Nutriomics of Millet Crops 1032230940, 9781032230948

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Nutriomics of

Millet Crops

Millets are popularly known as “nutri-cereals” due to their high calcium, dietary fiber, polyphenol, vitamins, and protein content. Millet crops have the potential to aid in food security efforts in regions where natural and manmade causes are deteriorating land resources. Nutriomics of Millet Crops emphasizes the importance of nutriomics of millet crops in the context of universal health, highlighting biotechnological advancements offering enrichment of the nutritional value of millets. Millet crops have the potential to be a staple crop, demonstrating an economically feasible approach to combat micronutrient malnutrition. Features: • Presents comprehensive studies on health-promoting nutritional components of millets. • Provides enumeration on molecular breeding strategies for improvement of millet nutraceuticals. • Discusses genomics-assisted breeding for enhancement of nutritional quality in millets. • Includes information related to sensory and biofortification of millet-based foods. By assessing the relevance of millets in sustainable global agro-ecosystems due to their nutritional and agronomic attributes, the United Nations celebrated 2023 as the “International Year of Millets.” This book complements this effort and is useful to researchers and policy planners working across the disciplines of plant breeding and food technology. Nutriomics of Millet Crops also encourages young researchers to explore this promising field.

Nutriomics of

Millet Crops

Edited by Ramesh Namdeo Pudake,

Amolkumar U. Solanke, and Chittaranjan Kole

First edition published 2024 by CRC Press 6000 Broken Sound Parkway NW, Suite 300, Boca Raton, FL 33487–2742 and by CRC Press 4 Park Square, Milton Park, Abingdon, Oxon, OX14 4RN CRC Press is an imprint of Taylor & Francis Group, LLC © 2024 Taylor & Francis Group, LLC Reasonable efforts have been made to publish reliable data and information, but the author and publisher cannot assume responsibility for the validity of all materi­ als or the consequences of their use. The authors and publishers have attempted to trace the copyright holders of all material reproduced in this publication and apologize to copyright holders if permission to publish in this form has not been obtained. If any copyright material has not been acknowledged please write and let us know so we may rectify in any future reprint. Except as permitted under U.S. Copyright Law, no part of this book may be reprinted, reproduced, transmitted, or utilized in any form by any electronic, mechanical, or other means, now known or hereafter invented, including photo­ copying, microfilming, and recording, or in any information storage or retrieval system, without written permission from the publishers. For permission to photocopy or use material electronically from this work, access www.copyright.com or contact the Copyright Clearance Center, Inc. (CCC), 222 Rosewood Drive, Danvers, MA 01923, 978–750–8400. For works that are not available on CCC please contact [email protected] Trademark notice: Product or corporate names may be trademarks or registered trademarks and are used only for identification and explanation without intent to infringe. ISBN: 9781032230948 (hbk) ISBN: 9781032230962 (pbk) ISBN: 9781003275657 (ebk) DOI: 10.1201/b22809 Typeset in Times by Apex CoVantage, LLC

Contents

About the Editors .....................................................................................................vii

Preface ......................................................................................................................ix

List of Contributors ...................................................................................................xi

Chapter 1 Nutrient Composition and Health Benefits of Millets ..........................1

Ishita Singh, Pratik Dighe, Prasad Rasane, Vasudha Bansal, Nitya Sharma, Jatindra K. Sahu, and Keshavan Niranjan Chapter 2 Health Benefits of Millet-Derived Bioactive Peptides ....................... 17

Jyoti Semwal, Mohammad Hassan Kamani, and M. S. Meera Chapter 3 Phenolic Phytochemicals from Sorghum, Millets, and Pseudocereals and Their Role in Human Health ............................... 43 V. M. Malathi, Sharma Kanika, Jacob Jinu, Ronda Venkateswarlu, Muricken Deepa, and A. Rohini Chapter 4 Millet Polyphenols and Influence of Food Processing on Their Availability ......................................................................................... 81 Gavirangappa Hithamani, and Jayapal Naveen Chapter 5 Processing of Millet Foods and its Impact on Nutraceutical and Health-Promoting Properties .............................................................99 Kwaku G. Duodu, Nwabisa N. Mehlomakulu, and Eugenie Kayitesi Chapter 6 Influence of Moisture Content on Nutritional and Processing Properties of Millets ......................................................................... 125 Ashish M. Mohite, and Neha Sharma Chapter 7 Nutritional Advancement in the Ethnic and Novel Foods Using the Diverse Minor Millets ................................................................ 141 Deepika Goswami, Harshad M. Mandge, Jagbir Rehal, and Hradesh Rajput

v

vi

Contents

Chapter 8 Sensory, Physical, and Nutritional Qualities of Traditional Food Prepared from Millets .......................................... 157 Ram Jatan, and Charu Lata Chapter 9 Genetic Diversity for Grain Nutrients Content in Finger Millet (Eleusine Coracana (L.) Gaertn.) Germplasm ................................. 175 Henry Fred Ojulong, Eric Manyasa, Sheunda Patrick, Chrispus Oduori, Scovia Adikini, Lameck Nyaligwa, and Hapson Mushoriwa Chapter 10 Genetic Enhancement of Grain Iron and Zinc Content in Millets ......201 Kathleen Hefferon Chapter 11 Current Status and Future Prospects of Molecular Marker Assisted Selection (MAS) in Millets................................................ 215 Krishnananda Ingle, Niranjan Thakur, M. P. Moharil, P. Suprasanna, Bruno Awio, Gopal Narkhede, Pradeep Kumar, Stanislaus Antony Ceasar, and Gholamreza Abdi Chapter 12 Millet Genomic Resources for Biofortification: An Opportunity for Improving Health Benefits .......................................................... 237 Megha Bhatt, and Mihir Joshi Chapter 13 A Review of Developments in Cereal Grain Omics and Its Potential for Millet’s Nutritional Improvement ................................ 249 Prashant Raghunath Shingote, Vaishnavi Sanjay Parma, Dhiraj Lalji Wasule, Ravindra Ramrao Kale, and Amolkumar U. Solanke Chapter 14 Nutrigenomics Studies in Millets ..................................................... 261

Theivanayagam Maharajan, Thumadath Palayullaparambil Ajeesh Krishna, and Stanislaus Antony Ceasar Chapter 15 Genomics and Sustainable Practices to Improve Nutrition of Millets with Changing Climate ........................................................ 279 Rohini Mattoo, and Suman B. M. Chapter 16 Proteomics Analysis of the Nutritional Quality of Millets .............. 295

Kerenhappuch Susan S. Index ...................................................................................................................... 311

About the Editors

Ramesh Namdeo Pudake is Assistant Professor at Amity University Uttar Pradesh, Noida, India. He earned his Ph.D. degree in Crop genetics and breeding from Chi­ na Agricultural University, Beijing, China. After his Ph.D. he has been engaged in research in a range of organisms but with a focus on crop genomics. He has also worked at Iowa State University of Science and Technology, Ames, IA, USA, on host–pathogen interaction and gene mapping. Currently, he is focusing on research on different application genomics in plant–microbes interaction. Dr. Pudake has pub­ lished more than 40 research publications, five books, and 20 book chapters, and has one scholarship award from the Chinese Government. He is also an expert reviewer for several journals of repute. Amolkumar U. Solanke is Senior Scientist at the ICAR-National Institute for Plant Biotechnology, New Delhi. Dr. Solanke earned his Ph.D. degree in plant molecular biology from Delhi University and later joined the Indian Council of Agricultural Re­ search, India. His research interest is functional genomics for biotic and abiotic stress management in crop plants, especially rice and finger millet. He has published more than 60 papers in peer-reviewed journals. He is executing a few funded research proj­ ects on millet and guiding M.Sc., Ph.D., and post-doctoral students. Chittaranjan Kole is an internationally reputed scientist with an illustrious profes­ sional career spanning over 35 years and original contributions in the fields of plant genomics, biotechnology, and molecular breeding leading to the publication of more than 170 quality research articles and reviews. He has edited over 100 books for lead­ ing publishers around the world. His scientific contributions and editing acumen have been appreciated by seven Nobel Laureates, including Profs. Norman Borlaug, Ar­ thur Kornberg, Werner Arber, Phillip Sharp, Günter Blobel, Lee Hartwell, and Roger Kornberg. He has been honored with several fellowships, honorary fellowships, and national and international awards, including the Outstanding Crop Scientist Award conferred by the International Crop Science Society. He has served all prestigious positions in academia, including Vice Chancellor of BC Agricultural University, Project Coordinator of the Indo-Russian Center of Biotechnology, India, and Direc­ tor of Research of the Institute of Nutraceutical Research, Clemson University, USA. He also worked at Pennsylvania State University and Clemson University, USA, as Visiting Professor. Recently, he has been awarded with the Raja Ramanna Fellow by the Department of Energy, Government of India. He is also heading the International Climate-Resilient Crop Genomics Consortium and the International Consortium for Phytomedomics and Nutriomics as their founding Principal Coordinator.

vii

Preface

The world population is expected to grow 11 billion by the end of this century. This enormous growth in the population is going to put immense pressure on limited agricultural resources. In addition to this, climate change is hampering the produc­ tion of major staple crops such as rice, wheat, and maize. Ultimately, nutritional insecurity is a major threat to the world population, which is highly dependent on a cereal-based diet that is deficient in micronutrients. In quest of finding alternatives to major crops, nutritionally rich millets have shown great promise, particularly in the countries of Asia and sub-Saharan Africa. The millets have the potential to guarantee food security in this region where the natural and manmade causes have deteriorated the land resources. By assessing the relevance of millets in future and sustainable global agro-ecosystems due to their nutritional and agronomic attributes, the United Nations (UN) decided to celebrate the year 2023 as the International Year of Millets (IYM 2023). The aim of this year is to further discuss and direct the research and policy development for the millet improvement programs worldwide and provide solutions to major challenges confronting the same. Millets are popularly known as nutri-cereals due to their richness in calcium, dietary fiber, polyphenol, vitamins, and protein contents (PCs). The science of “nutriomics”, a term coined by one of the editors of this book, Chittaranjan Kole, in 2010, has progressed extensively over the last decade to study food nutrition and nutraceuticals. Nutriomics studies in staple crops have contributed in designing an economical and sustainable approach to combat micronutrient malnutrition. The main objective of this book is to highlight the importance of nutriomics of millets in perspective of global health and nutritional crisis. The authors of the chapters have specifically highlighted the role that recent biotechnological developments have to offer for enrichment of its nutritional value and how they can utilize it in the field of nutritional biology by beginning new avenues for future research. This book will be useful for students, teachers, researchers, and policy planners working across disciplines. It is hoped that this book will encourage young research­ ers to explore this promising field. The present book contains 16 chapters contrib­ uted by 59 eminent subject specialists that covered the diverse aspects of nutriomics for achieving nutrition security. Chapter  1 discussed the nutrient composition and health benefits of millets, whereas the next chapter highlighted the health benefits of millet-derived bioactive peptides. The bioactivities and health benefits of millet phy­ tochemicals and phenolics as revealed by in vitro and in vivo studies, and the same, are revisited in Chapters 3 and 4. Chapter 5 has summarized the impact of processing method on nutraceutical and health-promoting properties. Chapter 6 summarizes the effects of moisture content on nutritional and processing properties of millets. Chap­ ters 7 and 8 discusses the health benefits and sensory aspects of traditional and novel food items prepared by using millets. Small millets include crops such as finger mil­ let and are widely cultivated as traditional crops in rain-fed areas, and their diversity is discussed in Chapter 9. Millets are naturally rich in micronutrients, and Chapter 10 has summarized the studies that are done for the genetic enhancement of grain iron ix

x

Preface

and zinc content. The molecular marker assisted selection (MAS) is the breeding method of using morphological, biochemical, or DNA markers as indirect selection criteria for selecting agriculturally important traits. Chapter 11 has reviewed the sta­ tus and prospects of MAS in these important crops. Chapter 12 reviewed the genomic resources for improvement of nutritional aspects of millets. Chapter 13 reviewed the developments in cereal grain omics and its potential for millet’s nutritional improve­ ment. Chapter  14 discussed nutrigenomic studies in millets. Studies on advanced techniques of proteomics and genomics for the nutritional quality of millets are sum­ marized in Chapters 15 and 16. Considering all the aspects discussed in the book, we are confident that these research efforts will help decipher the nutritional traits of millets and help popularize millets for nutrition safety. Along with the authors, we are grateful to the people who directly or indirectly contributed to compile the book. We thank Ms. Randy Brehm and Mr. Tom Connelly of the CRC Press/Taylor and Francis Group LLC. Editors are thankful to Science and Engineering Research Board, Department of Science and Technology, Government of India (TAR/2020/000166) for providing fund. We would also like to thank our families, friends, and colleagues for their support during all the activities done while writing this book. Editors Dr. Ramesh Namdeo Pudake, Noida, India Dr. Amolkumar U. Solanke, New Delhi, India Prof. Chittaranjan Kole, Kolkata, India

Contributors

Gholamreza Abdi Department of Biotechnology Persian Gulf Research Institute, Persian Gulf University Iran Scovia Adikini National Agricultural Research Organization (NARO) National Semi Arid Resources Research Institute (NaSARRI) Uganda Bruno Awio Jayashankar Telangana State Agricultural University India Vasudha Bansal Department of Foods and Nutrition Govt Home Science College India Megha Bhatt G. B. Pant University of Agriculture and Technology India Stanislaus Antony Ceasar Department of Biosciences Rajagiri College of Social Sciences Kalamassery India Muricken Deepa St Mary’s College India

