessment of tractor drawn seed cum fertilizer drill for line sowing of horsegram. J Crop Weed 14(1):55–57 Taylor AW, Gurney EL (1964) The dissolution of calcium, aluminium phosphate. Soil Sci Soc Am Proc 26:63–64 Thakur DR, Sharma SK (1992) Performance of horsegram under different dates of sowing and phosphorus levels in rainfed mid hills. Himachal J Agri Res 16:12–14 Tharmarajah SK, Herath MKW (1988) Studies on pioneer cropping of dry Patana grasslands in the up country of Sri Lanka. Trop Agric 144:99–100 Tiwari AK, Shivhare AK (2016) Pulses in India: retrospect and prospects. Government of India, Ministry of Agri. & Farmers Welfare (DAC&FW), Directorate of Pulses Development, Vindhyachal Bhavan, Bhopal Verenkar SV, Thorat ST (1988) A note on dry matter accumulation in horsegram as influenced by nitrogen and phosphorus fertilization. J Indian Soc Coastal Agric Res 6:89–90

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Virk DS, Chakraborty M, Ghosh J, Harris D (2006) Participatory evaluation of horsegram (Macrotyloma uniflorum) varieties and their on-station responses to on-farm seed priming in eastern India. Exp Agric 42:411–425

Plant Protection

12

Abstract

Horsegram is comparatively free from the attack of the pests and diseases. However, some disease pest complex has been reported to cause considerable damage to the crop. Yellow vein mosaic virus, dry root rot and wilt are the most serious diseases in India. Powdery mildew and leaf spot have been reported in high humid conditions. Leaf spot and web blight cause severe damage to the crop under high rainfall conditions. The seeds of the crop are attacked by storage pests; besides this, pod borers and rodents have also been reported as the major agents to reduce the seed yield during late season rains. A detailed account of fungal, bacterial, viral diseases and major insect pests of the crop has been discussed in this chapter.

12.1

Introduction

The success of any crop production programme cannot be possible without plant protection measures. It ensures the control of yield losses due to the biotic stresses resolves the quarantine issues and improves the yield (Schut et al. 2014). The issues related to weeds, diseases, insect pests, nematodes, etc. can be properly addressed with the plant protection measures. Horsegram is comparatively free from the attack of the pests and diseases. Nevertheless, some disease pest complex has been reported to cause considerable damage to the crop. Powdery mildew (Sphaerotheca fuliginea) and leaf spot (Cercospora dolichi) have been reported in high humid conditions, while yellow mosaic virus is the major constraint in peninsular India. Powdery mildew reduced the yield to an extent of 70–80% with the poor production of 20–30% quality grains. Leaf spot caused by Ascochyta sp. and web blight (Thanatephorus cucumeris) cause severe damage under high rainfall conditions. The seeds of the crop are attacked by storage pests (Callosobruchus sps.). Pod borers # The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 R. Pathak, Genetics, Physiology and Cultivation of Moth Bean, Cowpea and Horse Gram, https://doi.org/10.1007/978-981-19-9956-7_12

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and rodents have also been reported as the major agents to reduce the seed yield during late season rains (Barnabas et al. 2010; Bolbhat and Dhumal 2010). The crop faces various problems throughout the growing areas varying from specific regions and climatic conditions. The yellow vein mosaic virus (YMV), dry root rot and wilt are the most serious diseases in India. The YMV damages the plant by reducing the leaf area and leaflet abscission leading to heavy defoliation (McDonald et al. 1985). While the wilt-infected seedlings or young plants may be break off at the infected and weakened portions of the hypocotyls, besides these pod rotting and seed discoloration are also major problems (Schwartz et al. 2011). Foliar diseases may be managed by spraying certain fungicides (Smith and Littrell 1980), but their cost and availability are major constraints to the small-scale farmers of the arid and semi-arid tropics. Growing of resistant variety is the best environmentfriendly approach for reducing yield loss from these diseases (Subrahmanyam et al. 1995). Colletotrichum species have been reported to cause infection in horsegram (Sharma 1976) and causes anthracnose disease. Various species, namely, C. dematium (Neergaard 1977; Udayasankar et al. 2012), C. truncatum (Holliday 1995), C. lindemuthianum, C. lindemuthianum (Sharma 1976), C. capsici (Pangtey and Sinha 1980), C. dematium f. sp. truncatum (Bharadwaj and Singh 1986) and C. dematium have been identified as major pathogens causing anthracnose disease. The disease reduced seed germination and crop stand up to 65% (Saharan 1979). HPKC-39, HPKC-57 and HPKC-33 were found free from C. truncatum under field conditions (Chahota et al. 2005).

12.2

Proteases and Bowman–Birk Inhibitors

Proteases are essential for maintenance and survival of the host organisms, but their higher concentrations can be destructive so their activities need to be regulated. Many proteinaceous proteinase inhibitors have been reported from plants (Richardson 1991; Ryan 1990) that play a critical role in regulating proteases. The legume seeds have been noted for their proteinase inhibitor content due to large amount of reserve protein. Its synthesis starts by mechanical wounding or insect/ pathogen attack (Ryan 1990) and plays a key role against insect herbivory and combating proteinases of pests and pathogens in plant (Shewry and Lucas 1997; Chilosi et al. 2000). The Bowman–Birk inhibitors (BBIs) and Kunitz-type inhibitors have been well studied among legumes due to their specific inhibition of trypsin (Richardson 1991; Laskowski and Kato 1980; Bode and Huber 1992, 2000; Mosolov and Valueva 2005). Sreerama et al. (1997) isolated and characterized four BBIs from horsegram. The major BBI of horsegram (HGI-III) is a 76-amino acid single-chain polypeptide having two independent inhibitory domains (Sreerama et al. 1997). HGI-III is a group II BBI characterized by the Pro-Ala sequence near the second reactive site. The complete primary structure (Prakash et al. 1996) and the role of disulphide bonds have been established in maintaining the structural integrity of HGI-III (Ramasarma et al. 1995; Singh and Rao 2002). Muricken and Gowda

12.3

Fungal Disease

247

(2010) cloned major BBIs from horsegram (HGI-III) and functionally expressed in Escherichia coli (rHGI). They reported close resemblance of rHGI with HGI-III both in its structure and inhibitory characteristics and suggested that the functional expression of a BBI minus a fusion tag may serve as a platform to study the structural and functional effects of the special pattern of seven conserved disulphide bridges. The BBIs are present in the resting seed during the germination of horsegram (Sreerama and Gowda 1998). Kumara et al. (2002) purified three BBIs (HGGI-I, II and III) that appear in the cotyledons of 120 h germinated horsegram seeds and reported that the HGGI-I, HGGI-II and HGGI-III differ from each other and from the dormant seed inhibitors in amino acid composition, molecular size and charge. They suggested that all the three inhibitors are potent competitive inhibitors of trypsin and chymotrypsin and may serve as an effective cancer chemo-preventive agent (Sreerama and Gowda 1997).

12.3

Fungal Disease

Horsegram is susceptible to various fungal diseases, namely, powdery mildew, anthracnose, dry root rot, cercospora leaf spot, myrothecium, etc. A brief account of some of the fungal diseases is given below:

12.3.1 Anthracnose It is one of the major fungal diseases of horsegram caused by Glomerella lindemuthianum (Butler 1918), Colletotrichum dematium (Neergaard 1977), C. truncatum (Holliday 1995), C. lindemuthianum, etc. all over the world. Colletotrichum lindemuthianum (Sharma 1976), C. capsici (Pangtey and Sinha 1980), C. dematium f. sp. truncatum (Bharadwaj and Singh 1986), C. dematium, etc. are the pathogens found responsible for anthracnose disease in India. The mycelium of anthracnose is branched, septate and hyaline that aggregate below the epidermis to form stroma. The fruiting structure of the pathogen produces conidiophores and setae. The conidia are single celled and have oil globules. Seeds are the primary source while air-borne conidia are the secondary source of infection. The attack of the disease may be observed above the ground part of plant during any growth stage of the crop. It appears as water-soaked lesions as primary symptoms that become brown at later stages and forms circular spots of different sizes. Leaves and pods are the most susceptible plant parts of the disease. The lesions are higher in numbers under surface as compared to upper surface. Infection is also seen at the petiole of the leaf and stem of the plant. The severity of infection results into parallel splitting of the plant parts. The seedlings developed from the seeds of infected pods are blighted and die. Crop rotation, wider spacing and proper cleaning of field are the best strategies to combat the fungal infection. One-kilogramme seeds treated at the rate of 2 g of

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carbendazim may result in the reduction of primary infection. Spray of 0.1% carbendazim is found suitable to manage the disease incidence in the field (Thakur and Khare 1990).

12.3.2 Powdery Mildew It is also a major disease of the crop caused by Leveillula taurica (Lev.) Arnaudi which is an endophytic fungi having spongy parenchyma. It penetrates through its haustoria in the parenchymatous cells and forms cluster of conidiophores that emerge from the stomata. The conidia of the pathogen are hyaline of different sizes and shapes having small papilla-like projections and borne singly at the tip. The conidia produce a germ tube on germination. The fungus is air-borne and spread from one field/host to another. The infection appears on the leaves in form of white powdery growth and spreads through stem and other plant parts. The plant may be infected at any growth stage, but the flowering stage is the most susceptible phase. The severity of infection may wilt the entire plant. Naik and Rangaswamy (1994) studied the effect of date of sowing and application of chemicals on the incidence and control of powdery mildew in horsegram and reported that the crop sown during the first and second fortnight of August had significantly higher grain yield as compared to the crop sown during first fortnight of September. Powdery mildew severely influences the photosynthesis process and changes the normal physiological activities in horsegram leading to considerable yield losses (Dutta et al. 2020). Horsegram mutants were tested for powdery mildew resistance, and it was observed that the disease had amended the yield, yield attributing traits and maturity period in the horsegram mutants (Sudhagar et al. 2022). The maximum disease control of powdery mildew was obtained with tridemorph (0.05%), followed by dinocap (0.2%) in horsegram with higher cost: benefit ratio (Naik 2000). Two sprays of tridemorph (0.05%) have effectively reduced the disease with highest-cost benefit ratio (Naik 2000). Spray of 1% carbendazim solution and sowing of pathogen resistance varieties/cultivars and crop rotation are the best practices to avoid the disease.