Pratik Dighe Department of Food Technology and Nutrition School of Agriculture, Lovely Professional University India Kwaku G. Duodu Department of Consumer and Food Sciences University of Pretoria South Africa Deepika Goswami Food Grains and Oilseeds Processing Division ICAR-CIPHET India Kathleen Hefferon Department of Microbiology Cornell University USA Gavirangappa Hithamani Department of Molecular Nutrition CSIR -Central Food Technological Research Institute India Krishnananda Ingle College of Agriculture Koneru Lakshmaiah University India Ram Jatan CSIR-National Institute of Science Communication and Policy Research India

xi

xii

Jacob Jinu ICAR-Indian Institute of Millets Research India Mihir Joshi Gurukul Kangri (Deemed to be University) India Ravindra Ramrao Kale Vasantrao Naik College of Agricultural Biotechnology India Mohammad Hassan Kamani Food Chemistry and Technology Department Teagasc Food Research Centre Ireland Sharma Kanika ICAR-Central Institute for Research in Cotton Technology India Eugenie Kayitesi Department of Consumer and Food Sciences University of Pretoria South Africa Susan S. Kerenhappuch Innova Market Insights India Thumadath Palayullaparambil Ajeesh Krishna Department of Biosciences Rajagiri College of Social Sciences India Pradeep Kumar International Crop Research Institute for the Semi-Arid Tropics India

Contributors

Charu Lata CSIR-National Institute of Science Communication and Policy Research (NIScPR) India Suman B. M. Divecha Centre for Climate Change Indian Institute of Science India Theivanayagam Maharajan Department of Biosciences Rajagiri College of Social Sciences India V. M. Malathi ICAR-Indian Institute of Millets Research India Harshad M. Mandge Department of Post-Harvest Technology Banda University of Agriculture and Technology India Eric Manyasa International Crop research Institute for Semi-Arid Tropics (ICRISAT) Zimbabwe Rohini Mattoo Divecha Centre for Climate Change Indian Institute of Science India M.S. Meera Department of Grain Science and Technology CSIR- Central Food Technological Research Institute India

xiii

Contributors

Nwabisa N. Mehlomakulu Department of Consumer and Food Sciences University of Pretoria South Africa

Chrispus Oduori Kenya Agricultural and Livestock Research Organization (KALRO)-Kibos Kenya

M. P. Moharil Biotechnology Centre, Department of Agricultural Botany Post Graduate Institute India

Henry Fred Ojulong International Crop research Institute for Semi-Arid Tropics (ICRISAT) Zimbabwe

Ashish M. Mohite Amity Institute of Food Technology Amity University India

Vaishnavi Sanjay Parma Vasantrao Naik College of Agricultural Biotechnology India

Hapson Mushoriwa International Crop research Institute for Semi-Arid Tropics (ICRISAT) Zimbabwe Gopal Narkhede Kalash Seeds Pvt Ltd India

Sheunda Patrick International Crop Research Institute for Semi-Arid Tropics (ICRISAT) Kenya Hradesh Rajput ITM University India

Jayapala Naveen Department of Biochemistry CSIR-Central Food Technological Research Institute India

Prasad Rasane Department of Food Technology and Nutrition School of Agriculture, Lovely Professional University India

Keshavan Niranjan Department of Food and Nutritional Sciences University of Reading UK

Jagbir Rehal Department of Food Science and Technology Punjab Agricultural University India

Lameck Nyaligwa Tanzania Agricultural Research Institute-Hombolo Tanzania

A. Rohini St Mary’s College India

xiv

J. K. Sahu Centre for Rural Development and Technology Indian Institute of Technology India Jyoti Semwal Department of Grain Science and Technology CSIR- Central Food Technological Research Institute India Neha Sharma Amity Institute of Food Technology Amity University Uttar Pradesh India Nitya Sharma Centre for Rural Development and Technology Indian Institute of Technology Delhi India Prashant Raghunath Shingote Vasantrao Naik College of Agricultural Biotechnology India

Contributors

Ishita Singh Department of Foods and Nutrition Govt. Home Science College India Amolkumar U. Solanke ICAR-National Institute for Plant Biotechnology LBS Centre India P. Suprasanna Nuclear Agriculture and Biotechnology Division Bhabha Atomic Research Centre India Niranjan Thakur Vasantrao Naik Marathwada Agriculture University India Ronda Venkateswarlu ICAR-Indian Institute of Millets Research India Dhiraj Lalji Wasule Vasantrao Naik College of Agricultural Biotechnology India

1

Nutrient Composition and Health Benefits of Millets Ishita Singh1, Pratik Dighe2, Prasad Rasane2,

Vasudha Bansal1, Nitya Sharma3,

Jatindra K. Sahu3, and Keshavan Niranjan4

Department of Foods and Nutrition, Govt Home Science College, Sector 10, Chandigarh, India 2 Department of Food Technology and Nutrition, School of Agriculture, Lovely Professional University, Phagwara, Punjab, India 3 Centre for Rural Development and Technology, Indian Institute of Technology Delhi, Hauz Khas, New Delhi, India 4 Department of Food and Nutritional Sciences, University of Reading, Whiteknights Campus, Reading, UK 1

CONTENTS 1.1 1.2

Introduction ......................................................................................................1

Composition of Millets .....................................................................................3

1.2.1 Macronutrients......................................................................................3

1.2.2 Micronutrients ......................................................................................4

1.2.3 Phytochemicals.....................................................................................6

1.2.4 Antinutrients .........................................................................................7

1.3 Bioavailability of Nutritional Factors ............................................................... 8

1.3.1 Factors Affecting Bioavailability..........................................................9

1.3.1.1 Dietary Factors..................................................................... 10

1.3.1.2 Physiological Factors ........................................................... 10

1.4 Biological Activity of Millets ......................................................................... 10

1.4.1 Antioxidant Activity ........................................................................... 11

1.4.2 Anti-cancerous Activity...................................................................... 11

1.4.3 Antidiabetic Activity .......................................................................... 12

1.4.4 Antimicrobial Activity........................................................................ 12

1.5 Conclusion and Future Perspectives ............................................................... 13

References................................................................................................................ 13

1.1

INTRODUCTION

One of the earliest foods consumed by humans was millets. It is a plant that produces cereal and belongs to the Graminae grass family. It is related to species from five DOI: 10.1201/b22809-1

1

2

Nutriomics of Millet Crops

genera in the Paniceae tribe, namely Panicum, Setaria, Echinocloa, Pennisetum, and Paspalum, and one genus in the Chlorideae tribe, Eleusine (Malathi et  al., 2014). Millets have been a mainstay of the inhabitants of Asia and Africa’s semi-arid tropics for generations when other crops fail to thrive (Sharma and Niranjan, 2018). Millets are a rich source of nutrition and have been increasingly produced in recent dec­ ades to fulfill the nutritional needs of the world’s growing population. Millet grain is a nutrient-dense grain that is abundant in minerals, dietary fiber, phytochemicals, and vitamins. The most commonly used millets include sorghum, pearl millet, finger millet or ragi, kodo millet, barnyard millet, proso millet, little millet, and foxtail or Italian millet (Figure 1.1) (Thakur and Tiwari, 2019). Millets play an important role in the development of modern meals, such as multigrain and gluten-free (GF) cereals. They have also been shown to reduce fat absorption, slow sugar release [low glycemic index (GI)], and thus lower the risk of heart disease, diabetes, and high blood pressure due to their high content of polyphenols and other biologically active chemicals. They are becoming more popular as people become more aware of their

FIGURE 1.1 Classification of millets. Source: Adapted from Thakur and Tiwari (2019)

Nutrient Composition and Health Benefits of Millets

3

health-promoting properties (Kumar et al., 2018). Thus, millets are now being com­ monly used to augment cereal-based foods and have grown in popularity due to their gluten-free nature and nutritional and economic benefits. Small millets’ grains are nutritionally superior to rice and wheat because they are high in macronutrient and micronutrient and are therefore classified as nutri-cereals (Dayakar Rao et al., 2017). Wheat and rice may offer food security, but millets have the potential to serve food, health, nutrition, as well as livelihood security. This chapter provides a consolidated overview of the nutritional and antinutritional profile of millets, their bioavailabil­ ity, and associated bioactivities, along with the effect of various common process­ ing treatments on their properties. Since the United Nations-Food and Agriculture Organization (UN-FAO) has declared the year 2023 as the “International Year of Millets”, this cluster of information presented here would be of enormous value to understand the potential of millets as a food ingredient. It would also provide guid­ ance for basic and strategic research on diversifying the utilization of millets.

1.2

COMPOSITION OF MILLETS

Millets are a good source of proteins, minerals, vitamins, and phytochemicals. The nutritional composition of millets is similar to that of rice and wheat, except that they are high in fiber and micronutrients (Muthamilarasan et al., 2016). This section discusses the macronutrient, micronutrient, phytochemical, and antinutrient compo­ sition of some common millets.

1.2.1 Macronutrients Table  1.1 presents the macronutrient composition of some common millets. The carbohydrates in millets can be categorized as non-structural (sugars, starch, and fructosans) carbohydrates and structural (cellulose, hemicelluloses, and pectin sub­ stances) carbohydrates (Dayakar Rao et al., 2017). Among common millets, finger millets have the highest amount of carbohydrates, consisting of free sugars (1.04%), starch (65.5%), and non-starchy polysaccharides (dietary fiber) (11.5%). In addition, finger millets were found to possess lower amylose content (16%) compared to sor­ ghum (24.0%), pearl millet (21.0%), proso millet (28.2%), foxtail millet (17.5%), and kodo millet (24.0%) (Banerjee and Maitra, 2020). Another macronutrient, that is, protein, is the millet’s second most significant com­ ponent. Proso millet (12.5%), foxtail millet (12.3%), and pearl millet (11.6%) have higher amounts of protein than other non-millet cereals such as rice (7.2%) (Has­ san et al., 2021). Although millet’s protein level is similar to that of wheat grains, unlike millet protein, wheat proteins are deficient in critical amino acids, which are required to prevent protein-energy malnutrition. Furthermore, millet protein has fewer crosslinked prolamins, which contribute to their protein’s improved digestibil­ ity. However, millet proteins, such as cereal proteins, are low in lysine, but they work well with lysine-rich plants (leguminous) and animal proteins to create nutritionally balanced composites with high biological value (Sharma and Sahu, 2021). In terms of fats and lipids, finger millet has a lower fat content than pearl mil­ let, barnyard millet, little millet, and foxtail millet, which might explain why finger

4

Nutriomics of Millet Crops

millet can be stored better than other millets. Compared to maize, which has a fat level of 3.21–7.71%, pearl millet has a fat content of 5–7%. Furthermore, it has been stated that the lipid content of finger millet and pearl millet was 1% and 5%, respec­ tively (Hassan et al., 2021). In this, about 70–72% of finger millet lipids are neutral lipids, mostly triglycerides, with traces of sterols; 10–12% are glycolipids and the rest 5–6% are phospholipids (Banerjee and Maitra, 2020). In terms of fatty acids, fin­ ger millet comprises 46–62% oleic acid, 8–27% linoleic acid, 20–35% palmitic acid, and traces of linolenic acid (Banerjee and Maitra, 2020). However, pearl millet has a high content of fatty acids such as palmitic, stearic, and linoleic acids, and lower oleic acid compared to maize (Hassan et al., 2021). Macronutrient dietary fiber has been linked to lower blood cholesterol, lower blood sugar, and better bowel movement. This is because of its slow digestion, which leads to prolonged transit time, lowering blood glucose levels, and benefit­ ing non-insulin-dependent diabetics. In addition, the prolonged transit time of food from the stomach to the intestines also results in longer feeding intervals. Pearl mil­ let (20.8%) and finger millet (18.6%) have more total dietary fiber than sorghum (14.2%), wheat (17.2%), and rice (17.2%). Hemicelluloses A  are non-cellulosic β-glucans found in small, kodo, and barnyard millets, while hemicelluloses B are composed of hexose, pentose, and uronic acid (Chauhan et al., 2018).

1.2.2 Micronutrients Millets have a mineral composition equivalent to other cereals such as wheat and rice (Table 1.1), however, with significantly higher amounts of calcium and manga­ nese. Pearl millet has a calcium value of 40.6–48.6 mg/100 g (Kumar et al., 2020). On the other hand, finger millet has higher amounts of calcium, ranging from 162 to 487 mg/100 g depending on the genotype, which helps to build bones and reduce the incidence of fractures. High manganese content in millets may help the body fight illnesses such as cancer (Hassan et al., 2021). Millets also possess substantial amounts of phosphorus, which is a key component in the mineral matrix of bones, as well as adenosine triphosphate, or ATP, which is the body’s energy booster (Kumar

TABLE 1.1

Macronutritional Composition of Millets (g per 100 g)

Millets

Carbohydrates

Protein

Fat

Ash

Fiber

References

Pearl millet

67.0

11.8

4.8

2.2

2.3

(Muthamilarasan et al., 2016)

Finger millet

72.05

7.3

1.3

2.7

11.5

Foxtail millet

63.2

11.2

4.0

3.3

6.7

Proso millet

70.4

12.5

3.1

1.9

14.2

(Habiyaremye, et al., 2017)

Barnyard millet

68.8

10.1

3.9

2.1

12.5

(Kaur and Sharma, 2020)

Little millet

65.55

8.92

2.55

1.72

6.39

(Dayakar Rao et al., 2017)

Kodo millet

66.6

9.8

3.6

3.3

5.2

(Saleh et. al., 2013)

Sorghum

72.97

10.82

3.23

1.70

1.97

(Kumar et al., 2018)

(Shobana, et al., 2013)

(Jaybhaye et al., 2014)

5

Nutrient Composition and Health Benefits of Millets

TABLE 1.2 Mineral Nutritional Composition of Millets (mg per 100 g) Millets

Ca

P

Fe

Mg

K

Na

Mn

Cu

Zn

References

Pearl millet

46

379

8.0

137

442

12.0

1.8

1.06

3.1

(Chauhan et. al., 2018)

Finger millet

137.33

158.43

1.46

6.38

35.19

3.70

2.85

0.06

0.48

(Shamsudeen et al., 2019)

Foxtail millet

23

310

3.2

130

270

10

2.2

0.9

2.1

(Serna-Saldivar and Espinosa-Ramírez, 2019)

Proso millet

10

200

2.2

120

210

10

1.8

0.8

1.7

(Kumar et al., 2018; Serna-Saldivar and Espinosa-Ramírez, 2019)

Barnyard millet

22

280

18.6

82

-

-

0.96

0.60

3

(Chandra and Selvi, 2016)

Little millet

30

260

20

133

370

8.1

20

4

11

(Chauhan et al., 2018)

Kodo millet

32.33

300

3.17

110

141

4.8

1.10

1.60

32.7

(Kumar et al., 2018; Chandra and Selvi, 2016)

Sorghum

35.23

266.30

5.29

0.19

350

6

1.63

1.08

3.01

(Kumar et al., 2018; Chhikara et al., 2019)

et  al., 2020). Apart from this, barnyard millet and pearl millet are rich in another major micronutrient, that is, iron, and their diet can help pregnant women with anemia get the iron they need. Barnyard millet has an iron concentration of 17.47 mg/100 g, which is only 10 mg less than the daily need. Among all millets, foxtail millet has the highest concentration of zinc (4.1 mg/100 g) and is also a rich source of iron (2.7 mg/100 g) (Jaiswal et al., 2019). For example, zinc and iron are essential nutrients that help in improving immunity (Kumar et al., 2018). Among vitamins, small millets are high in vitamins such as thiamine, riboflavin, niacin, and vitamin C. Pearl millet, which has high oil content, is also thought to be a rich source of fat-soluble vitamin E (2 mg/100 g). In addition, the grain is an excellent source of vitamin A. Vitamin A  equivalent (8.3–10.5 mg) and vita­ min E (87–96 mg) were detected in the unrefined fat recovered from the kernel of common millet (Hassan et  al., 2021). Similarly, foxtail millet is high in thia­ min (0.59 mg/100 g), although proso millet has the highest quantity of riboflavin (0.28 mg/100 g). Rice and wheat had riboflavin levels of 0.04 and 0.1 mg/100 g, respectively (Table 1.1), which was much lower than those in other millets, par­ ticularly pearl millet, foxtail millet, and small millet (Muthamilarasan et al., 2016). Tables 1.2 and 1.3 present some major minerals and vitamins in different varieties of millets, respectively.

6

Nutriomics of Millet Crops

TABLE 1.3 Vitamin Composition of Millets (mg per 100 g) Millets

Thiamin (Vit B1)

Riboflavin (Vit B2)

Niacin (Vit B3)

Pearl millet

0.38

0.21

2.8

(Muthamilarasan et al., 2016; Chandra and Selvi, 2016)

Finger millet

0.48

0.12

1.30

(Ramashia et al., 2019)

Foxtail millet

0.48

0.12

3.70

(Devi et al., 2014)

Proso millet

0.55

0.17

5.11

(Serna-Saldivar and Espinosa-Ramírez, 2019)

Barnyard millet

0.33

0.10

4.2

(Jaybhaye et al., 2014)

Little millet

0.30

0.09

3.2

(Saleh et al., 2013)

Kodo millet

0.15

2.0

0.09

(Kumar et al., 2018)

Sorghum

0.237

0.142

2.972

(Chhikara et al., 2019)

References

1.2.3 PhytocheMicals Table  1.2 presents the phytochemical composition of some common millets. Mil­ lets’ outer layers contain a high concentration of phytochemicals, including phe­ nolic acids, flavonoids, and phytosterols, which are important biologically active substances (Sharma et  al., 2021). These compounds exhibit several health-related benefits due to their anti-inflammatory, anti-tumor, antidiabetic, and antioxidant properties (Mudau et al., 2022). Phenolic acids in millet grains are bound at 60%, with the remaining 40% occurring in free forms. Ferulic, sinapic, and caffeic acids constitute the majority of the phenolic acids found in soluble extracts, which contain more than 80% of them, whereas coumaric and ferulic acids predominate in con­ jugated fractions (Pradeep and Sreerama, 2018). The phenolic acid content varies greatly within different varieties of millets. For instance, as per Kumari et al. (2016), finger millet has a higher total phenolic content (TPC) than foxtail and proso millet in its soluble extracts. In addition to epicatechin, catechin is the main phenolic com­ ponent found in finger millet (Xiang et al., 2019; Chandrasekara and Shahidi, 2011). Variation with color of millets was also observed by Chandrasekara and Shahidi (2010), who found that compared to light-colored millets such as those with white or yellow testa, those with dark-colored testa and pericarp pigments have more soluble phenolic compounds. The pericarp and testa of the millet grain also contain other phytochemicals, including flavonoids. Flavonoids are significant antioxidants that lower the chance of developing chronic diseases. Compared to foxtail and proso millets, finger mil­ let has a higher quantity of flavonoids, with flavanols being the primary subclass (Chandrasekara and Shahidi, 2010, 2011). Flavones, isoflavonoids, flavonols, and dihydroflavonols, as well as their glycosides, are additional phenolic substances that fall under different flavonoid subclasses. The same flavonoid subclasses have been found in the soluble extract of barnyard millet (Ofosu et al., 2020). The authors also reported other flavonoids in barnyard millet, including formononetin, kaempferol,

7

Nutrient Composition and Health Benefits of Millets

TABLE 1.4 Phytochemical Composition of Millets Pearl Millet

Finger millet

Foxtail millet

Proso millet

Barnyard millet

Little millet

Kodo millet

References

Total Phenol (mg gallic acid equivalent/g)

2.6

10.2

2.0

0.9

0.8

2.12

19.7

(Serna-Saldivar and Espinosa­ Ramírez, 2019; Chandra and Selvi, 2016)

Flavonoids (mg catechin equivalent/g)

0.6

2.4

0.7

0.5

0.6

-

11.1

(Serna-Saldivar and Espinosa­ Ramírez, 2019)

-

-

-

Phytosterols (mg/100 g)

58

-

57

26

(Duodu and Awika, 2019)

apigenin, isorhamnetin, and 3,7-dimethylquercetin. Similar to phenolic compounds, millets’ flavonoid content is directly correlated with the color of the grains. For instance, four varieties of finger millet with seed coatings that were brown, white, reddish, and red were studied by Xiang et  al. (2019) to determine their bioactive component. They noted that red finger millet grains had the highest quantity of flavo­ noids, followed by brown, reddish, and white seed coat grains. Phytosterols serve as a precursor to produce a variety of bio-functional substances, including steroidal glycoalkaloids, brassinosteroids, steroidal saponins, and phyto­ ecdysteroids (Moreau et al., 2018), while, squalene, a long-chain triterpene molecule with a high degree of unsaturation in nature, functions as a precursor in millets’ route for producing phytosterols (Ji et  al., 2019). Campesterol, stigmasterol, and β-sitosterol make up the phytosterols in Italian finger millet, with β-sitosterol mak­ ing up 85% of the total (Bhandari and Lee, 2013). In addition to millet grains, the phytosterol composition of foxtail millet bran oil has been studied. It was discovered to contain stigmastanol, campesterol, and β-sitosterol, along with trace amounts of fecosterol, ergostanol, and campesterol (Pang et al., 2014). Although both sterols and stanols have the comparable effects on human health, stanols are more significant for millets’ bioactivity (Duodu and Awika, 2019). Table 1.4 presents different classes of phytochemicals possessed by millets.

1.2.4 antinutrients Antinutrients are harmful elements found in grains and legumes that prevent nutri­ ents from being absorbed and decrease their bioavailability in the body. They are thought to reduce mineral bioavailability, impede proteolytic and amylolytic enzy­ matic activities, and decrease the digestibility of protein and starch in pearl and finger millets (Hassan et  al., 2021). The two antinutritional components of millet grains that have been the subject of the most research among the different antinutrients present in cereals are tannins and phytates. In the case of phytic acid, it is known that they reduce the bioavailability of minerals and the activity of enzymes due to their

8

Nutriomics of Millet Crops

TABLE 1.5 Antinutritional Composition of Millets Grains

Tannin (mg/g)

Phytate (mg/g)

Reference

Pearl millet

2.75

5.92

(Amalraj and Pius, 2015; Serna-Saldivar and Espinosa-Ramírez, 2019)

Finger millet

2.64

5.29

(Amalraj and Pius, 2015; Serna-Saldivar and Espinosa-Ramírez, 2019)

Foxtail millet

0.028

9.9

(Sharma et al., 2021)

Proso millet

0.003

7.2

(Pawar and Machewad, 2006; Sharma et al., 2021)

Barnyard millet

3.51

3.53

(Panwar et al., 2016; Sharma et al., 2021)

Kodo millet

1.1

1.3

(Sharma et al., 2021)

tendency to bind to and precipitate proteins and minerals. Mineral deficiency caused by phytate – metal-insoluble complexes – may result in decreased absorption of sev­ eral minerals, including zinc, iron, calcium, and magnesium. On the other hand, by building complexes with proteins or sporadically interacting with minerals, tannins can affect how food is digested (Raes et al., 2014). Tannins can be found in hydro­ lyzable or condensed forms; the latter are less likely to be absorbed during diges­ tion and are more likely to produce hazardous toxins after hydrolysis (Adeyemo and Onilude, 2013). The highest concentrations of inositol hexaphosphates were found in proso and barnyard millet, while the highest concentrations of condensed tannins were found in kodo, finger, and barnyard millet (Sharma and Gujral, 2019). Table 1.5 presents the tannin and phytate content in different classes of millets.

1.3 BIOAVAILABILITY OF NUTRITIONAL FACTORS The term “bioavailability” refers to the portion of a nutrient that may be ingested during a meal and utilized by the body through normal metabolic pathways. Since not all amounts of a nutrient taken are utilized properly by the human body, it is an important phrase that reflects nutritional efficacy. Therefore, the term “bioavailabil­ ity” describes the proportion of a nutrient or bioactive component that is consumed that enters the systemic circulation and is ultimately used by the body (Tharifkhan et al., 2021). Bioavailability is significantly impacted by the mechanical breakdown of foods and the enzymatic hydrolysis of nutrients, leading to the release of absorbable nutrients in the GI tract (Lemmens et al., 2014). The type of matrix in which the nutrients are included, chemical binding form, interference from other foods, and their ingredients in enhancing or inhibiting absorption, post-absorption metaboliza­ tion, and host-associated factors such as health status, genetics, age, and lifestyle, among other person-specific factors, have all been connected to variations in the bioavailability of nutrients (Shubham et al., 2020). Recently, it has been identified that non-effective delivery methods and bioavailability of the bioactive peptides from millet can limit their therapeutic applications. These difficulties result from several crucial inherent physicochemical and biological characteristics of peptides,

Nutrient Composition and Health Benefits of Millets

9

including molecular size, charge, lipophilicity, solubility, and administration method. Therefore, extensive research is required to identify the methods for successful trans­ lation of millet bioactive peptides to therapeutics as well as nutraceutical applications (Majid and Priyadarshini, 2020). In the case of millets, the bioavailability of nutrients is low due to the instance of antinutritional factors. Certain phenolic compounds, phytates, and tannins are examples of antinutritional parameters that impact iron and zinc bioavailability (Hassan et al., 2021). However, typical domestic food-processing processes, such as decortication, milling, soaking, malting, germination, fermentation, popping, and cooking, might mitigate the deleterious effects of these antinutrients. These approaches lower the quantity of phytates, phenol, tannins, and trypsin inhibitor activity in millets, as well as improve the digestibility and mineral bioavailability (Dayakar Rao et al., 2017).

1.3.1 Factors aFFecting BioavailaBility The bioavailability of nutrients in millets is influenced by both dietary and physio­ logical variables, including initial digestion, enzymatic/chemical breakdown of the consumed meal, and nutrient release (Tharifkhan et al., 2021). Figure 1.2 enlists the factors responsible for the bioavailability of millet nutrients.

FIGURE 1.2

List of factors affecting millet nutrients bioavailability.

10

Nutriomics of Millet Crops

1.3.1.1 Dietary Factors Bioavailability in the lumen is influenced by the physio-chemical form and solubility of nutrients produced from the dietary matrix. The absorption of ascorbate, carbo­ hydrates, organic acids, amino acids, and certain fatty acids is enhanced by their consumption. Enhancers control the solubility of nutrients and/or prevent inhibitors from interacting with them (Tharifkhan et al., 2021). Millets’ phytic acid has demonstrated a potent propensity to bind to calcium, zinc, and iron to form insoluble complexes. With a strong ability to chelate and a tendency to form complexes with monovalent and multivalent cations of calcium, potassium, zinc, iron, and magnesium, phytate, the salt of phytic acid (myoinositol 1,2,3,4,5,6-hexakisphosphate), serves as a major phosphorous and mineral storage form. This chelation ability reduces bioavailability (Boncompagni et al., 2018). 1.3.1.2 Physiological Factors Physiological factors that affect nutrient bioavailability include gastric acidity, intes­ tinal secretions, gut motility, lumen redox state, body status (including tissue lev­ els and nutrient stores), mucosal absorptive cell-mediated homeostasis, endocrine system effects, genetic polymorphisms, inborn metabolic errors, and gut microflora.  Bioavailability is affected by the binding of dietary elements with vitamins or minerals in general. When concentrations exceed threshold limits, competitive inhibitors can affect bioavailability. Copper, zinc, and iron are transition metals with comparable chemical characteristics that approach the same binding sites or carriers. Estimating the bioavailability of lipid-soluble nutrients can be done by measuring the degree of mixed micelle incorporation after digestion (Tharifkhan et al., 2021).