12.3.3 Dry Root Rot The infection of disease is mostly observed at flowering and pod formation stage caused by Macrophomina phaseolina. It is a facultative parasite that survives on the dead organic tissues and produces sclerotial bodies that invade host tissues inter- and intra-cellularly and kill the plant cells speedily. Pycnidia are produced by the fungus when the temperature is above 30 °C and are the most robust form of the fungus that survive over the years. The fungus is soil dweller and spread from one plant to another through irrigation, tools and implements. The sclerotia and pycniospores may be air-borne and cause further spread of disease. Sclerotia favours the low soil

12.3

Fungal Disease

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water potential and flourishes well (Olaya and Abawi 1996). The disease appears with yellowing of the leaves in patches and becomes severe during dry period. The leaves drop off within 3–4 days, and affected plant dies within a week. The black powdery masses of the fungal sclerotia are found at the root and basal stem of the crop. The disease incidence can be controlled with the application of farm yard manure and neem cake. Enhancement of soil moisture and seed treatment with Trichoderma viride/Pseudomonas fluorescens is effective to control the disease incidence in legumes (Lodha 1996). Vanitha and Alice (2008) evaluated the efficacy of Trichoderma viride and organic amendments on root rot incidence of horsegram and reported that the treated plots along with organic amendments and T. viride showed their superiority over the control. Besides this, they observed lowest disease incidence with the seed treated with carbendazim (2 g/kg) and recorded yield of 1504 kg per ha.

12.3.4 Leaf Spot The disease is caused by Cercospora dolichi (Ell. & Evr.). The fungus produces multi-celled conidia and short conidiospores. Water-soaked lesions are noticed on the leaf blades during the initial stage of the infection. These lesions become brown to reddish brown developing purplish boarder and vein; simultaneously the centre of the leaf turns grey. The spotting is mostly confined to the leaf blades, but sometimes it may be seen on the fruit and floral parts. Pangtey and Sinha (1980) described symptoms of leaf spot diseases on horsegram caused by Colletotrichum capsici and Phoma medicaginis and reported that these fungi were associated with the seed. They confirmed their seed-borne nature through pathogenicity tests. Seed treatment with captan (3 g/kg) and spray of mancozeb (0.2%) or carbendazim (1%) can reduce the incidence of disease. Tillage and crop rotation are effective ways to reduce the survival of these fungi from season to season on infested crop residues (Kumar 2007).

12.3.5 Rust The disease is caused by Uromyces phaseoli typica (Arth.). The fungus is an obligate parasite and its uredia bear uredospores. The uredial stage of the fungus repeats several times during cropping season and produces uredospores that spread by wind and cause secondary infections. Teliospores are also produced by the fungus. Rust pustules are the major characteristics of the fungus which are mostly found on the leaf blades. These pustules are higher on the under leaf surfaces (Kumar 2007). Young stems are also susceptible to the infection. Severity of infection turns the plant into brown tinge. Adjustment in the sowing dates and sowing of resistant varieties are the best options to avoid the infection (Kumar 2007).

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12.3.6 Blight It is one of the major diseases of horsegram leading to 10–60% yield loss. The disease is caused by Rhizoctonia solani (Kuhn) and is observed on the foliage in form of irregular water-soaked lesions. The infection causes root rot and plants start yellowing followed by wilting. The perfect stage of the fungus is known as Thanatephorus cucumeris (Fr.) Donk. Its hyphae and sclerotia are colourless and turn to yellowish brown on maturity. It is a soil-borne fungus that can rot the seeds prior to emergence from the soil (Kumar 2007). Irregular water-soaked spots are seen on the foliage that combine together rapidly under atmospheric humidity and cover the large part of the leaf lamina. Sometimes white mycelial growth is also seen on the affected part. Severity of disease leads to defoliation of plants in large numbers. Tan abrasion and the rising mycelial threads leading to strapping were observed in the horsegram field. The abrasions on the leaves increased in size and developed into distinct spots. The infected leaves were tested for identification of pathogen and for its further confirmation through molecular technique. The study revealed identification of a new blight disease caused by Athelia rolfsii on horsegram from Southern India (Mahadevakumar et al. 2022). Timely identification of the leaf spot disease may be useful to adopt appropriate measures to control the disease. The pathogen is saprophytic and its surviving ability in soil makes it very difficult to manage. Significant reduction in mycelial and sclerotial production has been observed with the application of Trichoderma viride, T. harzianum and Gliocladium virens (Dubey 1998). Seed treatment with 2 g of captan at the rate of per kg of seed should be done to avoid the fungal infection. Early sowing of the crop should be avoided in the areas where the disease prevails.

12.3.7 Wilt Neocosmospora vasinfecta is a major pathogen causing wilt in horsegram (Mishra 1988). The pathogen has a wide distribution in tropical and temperate regions and is usually associated with roots of leguminous crops. Plants wilt during higher temperatures especially under dry conditions and often stunted. Infected seedling or young plants may be break off from the infected portions. Lesions may also develop on pods during moist soil surface. The affected area may be drenched with 0.1% carbendazim solution to avoid the infection (Kumar 2007).

12.4

12.4

Viral Diseases

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Viral Diseases

12.4.1 Yellow Mosaic Virus It is also known as mung bean yellow mosaic gemini virus. The disease is spread through an insect vector Bemisia tabaci (silver leaf whitefly). Indigofera hirsute is reported as the natural reservoir of horsegram mosaic virus (Muniyappa and Reddy 1976). Small yellow patches are observed on the leaves during the initial stage of the infection that increases with time, and the leaves completely turn into yellow colour. The infected plant has few flowers and small and distorted pods and usually matures late. The seed are shrivelled and reduced in size. Barnabas et al. (2010) observed that the virus causing horsegram yellow mosaic disease resembled to a typical old world bipartite begomovirus. They identified the virus using partial tandem repeat clones of DNA-A and DNA-B and recorded their identity with the corresponding sequences of all the begomoviruses in the databases as horsegram yellow mosaic virus. Horsegram yellow mosaic virus infects several legumes including horsegram in India, and it has been reported as the major threat for legume cultivation (Monger et al. (2010). The yield and stability of horsegram have been susceptible to yellow mosaic disease and resulted in 30–50% yield losses (Muniyappa et al. 1975; Smartt 1990). Prema and Rangaswamy (2020) carried out the molecular characterization of horsegram yellow mosaic virus and studied its management. Silicon and nano-silver were used to manage the virus but it was found to be ineffective. Goud et al. (2013) observed leaves of horsegram having necrotic spots with wrinkled margins, together with plant stunting and wilting. They observed the symptoms similar to those caused by tobacco streak virus (TSV) infection in several hosts (Vemana and Jain 2010). On the basis of positive reactions with a polyclonal TSV antiserum using DAS- ELISA technique, they confirmed the TSV infection. TSV is pollen-borne and is easily spread by thrips under field conditions (Prasada Rao et al. 2003). The incidence of TSV in horsegram ranged from 5 to 20%, and yield loss depends on the stage of infection. Precautionary measures were advocated to control the disease by removal of infected plants (Prasada Rao et al. 2003). Durga et al. (2014) studied the relative resistance of different seed coat colours among horsegram accessions to wilt and yellow vein mosaic virus and reported that the wilt incidence was more in straw coloured accessions followed by black coloured and light straw coloured accessions while YMV incidence was higher in straw coloured accessions followed by light straw coloured and black coloured accessions. They reported accessions HG-54, HG-72 and HG-49 as high resistance towards YMV and wilt incidence. Removal of infected plant and sowing of resistant varieties/cultivars are the best options of disease management. Periodic spray of 0.1% monocrotophos or 3% neem oil soap emulsion (Sethuraman et al. 2001) and sowing of crop during the first fortnight of August and September (Naik 2001) may reduce the disease incidence. The population of the vector can be controlled with the spray of metasystox at the rate of 1 mL per litre of water. Rajkaur et al. (2009) screened 500 genotypes of horsegram against yellow mosaic virus (HgMV) under field conditions and found

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only seven genotypes, namely, AK-21, AK-34, AK-38, AK-26, DPI-2278, Tcr-512 and AK-36, which were resistant towards HgMV. Spray of oxydemeton methyl 25 (at 2 mL/litre water) may be done to control the white fly (Tiwari et al. 2020); if required, the chemical may again be sprayed after 15 days.

12.5

Bacterial Disease

12.5.1 Bacterial Leaf Spot Horsegram is the minor host of Xanthomonas phaseoli var. sojansis causing bacterial leaf spot at any stage of growth. Pre-flowering appearance of the disease causes economic losses in yield. Small, black lesions are seen on the older leaves as initial symptoms. The lesions enlarge and the largest lesions have concentric rings in the centre. The tissues surrounding the spots may turn yellow. The disease is also observed on the stem during severe conditions. The heavy infections cause pre-mature defoliation and also result into reduction in seed size and its quantity (Kumar 2007). Seeds are the primary sources of infection. Warm, rainy and wet weathers are the most favourable conditions for the growth of bacterium. The development and spread of the disease are highest during rains. Early seed sowing and maintenance of proper drainage in the field are the best managements of the disease (Kumar 2007).

12.6

Nematode

Meloidogyne incognita and M. javanica are the major causal agents of root knot disease in the various pulses including horsegram (Ali and Askary 2005). Optimum soil temperature (22–28 °C) is the most suitable condition for the development of nematodes. The infection can be seen in the form of patches on infected plants. Formation of galls on the root system is the basic symptom of the disease. The infected roots become knobby and knotty due to the infection of nematode. Severely infected plants have reduced root system and rootlets are absent. Nematode-infected plants are highly susceptible to fungal and bacterial root pathogens. Mohanty et al. (1990) studied the chemical changes in horsegram-infected plants with root knot nematode and found that the roots of infected plants had higher percentage of nitrogen, phosphorus, potassium and crude protein, while the values of these nutrients except phosphorus were lower in the shoots as compared to control plants. Various growth characteristics, namely, root length, shoot length, fresh and dry weight of root, fresh and dry weights of shoot, leaf area, water contents of the roots and shoots and root gall index of horsegram affected by root knot nematode, were assessed by the acetone extract of Aegle marmelos leaves. It was observed that shoot and root lengths and leaf area of the inoculated plants were increased with increasing concentrations of the leaf extract (Azhagumurugan et al. 2013). The leaf

12.7

Insect Pests of Horsegram

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extract of A. marmelos showed significant nematicidal properties and can be used in the control of plant root knot nematodes at small scale (Azhagumurugan et al. 2014). Deep ploughing of fields during summer helps to manage the juvenile population of nematodes. Covering of beds with polythene sheets (75 gauge thickness) before 6 weeks of sowing also reduces the soil-borne pests along with nematodes (Kumar 2007).