1.4 BIOLOGICAL ACTIVITY OF MILLETS Plant-based diets are preventative against a number of degenerative diseases, such as Parkinson’s disease, cancer, cardiovascular disease (CVD), diabetes,

FIGURE 1.3 Mechanism of action of the biological activities of millets. Source: Adapted from Majid and Priyadarshini (2020)

Nutrient Composition and Health Benefits of Millets

11

and metabolic syndrome. Millets are also recognized as functional foods and nutraceuticals since they supply essential nutrients such as dietary fibers, pro­ teins, energy, minerals, vitamins, and antioxidants. Millets have been linked to a variety of health benefits, including prevention of cancer and CVDs, along with prominent antioxidant and antimicrobial activities (Chandrasekara and Shahidi, 2012; Saleh et al., 2013). Figure 1.3 represents the mechanism of the biological activity imparted by millets.

1.4.1 antioxidant activity Millet grains are a rich source of antioxidants due to the abundance of phenolic compounds in them. In addition to xylo-oligosaccharides, insoluble fiber, and pep­ tides, millet grains include a variety of naturally occurring phenolic components, such as phenolic acids, flavonoids, and tannins (Liang and Liang, 2019). Along with micronutrients (carotenoids and tocopherols), which also possess antioxidant capabilities, these chemicals are primarily found in the bran layers. Additionally, millets can be enhanced with antioxidants (i.e., phenolics and flavonoids) by pro­ cedures such as germination and fermentation. Due to the production of phenolic compounds, dry heat treatment has been demonstrated to increase the antioxidant activity of millets, whereas wet thermal treatment has been shown to decrease the activity and has an adverse effect on the activity (Liang and Liang, 2019). In a study on the impact of processing on the nutrient content and antioxidant activity of little millets (Panicum sumatrense), it was found that roasting samples significantly improved their nutrient content and free radical-scavenging abilities (Pradeep and Guha, 2011). Studies on millets’ antioxidant characteristics have focused on their ability to chelate metals, quench singlet oxygen radicals, have reducing power, and scavenge free radicals (Sharma et  al., 2021). According to Kaur et  al. (2019a) and Kaur et  al. (2019b), numerous in vitro studies demonstrated the protective effects of antioxidants against age-related issues, chronic degenerative diseases, and other contemporary lifestyle disorders, such as celiac disease, coronary heart diseases, and diabetes. For instance, a study was done by Wei et  al. (2018) using animal models to evaluate the impact of high salt on hypertension and the cardiac dam­ age brought on by a millet-enriched diet. The authors discovered that a diet rich in millet had a significant impact on lowering blood pressure, and concluded that millet’s anti-oxidative stress effect helps to prevent cardiac damage brought on by high salt ingestion.

1.4.2 anti-cancerous activity Uncontrolled cell division is a key aspect of cancer’s growth and progression (Majid and Priyadarshini, 2020). Cancer therapy includes inhibiting or delaying the fast multiplication of tumor tissue, which may help to halt the growth of cancer cells. Natural dietary components that prevent DNA damage and slow cancer cell growth have been studied (Chandrasekara and Shahidi, 2011). Millets are high in antinu­ trients such as phenolic acid, tannins, and phytate that have been found to diminish

12

Nutriomics of Millet Crops

the incidence of colon and breast cancer in animals. Millet phenolics have also been shown to be useful in preventing cancer development and progression in vitro (Sarita and Singh, 2016).

1.4.3 antidiaBetic activity Diabetes is a metabolic condition caused by changes in energy metabolism and is defined by unbalanced glucose homeostasis, where insulin secretion is hampered and insulin resistance develops (Majid and Priyadarshini, 2020). Diabetes rates have been found to be lower among the millet-eating population. Millets have demonstrated the benefits of lowering α-glucosidase and pancreatic amylase levels, lowering postpran­ dial hyperglycemia, and decreasing enzymatic hydrolysis of complex carbohydrates. The control of glucose-induced oxidative stress and inhibition of starch-digesting enzymes by millet active biomolecules gives them potential antidiabetic properties. For instance, finger millets’ antinutrients have been demonstrated to slow down the digestion and absorption of carbohydrates, which reduces the glycemic response (Kumari and Sumathi, 2002). Similarly, the protein concentrates derived from mil­ lets have been shown to significantly reduce insulin levels, increase plasma adi­ ponectin, and improve glycemic responses in type 2 diabetic mice (Choi et al., 2005; Park et al., 2008). In 2010, the National Institute of Nutrition (ICMR) collaborated with the Indian Institute of Millets Research in Hyderabad to examine the GI of sorghum-based meals as part of the National Agricultural Innovation Project (NAIP). The findings revealed that meals made from sorghum had a low GI and were respon­ sible for lower postprandial blood glucose levels. Furthermore, due to the presence of considerable amounts of magnesium, millets also aid in the prevention of type II diabetes. Magnesium is a vital element that enhances the effectiveness of insulin and glucose receptors by creating several carbohydrate-digesting enzymes that regulate insulin functions (Kam et al., 2016).

1.4.4 antiMicroBial activity The secondary metabolites found in millet grains exhibit a wide range of biological characteristics. The phenolic and flavonoid compounds found in the bioactive sec­ ondary metabolites of some millet cultivars have antibacterial and antifungal proper­ ties (Nithiyanantham et al., 2019). According to the authors, finger millets’ phenolic and flavonoid compounds have been discovered to play a significant role against the proliferative inhibitory activity of bacterial pathogens, including Escherichia coli, Bacillus cereus, Listeria monocytogenes, Staphylococcus aureus, Streptococcus pyogenes, Serratia marcescens, Proteus mirabilis, and Pseudomonas aeruginosa. In addition, a recent study reported that the addition of finger millet bran extract in chitosan/gelatin-based films significantly improved the antibacterial activity against E. coli and antifungal activity against Penicillium nettle (Xu et al., 2022). Millets have been shown to possess exceptional bioactivities. However, to con­ clude their health benefits, sufficient evidence-based studies are required. This can include investigating the mechanism of action of the millets and their constituents using various in vitro and in vivo models, and pharmacodynamics and kinetic studies.

Nutrient Composition and Health Benefits of Millets

13

Studies can also be carried out to evaluate the effect of millets on various other less explored lifestyle-related disorders.

1.5

CONCLUSION AND FUTURE PERSPECTIVES

As the population grows, there is an increasing need for a well-balanced diet. Mil­ lets have pertinent amounts of nutrients and are widely accessible and inexpensive. Millets are rich in iron, calcium, manganese, magnesium, zinc, potassium, and phos­ phorus, among other nutrients. For this reason, they could be the best alternative cereal grain for human consumption. To shield the body from numerous oxidative stresses, millet grains can be employed as a readily available supply of natural anti­ oxidants. Millets have recently been found to be effective in treating conditions such as hypoglycemia and hypolipidemia. These millet grains also have significant uses as anti-tumor, antidiabetic, and antimicrobial agents. Millets offer several health benefits, making it worthwhile to incorporate these old, treasured grain-like seeds into our regular diet. Millets’ health benefits are already well known. Nonetheless, their use and popularity are limited due to the presence of antinutrients (phytate, oxalate, and tannins), which have a detrimental effect on min­ eral bioavailability and protein and carbohydrate digestion. However, with the right scientific inputs, not only can these limitations be overcome, but also the remarkable biological properties of millets can be utilized. Future research should therefore focus on the assessment of millets’ in vivo bioavailability, pharmacokinetics, as well as their precise molecular mechanism of action in order to use millets as health-promoting agents in food systems in the development of new nutraceuticals/functional foods/food supplements. Some of the aspects are reviewed in the rest of the chapters of this book.

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Nutriomics of Millet Crops

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Nutriomics of Millet Crops

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2

Health Benefits of MilletDerived Bioactive Peptides Jyoti Semwal1,2, Mohammad Hassan Kamani3, and M. S. Meera1,2 Department of Grain Science and Technology, CSIR-Central Food Technological Research Institute, Mysore, India 2 Academy of Scientific and Innovative Research, Ghaziabad, India 3 Food Chemistry and Technology Department, Teagasc Food Research Centre, Moorepark, Fermoy, County Cork, Ireland 1

CONTENTS 2.1 2.2 2.3 2.4

Introduction .................................................................................................. 18

Bioactive Peptides......................................................................................... 19

Sources of Bioactive Peptides.......................................................................20

Production and Processing of Bioactive Peptides from Millets ................... 21

2.4.1 Enzymatic Methods of Protein Hydrolysis....................................... 21

2.4.2 Fermentation and Germination.........................................................28

2.4.3 Hybrid Methods ................................................................................ 29

2.5 Bioactivities of Millet Peptides..................................................................... 29

2.5.1 Antioxidant Activity ......................................................................... 30

2.5.2 Antimicrobial Property..................................................................... 31

2.5.2.1 Antibacterial Property ....................................................... 31

2.5.2.2 Antifungal and Antiviral Property .................................... 31

2.5.3 Enzyme Inhibitory Property............................................................. 32

2.5.4 Anti-inflammatory Activity.............................................................. 32

2.6 Role of Peptides in Disease Prevention ........................................................ 33

2.6.1 Cancer............................................................................................... 33

2.6.2 Hypertension and Cardiovascular Diseases .....................................34

2.7 Functional and Physicochemical Properties of

Millet Peptides..............................................................................................34

2.8 Bioavailability, Bioaccessibility, and Delivery of Bioactive Peptides ..........34

2.9 Correlation of Bioactivities and Peptide Size ............................................... 36

2.10 Conclusions................................................................................................... 37

References................................................................................................................ 37

DOI: 10.1201/b22809-2

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Nutriomics of Millet Crops

2.1 INTRODUCTION Millets are grass species belonging to the Poaceae family and are cultivated for their small grains. They are considered “super crops” due to their nutritional values, health benefits, usage as animal feed, and use during food crisis (Joshi and Agnihotri, 1984; Yenagi et al., 2010). Millets are economically important crops grown in semi-arid regions of Africa and Asia, which experiences water scarcity and less fertilizer input. Hence, compared to other crops, they are the staple food crops in famine-prone regions (Tadele, 2016). Millets are heat and drought-tolerant and have superior pho­ tosynthetic efficiency, high dry matter productivity, and tolerant to saline, acidic, and aluminium toxic soil conditions (Yadav and Rai, 2013). The most commonly cultivated millets include pearl millet (Pennisetum glaucum), foxtail millet (Setaria italic), finger millet (Eleusine coracana), little millet (Panicum umatrense), sorghum (Sorghum bicolor), barnyard millet (Echinochloa esculenta), proso millet (Penicum iliaceum), and kodo millet (Paspalum setaceum). Besides their agricultural and economic advantages, millets are a boon to human health as they are a dense source of nutrients in comparison to the commonly con­ sumed wheat and rice (milled) grains (Parameswaran and Sadasivam, 1994). This is attributed to appreciable amounts of protein, dietary fiber (DF), essential fatty acids, B-vitamins, and minerals contained in these grains that depended on the crop (Rao et al., 2017). Finger millet is superior in calcium content (>350 mg/100 g); foxtail millet and little millet have a fair amount of fat (>4.0%); proso millet and barnyard millet are rich in protein (>10%); little millet, barnyard millet, and foxtail millet are remarkably high in crude fiber (6.7–13.6%), and barnyard millet and little millet contain a substantial amount of iron (9.3–18.6 mg/100 g) (Dwivedi et al., 2012; Kam et  al., 2016). Millet grains are gluten-free and, hence, are safe for celiac patients (Saleh et al., 2013). Millets have antioxidant, immune modulatory, and detoxifying properties due to the presence of polyphenols, lignans, phytosterols, phytoestro­ gens, and phytocyanins. The aforementioned factors also impart protection against age-related degenerative diseases such as Parkinson’s and cardiovascular diseases (CVDs), metabolic syndrome, diabetes, and cancer (Figure  2.1) (Manach et  al., 2005; Scalbert et al., 2005; Chandrasekara and Shahidi, 2012). These characteristics make millets suitable crops in the changing climatic conditions as well as for tackling modern human health disorders. In recent years, there has been a surge in the lifestyle-related non-communicable disorders primarily associated with eating habits and, hence, an increase in the demand for food with additional health benefits. Food that provides health benefits by exerting physiological effects other than the basic nutrition is known as func­ tional foods (Jones, 2002). The biological/physiological activities of functional foods are attributed to vitamins, minerals, fiber, protein, or peptides. Peptides among these food components demand special attention due to their extraordinary biolog­ ical activities and health-related benefits to combat the lifestyle-related degenera­ tive diseases. Peptides are small fragments of proteins consisting of 2–20 amino acid subunits linked through peptide bonds. Peptides have the potential to regulate important biological functions through an array of activities that includes antioxi­ dant, anti-thrombotic, antimicrobial, anti-hypertensive, immune modulatory, opioid,

Health Benefits of Millet-Derived Bioactive Peptides

19

MILLETS Starch, Protein and Fat

Minerals and Vitamins Polyphenols and Flavonoids

Prevention against life-style related diseases

Obesity

FIGURE 2.1

Diabetes

Cancer

Cardiovascular diseases Parkinson’s disease

Millet constituents and their related health benefits.

and mineral binding functions (Sánchez and Vázquez, 2017; Chakrabarti et al., 2014; Soory, 2012; Rutherfurd-Markwick, 2012). Such peptides are collectively known as bioactive peptides. Bioactive peptides can be obtained from several protein-rich sources of animals (marine) or plants. Recently, millet proteins have been identified as the novel source of bioactive peptides, although further detailed studies are required. In this chapter, attempts are made to throw light on the bioactive peptides of millets, their meth­ ods of production, biological activities, disease prevention, bioavailability, and bioaccessibility.

2.2

BIOACTIVE PEPTIDES

Bioactive peptides are peptides with specific amino acid sequences encrypted in the parent protein and extend health benefits by modulating the body functions and con­ ditions (Sharma et al., 2011; Sánchez and Vázquez, 2017). Peptides are low molecu­ lar weight (MW, BWB with better appearance, color, flavor, test, and texture. This result suggested that millets could partially replace wheat in bread (Singh et al., 2012). Co-fermentation of a mixture of finger millet and horse gram (Macrotyloma uni­ florum L.) flour in various ratios (2:1, 3:1, 4:1, and 5:1) has reportedly been accom­ plished for 24 h (Palanisamy et al., 2012). At 16 h, biochemical analysis revealed a substantial decline in starch content (25.52%) and pH and a significant increase in soluble proteins (1.1-fold), free amino acids (2.6-fold), and titratable acidity. Lysine content has also been reported to increase from 5.87 to 6.73 g/100 g of total amino acids. A 16 h co-fermented blended batter of finger millet and horse gram in a 4:1 ratio has been reported to provide a low-cost protein-rich breakfast food, dosa, and significantly maintain the product quality with better sensory attributes (Palanisamy et al., 2012). The impact of feed composition (X1), feed moisture content (X2), and screw speed (X3) has been analyzed by response surface methodology using a single screw extruder on nutritional qualities, amino acid, and sensory assessment during extru­ sion of cowpea and pearl millet flour blends for the production of fura (Filli et al., 2012). The influence of variables on the physical properties and system parameters could be in the sequence of X1 > X2 > X3. The optimum values have been reported for feed composition with 36.5% cowpea level, feed moisture with 22.3%, and screw speed with 186.7 rpm. The lysine content of the extrudates ranged from 5.1 to 6.6 g/100 g protein, while the methionine content ranged from 1.3 to 3.8 g/100 g protein (Filli et al., 2012). Millet grains are gluten-free (GF) with nutritional properties comparable to cere­ als. Three bread flour formulations, namely, proso millet (100%), proso millet and

Sensory, Physical, and Nutritional Qualities of Millets Food

167

corn starch (1:1), and proso millet and potato starch (1:1), have been used to eval­ uate the influence of starch addition on color, volume, and firmness of millet-based GF bread (Woomer et  al., 2019). The addition of starch softened the bread while brightening its color. The older age group consumed more GF products compared to the younger age group according to sensory results. People preferred the 100% millet-based formulation based on flavor, crumb aroma, crust color, and overall sen­ sory acceptability range (Woomer et al., 2019). The linear programming (LP) model has been used for the preparation of the tra­ ditional food item achikae from small millets. To reduce the overall cost of the final product, dehulled small millet (51.0%) and (32.8%) and sugar (16.2%) mixture for­ mulations have been reported to prepare employing the LP approach (Balasubra­ manian and Shukla, 2020). The nutritive value and sensory evaluation result of LP formulated achikae mix have provided 5.96–7.72 mg of iron, 140 mg of calcium, and 5.05–6.53 g of protein with sensory acceptability range (Balasubramanian and Shukla, 2020).

8.6 IMPROVEMENT OF NUTRITIONAL BIOAVAILABILITY IN MILLETS USING MODERN AGRICULTURAL BIOTECHNOLOGICAL TOOLS Minimally processed whole grains of millets have intact structures and maintain bio­ activity of components that have numerous health benefits. Millet grains also have antinutrients such as phytates, polyphenols, tannins, and trypsin inhibitors (Tha­ rifkhan et  al., 2021). Processing of millet grains, such as germination, fermenta­ tion, milling, and soaking, affects these antinutrients and breaks the structure, thus enhancing or reducing the bioavailability of macronutrient and micronutrient (Gupta et al., 2015; Tharifkhan et al., 2021). Some of these antinutrients exhibited enzyme inhibition and metal-chelating activity to form insoluble salts, resulting in a signif­ icant reduction of mineral bioavailability (Tharifkhan et  al., 2021). The germina­ tion process of finger millet grains has been reported to enhance the bioavailability of minerals (Ca and Fe), dietary fiber, and proteins while decreasing antinutrients, including tannin, phytic acid, oxalic acid, and trypsin inhibitor activity (Chauhan and Sarita, 2018). For the improvement of nutritional bioavailability of Fe, Se, Zn, and any other macronutrient and micronutrient, genetic resource screening for high nutrients, traditional plant breeding, molecular breeding (including high-throughput genomics and phenotyping), and transgenic/genome-editing methods coupled with novel agronomic and edaphic management strategies are required (Hefferon, 2020). Biofortification of millets using modern biotechnology techniques for enhancing accumulation of beneficial nutrients, such as calcium, iron, and zinc, and reducing antinutrients within edible tissue is under development. Traditional plant breeding methods or transgenic approaches can be applied to generate biofortified pearl millet having higher Zn and Fe levels (Hefferon, 2020). Members of Zn- and Fe-regulated transporter-like protein (ZIP) family have been reported to involve in the homeo­ stasis of Zn through intracellular uptake or translocation (Vinoth and Ravindhran, 2017). Overexpression of OsZIP1 in finger millet under constitutive (35S) and

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endosperm-specific promoters (Bx17) has been shown to have significantly higher Zn in seeds compared to the wild-type finger millet (Ramegowda et al., 2013). As the finger millet has higher amount of calcium, different research works have employed high-throughput transcriptome sequencing to investigate calcium sens­ ing, transport, and accumulation mechanisms across genotypes that differ in grain calcium content (Kumar et  al., 2014; Singh et  al., 2014). Transcriptome analysis reported that the genes for calcium transporter [CALCIUM EXCHANGER-1 (CAX­ 1), protein kinase (CaMK1 and 2), pore channel [two pore channel 1 (TPC1)] and Ca2+ ATPase), and CAX-3] and calcium sensor (CIPK-24 and CaM) are significantly abundant in the finger millet along with calcium translocation, uptake, and accumu­ lation (Kumar et al., 2014; Mirza et al., 2014). Increased calcium content has been reported in the edible part of the different transgenic plants by the overexpression of genes for calcium transporters [CAX-1 and VAX-1 (vacuolar Ca2+/H+ antiporter)], calcium binding, and calcium channel (LCT1) (Sharma et al., 2017). Taken together, overexpression of genes for calcium transporters, calcium binding, and calcium channel in millets will provide biofortified transgenic varieties along with higher calcium content. Genetic engineering has the capacity to lower the prevalence of food insecurity and hidden hunger across the world. Mineral and vitamin-enriched genetically engi­ neered foods are thought to be the next generation of genetically modified organ­ isms (GMOs). For example, golden rice has been biofortified for pro-vitamin A (β-carotene) and folate (vitamin B9) fortification has also been done in rice (Ye et al., 2000; Paine et  al., 2005; Storozhenko et  al., 2007; Blancquaert et  al., 2014). The biofortification of β-carotene in rice calli has been accomplished through clustered regularly interspaced short palindromic repeats (CRISPRs)/CRISPR-associated pro­ tein 9 (Cas9)-mediated modification of the rice Orange (Osor) gene (orthologue of the cauliflower or gene) (Endo et al., 2019). The enzyme Cas9 is responsible for the creation of CRISPR, which uses a guide RNA to identify precise sequences of DNA and subsequently modifies the target DNA either by the insertion of new sequences or disruption of genes (Ledford, 2015). In the area of crop science, CRISPR/Cas9 approach is beneficial since it is very effective and reliable, has a lower risk, and allows for a wide range of agricultural applications. Furthermore, as ncRNAs are the best indicator of genetic diversity, the identification of differentially expressed genes (DEGs) is critical in signaling pathways (Budak et al., 2020). MicroRNAs (miRNAs) are ncRNAs that modulate stress responses and expression of transporters and allow to uptake of minerals as well as maintain nutrient homeostasis (Paul et  al., 2015; Jatan et al., 2019, 2020). Overall, to produce biofortified transgenic varieties, mod­ ern agricultural biotechnological tools, including multigene editing technology for co-expression of minerals, vitamins, and nutritional protein-coding genes in millets, could play a crucial role.

8.7 CONCLUSION AND FUTURE PERSPECTIVES Overall, this chapter described the nutritional profile of millets and the use of their grains or flour for the preparation of traditional-based food. All the major and minor millets are now used in a variety of products such as bread, biscuits, snacks, halwa,

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chapatti, porridge, upma, idli, and dosa. Varieties of millets have comparable quan­ tities of macronutrient and micronutrient and hence can be considered as superfoods in the nutritional sense. Gluten-free food items, minerals, vitamins, and nutritional proteins from the major and minor millet varieties may help reduce the risk of obe­ sity, cardiovascular disease, cancer, and celiac disease. Therefore, the development of biofortified transgenic varieties and food products from millets using modern agri­ cultural biotechnological tools is required.

acKnoWledgMents CL acknowledges the financial support from the Council of Scientific  & Indus­ trial Research (CSIR) vide grant no. NIScPR/OLP/0008/2021 and NIScPR/ OLP/2022/08746. The authors acknowledge the Director, CSIR-NIScPR, New Delhi, for providing support and facilities for the study.

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Muniappan K, Raghavan V, Nachimuthu V, Raveendran M, Panaiyuran S, Vediyappan V, Nayak BK (2018). CIFSRF final technical report: Scaling up small millet post-harvest and nutritious food products project (CIFSRF Phase 2). https://idl-bnc-idrc.dspacedirect.org/ bitstream/handle/10625/57029/IDL-57029.pdf Muthamilarasan M, Singh NK, Prasad M (2019). Multi-omics approaches for strategic improvement of stress tolerance in underutilized crop species: A climate change perspec­ tive. Advances in Genetics, 103: 1–38. Paine JA, Shipton CA, Chaggar S, Howells RM, Kennedy MJ, Vernon G, Wright SY, Hinchliffe E, Adams JL, Silverstone AL, Drake R (2005). Improving the nutritional value of Golden Rice through increased pro-vitamin A content. Nature Biotechnology, 23(4): 482–487. Palanisamy BD, Rajendran V, Sathyaseelan S, Bhat R, Venkatesan BP (2012). Enhancement of nutritional value of finger millet-based food (Indian dosa) by co-fermentation with horse gram flour. International Journal of Food Sciences and Nutrition, 63: 5–15. Park KO, Ito Y, Nagasawa T, Choi MR, Nishizawa N (2008). Effects of dietary Korean proso­ millet protein on plasma adiponectin, HDL cholesterol, insulin levels, and gene expres­ sion in obese type 2 diabetic mice. Bioscience, Biotechnology, and Biochemistry, 72(11): 2918–2925. Paul S, Datta SK, Datta K (2015). miRNA regulation of nutrient homeostasis in plants. Frontiers in Plant Science, 6: 232. Ramadoss DP, Sivalingam NA (2017). Vanillin extracted from proso millet and barnyard millet induce apoptosis in HT-29 and MCF-7 cell line through mitochondria mediated pathway. Asian Journal of Pharmaceutical and Clinical Research, 10: 226–229. Ramashia SE, Mashau ME, Onipe OO (2021). Millets cereal grains: Nutritional composition and utilisation in sub-Saharan Africa. In  Cereal Grains-Volume 1. IntechOpen. http:// dx.doi.org/10.5772/intechopen.97272 Ramegowda Y, Venkategowda R, Jagadish P, Govind G, Hanumanthareddy RR, Makarla U, Guligowda SA (2013). Expression of a rice Zn transporter, OsZIP1, increases Zn concentration in tobacco and finger millet transgenic plants. Plant Biotechnology Reports, 7(3): 309–319. Rao DB, Bhaskarachary K, Arlene Christina GD, Sudha Devi G, Vilas AT, Tonapi A (2017). Nutritional and health benefits of millets. ICAR: Indian Institute of Millets Research (IIMR), Hyderabad, 112. Samtiya M, Aluko RE, Dhewa T (2020). Plant food anti-nutritional factors and their reduction strategies: An overview. Food Production, Processing and Nutrition, 2(1): 1–14. Sanhueza L, Durruty P, Vargas C, Vignolo P, Elgueta K (2019). Diabetes mellitus: A group of genetic-based metabolic diseases. In Cellular Metabolism and Related Disorders. IntechOpen. https://doi.org/10.5772/intechopen.89924. www.intechopen.com/ chapters/69844 Sharma D, Jamra G, Singh UM, Sood S, Kumar A (2017). Calcium biofortification: Three pronged molecular approaches for dissecting complex trait of calcium nutrition in finger millet (Eleusine coracana) for devising strategies of enrichment of food crops. Frontiers in Plant Science, 7: 2028. Siegel RL, Miller KD, Fuchs HE, Jemal A (2022). Cancer statistics, 2022. CA: A  Cancer Journal for Clinicians, 72(1): 7–33. Singh K, Mishra A, Mishra H (2012) Fuzzy analysis of sensory attributes of bread prepared from millet-based composite flours. LWT-Food Science and Technology, 48: 276–282. Singh UM, Pandey D, Kumar A (2014). Determination of calcium responsiveness towards exogenous application in two genotypes of Eleusine coracana L. differing in their grain calcium content. Acta Physiologiae Plantarum, 36(9): 2521–2529. Storozhenko S, De Brouwer V, Volckaert M, Navarrete O, Blancquaert D, Zhang GF, Lambert W, Van Der Straeten D (2007). Folate fortification of rice by metabolic engineer­ ing. Nature Biotechnology, 25(11): 1277–1279.