12.7

Insect Pests of Horsegram

Several insect pests infest the crop during different plant stages, for example, during seedling stage, the crop is infested by Monolepta signata, while during the pod maturity, the crop is infested by Etiella zinckenella, Omiodes indicata, Bagrada cruciferarum and Nezara viridula. Anticarsia irrorata, Colemania sphenarioides and Tetranychus neocaledonicus are the major pests found associated during the vegetative stage of horsegram (Singh et al. 1997; Saha 1995; Fotedar 1978). A brief account of some major insect pests associated with the crop is given below:

12.7.1 Pod Caterpillar It is a polyphagous insect from the species of Helicoverpa armigera and is an important pest of the crop. Initially, the larva feeds on the tender leaves, buds and flowers. Its larva is about 35–45 mm long and has dark greenish stripes on the body. The caterpillar makes hole in pods and feeds on the seeds with its head (Kumar 2007). The adult lays single egg on tender leaves and shoots. The adults are nocturnal and can be attracted using light trap or pheromone lure to kill. Monocrotophos 36 EC or NPV at the rate of 250 LE per ha may be used to manage the attack of the insect (Tiwari et al. 2020).

12.7.2 Leaf Miner Leaf miners are the insects of Liriomyza trifolii species. They are minute pale yellow adult flies of about 1–1.5 mm long and lay eggs on the leaf surface. The emerging maggots excavate the leaves and feed the mesophyll of the leaves. During the feeding, the maggots make serpentine-like structures on the leaves; therefore they are known as leaf miner (Kumar 2007). The severe attack of the fly may results into defoliation of the crop. The pest infestation may be managed by destroying the affected leaves. Spray of 5% neem oil emulsion on the leaves is effective in managing the infestation (Kumar 2007).

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12.7.3 Leaf Hopper The insect belongs to species Empoasca kerri of Cicadellidae family. The adult insect is of yellowish-green colour and lays eggs on the lower side of the leaf inserted into the leaf veins. Its nymphs are very active (Karthikeyan 2003). Both nymphs and adults are found underneath the leaves and suck the leaf sap. The affected leaves become light green and later they become brown, turn upwards and get dried. Spray of dimethoate 30 EC (0.05%) and imidacloprid at the rate of 20 g active ingredient per ha (Karthikeyan 2003) gives effective management to check the population. Other chemicals, namely, methyl demeton, dimethoate and phosphamidon, may be sprayed at the rate of 2 mL per litre of water to control the pest.

12.7.4 Pod Bug The bugs of species Clavigralla gibbosa are found to be associated with the pods of the crop. The greenish brown bugs and their nymphs suck the sap of seeds from green pods. Patches of light yellow colour are seen on the infested pods; in the later stage, the pods shrink and die. The pest population can be managed with the spray of 0.05% malathion (Kumar 2007).

12.7.5 Pod Fly The flies of species Melanagromyza obtusa also affect the crop. The small black flies having greenish and black abdomen pierce the pods and lay eggs within it. The needle-shaped eggs can be seen projecting from the wall of the pods. The maggot of the flies feeds on the seeds and causes damage to the pods. The affected pods become light green and remain undersized (Kumar 2007). The flies may be attracted by fish meal and killed. Spray of 0.2% carbaryl 50 WP or 0.05% dimethoate 30 EC should be done during the early stage of the attack of flies (Tiwari et al. 2020).

12.7.6 Thrips Thrips of Megalurothrips usitatus species infest the flower of the crop and cause abnormality in the flowers. The severe infestation results into shedding of flowers before their opening. Nymphs and adults of the thrips of Frankliniella species feed on the leaves of the crop and cause crinkling of leaves. Spray of 5% neem oil, oxydemeton methyl 25 (at 1 mL/litre water), 0.05% phosalone, 0.1% malathion and 0.03% dimethoate should be done during the bud formation stage to check the infestation (Tiwari et al. 2020).

12.8

Integrated Disease Management

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12.7.7 White Fly The silver leaf whitefly (Bemisia tabaci) is the vector of yellow mosaic virus disease in horsegram. It is highly polyphagous and its nymphs are found on the under surface of leaves and suck the sap (Kumar 2007). It can be managed with the spray of 40 g active ingredients of imidacloprid in 1 ha of area. Various other chemicals, namely, methyl demeton, dimethoate and phosphomidan, may be sprayed at the rate of 2 mL per litre of water to control the pest. Spray of oxydemeton methyl 25 (at 2 mL/litre water) and/or its repeat spray after 15 days may be done to control the white fly (Tiwari et al. 2020).

12.7.8 Pod Borer The spotted moths of Maruca testulalis species lay eggs on or near the flower buds. The greenish caterpillar of the moths enters into the buds, flowers or pods and plugged the hole with excreta. It feeds on the seeds inside the pod. The larvae bore the tender stem also. Spray of NPV (at 250 LE/ha) or quinolphos 25 EC (at 2 mL/liter water) may be done to control the pest infestation (Tiwari et al. 2020).

12.7.9 Leaf Roller The yellowish brown moths of Necoleia vulgaris has been found associated with the crop. Its larvae feed on the green matter of the leaves during early stage, and in the later stage, it webs the leaves together causing serious loss to the crop (Kumar 2007). The infested rolled leaves should be collected and destroyed to control its infestation.

12.7.10 Hairy Caterpillar The caterpillar of the insect belonging to the species Spilosoma obliqua feeds on the leaves, tender stem and branches. The severe infestation results into bared crop within few days. The crop should be inspected regularly, and the infested plant should be uprooted and buried (Kumar 2007).

12.8

Integrated Disease Management

Integrated disease management (IDM) is essential to cope up with several diseases in an environmental-friendly way and also address the toxic impact of chemical pesticides. It has several benefits including safety to environment, pesticide-free commodities, low input for crop production, etc. (Kumar 2014). An IDM approach for the horsegram crop is summarized as follows:

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• Soil solarization followed by deep ploughing in the month of May is found to be the most effective measure in checking soil-borne pathogens including nematodes. • Timely sowing of short duration and recommended varieties of the region escape the disease incidence. • Crop rotation and proper sanitation of the field are the best ways to reduce pathogens. • Row sowing provides optimum moisture to the crop for better establishment. • Weed control and its management are essential to realize higher yields. • Timely removal of infected plants is the best strategy to check the spread of diseases. • Seed treatment with hot water and with Trichoderma viride prevents the crop from soil-borne fungal infection. • Required amount of approved pesticides for that particular area should be purchased and should be stored away from food, feed and fodder. • Balanced doses of fertilizers and pesticides should be applied.

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Physiology and Abiotic Stresses

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Abstract

Horsegram can adapt harsh environmental conditions and has fairly good tolerant capacity towards various physiological and abiotic stresses. However, better seed production can be realized by addressing various issues related to physiological and abiotic stresses. Physiological aspects associated with seed colour, germination and seedling growth, seed yield, storage along with effect of heavy metal, water stress, drought condition and salt tolerance have been discussed in this chapter.

13.1

Introduction

Abiotic stresses are the essential part for the crop production under the climate change scenario and are responsible for major limiting factor of seed yields (Abhinandan et al. 2018). There are several abiotic factors including scarcity of water, drought, flooding, waterlogging, chilling, heating, frosting, presence of higher and lower salts, minerals, metals, etc. that encounter the plants and prevent them to reveal their complete genetic prospective. The adverse effects of abiotic stresses manipulate the plant physiology, growth and yield. These stresses are major threats for agriculture as they cause unbearable economic losses. Sha-Valli-Khan et al. (2014) advocated that abiotic stress may decrease crop production by 70%. Abiotic stresses are common features of natural environment, and prediction of their duration, occurrence and intensity are very difficult under changing climatic scenario (Mittler and Blumwald 2010). These stresses are basically unavoidable and are mainly caused by intense sunlight, temperature, wind and moisture deficiencies. The continuous climatic changes and deterioration of environment due to human activities are also responsible for abiotic stresses (Huang et al. 2013). Improper management of irrigation and defective agronomic practices has increased the # The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 R. Pathak, Genetics, Physiology and Cultivation of Moth Bean, Cowpea and Horse Gram, https://doi.org/10.1007/978-981-19-9956-7_13

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salinity of lands. Sowing of salt-tolerant species and crop varieties along with the reclamation of soil is the best strategy to cope up with the problem (Maas and Hoffman 1976). Environmental stress has been reported to alter the gene expression in a variety of plants (Sachs and Ho 1986) and have high influence on the viability, growth, morphology and reproduction (Deborah et al. 2011). Horsegram can adapt harsh environmental conditions (Kumar 2006) and has fairly good salt-tolerant capacity (Nigwekar and Chavan 1987). High temperature (43–45 °C) and salt stress (0.6 M) caused typical stress responses in horsegram (Naji and Devaraj 2011). It is suggested that the tolerance capacity of horsegram is mainly due to existence of antioxidant and osmolyte biosynthesis pathways in this crop. These pathways make the crop robust to survive for longer periods under drought situations (Bhardwaj and Yadav 2012). Horsegram showed better responses in terms of germination percentage under elevated CO2 conditions (Raghu Ram Reddy et al. 2012). Higher concentration of CO2 may improve the negative effects of erratic temperature and relative humidity under the changing climatic conditions. On the basis of growth conditions and life cycle of the crop, Reddy et al. (2008) hypothesized that horsegram may have higher number of stress-tolerant genes that can be exploited to create stress tolerance in other legume crops. Besides this, medicinal properties, nutritious composition and pest resistance (Ghani 2003; Bolbhat and Dhumal 2009) provide the crop a symbol of potential food source for future (Kadam et al. 1985). Horsegram is highly adapted to stress conditions, and therefore, it can be considered as a model crop to understand the tolerance mechanism using genomics and proteomics (Sairam and Tyagi 2004).