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Suma P, Urooj A (2012). Antioxidant activity of extracts from foxtail millet (Setaria italica). Journal of Food Science and Technology, 49(4): 500–504. Taylor JR, Emmambux MN (2008). Gluten-free foods and beverages from millets. In GlutenFree Cereal Products and Beverages (pp. 119-V). Academic Press. Tharifkhan SA, Perumal AB, Elumalai A, Moses JA, Anandharamakrishnan C (2021). Improvement of nutrient bioavailability in millets: Emphasis on the application of enzymes. Journal of the Science of Food and Agriculture, 101(12): 4869–4878. Thejaswini BN, Ramesh D, Prakash J (2017). Nutritional composition and sensory quality of cookies incorporated with Little Millet (Panicum Milliarae). International Journal of Food, Nutrition and Dietetics, 5(1). http://dx.doi.org/10.21088/ijfnd.2322.0775.5117.2 Ugare R, Chimmad B, Naik R, Bharati P, Itagi S (2014). Glycemic index and significance of barnyard millet (Echinochloa frumentacae) in type II diabetics. Journal of Food Science and Technology, 51(2): 392–395. Varshney RK, Shi C, Thudi M, Maria CC, Wallace J, Qi P, Zhang H, Zhao Y, Wang X, Rathore A, Srivastava RK (2017). Pearl millet genome sequence provides a resource to improve agronomic traits in arid environments. Nature Biotechnology, 35(10): 969–976. Verma S, Srivastava S, Tiwari N (2015). Comparative study on nutritional and sensory qual­ ity of barnyard and foxtail millet food products with traditional rice products. Journal of Food Science and Technology, 52(8): 5147–5155. Vinoth A, Ravindhran R (2017). Biofortification in millets: A sustainable approach for nutri­ tional security. Frontiers in Plant Science, 8: 29. Woomer J, Singh M, Vijayakumar PP, Adedeji A (2019). Physical properties and organoleptic evaluation of gluten-free bread from proso millet. British Food Journal, 122: 547–560. Ye X, Al-Babili S, Kloti A, Zhang J, Lucca P, Beyer P, Potrykus I (2000). Engineering the provitamin A (β-carotene) biosynthetic pathway into (carotenoid-free) rice endosperm. Science, 287(5451): 303–305. Yousaf L, Hou D, Liaqat H, Shen Q (2021). Millet: A review of its nutritional and functional changes during processing. Food Research International, 142: 110197.

9

Genetic Diversity for Grain Nutrients Content in Finger Millet (Eleusine Coracana (L.) Gaertn.) Germplasm Henry Fred Ojulong1, Eric Manyasa1,

Sheunda Patrick2, Chrispus Oduori3, Scovia Adikini4,

Lameck Nyaligwa5, and Hapson Mushoriwa1

International Crop research Institute for Semi-Arid Tropics (ICRISAT), Bulawayo, Zimbabwe 2International Crop Research Institute for Semi-Arid Tropics (ICRISAT), Nairobi, Kenya 3 Kenya Agricultural and Livestock Research Organization (KALRO)-Kibos, Kisumu, Kenya 4 National Agricultural Research Organization (NARO), National Semi Arid Resources Research Institute (NaSARRI), Serere, Soroti, Uganda 5Tanzania Agricultural Research Institute, Hombolo, Dodoma, Tanzania 1

CONTENTS 9.1 9.2

Introduction .................................................................................................. 176

Nutrient Content ........................................................................................... 179

9.2.1 Calcium Content ............................................................................... 181

9.2.2 Iron Content ...................................................................................... 183

9.2.3 Zinc Content ..................................................................................... 185

9.2.4 Protein Content ................................................................................. 186

9.2.5 Trait Correlation ............................................................................... 186

9.3 Nutrient Association with Other Traits and Parameters............................... 187

9.3.1 Nutrient Association with Country of Origin................................... 187

9.3.2 Nutrient Association with Yield-Related Traits................................ 190

9.3.3 Nutrient Association with Color ....................................................... 192

9.3.4 Glume Covering................................................................................ 193

9.4 Conclusion .................................................................................................... 193

References.............................................................................................................. 194

DOI: 10.1201/b22809-9

175

176

9.1

Nutriomics of Millet Crops

INTRODUCTION

Finger millet (Eleusine coracana L. Gaertn.) is a staple crop upon which millions of people living in marginal areas of sub-Saharan Africa and Asia depend on for food, nutrition, and income in rural households (Chivenge et al., 2015). Finger millet originated in the highlands of Uganda and Ethiopia and domestication began there around 5000 years ago, as evident from the archaeological records of early African agriculture (Hilu and de Wet, 1976; NRC, 1996). It arrived in India probably more than 3000 years ago. The genus Eleusine includes nine annual and perennial species as recognized by Phillips (1972), with eight African species and one New World species (Eleusine tristachya Lam.) native to Argentina and Uruguay (Lovisolo and Galati, 2007). The range of the genus has been extended by widespread introduc­ tion of the crop (E. coracana) throughout the tropics, and the common weed often associated with cultivation, Eleusine indica (L.) Gaertn., East Africa, is considered the center of diversity of the genus and eight species (Eleusine africana, E. cora­ cana, Eleusine kigeziensis, E. indica, Eleusine floccifolia, Eleusine intermedia, Ele­ usine multiflora, and Eleusine jaegeri) occur in this region (Mehra, 1963; Phillips, 1972). The species of Eleusine are distributed in the tropical and subtropical areas of India, Myanmar, Sri Lanka, Nepal, China, and Japan in Asia; while in Africa, it is grown in Uganda, Kenya, Tanzania, Ethiopia, Eritrea, Rwanda, Zaire, and Soma­ lia (Upadhyaya et al., 2010). It is an annual allotetraploid (2n  =  4X  = 36, AABB) that includes two distinct subspecies: E. coracana ssp. coracana (L.) Gaertn. and E. coracana ssp. africana (Kennedy-O’Byrne, 1957; Hilu and de Wet, 1976; Hilu, 1994). Coracana is the cultivated species, while africana is the wild one. The cul­ tivated species coracana was domesticated from wild populations of E. coracana ssp. africana as suggested by morphological and cytogenetic evidence and through molecular studies (Chennaveeraiah and Hiremath, 1974; Hilu and de Wet, 1976; Hilu and Johnson, 1992). Both cultivated and wild species are important from the point of germplasm collection, conservation, and utilization since they collectively form the primary gene pool. Hybridization between the wild and cultivated populations has given rise to many morphological intermediates that are completely fertile. These hybrids are aggressive colonizers and are grouped under the race spontanea (de Wet et al., 1984; Kennedy-O’Byrne, 1957; Mehra, 1962; Phillips, 1995). Finger millet is widely cultivated in Africa and South Asia under varied agrocli­ matic conditions (Dida et al., 2008). In Africa, it is extensively cultivated in Uganda, Kenya, Tanzania, Ethiopia, Rwanda, Burundi, Zambia, and Malawi (Mnyenyembe and Gupta, 1998; Obilana et al., 2002). In South Asia, finger millet is widely culti­ vated in India and Nepal (Upadhyaya et al., 2007). Its global production is 4.5 mil­ lion tons per annum with 2.0 million tons being produced in Africa (Sakamma et al., 2018). The striking feature of finger millet is centered on its ability to adjust to different agroclimatic conditions (Hegde and Gowda, 1989), is adapted to adverse agro-ecological conditions, and requires minimal input (Adekunle, 2012). Once ade­ quate moisture is available (the minimum water requirement is 400  mm) and the temperature is above 15 °C, finger millet can be grown throughout the year (Hegde and Gowda, 1989). It is well adapted to higher elevations and is grown in the Him­ alayas up to an altitude of 2400 m (NRC, 1996). It is drought-tolerant (Dass et al.,

Genetic Diversity for Grain Nutrients Content in Finger Millet

177

2013; Hegde and Gowda, 1989; Maitra et al., 2022); disease resistant (Kerr, 2014); effective in suppressing weed growth (Samarajeewa et al., 2006); and able to grow on marginal lands with poor soil fertility. Globally, in terms of cereal production in semi-arid regions, finger millet is ranked third after sorghum and pearl millet (Thila­ karathna and Raizada, 2015). Finger millet has high genetic diversity for agronomically and nutritionally impor­ tant traits (Goron and Raizada, 2015). The grains are comparatively richer in miner­ als and micronutrients than other main cereals (Vadivoo et al., 1998). It is the richest source of calcium (Kumar et al., 2018), containing about 3400 mg/kg compared with 100–600 mg/kg in most other cereals (Kumar et al., 2018; Gupta et al., 2017). Barbeau and Hilu (1993) observed a wide variation in the protein (7.5–11.7%), cal­ cium (3760–5150 mg/kg), and iron (3.7–6.8 mg/kg) content in two wild and eight domesticated cultivars. Its grain is rich in methionine, tryptophan, cysteine, tyros­ ine, calcium, phosphorous, and iron, making the crop an excellent nutritional source compared to other major cereals (Gupta et al., 2017). The high proportion of carbo­ hydrates in form of non-starchy polysaccharides and dietary fibers in finger millet grain helps in reducing cholesterol. Slow release of glucose during digestion makes it suitable for diabetic patients. The nutritional quality of finger millet grain makes it an ideal food for expectant women, breastfeeding mothers, children, the sick, and diabetics (National Research Council, 1996). This in addition to the high-quality protein content makes finger millet a “super crop” in nutritional terms. Most of the regions where finger millet is grown have an agriculture-based econ­ omy and large segments of these populations are typically dependent on what they grow and produce for their nutrient needs. In such situations, staple crops that can offer adequate nutrient requirements such as Ca and Fe, especially for people of low-income groups, are highly recommended. One such nutrient-rich, traditional, and locally well-adapted crop is finger millet (Ojulong et al., 2021). As opposed to nutritionally deficient cereals, such as rice and maize, its regular consumption has a vast potential to curb the incidences of Ca, Fe, and Zn deficiency. Finger millet also possesses many other health-benefitting traits. For example, it has been highlighted that as a model nutraceutical crop, finger millet can provide excellent solutions to food and health security issues (Kumar et al., 2016; Puranik et al., 2017). Being a stress-resilient crop requiring minimal inputs for growth, it is especially suited for sustainable agriculture (Gupta et al., 2017). Intake of diet poor in iron (Fe), zinc (Zn), and protein is the major cause of micronutrient and protein malnutrition. Iron deficiency leads to anemia. About 79% of pre-school children between 6 and 35 months of age and 56% of women between 15 and 49 years of age are anemic in poor countries (Krishnaswamy, 2009). Protein deficiency causes retarded physical and mental growth. Zinc deficiency leads to diar­ rhea, pneumonia, and reduced immunity to diseases, and increased infant mortality (Gibson et al., 2008). Deficiencies of Fe and Zn are widespread worldwide (FAO/ WHO, 2001; Cakmak, 2008), especially in sub-Saharan Africa and South and South­ east Asia (Reddy Belum et  al., 2005). In its report, FAO et  al. (2014) singled out sub-Sahara Africa as having the highest prevalence of under nutrition in the world, with one in three people being chronically hungry. A large proportion of people in this part of Africa, especially in the rural communities, are poor and live on a diet

178

Nutriomics of Millet Crops

composed primarily of staple foods prepared from cereals (Oniang’o et al., 2003). Finger millet being a promising source of micronutrients and protein (Malleshi and Klopfenstein, 1998) besides energy can contribute to alleviating micronutrient and protein malnutrition (Underwood, 2000). Because of its high nutrient contents, finger millet is gaining importance in eastern and southern Africa for its potential use in the preparation of a variety of foods such as porridge, bread, biscuits, pastas, instant baby food, and composite flour (Dendy, 1993; Saha et al., 2016). Wide adaptability (Upadhyaya et al., 2007), higher nutritional quality (Gopalan et al., 2002), higher multiplication rate, and longer shelf life (Iyengar et al., 1945) make finger millet an ideal crop for use as a staple food and for famine reserve. The crop has dual importance as a source of food grain as well as straw for fodder. Finger millet is a rich source of calcium (Ca) (344 mg/100 g), which is 5–30 times more than in most cereals, making it the richest plant source (Gopalan et al., 2002; Gupta et al., 2017; Antony Ceasar et al., 2018; Kumar et al., 2018). The grain has a fair amount of protein (7.3 g/100 g) (Malleshi and Klopfenstein, 1998; Sharma et al., 2017), dietary fiber (15–20%) (Chethan and Malleshi, 2007), and fat content less (1.5 g/100 g) compared to maize and brown rice with 4.6 and 2.7 g/100 g, respec­ tively. Carbohydrates in finger millet have the unique property of slower digestibility making it a food for long sustenance. All these are deficient in most cereals and are crucial to human health and growth, which qualify finger millet as an important crop against malnutrition. In recent years, various efforts have been made by geneticists and breeders to identify naturally occurring genetic diversity in finger millet (Puranik et al., 2017). Currently, finger millet genebanks across the globe conserve more than 37,000 acces­ sions with India, Kenya, Ethiopia, Uganda, and Zambia housing the major collections (Vetriventhan et al., 2015). The International Crops Research Institute for the SemiArid Tropics (ICRISAT) Genebank is one of the largest international gene banks that serves as a world repository for finger millet. ICRISAT currently has a collection of 7519 accessions (http://genebank.icrisat.org/IND/Passport?Crop=Finger+millet) from several Asian and African countries. ICRISAT has the world mandate for finger millet research, with some of its core activities being the collection, characteriza­ tion, regeneration, preservation, and distribution of germplasm. The subsp. coracana accessions were represented by 97.4%, while those from subsp. africana were 2.6% only (Upadhyaya et al., 2010). Most of the collection constitutes traditional cultivars and landraces (7121). As of now, the entire genetic diversity present among the finger millet germplasm is available as small sets (core) and sub-sets (mini-core) collec­ tions (Vetriventhan et al., 2015). The core collection has 622 accessions represent­ ing geographical regions and biological races from the entire collection. Accessions from Africa (58.7%) and Asia (35.8%) were predominant in the core, while those from America and Europe were represented by 0.8–1.1% only. National Bureau of Plant Genetic Resources (NBPGR), India, has 10,507 acces­ sions and the National Active Germplasm Collection Site (NAGS) located at All India Coordinated Small Millets Improvement Project (AICSMIP), Bengaluru, has 7070 accessions (Mirza and Marla, 2019; Antony Ceasar et al., 2018). Kenya Agri­ cultural and Livestock Research Organization (KALRO), Kenya (2875), Institute of Biodiversity Conservation (IBC), Ethiopia (2156), USDA Agricultural Research

Genetic Diversity for Grain Nutrients Content in Finger Millet

179

Service (USDA-ARS), USA (1452), and Serere Agricultural and Animal Production Research Institute (SAARI), now NaSARRI, Uganda (1115) are also maintaining fingermillet accessions (Goron and Raizada, 2015; Saha et al., 2016; Gupta et al., 2017). The ARS-USDA in Griffin, Georgia, maintains 766 finger millet accessions from 11 countries (Ethiopia, India, Kenya, Nepal, Pakistan, South Africa, Tanzania, Uganda, Zaire, Zambia, and Zimbabwe), of which 17 are wild relatives (E. floccifo­ lia, E. indica, E. jaegeri, E. multiflora, and E. tristachya). Studying the germplasm diversity and selection of superior genotypes are pre­ requisites for a successful breeding program for crop improvement. For success in any breeding program and crop improvement effort, it is crucial to understand the amount and distribution of variability present in a gene pool. As finger millet is culti­ vated under diverse climatic conditions in Asia and Africa, understanding the genetic diversity is vital to identifying genotypes resilient to climate change (Mercer and Perales, 2010). The most cost-effective approach for mitigating micronutrient and protein mal­ nutrition is to introduce finger millet varieties selected and/or bred for increased Ca, Fe, Zn, and protein contents (Ojulong et al., 2021). Plant breeding approach scores over others (such as food fortification, micronutrient supplements, dietary strate­ gies, and medical interventions) because it complements the existing approaches to combat micronutrient deficiency. It does not require any special program to change the behavior of farmers/consumers. Cultivars rich in Ca, Fe, Zn, and protein with farmer-preferred grain quality and adaptation traits are readily accepted (Welch and Graham, 2004; Graham et al., 2007; Pfeiffer and McClafferty, 2007; Prasad, 2010). Furthermore, the consumption of biofortified foods does not have side effects such as change in taste, bioavailability, and risk of developing disease usually associated with inorganic fortification and taking of supplements (Bolland et al., 2010; Institute of Medicine, 2011). Attempts to breed finger millet for enhanced grain micronutrient and protein con­ tents are still in their infancy. Exploitation of existing variability among germplasm accessions is viewed as the low-hanging fruit and short-term strategy for developing and delivering micronutrient and protein-dense finger millet cultivars to address the micronutrient and protein malnutrition in the target population (Upadhyaya et  al., 2010). The objective of this chapter is to summarize the studies done to assess the genetic diversity present in the finger millet germplasm to establish if enough diver­ sity exists for nutrient improvement of varieties.

9.2

NUTRIENT CONTENT

Very high variability was observed in all the quality traits determined. It was found that calcium ranged from 1555 to 5440 mg/kg, iron ranged from 24.0 mg/kg to 71.5 mg/100 g, zinc ranged from 10.2 to 101.3 mg/kg, and potassium ranged from 2824 to 4873 mg/kg (Table 9.1). Also, magnesium ranged from 1070 to 1850 mg/kg, man­ ganese ranged from 6.8 to 50.8 mg/kg, phosphorous ranged from 2824 to 4873 mg/ kg, sulfur ranged from 4092 to 4092 mg/kg, and protein content ranged from 9.1% wt to 18.6% wt with a mean of 5.86% wt is reported. Accessions with high content compared with the universal values were identified. Country and continent of origin

180

Nutriomics of Millet Crops

TABLE 9.1 Summary Table of the Nutrient Content Values of Ten Nutrient Traits Evaluated in 610 Finger Millet Accessions during at ICRISAT-Kiboko, Kenya Ca (mg/ kg)

Fe (mg/ kg)

Zn (mg/ kg)

Cu (mg/ kg)

K (mg/ kg)

Mg (mg/ kg)

Mn (mg/ kg)

P (mg/ kg)

Protein (%)

S (mg/ kg)

Universal mean

3440

39.0

23

4.7

4080

1370

54.9

2830

7.3

 

Minimum

1555

24.0

10.2

1.7

3823

1070

6.8

2824

9.1

994.

Maximum

5440

71.5

101.3

19.2

7758

1850

50.8

4873

18.6

4092

Mean (N = 610)

3237

43.4

19.5

4.7

5170

1491

12.7

3881

14.0

1383

Standard deviation

590.6

8.1

5.3

2.0

483.5

130.4

2.3

299.7

1.3

155

Standard error of mean

24.44

0.33

0.22

0.1

19.6

5.3

0.09

12.14

0.05

6.3

Coefficient of variation

18.3

18.7

27.2

42.8

9.4

8.7

18.4

7.7

9.4

11.2

 

were highly significant (P < 0.001) for Ca, P, K, and Mg; significant (P < 0.05) for Fe; and not significant for Zn, Cu, Mn, protein, P, and S. At the continent level, acces­ sions from Asia had higher average nutrient contents of the target traits Ca (Asia: 3446 mg/kg; Africa 3099 mg/kg), Fe (Asia: 43.9 mg/kg; Africa 42.8 mg/kg), and Zn (Asia: 19.7 mg/kg; Africa 19.4 mg/kg) than those from Africa, although only Ca levels were significantly different. Accessions from both continents had the average protein level of 14.0%. Highest diversity for most traits was observed in accessions from India, Uganda, Zimbabwe, Kenya, Nepal, Malawi, and Zambia (Table  9.2). Africa and Asia accessions had the highest diversity for all the accessions followed by Unknown, Europe, and Asia. Accessions from Africa showed higher diver­ sity for all the traits except in Ca; where Asian accessions were more diverse (σ2 = 384409), compared to the African (σ2 = 271857). African accessions had σ2  =  70.7 compared to σ2  =  56.1 in Asian accessions, σ2  =  37.1 compared to σ2 = 15.0 for zinc, and σ2 = 1.89 compared to σ2 = 1.44 for protein for the main target traits. Potassium had variance σ2 = 263791 and σ2 = 191587, Mg had var­ iance σ2 = 16751 and σ2 = 15153, Mn had variance σ2 = 7.558 and σ2 = 2.521, P had variance σ2 = 97413 and σ2 = 72180, and S had variance σ2 = 12038 and σ2 = 10426 for African and Asian accessions, respectively. According to previ­ ous reports, African germplasm is more diverse compared with Asian germplasm (Dida et al., 2008; Panwar et al., 2010; Bharathi, 2011; Arya et al., 2013; Kalyana Babu et  al., 2014; Kumar et  al., 2016; Ramakrishnan et  al., 2016; Babu et  al., 2017; Backiyalakshmi et al., 2021).

181

Genetic Diversity for Grain Nutrients Content in Finger Millet

TABLE 9.2 Mean Contents by Country of the Different Nutrient Traits Evaluated in 610 Accessions Established at ICRISAT-Kiboko, Kenya

Origin

Fe Zn Ca mg/ (mg/ (mg/ kg kg) kg)

P (mg/ kg)

K (mg/ Mg (mg/ S (mg/ kg) kg) kg)

Cu (mg/ kg)

Mn (mg/ Protein kg) (%)

Germany

3741

59.7

22.5

4467

5636

1681

1485

4.6

14.4

14.9

Mexico

3977

56.5

20.5

4322

4728

1808

1527

5.2

15.2

16.5

Pakistan

3829

53.7

20.3

3356

5539

1435

1355

4.2

12.9

13.0

UK

3502

50.2

21.9

3666

4515

1509

1313

3.6

11.2

13.3

Unknown

3431

47.0

21.1

3992

5187

1512

1399

5.2

12.8

14.6

Maldives

3000

47.0

17.1

4045

4731

1604

1379

3.6

12.1

13.5

Malawi

3083

45.7

19.8

3994

5120

1494

1361

4.6

12.6

14.4

Congo

3771

45.4

18.1

4121

5165

1555

1470

4.5

10.5

15.0

Zambia

3006

45.1

21.2

3869

5145

1426

1372

4.5

12.1

14.4

Nepal

3392

44.6

19.7

3856

5378

1503

1381

5.3

12.9

14.0

Kenya

3135

43.9

19.1

3845

5179

1458

1336

4.6

12.6

13.9

India

3462

43.6

19.6

3909

5023

1533

1404

4.4

13.2

14.0

Uganda

3130

42.1

19.5

3872

5208

1489

1402

4.5

12.6

14.0

Ethiopia

2669

41.6

19.2

3820

5182

1465

1284

5.5

12.2

13.5

Zimbabwe

3064

41.5

19.3

3830

5194

1469

1368

4.6

12.3

13.9

Nigeria

4013

40.9

20.8

3811

5175

1485

1425

7.3

12.0

14.7

Italy

2220

39.8

17.0

4601

5814

1574

1341

5.6

12.7

15.2

South Africa

2771

39.5

18.1

4226

7016

1519

1417

4.2

10.5

13.4

Tanzania

3119

38.9

15.8

4159

5769

1437

1406

7.1

12.3

13.1

Sri Lanka

2671

38.0

19.9

3971

5095

1435

1419

5.6

9.5

15.5

USA

2883

37.9

17.5

3763

4821

1357

1994

5.1

12.8

13.1

Mozambique

4039

33.9

16.9

3675

5734

1404

1346

3.3

10.7

12.8

Senegal

2867

32.9

17.9

4103

5068

1542

1364

3.3

12.7

14.5

Burundi

3658

31.6

14.2

3460

5341

1322

1328

4.3

11.4

13.3

Mean N = 610 LSD Senegal CV

3237*** 43.4* 19.5NS 3881*** 5170*** 1491*** 1383NS 468NS 12.7NS 14.0NS 1006

14.3

9.6

525

836

228

263

3.6

4.2

2.4

561

8.0

5.4

293

466

127

147

2.1

2.3

1.3

17.32

18.5

27.5

7.5

9

8.5

10.1

42.7

18.4

9.4

9.2.1 calciuM content Calcium content is highly variable. Ojulong et al. (2021) while working on 628 acces­ sions from the core germplasm, farmer-preferred, and released varieties in East and South Asia (ESA) found Ca to vary from 1555 to 5540 mg/kg with a mean of 3215

182

Nutriomics of Millet Crops

mg/kg. They found the highest ten Ca content accessions to have been collected from India, Nigeria, Zimbabwe, Malawi, Kenya, Nepal, and Uganda. The farmer-preferred and released varieties, Okhale 1, Ending, Nakuru FM 1, P224, and U15, had low Ca values of 2300, 2480, 2930, 3110, and 3190 mg/kg, respectively. They all fall below the conventionally reported global Ca average value for finger millet of 3440 g/kg. Okhale 1, the variety with the lowest estimated Ca content, is a variety popular among farmers in western Kenya, and Ending, the variety with the second lowest Ca content, is a farmer local variety preferred by farmers in eastern and northern Uganda. The high Ca content accessions also compared well with the adapted varieties in Zn and protein content, maturity period [days to flowering (DF)], and grain yield. In another study, calcium values of 610 accessions selected from more than 3000 germplasm accessions for adaptation under ESA conditions were found to range from 1555 to 5540 mg/kg with a mean of 3237 mg/kg (Ojulong, unpublished). Accessions with the highest content were IE 2008 (India) with 5440 mg/kg, IE 6541 (Nigeria) with 4833 mg/kg, IE 3038 (India) with 4753 mg/kg, IE 4491 (Zim­ babwe) with 4708 mg/kg, and IE 2644 (Malawi) with 4683 mg/kg. These represent 36–58% higher content than the universal average. Accessions with low Ca content were IE 3391 from Zimbabwe (1555 mg/kg) followed by IE 2341 from Kenya (1683 mg/kg), IE 5992 from Nepal (1799 mg/kg), IE 2760 Malawi (1852 mg/kg), and IE 6928 from Unknown (1856 mg/kg). These represent 46–55% less Ca con­ tent compared to the universal average. Countries with accessions with the highest average Ca levels were Mozambique (4039 mg/kg), Nigeria (4013 mg/kg), Mexico (3977 mg/kg), Pakistan (3829 kg/kg), Congo (3771 mg/kg), Germany (3741 mg/ kg), Burundi (3658 mg/kg), UK (3502 mg/kg), India (3462 mg/kg), and Unknown (3431 mg/kg). The greatest diversity within country of origin was from accessions from India (σ2 = 397787), Malawi (σ2 = 347182), Nepal (σ2 = 339316), Unknown (σ2 =337471), Zambia (σ2  =  332953), Kenya (σ2  =  313896), Zimbabwe (σ2  =  285976), Nigeria (σ2 = 283092), Ethiopia (σ2 =257337), and Uganda (σ2 =172807). At the continental level, Europe and America were dropped from further discussion as they contained a few numbers of accessions. The greatest diversity was found among accessions from Asia (σ2 = 384409) followed by Unknown (σ2 = 337471) and from Africa (σ2 = 271857). Upadhyaya et al. (2010), working on the core collection in India, found accessions to have the Ca range of 3860–4890 mg/kg with a mean of 4300 mg/kg. They found that accessions with the highest Ca content were collections from Zimbabwe, India, Nigeria, Burundi, Kenya, Germany, Malawi, and Kenya. Upadhyaya et al. (2006), using 622 core accessions, found substantial variability Ca = 1840–4890 g/kg. They estimated the phenotypic coefficient of variation (PCV) and genotypic coefficient of variation (GCV) of 18.80% and 17.75%, respectively. In other studies, Ca content was found to vary from 1620 to 4870 mg/kg with a mean value of 3208 mg/kg grain in 36 genotypes of finger millet (Vadivoo et  al., 1998), 2930–3900 mg/kg in six varieties of finger millet (Babu et  al., 1987), and 500–3000 mg/kg in another set of six varieties (Admassu et al., 2009). High calcium content, 4500 mg/kg (Panwar et al., 2010) and 4890 mg/kg (Upadhyaya et al., 2011), has been reported in few finger millet genotypes. The studies agree that high varia­ bility in Ca exists in finger millet germplasm.