13.2

Seed Coat Colour

Seed coat of legume is responsible for the seed development and simultaneously seed yield (Patrick and Offler 2001). High temperature and drought conditions during the seed development can modify the morphology of seed coat leading to deterioration of seed quality and vigour (Egli et al. 2005; Smith et al. 2008). Seed coat colour is heterogeneous in some legumes and provides an important outlook for sorting of quality seeds. Singh et al. (2009) studied the effect of seed coat colour for quality assessment and storability in horsegram. They recorded germination percentage, seedling vigour and seed storability to study the genetic basis of heterogeneity in seed coat colour using random amplification of polymorphic DNA (RAPD) markers. They observed that the seeds having lighter seed coat colour exhibited maximum germination and seedling vigour followed by medium and dark coloured seeds. These seeds also had better storability after three years of ambient storage. They suggested that the seed coat colour can be one of the visual indicators of seed quality and storability in horsegram. A study was conducted to assess the seed polymorphism and influence of seed coat colour on several physical and physiological characteristics of horsegram (Latha et al. 2013). The study revealed that the environmental effect had minimum effect on the expression of these traits. Similarly, the physiological attributes had non-significant association with the physical

13.4

Storage

263

characteristics of the seeds suggesting that physiological attributes are independent on the physical characteristics of the seeds in horsegram. Durga and Keshavulu (2015) screened horsegram genotypes for seed longevity and reported that the seeds having light straw coloured seed coat exhibited higher and speedy germination, dry matter production, seedling vigour index and seedling growth rate.

13.3

Germination and Seedling Growth

The germination of seed is the most susceptible stage in life cycle of the plants that regulates seedling establishment and plant growth. The absence of water germination from inactive dry seed is impossible (Bewley 1997). Seed germination is regulated by various abiotic factors including temperature and moisture (Bewley and Black 1994; Baskin and Baskin 2001). Drought stress, higher salinity and lack of soil moisture are the most unfavourable situations for germination of seeds (Mwale et al. 2003). The effect of salinity (NaCl at 0–2.5%) was studied on the germination, root/shoot length, fresh weight, moisture and proline content of horsegram (Nigwekar 1990) that varied with cultivars. Higher (2.5%) NaCl concentration hindered the germination and root/shoot growth. The proline content also decreased with the increasing salinity. Chakraborty et al. (2007) studied the effect of seed soaking (priming) on germination and other growth parameters on seeds of horsegram and recorded its positive effects on seed yield and other growth parameters. They observed that the seed priming not only increased the per cent germination but also the number of plant at harvest and other growth parameters. These effects ultimately resulted into higher seed yield of the crop. It was also observed that the level of tannin and phytate reduced as the soaking progressed, and after germination, it was degraded (Rodge et al. 2006).

13.4

Storage

Higher relative humidity and temperatures are the major difficulties in maintaining the seed vigour and viability of seeds (Agarwal and Siddiqui 1973). Several chemicals including hormones, retardants, redox chemicals, phenols, vitamins, salts, etc. have been examined for the maintenance of seed health under storage conditions (Basu et al. 1974; Dharmalingam and Basu 1978; Das et al. 2003; Chakrabarti et al. 2005). Kanp et al. (2009) studied the storage potential of seeds and field performance of horsegram using sodium dikegulac (Na-DK) and chlorocholine chloride (CCC) and observed that both the chemicals effectively enhanced the storage potential and improved the plant performance. Na-DK and CCC decreased the loss of germinability under in vitro accelerated relative humidity and room temperatures. Pulse beetle [Callosobruchus chinensis (L.), Bruchidae] has been reported as the most critical species of stored grain legumes (Divya et al. 2016). Seed weight loss

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(55–60%) and protein losses (45.5–66.3%) have been reported due to bruchid infestation in stored legumes (Gujar and Yadav 1978). The effect of modified atmosphere with elevated levels of CO2 was studied against pulse beetle in the stored horsegram seeds (Divya et al. 2016). CO2 concentration of 40% and 50% inhibited seed infestation and reduced the weight loss of seeds as compared to normal atmosphere. Horsegram seeds stored under rich CO2 atmosphere had maintained seed quality, and no unfavourable effect on seed germination and seedling vigour was recorded up to six months of storage (Divya et al. 2016).

13.5

Water Stress and Drought Tolerance

Sufficient moisture is essential for the ordinary growth of plant and its sustainability (Zhu 2002). The absence of required water causes water stress which is a common characteristic of arid and semi-arid regions. Inadequate and inconsistent rainfalls and poor irrigation under rainfed areas are prone to water stress (Wang et al. 2005). The shortage of water causes oxidative stress due to disparity between the captured light and its consumption and disturbs the physiological process of the plant (Morgan 1992). Reddy et al. (1990) studied the water stress-induced changes in enzymes of nitrogen metabolism in horsegram and observed that the root and shoot activities of nitrate reductase and glutamine synthetase were decreased due to stress conditions. They also noticed that the ammonia and glutamine concentrations were, respectively, increased and decreased in stressed plants. It was observed that the glutathione reductase and guaiacol peroxidase activities in horsegram were enhanced while catalase activities were decreased under drought stress (Murthy et al. 2012). Similarly, concentration of ascorbic acid and hydrogen peroxide increased with the increasing concentration of polyethylene glycol. Naji and Devaraj (2013) also observed an increase in the peroxidase, superoxide dismutase and glutathione reductase and a decrease in the catalase activities in horsegram under dehydration stress. They found that the seedlings of the crop show comparable biochemical resistance upon water stress conditions. The existence of alternate defence mechanisms for combating moisture stress in horsegram was investigated to analyse variations in the magnitude of different enzyme activities among the surviving accessions (Yasin et al. 2014), and it was observed that the catalase activity and superoxide dismutase increased during moisture stress condition while polyphenol oxidase and ascorbic acid oxidase activity was reduced. The study also revealed that various mechanisms, namely, differential enzyme activity, reduction in total sugar production and structural compaction, are involved in the energy conservation of the crop to resist moisture stress. The enzyme band pattern of horsegram exhibited differences in the expression of isoform (Naji and Devaraj 2009) and changed during salt and temperature stresses suggesting the involvement of some response mechanism in the form of stress elicitor in the plant during the stress conditions (Naji and Devaraj 2011).

13.6

Salt Tolerance

265

Thiourea is a sulfhydryl compound that is known as a drought ameliorant and found beneficial in increasing the productivity of pulses. The beneficial effect of thiourea has been reported on seed germination, seedling growth, chlorophyll content, protein content, biomass production and better dry matter partitioning (Parihar et al. 1988; Sahu et al. 1993; Anitha et al. 2004). It stabilizes the enzymes and proteins and increases the net photosynthates and nitrate reductase activities. It also improves the plant growth and development of the crop grown in arid and semiarid regions (Sahu et al. 1993). Seeds soaked in thiourea and subsequent foliar sprays have improved the seed yield in arid legumes including horsegram as compared to control (Anonymous 1999). Anitha et al. (2006) studied the response of horsegram to thiourea application under rainfed conditions and reported its significant influence on the productivity of the crop. They soaked horsegram seeds in 500 ppm thiourea and applied its two spraying during vegetative and flowering stage of the crop and observed 57.88% increase in the seed yield. Murthy et al. (2016) studied the effect of osmotic stress on growth, relative growth rate, dry matter and associated morphological changes in in vivo and in vitro plants of horsegram and found that the water stress affected many morphological, physiological and biochemical responses in the plant. The relative growth rate, dry matter and biomass of in in vivo plants decreased as compared to in vitro plants of horsegram, and the plants under controlled conditions showed better adaptation towards stress. The drought tolerance potential of horsegram was examined with the help of genome-wide association studies by discovering 20,241 single nucleotide polymorphisms (SNPs) (Choudhary et al. 2022). The study also identified several SNPs linked with the QTLs (quantitative trait loci) regulating drought tolerance in horsegram.

13.6

Salt Tolerance

Salt stress is one of the major abiotic stresses for agriculture (Epstein et al. 1980). Higher concentration of salt exceeds the osmotic potential of plant cell and restricts the uptake of nutrients and interferes the function of proteins, photosynthesis, photorespiration and carbohydrate synthesis resulting into metabolic imbalances (Murakeozy et al. 2003; Munns et al. 2006; Sengupta and Majumder 2009). Thus, it decreases the growth and yield of the crop. In extreme conditions, the cell expansion, assimilated production and membrane function are highly inhibited, and cytosolic metabolism and production of reactive oxygen intermediates are also decreased. It also results into leaf chlorosis, leaf bleaching and necrosis leading to the death of the plant (Parker et al. 1987; Marschner 1995). Salinity also disturbs phytohormones and its synthesis (Davies 1995). Drought, salt and oxidative stresses are interlinked and are responsible for cellular damage (Serrano and RodriguezNavarro 2001; Zhu 2001). Horsegram had good tolerance capacity, but the salt concentration above 100 mM had detrimental effect on the seed yield (Nigwekar and Chavan 1987). The salt stress conditions influenced the accumulation of sodium, phosphorus, manganese and iron

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in all parts of the plant, and it was higher in the roots and stem part. The salt stress increased the calcium content in roots and leaves and chloride content in the leaves, while reduced manganese content was observed in the leaves due to salt stress (Nigwekar and Chavan 1987). The effect of NaCl, exopolysaccharide production, mercuric chloride tolerance and metal chloride was studied on the growth of Rhizobium sp. nodulating horsegram (Edulamudi and Konada (2007, 2008, 2009a, b, 2011), and it was observed that the rhizobia associated with the crop has significant tolerance potential to these compounds. The genetic diversity among the nodules isolated of horsegram was found to be comparable with other legumes (Edulamudi et al. 2015). In general, horsegram is found to be nodulated with Bradyrhizobium spp. (Trinick 1982; Appunu et al. 2011), but Edulamudi et al. (2011) reported that Caulobacter belonging to the family Caulobacteraceae also nodulate the crop. The plant height, leaf area, fresh dry weight total chlorophyll and chlorophyll a and chlorophyll b decreased in horsegram under salinity stress (Kanagaraj and Sathish 2017). Variety Paiyur-2 exhibited comparatively lower reduction in growth, photosynthetic pigments and soluble protein content under salinity stress. The rhizobia associated with horsegram were found to be highly salt tolerant (Edulamudi and Mallaiah 2007).