Genetic Diversity for Grain Nutrients Content in Finger Millet

183

9.2.2 iron content Very high Fe values were estimated for the accessions as compared to the oftencited average value of 39 mg/kg. Ojulong et al. (2021) reported Fe to range from 13.7 to 300.4 mg/kg. The highest content was recorded in accessions from Kenya, Unknown, Zimbabwe, Nepal, India, and Uganda, while accessions with the lowest were also from Uganda, Zimbabwe, India, and Kenya showing the diversity of acces­ sions from these countries. They reported higher diversity in Fe and other nutrients and attributed this to inclusion of core collection, locally cultivated and released varieties in the east and southern Africa region. The best ten accessions for Fe con­ tent had values five times higher than the cited average Fe content and included KNE 628 (30.04 mg/100 g), Acc 32 (26.83 mg/100 g), IE 6321 (24.54 mg/100 g), IE 4245 (23.84 mg/100 g), IE 2818 (23.57 mg/100 g), IE 5831 (21.78 mg/100 g), IE 2014 (21.33 mg/100 g), IE 5485 (21.31 mg/100 g), IE 3704 (21.29 mg/100 g) and IE 3780 (20.54 mg/100 g). Released and farmer-preferred varieties had values higher than the global average, but four times lower than those of the high Fe content accessions. In another study, Iron values ranged from 24.0 to 71.5 mg/kg with a mean of 43.4 mg/kg (Table  9.1) (Ojulong, unpublished). The highest Fe content estimates were recorded in IE 4984 (Uganda) with 71.5 mg/kg, IE 2476 (Kenya) with 70.7 mg/kg, IE 6059 (Nepal) with 69.3 mg/kg, IE 4525 (Zimbabwe) with 69.0 mg/kg and IE 3901 (Uganda) with 68.4 mg/kg. Accessions with the lowest Fe content were IE 4116 from Uganda (24.0 mg/kg), IE 3723 from Uganda (25.0 mg/kg), IE 4339 from Zimbabwe (25.8 mg/kg), IE 5435 from Kenya (26.0 mg/kg) and IE 4147 from (27.2 mg/kg). By country-of-origin accessions from Germany (59.7 mg/kg), Mexico (56.5 mg/kg), Pakistan (53.7 mg/kg), UK (50.2 mg/kg), Unknown (47.0 mg/kg), Malawi (45.7 mg/ kg), Zambia (45.1 mg/kg), Nepal (44.6 mg/kg), Kenya (43.9 mg/kg) and India (43.6 mg/kg) had the highest average Fe content. The highest diversity was recorded in accessions from Uganda (range 47.5 mg/kg), Kenya (range 44.8 mg/kg), Zimbabwe (43.2 mg/kg), Nepal (range 41.5 mg/kg), India (range 41.1 mg/kg), Malawi (range 35.8 mg/kg), Zambia (range 31.8 mg/kg) and Unknown (range 26.9 mg/kg). At the continent level accessions from Africa were more diverse (range 47.5 mg/kg), fol­ lowed by Asia (range 42.0 mg/kg), and Unknown; with the least diverse being from Americas (range 27.8 mg/kg) (Table 9.3). Upadyhaha et al. (2011), working on the finger millet core collection, reported Fe content to range from 21.7 to 65.2 mg/kg with a mean of 29.3 mg/kg, with acces­ sions from Burundi, Malawi, Burundi, India, Nepal, Zimbabwe, Uganda, and Kenya recording the highest values. Upadhyaya et  al. (2006), using 622 core accessions, found substantial variability in Fe content (21.71–65.23 mg/kg) and estimated PCV of 22.87% and genotypic coefficient of variation of 17.87%. In previous studies, Babu et al. (1987) reported Fe content of finger millet ranged from 3.3 to 14.8 mg/kg. Singh and Srivastava (2006), working on 16 finger millet varieties, reported Fe content to range from 36.1 to 54.2 mg/kg with a mean value of 44.0 mg/kg. According to Kumar et al. (2018), finger millet grain contains 0.32% iron, whereas Admassu et  al. (2009) reported grain iron to range from 0.05% to 0.54%. Singh and Srivastava (2006) reported that the iron content in 16 landraces of finger millet ranged between 0.36% and 0.54% with a mean value of 0.44%.

184

TABLE 9.3 Ranges of the Nutrient Content of the Different Traits Evaluated in 610 Diverse Accessions in Kiboko, Kenya Calcium (mg/kg)

Iron (mg/ kg)

Zinc (mg/ kg)

Potassium (mg/kg)

Magnesium (mg/kg)

Manganese (mg/kg)

Phosphorous (mg/kg)

Copper (mg/kg)

Africa

3152

47.5

91.1

1288

745

44.0

2049

Americas

1716

27.8

4.7

3935

539

3.6

723

Asia

3642

42.0

20.3

917

658

8.7

Continent

Sulfur (mg/ kg)

Protein (%)

16.8

885

8.8

3.6

2859

4.6

1475

17.0

586

6.7

1767

28.9

9.7

2135

190

4.8

1125

3.7

203

3.9

Unknown

2661

26.9

18.7

1599

520

5.4

1227

9.5

528

6.3

Nutriomics of Millet Crops

Europe

Genetic Diversity for Grain Nutrients Content in Finger Millet

185

Ramachandra et  al. (1977) reported Fe to range from 4.2% to 8.47%, and Maloo et al. (1998) reported a range of 2.70–5.57% of iron on 12 finger millet varieties. Kadkol and Swaminathan (1954) reported that the proximate analysis of Fe of eight finger millet varieties ranged from 59 to 69 mg/kg. Balakrishna Rao et  al. (1973) reported the Fe range of 30–200 mg/kg for 15 finger millet genotypes. Indira and Naik (1971) reported the mean of Fe (130 mg/100 g) content on five finger millet genotypes.

9.2.3 zinc content Various studies have reported a wide range of Zn content depending on the gen­ otype used. Zinc content ranged from 0.4 to 37.3 mg/kg with a mean of 10.9 mg/ kg. Accessions from Zambia, Zaire, Uganda, Unknown, Kenya, and Nepal had the highest Zn content, while the lowest content was from accessions collected from Zimbabwe, Unknown, Zimbabwe, Unknown, India, and Zambia (Ojulong et  al., 2021). The highest diversity was expressed by collections from Zimbabwe, Kenya, Unknown, Uganda, and India. Upadhyaya et al. (2011) estimated the Zn content of the core millet collection to range from 18.4 to 48.9 mg/kg and a mean of 19.9 mg/ kg, with accessions from India, Ethiopia, Nigeria, Kenya, Nepal, and Unknown hav­ ing the highest content. Work by Ojulong (unpublished) found zinc content in 610 accessions to range from 10.2 to 101.3 mg/kg with a mean of 19.5 mg/kg compared to the global acceptable mean of 23.0 mg/kg (Table 9.1). Accessions with the high­ est Zn content were IE 3392 from Zimbabwe (101.3 mg/kg), IE 3492 from Kenya (37.2 mg/kg), IE 2689 Malawi (36.0 mg/kg), IE 6766 from Unknown (32.6 mg/ kg), and IE 3901 from Uganda (32.6 mg/kg). Accessions with the lowest Zn content were IE 2608 from Malawi (10.2 mg/kg), IE 4312 from Zimbabwe (10.2 mg/kg), IE 7199 from Kenya (10.9 mg/kg), IE 4116 from Uganda (11.1 mg/kg), and IE 5672 from Nepal 11.1 (mg/kg). Accessions from Germany (22.5 mg/kg), UK (21.9 mg/ kg), Zambia (21.2 mg/kg), Unknown (21.1 mg/kg), Nigeria (20.8 mg/kg), Mexico (20.5 mg/kg), Pakistan (20.3 mg/kg), Sri Lanka (19.9 mg/kg), Malawi (19.8 mg/ kg), and Nepal 19.7 (mg/kg) had the highest average Zn content. Greater diversity was observed among accessions from Zimbabwe (σ2 = 79.42), Nigeria (σ2 = 35.79), Malawi (σ2 = 34.71), Unknown (σ2 = 28.47), UK (σ2 = 25.11), Uganda (σ2 = 19.92), Zambia (σ2 = 16.62), Nepal (σ2 = 15.96), Ethiopia (σ2 = 15.01), Kenya (σ2 = 14.91), and India (σ2 = 14.46). At the continent level, Unknown had a higher Zn average (21.1 mg/kg), while Asia (19.7 mg/kg) and Africa (19.4 mg/kg) had values that were not significantly different. Previous work by Upadhyaya et al. (2006) using 622 core accessions found sub­ stantial variability in Zn content of 16.58–25.33 mg/kg and estimated PCV of 12.69% and GCV of 8.85%. Singh and Srivastava (2006) observed that the Zn content of 16 varieties of finger millet ranged from 9.2 to 25.5 mg/kg with a mean value of 13.4 mg/kg. They observed that as in other nutrients, released and farmer-preferred varie­ ties had lower levels. These results were compared well with what has been found in other crops. Madibela and Modiakgotla (2004) reported a mean of 20.5 mg/kg in for­ age finger millet and 29.1 mg/kg in straw of finger millet. In another study, reported a range of Zn content of 10 mg/kg to as high as 270 mg/kg, in 333 genotypes of finger

186

Nutriomics of Millet Crops

millet. However, Yamunarani et al. (2006) reported a narrow range of 15–65 mg/kg zinc on 35 finger millet genotypes.

9.2.4 Protein content Finger millet is known to contain a fair amount of protein compared to other cere­ als. Ojulong et  al. (2021) reported protein to range from 2.8% wt to 10.1% wt with a mean of 5.86% wt. The highest protein content was recorded in accessions collected from India, Kenya, Unknown, UK, Zimbabwe, and Uganda, while the lowest protein content was recorded in accessions collected from Kenya, India, Zimbabwe, India, Zambia, and Unknown. Upadhyaya et al. (2011) reported protein to range from 9.1% to 18.6% with a mean of 7.3% and the highest concentrations estimated in accessions originating from Nigeria, India, Burundi, Malawi, Zimba­ bwe, Cameroun, and Nepal. Upadhyaya et al. (2006), using 622 core accessions, found substantial variability in protein content of 6.00–11.09%. Other studies have reported variations in protein content from 5.6% to 12.7% (Ravindran, 1991; Rao, 1994; Marimurthu and Rajagopalan, 1995; Antony et  al., 1996; Vadivoo et  al., 1998; Mushtari, 1998; Bhatt et al., 2003). Singh and Srivastava (2006) analyzed 16 finger millet varieties and found that protein content ranged from 4.88% wt to 15.58% wt with a mean value of 9.73% wt. Vadivoo et al. (1998) analyzed 36 gen­ otypes of finger millet and reported their protein content in the range of 6.7 to 12.3 mg/100 g with the mean of 9.7 mg/100 g. In the study by Ojulong (unpublished), protein concentrations ranged from 9.1% to 18.6% with the highest concentrations estimated in IE 6928 from Unknown (18.6%), IE 2653 from Malawi (17.8%,) IE 2710 from Malawi (17.5%), IE 196 from India (17.4%), and IE 2118 from India (17.3%). The lowest concentrations were estimated in accessions IE 2393 from Kenya (9.1%), IE 2386 from Kenya (9.1%), IE 7179 from Kenya (9.3%), IE 7092 from Kenya (10.2%), and IE 6575 from Uganda (10.4%). Accessions with the highest average protein content by country originated from Mexico (16.5%), Sri Lanka (15.5%), Italy (15.2%), Congo (15.0%), Germany 14.9%), Nigeria (14.7%), Unknown (14.6%), Senegal (14.5%), Malawi (14.4%), and Zambia (14.4%).

9.2.5 trait correlation Correlation analysis among the different nutrients showed high correlation (