13.7

Heavy Metal

Heavy metal contamination has become a serious problem in the environment. Heavy metals are part of soil and are found naturally in the soil. The human interferences, use of pesticides, mining, untreated industrial wastes, burning of fossil fuels and metallurgical operations are the major sources that release various heavy metals in the environment (Raskin et al. 1994; Shen et al. 2002; Chandra et al. 2009). These metals, namely, cadmium, mercury, lead, etc., have no biological role and are disadvantageous to the organisms even at very low concentration (Rathnayake et al. 2009). The higher concentration of heavy metal, namely, copper, cobalt, zinc, lead and nickel, affects the physiological and biochemical processes resulting into reduced plant growth and yield (Oncel et al. 2000). These metals also influence the microbial population by affecting their growth, morphology and biochemical activities, ultimately resulting in decreased biomass and diversity (Roane and Pepper 1999). Mercury is known to be a highly toxic metal to microorganisms and is not essential for biological functions even at low concentration (Gadd 1993). Many approaches have been used for the assessment of the risk posed by these metals in soil and water bodies (Rathnayake et al. 2009). The tolerance of soil bacteria has been proposed as an indicator of the potential toxicity of heavy metals (Hassen et al. 1998) resulting in the interest on studying the interactions of heavy metals with microorganisms, and approaches are being made to develop tools to assess the metal levels in the environment (Rathnayake et al. 2009). Metal-resistant microorganisms may be useful as indicators of toxicity to other forms of life (Jayasekar et al. 2008). However, slow rates of metal accumulation over the years

References

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favoured adaptation of the rhizobia to the metal and the selection of metal-tolerant organisms (Azmat et al. 2005; Delorme et al. 2003; Scott Angle et al. 1991). Horsegram tolerates severe adverse environmental conditions including heavy metal contaminations (Reddy et al. 2005). Sahoo and Sahoo (2016) investigated the toxic effects of nickel on plant growth and anti-oxidative enzyme activity in horsegram. They observed that the higher concentration of nickel reduced the protein content and root and shoot length, while its lower concentration regulated de novo synthesis of anti-oxidative enzymes. Cadmium had toxic effect on horsegram seed germination. Keerthi-Kumari et al. (2016) observed 45% and 30% seed germination with 50 and 100 ppm cadmium, respectively, while manganese had not affected the germination. Nevertheless, root length decreased with the increasing concentration of manganese. The stress of heavy metals, namely, aluminium, bismuth, lithium and nickel, was studied to assess the photosynthetic ability of horsegram plants inoculated with the four metal tolerant rhizobial strains (Edulamudi et al. 2017), and it was observed that the crop had heavy metal tolerance and can be utilized for reclamation of soil as phytoremediation agent. Edulamudi et al. (2012) isolated 22 rhizobia from the fresh healthy root nodules of horsegram and observed that all the rhizobia were able to grow at 10 ppm mercuric chloride concentration whereas isolates HGR-11, HGR-16, HGR-30 and HGR-31 were able to grow at 30 ppm concentration. They reported that the halotolerant Rhizobium sp. of horsegram are tolerant to mercuric chloride and can be used as agents to decline the metal pollution in reclamation of saline as well as non-saline soils. The root nodule rhizobia of horsegram were screened for nickel tolerance under controlled conditions, and it was reported that horsegram showed higher level of tolerance towards nickel (Edulamudi et al. 2021).

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Sachs MM, Ho DT (1986) Alteration of gene expression during environmental stress in plants. Ann Rev Plant Physiol 37:363–376 Sahoo R, Sahoo S (2016) Antioxidative enzyme activities and biochemical parameters in two varieties of Macrotyloma uniflorum (lam) Verdc. Under nickel stress. Int J Sci Environ Technol 5(6):3651–3662 Sahu MP, Solanki NS, Dashora LN (1993) Effect of thiourea, thiamine and ascorbic acid on growth and yield of maize (Zea maize L.). J Agron Crop Sci 171:65–69 Sairam RK, Tyagi A (2004) Physiology and molecular biology of salinity stress tolerance in plants. Curr Sci 86:407–421 Scott Angle J, Grath SP, Chaudri MA (1991) Effects of media components on toxicity of Cd to rhizobia. Water Air Soil Poll 64:627–633 Sengupta S, Majumder A (2009) Insight into the salt tolerance factors of a wild halophytic rice, Porteresia coarctata: a physiological and proteomic approach. Planta 229:911–929 Serrano R, Rodriguez-Navarro A (2001) Ion homeostasis during salt stress in plants. Curr Opin Cell Biol 13:399–404 Sha-Valli-Khan PS, Nagamallaiah GV, Rao MD, Sergeant K, Hausman JF (2014) Abiotic stress tolerance in plants: insights from proteomics. In: Ahmad P, Rasool S (eds) Emerging technologies and management of crop stress tolerance. Academic Press, San Diego, pp 23–68 Shen Z, Li X, Wang C, Chen H, Chua H (2002) Lead phytoextraction from contaminated soil with high-biomass plant species. J Environ Qual 31(6):1893–1900 Singh N, Devi C, Kak A (2009) Influence of seed coat colour associated heterogeneity on quality and storability in horsegram (Macrotyloma uniflorum). Seed Sci Technol 37:232–240 Smith JR, Mengistu A, Nelson RL, Paris RL (2008) Identification of soybean accessions with high germinability in high temperature environments. Crop Sci 48:2279–2288 Trinick MJ (1982) Host-rhizobium associations. In: Vincent JM (ed) Nitrogen fixation in legumes. Academic Press, New York, pp 111–122 Wang FZ, Wang QB, Kwon SY, Kwak SS, Su WA (2005) Enhanced drought tolerance of transgenic rice plants expressing a pea manganese superoxide dismutase. J Plant Physiol 162: 465–472 Yasin JK, Nizar MA, Rajkumar S et al (2014) Existence of alternate defense mechanisms for combating moisture stress in horsegram [Macrotyloma uniflorum (lam.) Verdc.]. Legume Res 37(2):145–154 Zhu JK (2001) Plant salt tolerance. Trends Plant Sci 6:66–71 Zhu JK (2002) Salt and drought stress signal transduction in plants. Annu Rev Plant Biol 53:47–273

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Abstract

Horsegram is a self-pollinated crop; therefore variation in the DNA polymorphism is not much expected. Limited work has been done on the aspect of molecular markers of horsegram. The genes, antioxidant and osmolyte biosynthesis pathways identified suggest efficient regulation leading to active adaptation as a basal defense response against drought stress by horsegram. A brief account of various marker techniques, namely, RAPD (random amplified polymorphic DNA), SSR (simple sequence repeats), ISSRs (inter simple sequence repeats), RFLP (restriction fragment length polymorphism), ESTs (expressed sequence tag), ILP (intron length polymorphism), etc., along with biochemical markers exploited for different analyses in horsegram has been described in this chapter.

14.1

Introduction

Genomic resources are the wealth for the genetic enhancement of any crop. The knowledge of genetic variation found within and between plant populations provides the effective exploitation of plants (Rao and Hodgkin 2002). Similarly, information on evolutionary relatedness and gene flow reveal the level of presence of variation (Rutherford et al. 2018). These resources are essential for creation of linkage maps during the application of molecular breeding approaches for development of elite cultivars. The genetic diversity and other traits have been assessed with the help of various morphological parameters. But these parameters are highly influenced by the environmental factors and sometimes found having some errors. Therefore, the assessment of genetic diversity has been shifted from morphological to protein and then molecular markers. The molecular markers are based on the inheritance patterns suggested by Mandel and reveal the heritable changes between the homologous chromosomes at corresponding locations of DNA sequences. With the advent of # The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 R. Pathak, Genetics, Physiology and Cultivation of Moth Bean, Cowpea and Horse Gram, https://doi.org/10.1007/978-981-19-9956-7_14

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technologies, the information on the genome sequences of plants has increased tremendously during last 30–35 years revealing the importance of molecular aspect of plant breeding. Limited work has been done on the molecular markers of horsegram. The genetics for various agronomic traits in this crop is less exploited as compared to other important crops. The biochemical studies revealed that horsegram had a monomeric protein with a molecular mass of 95 ± 5 kDa (Thyagaraju et al. 2007). The genetic diversity among horsegram accessions was assessed using isozyme (Rahar et al. 2007); the isozyme pattern of catalase enzyme had no alteration in the banding pattern and revealed non-significant role of this enzyme in horsegram (Naji and Devaraj 2011). The horsegram protease has been reported as an antifeedant and anti-fungal agent (Kuhar et al. 2013), and the protein can be utilized for developing transgenic plants resistant to insect pests and fungal pathogens. Various molecular marker techniques, namely, RAPD (random amplified polymorphic DNA), SSR (simple sequence repeats), ISSRs (inter simple sequence repeats), RFLP (restriction fragment length polymorphism), ESTs (expressed sequence tag), ILP (intron length polymorphism), etc., has been exploited for different analyses in horsegram. The drought tolerance capacity of horsegram is mainly due to antioxidant and osmolyte biosynthesis pathways. These pathways make the crop robust to survive for longer periods under drought situations (Bhardwaj and Yadav 2012).

14.2

Biochemical Markers

The biochemical markers are based on proteins and polymorphism among the genotypes is estimated for the assessment of genetic analysis. During early 1930s, the biochemical markers, namely, terpenes and isozymes, came in existence and have been used to study pattern of genetic variation in the plant species. Isozymes still have been advocated as important techniques for genetic assessment due to easier interpretation of results and cost effective means (Obara-Okeyo et al. 1998; Kannenberg and Gross 1999). The isozymes are enzymes that catalyse the same reaction in various ways. The concept of isozyme was given in 1959 by Markert and Moller where they reported different molecular forms in which proteins may exist with the same enzymatic specificity (Buth 1984). During analysis of isozymes, two general forms of protein data are collected using electrophoretic methods in which one data is derived from isozymes and another is from allozymes. Allozymes exhibit the codominant appearance, so that plants which are heterozygous at an isozyme locus may be distinguished from either homozygote. The results obtained from biochemical markers are based on small number of different marker loci. The major limitation of these makers is that the information may not represent the gene of entire genome. The limitations of biochemical markers have forced to shift to the molecular- or DNA-based markers in the beginning of the 1980s. Thyagaraju et al. (2007) purified and assessed electrophoretic homogeneity of horsegram lipoxygenase and reported that it was a monomeric protein with a

14.3

Molecular Markers

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molecular mass of 95 ± 5 kDa. It had α-helix and β-pleated structure showing preferred activities towards linolenic acid. They suggested that the horsegram lipoxygenase may be related to the soybean lipoxygenase. Rahar et al. (2007) assessed the genetic diversity among horsegram accessions using isozyme and DNA markers and reported that the banding pattern combined over three enzymes generated 24 markers, of which 23 were polymorphic. Naji and Devaraj (2011) studied the antioxidant and other biochemical defense responses of horsegram under high temperature and salt stress conditions using isozyme analysis and observed that the SDS-PAGE (sodium dodecyl-sulphate polyacrylamide gel electrophoresis) analysis of temperature and salt stress seedlings had varied protein profiles. They also noticed that the isozyme pattern of catalase enzyme had no alteration in the banding pattern revealing non-significant role of this enzyme in horsegram. Gadgil et al. (2016) isolated and characterized acid phosphatase enzyme from seedlings of horsegram and observed their effect on organophosphate pesticide degradation. The acid phosphatase activity of the seedlings was inhibited by HgCl2 and FeCl3 and was activated by metal salts NaCl, CoCl2 and CaCl2. Naji and Devaraj (2009) purified an isoform of guaiacol peroxidase (GPOX) which expressed in horsegram tissue culture during dehydration stress process. The anionic GPOX was analogous to cytosolic peroxidase and was stable at low and neutral pH, while it showed lesser stability at higher temperatures. The expression of GPOX increases the resistance of the plant against dehydration stresses. Gupta et al. (2013) purified and characterized α-amylase inhibitors (AI) from the seeds of horsegram and found that it had high affinity for human salivary amylase and was more thermostable as compared to the AI of mung bean. Twenty-two horsegram genotypes identified on the basis of seed response to standard phenol, modified phenol, sodium hydroxide, potassium hydroxide and isozyme polymorphism (Umarani et al. 2013a) revealed that no single chemical was able to differentiate all the genotypes; however, isozyme study distinguished all the genotypes. The esterase isozyme profile was reported to be more accurate for genotype characterization in horsegram (Umarani et al. 2016). Kuhar et al. (2013) reported anti-feedant and anti-fungal activities of horsegram protease inhibitor on a single protein. They observed that horsegram varieties had both protease inhibitor and in vitro inhibitory activities against Helicoverpa armigera gut protease. The inhibitor also exhibited antifungal activity against Alternaria alternata, Fusarium oxysporum and Aspergillus niger with minimum inhibitory concentration. The inhibitor protein can be utilized for developing transgenic plants resistant to insect pests and fungal pathogens (Kuhar et al. 2013).

14.3

Molecular Markers

DNA-based markers are basically the study of nucleotide sequences revealing the presence of polymorphism between the DNA sequences. Duplication, insertion, deletion, point mutation and translocation are the bases of these polymorphisms. The DNA marker should be co-dominant and distributed through genome; it should

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have the ability to detect higher level of polymorphism (Mondini et al. 2009). DNA-based markers are becoming essential choice in taxonomy, physiology, pathology, etc. (Collard and Mackill 2008). The data obtained from DNA markers can be analysed objectively, and the results are not influenced by the environmental factors. These markers have given new heights in the field of plant breeding for the development of new varieties within limited time span. The molecular markers are frequently being improved to enrich its utilization with the advent of PCR (polymerase chain reaction) that has enabled gene tagging, genetic mapping, studies on genetic diversity, etc. (Adhikari et al. 2017). Various molecular markers have been developed and are being used for different analyses in the agricultural crops. These markers may be co-dominant or dominant and may be hybridization based or PCR based, and their mode of transmission may be different. RFLP has been the foremost hybridization-based molecular marker technique in which DNA was subjected to restriction enzyme. The technique is expensive and time consuming and yields low polymorphism. PCR-based markers are highly sensitive markers and provide higher amount of polymorphism. Molecular breeding provides faster possibilities for exploitation of land races and related germplasm; however, studies of markers, closely associated with agronomic traits, are essential. In case of horsegram, the studies pertaining to molecular aspect are limited with some of the studies on the DNA polymorphism using RAPD, ISSR and SSR (Sharma et al. 2015a, b). EST-SSRs are the most advantageous tools for the genetic analysis. The technique was used in horsegram, but low polymorphism remained bottleneck in the genetic analysis (Sharma et al. 2015b). The genetic diversity studies in horsegram have been carried out mainly on the basis of morphological and biochemical traits, and least studies are available on the basis of molecular tools (Prakash et al. 2010). The genetic assessment on the basis of molecular markers is the most reliable approach to characterize the germplasm. The information over horsegram genetic resources is meagre as compared to other plants and limited expressed sequence tags (ESTs) available at NCBI (National Center for Biotechnology Information). Since horsegram is a stress-adapted leguminous crop, its ESTs may have great significance in the studies of other stress-adapted crops. Reddy et al. (2008) isolated 1050 ESTs of horsegram and recorded 531 unique sequences. They also found that about 30% sequences have no homology to other known protein sequences in the database. Bhardwaj et al. (2013) studied the de novo assembly, functional characterization and comparative analysis in relation to drought stress for comprehensive transcriptomic study on horsegram and generated several pathways over horsegram genomics. The genes and pathways identified Bhardwaj et al. (2013) suggest efficient regulation leading to active adaptation as a basal defense response against drought stress by horsegram. The knowledge can be further utilized for exploring other underexploited plants for stress responsive genes and improving plant tolerance. The estimated genome size of horsegram is 400 Mb. Sharma et al. (2015b) developed and characterized simple sequence repeat (SSR) and intron length polymorphism (ILP) primers from public sequence data in horsegram. Their study suggests that newly characterized and distinguished SSR and ILP markers can advance molecular breeding research in horsegram and may be

14.4

PCR-Based Markers

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helpful in germplasm characterization, diversity studies, mapping and comparative genomic studies.

14.4

PCR-Based Markers

PCR-based technique has the ability to amplify small quantity of DNA. Denaturation, annealing and extension are the steps required for a PCR with the help of primers that are carried out in a thermocycler. The technique produces many markers within limited time and provides reliable data about the subjected DNA sample. Primers play an important role in the sensitivity and efficiency of the reaction because they are responsible for in vitro DNA synthesis (He et al. 1994). Therefore, quantity, quality and design of the primer are very important for PCR along with other components. PCR-based marker techniques, namely, RAPD (random amplified polymorphic DNA), SSR (simple sequence repeats), ISSRs (inter simple sequence repeats), RFLP (restriction fragment length polymorphism), ESTs (expressed sequence tag), ILP (intron length polymorphism), etc., have been exploited for different analyses in horsegram. An account of these techniques is given below:

14.4.1 RAPD and ISSR RAPD technique was developed independently by Williams et al. (1990) and Welsh and McClelland (1990) for amplification of genomic DNA using single, random primers of 8–10 bp. The amplified fragments depend on the size and length of the target genomes and primer (Jiang 2013). DNA quality, quantity, concentration of PCR buffer, other components and annealing temperature are the important factors to get reproducible amplicon under this technique (Wolff et al. 1993). Single species of primer anneals to the genomic DNA at two different sites on complementary strands of DNA template during the reaction, and amplicons are formed through thermocyclic amplification (Pathak 2015). ISSR technique allows amplification of DNA between two identical microsatellite repeat regions with the help of primers having di-, tri- and tetra- or penta-nucleotide repeats of 15–25 bp length and was reported by Zietkiewicz et al. (1994). These primers may be unanchored (Meyer et al. 1993; Wu et al. 1994) or anchored (Zietkiewicz et al. 1994). ISSR markers are usually known as dominant markers (Wang et al. 1994). Though in some incidences, it has been reported as co-dominant markers (Wang et al. 1994; Sankar and Moore 2001). Vigna and phaseolus SSRs and ISSRs were used for amplification of horsegram genomic DNA (Rahar et al. 2007); the RAPDs were found to be the most polymorphic (78.8%), as compared to SSRs (71.4%) and ISSRs (18.6%). Appunu et al. (2011) analysed 69 root nodule isolates by generation rate, acid/alkali reaction on YMA medium, RFLP analysis of 16S–23S rDNA intergenic spacer region (IGS) and sequence analyses of IGS and housekeeping genes glnII and recA and observed that

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the isolates within each IGS type varied in their ability to fix nitrogen. They suggested that the high symbiotic effective strains could be beneficial for horsegram production in poor soils. Edulamudi et al. (2015) carried out genetic characterization of rhizobia associated with horsegram using RAPD and RFLP markers and reported that horsegram rhizobial population had high genetic diversity. Sharma et al. (2015a) studied the genetic structure and diversity of M. uniflorum using RAPD and ISSR markers. They also included M. axillare and M. sargharwalensis to assess the genetic inter-relationships and reported that M. sargharwalensis was more distantly related to M. uniflorum as compared to M. axillare. They constructed a dendrogram on the basis of 156 RAPD and ISSR fragments from 51 horsegram genotypes and observed that all the genotypes fell into two main groups and the wild species, namely, M. axillare and M. sar-gharwalensis, remained as out group. Interestingly, it was observed that the genotypes from Central and Southern India were grouped together while the genotypes from Himalayan regions formed a separate group (Sharma et al. 2015a) showing the wide genetic diversity of the species.

14.4.2 SSR, EST and ILP SSRs are microsatellites having 2–6 bp of DNA sequences and are found in tandem manner as di-, tri- or tetra-nucleotides through the genome (Morgante et al. 2002). These markers are highly polymorphic, and length polymorphisms can be easily identified on the electrophoresis. SSRs are co-dominant markers and show high allelic diversity (Rakoczy-Trojanowska and Bolibok 2004); that is why it is one of the most appropriate markers for development of high-density linkage maps, QTL mapping, identification of genotypes, diversity analysis and marker-assisted selection of genotypes. EST is a short sub-sequence of DNA within a coding region of a gene, which is generated by cDNA clones (Adams et al. 1991). The cDNA represents the expressed DNA sequences created from mRNA. The mRNA represents the exons by excising the intron regions and provides a template for protein synthesis, but it is very unstable outside the cell. It is converted in cDNA with the help of an enzyme to make it stable. On the basis of isolated expressed gene, nucleotides can be sequenced either from 5′ or 3′ end to obtain 5’ ESTs or 3’ ESTs, respectively (Jongeneel 2000). ESTs have been considered as an important tool for identification of gene transcripts and estimating data on sequence estimation, gene expression and regulation. The cloning of some specific genes, genome sequencing and mapping of functional genes are possible with EST markers. Intron length polymorphism (ILP) is a suitable marker for various genetic analyses that can be identified with the primers designed using the exon regions flanking the intron (Wang et al. 2005). It was also known as exon-primed introncrossing PCR or EPIC-PCR (Bierne et al. 2000). The major constraint associated with ILP was to have knowledge on position of introns in the genes. The problem was rectified by designing the primers for EPIC-PCR on the basis of cDNA/EST

14.4

PCR-Based Markers

279

sequences flanking the intron position (Yang et al. 2007) because exon-intron structures are highly conserved. Umarani et al. (2013b) characterized 22 horsegram genotypes using 10 SSR primers and amplified 26 alleles (at least 2 alleles per primers). She recognized some primers (CA910489, CA910598, CA911600, CA911990 and CA912170) that amplified three alleles. Out of 22 genotypes, BGM-1, AK-38 and VLG-22 were found as the most promising genotypes for crop improvement in horsegram (Umarani et al. 2013b). Sharma et al. (2015b) developed SSR and ILP markers in horsegram, characterized them for public sequence data and assessed the crossamplification of these markers across 12 related legume species. They suggested that these markers can be exploited in genetic diversity analysis, population genetic studies, phylogenetic analysis, development of linkage maps, genetic mapping and QTL analysis in horsegram. Gautam et al. (2016) studied the molecular diagnosis and intraspecific genetic variability of root pathogens of arid legumes including horsegram using RAPD and internal transcribed spacer (ITS) amplification. They observed that the root pathogens of the arid legumes were neither restricted to geographical location nor were host specific. Mishra et al. (2017) carried out the molecular characterization of rhizobium isolates isolated from the root nodules of horsegram and reported that the rhizobium isolates are closely related to each other as only two major clusters were formed based on Jacquards’ similarity coefficient. Chahota et al. (2017) developed a set of SSR markers to examine genetic diversity and population structure of horsegram germplasm along with its two wild species, namely, M. axillare and Macrotyloma sar-gharwalensis, and identified 6418 SSRs from 23,305 potential SSR motifs and 5755 primers for the development of microsatellite markers in this crop. They observed that the SSR frequency was lower in the horsegram genome in comparison to other plant species. Kaldate et al. (2017) used next-generation sequencing (NGS) technology for genome-wide development and characterization of novel simple sequence repeat markers in horsegram. They designed 2458 SSR markers from NGS data and characterized 117 SSRs in 48 lines of horsegram. The cross transferability of these markers was also checked in M. sar-gharwalensis, Cicer arietinum, Vigna unguiculata, Lens culinaris, Vigna mungo, Pisum sativum, Trifolium pratense, Vigna umbellata and Phaseolus vulgaris (Kaldate et al. 2017). Genetic diversity and structure analysis was carried out in horsegram, and transcriptomewide SSR markers were developed (Kumar et al. 2020). The study revealed the development of 7352 SSR markers; out of these, 150 SSR markers were tested against 58 horsegram genotypes, and higher level of polymorphic markers and loci was reported suggesting the presence of genetic diversity (Kumar et al. 2020). 16S rRNA sequencing was carried out to assess the presence of bacterial population, and the presence of proteobacteria, actinobacteria, firmicutes, acidobacteria, bacteroidetes, planctomycetes and gemmatimonadetes was reported among all the four domains (soil, rhizosphere region, root nodules and seeds) of the horsegram (Evangilene and Uthand 2022). Prevalence of ammonium-oxidizing, nitrite-reducing and nitrogen-fixing metabolism mechanisms was observed in all the studied samples on the basis of 16S rRNA gene analysis. The study also suggests that the

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microbes linked with horsegram may be utilized in the preparation of organic fertilizer (Evangilene and Uthand 2022).

14.5

Transcriptomic Studies

The tolerance capacity of horsegram to the drought conditions is found due to antioxidant and osmolyte biosynthesis pathways. These pathways make the crop robust to survive for longer periods under drought situations (Bhardwaj and Yadav 2012). The medicinal properties, nutritious composition and pest resistance (Ghani 2003; Bolbhat and Dhumal 2009) provide the crop a symbol of potential food source for the future (Kadam et al. 1985). On the basis of growth conditions and life cycle of the crop, Reddy et al. (2008) hypothesized that horsegram may be comprised of higher number of stress-tolerant genes that can be exploited to transform these stress tolerances in other legume crops. A stress-responsive NAC transcription factor isolated from horsegram improved the tolerance of multiple stresses, namely, PEG, NaCl and CuSO4 in bacterial cells (Pandurangaiah et al. 2013), and demonstrated substantial response to abiotic stresses in groundnut (Pandurangaiah et al. 2014). The word NAC was coined from the names of three proteins, namely, NAM (no apical meristem), ATAF (arabidopsis transcription activation factor) and CUC (cup-shaped cotyledon), having analogous DNA-binding domain (Souer et al. 1996; Aida et al. 1997). The NAC transcription factors are found to regulate senescence, cell division and wood formation (Zhong et al. 2007; Fang et al. 2008). Bhardwaj et al. (2013) carried out a comprehensive transcriptomic study in horsegram using de novo transcriptome discovery and associated analyses to decode its genetic makeup. The study could generate different information on the genomics of the crop. The recognized genes and pathways suggested the active adaptation of horsegram against drought stress. The molecular transcript-based information of drought-tolerant crop enables to develop drought-tolerant genetic resources. Pandurangaiah et al. (2013) isolated, cloned and characterized a salt stressinducible NAC gene from horsegram. Its expression revealed the regulation across the salinity, cold, drought and dehydration stress conditions. Abiotic stressresponsive WRKY (worky genes) transcription factors were reported in horsegram (Kiranmai et al. 2016) from drought and salt stress conditions, and it was observed that the genes were capable for modulation and enhancement of abiotic stress tolerance in sensitive crops. WRKY transcription factors play an important role in biotic and abiotic stress responses. Vijayakumar et al. (2016) studied the genetic diversity among germplasm lines of horsegram and reported that the genetic diversity is not related to the geographic diversity. They found PHG-21 as most promising parent to obtain potential hybrid. Kiranmai et al. (2018) isolated WRKY transcription factor gene from horsegram and reported that the protein encoded by this gene comprises conserved regions of two WRKY domains and two C2H2 zinc-finger motifs. They suggested that the isolated gene can be utilized for the improvement of stress resistance in other plants.

14.6

14.6

Callus Induction and Regeneration Protocol

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Callus Induction and Regeneration Protocol

Transmission of desirable genes is one of the best methods of crop improvement that can be carried out with the help of various biotechnological tools including tissue culture. The in vitro culture has been widely exploited in crop improvement to obtain virus-free material, clonal propagation and conservation of germplasms. Techniques of tissue culture have principally been included in biotechnology that allows the regeneration of plants either as clones or somaclones. Regeneration systems are basic requirement for any genetic transformation and provide basis of crop improvement. It may include somatic hybridization, in vitro selection and genetic transformation for amendment of property of the plant. The embryogenic suspension cultures have played important roles in the crop improvement. It can be achieved through clonal propagation, in vitro selection, genetic transformation and synthetic seed production. The study pertaining to the field of tissue culture in horsegram is limited. Callus induction (Varisai Mohamed and Jayabalan 1996), direct shoot regeneration from the shoot tip, cotyledonary node explants (Sounder Raj et al. 1989; Varisai Mohamed et al. 1998, 1999) and formation of somatic embryos (Varisai Mohamed et al. 2004) has been reported in horsegram. Various studies have been conducted to obtain multiple shoots through proliferation from shoot tips and cotyledonary nodes of horsegram (Sounder Raj et al. 1989; Varisai Mohamed et al. 1998, 1999, 2004). Sounder Raj et al. (1989) studied the shoot tip culture in horsegram using seedlings of sterilized seed on MS medium containing sucrose and agar supplemented with naphthaleneacetic acid (NAA) and 6-benzylamino purine (BAP) at various concentrations. They observed that higher concentration of BAP favoured the callusing, but it inhibited the shoot growth and formation of multiple shoot buds and root. They further noticed dark incubation as inciting factor for stem elongation and induction of multiple shoot buds due to higher activity of polyphenolic compound during dark incubation. Varisai Mohamed et al. (1998) studied the effect of ADS (adenine sulphate), BAP and IBA (indole-3-butyric acid) on the plant regeneration from horsegram and could be successful in inducing multiple shoots from tip explants. In another derived callus, its protoplast cultures and their morphogenic potential were studied in horsegram variety BR-10 (Sinha and Das 1986), and it was observed that the anthers containing pollen mother cells had maximum response. Varisai Mohamed and Jayabalan (1996) developed a protocol for horsegram callus induction using variety CO-1 and BGM-1. They were successful in the development of explants of epicotyls, hypocotyls and cotyledons on MS medium. The callus got browned after 25 days at higher concentrations of (2.5 mg per L) auxins. A protocol was developed for the regeneration of multiple shoots from the callus for horsegram (Tejavathi et al. 2010) using shoot apices and cotyledonary nodes from nine-day-old seedlings onto MS, L2 and MMS media supplemented with various growth regulators. They obtained 17 proliferated shoots after 16 days of culture and could regenerate about 14 and 20 shoots from the callus on different media after 30 days of culture. The regenerated shoots were rooted and up to six

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roots per shoot was obtained. They transferred the rooted shoots in various pots and observed 60% survival rate. Varisai Mohamed and Jayabalan (1996) developed a protocol for callus induction in horsegram and reported that a medium with indole-3-acetic acid/2, 4-dichlorophenoxyacetic acid (IAA/2, 4-D; 2 mg per L) in combination with coconut milk (15%) and 6-benzylaminopurime (BAP; 0.5 mg per L) was optimum for callus induction in horsegram. They found 2, 4-D as the most important auxins and BAP as more effective cytokinins. The young leaves were the better explant for callus induction. The effect of cytokinins on proliferation of multiple shoots was studied, and a method was described for the purpose with the help of cotyledonary nodes and shoots of horsegram (Varisai Mohamed et al. 1999). The highest rate of shoot proliferation was observed from MS media supplemented with BAP 1.5 mg per L. Varisai Mohamed et al. (2004) studied the in vitro regeneration of horsegram through cell suspension culture. The hardened plants were established in soil. They also recorded the effects of auxins, cytokinins, carbohydrates, amino acids and other additives on induction and germination of somatic embryos and found that the medium supplemented with 7.9 mM 2,4-D, 3.0% sucrose, 40 mg per L L-glutamine and 1.0 mM abscisic acid was effective to achieve high frequency of somatic embryo induction, maturation and further development. Further, in another study, they created cell suspension cultures from immature cotyledon-derived calli from horsegram on MS solid medium having 1.0 mM zeatin and 4.5 mM NAA (Varisai Mohamed et al. 2005). They were also able to convert about 5% of somatic embryos into true-to-type fertile plants. Tejavathi et al. (2010) developed a protocol for regeneration of multiple shoots from the callus derived from the shoot tip and cotyledonary node of horsegram. They used shoot apices and cotyledonary node from nine-day old aseptically grown seedlings. The protocol comprised of MS, leguminous medium and modified MS media supplemented with various growth regulators. They found 60% survival rate of the plants on hardening. Muricken and Gowda (2011) expressed stable anti-tryptic domain of Bowman-Birk inhibitor (BBI) from horsegram and reported that the horsegram anti-tryptic peptide was a potent inhibitor of trypsin and human tryptase. Earlier polypeptide, a major BBI, had been noticed that exhibited robust anti-tryptic activities (Sreerama et al. 1997). The influence of various growth regulators was studied on callus formation of horsegram developed by leaf explants taken from plants grown on heavy metal-polluted soil (Jagpal and Pillay 2020). The effect of heavy metal was clearly visible on the development of callus in terms of growth, texture and colour of the developed callus. A binary vector pCAMBIA2301 was applied for genetic transformation in horsegram using various factors such as agrobacterium cell density, co-cultivation and sonication along with vacuum infiltration (Amal et al. 2020), and it was observed that cell density coupled with sonication and vacuum infiltration has enhanced the transgenic competence in horsegram.

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Part III Moth Bean

Introduction

15

Abstract

Moth bean, a tall and annual herb having shorter internodes and longer trailing branches, is a drought-tolerant legume cultivated in the arid and semi-arid regions of the country. The harsh climatic conditions of hot arid regions of India provide the most favourable agro-climatic environment for the successful cultivation of moth bean. The green and immature pods of the crop are good source of economic protein, while its dried seeds are major source of several confectionary preparations, namely, papad, mangori, mogar, bhujia-namkins, etc. The chapter briefly describes the taxonomic classification, floral characteristics, origin and uses of moth bean.

15.1

Introduction

The moth bean (Vigna aconitifolia (Jacq.) Marechal) is a drought-tolerant legume of genus Vigna belonging to the family Fabaceae. It is grown in arid and semi-arid regions of India Afghanistan, Pakistan, Nepal, Sri Lanka, Myanmar and some African countries. Moth bean can be easily grown under harsh climatic condition regions having 45 °C temperatures and 200–300 mm annual rainfall (Brink and Jansen 2006). India is the largest producer of moth bean, with a production area of 1.5 Mha, while Rajasthan is the major moth bean growing state in India contributing about 86% area of the country (Brink and Jansen 2006), where it is the most widely grown as drought-tolerant legume followed by Gujarat. The yield of the crop in Rajasthan is low in the comparison of national average yield. The legume is known by different names, namely, dew bean, Mat, Kheri, Madike, Bhioni, Kunkuma, Matki, etc., in different parts of India suggesting its extensive social and geographical adaptability. It has ground-hugging plants that resemble like a mat; probably its name mat bean came from its resemblance with a mat. It is an # The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 R. Pathak, Genetics, Physiology and Cultivation of Moth Bean, Cowpea and Horse Gram, https://doi.org/10.1007/978-981-19-9956-7_15

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annual drought hardy legume having deep and fast-growing root system generally grown under arid and semi-arid regions of northwest regions of India. The crop can survive up to 30–40 days in open field at more than 35 °C temperature and under lesser soil moisture. The broad canopy, viny and semi-trailing growth habit of the crop helps in lowering the soil temperature and reduces soil erosion. These features of moth bean make it the best suited crop of arid regions that can be grown with limited agronomic care and inputs. It can be easily grown under different cropping systems including agri-horticulture, silvi-pastoral, agro-forestry, mix-cropping, intercropping, sole cropping, etc. In general, moth bean is not taken as national legumes crop in terms of its production and productivity, but it is one of the most important leguminous crops of hot arid regions. The moth bean germplasms have wider genetic variability, and more than 1000 accessions have been conserved at NBPGR (National Bureau of Plant Genetic Resources), New Delhi. RMO-40 and RMO-225 are mostly cultivated varieties in India. It has 15–40 cm tall plants having shorter internodes and longer trailing branches. The stems of the plant are angular and hairy. The plant has several primary branches of 30–130 cm length arising from the main axis of the stem. The primary branches have larger internodes and trail horizontally on the ground. It has deep lobed leaflets and 2–6-cm-long papilionaceous flowers. The pods of moth bean are glabrous, about 2.5–5 cm long, yellowish brown in colour having short stiff bristles and short and curved beak. Its stipules are smaller in size. Each pod bears about 4–10 seeds, and the seeds of moth bean are small in size (about 5 mm) having yellowish brown colour. The hilum of the seed is linear and white. The plant type of moth bean is primitive in nature suggesting its evolution for survival; therefore, its productivity is low. Genetical modification in the plant habit may be beneficial for higher yields. Development of insect- and disease-resistant varieties including yellow mosaic viruses and bacterial leaf spot disease is another consideration for potential yields. Early maturing varieties having early flowering and maturity would be the best strategies for crop improvement in moth bean. Earlier various workers have found better results with this strategy (Sharma 1997).

15.2

Origin

Prior to cultivation of lentil and chickpea, Vigna species including mung bean, urd bean, moth bean and rice bean were known as grams (Albala 2007) suggesting that moth bean is one of the oldest crops under cultivation. Moth bean has been grown in India since ancient times as a drought-tolerant legume for several purposes including assured gain in terms of vegetable and fodder. India is supposed to be centre of origin due to occurrence of wild and cultivated forms of moth bean (Vavilov 1926; de Candolle 1885), while some workers suggested that Sri Lanka and Pakistan may be diverse centre of moth bean (Marechal et al. 1978). It has been reported that all the species in Vigna genus except moth bean have wild form (Marechal et al. 1978). However, wild forms of moth bean have been reported from India (Takahashi et al. 2016), but the wild and domestic moth bean had no variation unlike other species of

15.4

Botany

291

Vigna. Perhaps moth bean is still in the course of domestication and requires several improvements in terms of agronomic- and yield-related traits. However, the seeds of the wild forms were smaller having a water-proof semitransparent seed coat, while the seeds of domestic moth bean were larger in size having water-permeable seed coat (Takahashi et al. 2016). The wild form of moth bean has also been documented in India (Arora and Nayar 1984). Southeastern India has also been hypothesized as primary habitat of wild form of moth bean (Takahashi et al. 2016). However, several studies have considered Rajasthan as the origin centre of cultivated form of moth bean (Piper and Morse 1974; Jain and Mehra 1980; de Condolle 1986).

15.3

Taxonomic Classification

Moth bean was earlier grouped into genus Phaseolus but upon revision in Phaseolus linn and Vigna savi, the yellow flowered species of Phaseolus under the sub-genus Ceratotropis were shifted to genus Vigna (Verdcourt 1970) resulting into the increase of number of species under the genus (Marechal et al. 1978). The cultigens and wild form of moth bean could not be distinguished (Marechal et al. 1978) and have been included into Asiatic group of Vigna species having Indian sub-continents as its centre of origin (Jain and Mehra 1980). A detailed taxonomic classification of moth bean is given below: Domain: Eukaryota Kingdom: Plantae Phylum: Spermatophyta Subphylum: Angiospermae Class: Dicotyledonae Order: Fabales Family: Fabaceae Subfamily: Papilionoideae Genus: Vigna Species: aconitifolia (Jacq.) Marechal

15.4

Botany

Moth bean belongs to the family Fabaceae and subfamily Papilionoideae. It is selfpollinated crop with 2n = 22 chromosomes (Darlington and Wylie 1955). The plants of moth bean have a prostrate creeping habit having slender, erect main stem of about 40 cm. It has about 12 trailing primary prostrate branches that may be of about 60–150 cm in length. The leaves are alternate, petiolated, compound and 3-foliolate while leaflets are deeply lobed and are of about 5–12 cm in length. The fruits of the crop are hairy, brown or pale grey cylindrical pods of about 2.5–5 cm long and 0.5 cm broad. The pods contain 4–10 rectangular to cylindrical whitish green, yellow to brown coloured seeds. The 1000-seed weight of moth bean ranged from 10 to 35 g (Adsule 1996; Brink and Jansen 2006).

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Jungle moth bean (Phaseolus trilobus syn. Vigna trilobus) is a wild species of moth bean and is considered as the progenitor of moth bean (Biswas and Dana 1976), but it is becoming endemic in India. Several workers reported that Vigna trilobus is the wild form of Vigna aconitifolia (Sampson 1936; Whyte et al. 1953), and both the species are diploid and have similar numbers of chromosomes, that is, 2n = 22 (Darlington and Wylie 1955). Nevertheless, some biochemical studies suggested that both Vigna trilobus and Vigna aconitifolia are quite distinct species (West and Garber 1967). At later stage, the species was classified with Vigna radiate and Vigna mungo (Dana 1980), but reports suggested that moth bean is different from these species (Jaaska and Jaaska 1990; Kaga et al. 1996).

15.5

Floral Characteristics

Moth bean is a strictly self-pollinated and self-fertile diploid crop due to its cleistogamous nature. The flowers are bisexual, typically papilionaceous, borne on small or long peduncles, sessile and about 4–4.5 mm long. The bracteoles of the flower are longer than the calyx and their tips are stuck out the buds. Light yellow colour flowers are more or less hooded and emerge at the apex. It has bright yellow wings and the left wing is coiled around the keel while the right one encloses the keel. The flower has ten stamens that are arranged in two groups, that is, 9 + 1. Nine stamens are fused to make a tube while on stamen remain free. The keel bounded with wing and standard petals firmly enfolds all the stamens, style and stigma (Mahla and Sharma 2022). Flowering in moth bean may be regulated with the application of suitable combinations of auxin and cytokinins (Saxena et al. 2005). The ovary has twisted style and a flat feathery stigma. The inflorescence of moth bean is an axillary, thick false raceme borne on a 5–10-cm-long hairy peduncle (Brink and Jansen 2006).

15.6

Cytogenetics

The karyotype formula proposed for moth bean is 1- (2.7–3.5 μm) sub-median centromere long +5 medium (1.96–2.6 μm) sub-median centromere +1 medium median centromere and four small (