Crop Genetic Diversity in the Field and on the Farm: Principles and Applications in Research Practices 9780300220827

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Yale Agrarian Studies Series James C. Scott, series editor

The Agrarian Studies Series at Yale University Press seeks to publish outstanding and original interdisciplinary work on agriculture and rural society—for any period, in any location. Works of daring that question existing paradigms and fill abstract categories with the lived experience of rural people are especially encouraged. —James C. Scott, Series Editor James C. Scott, Seeing Like a State: How Certain Schemes to Improve the Human Condition Have Failed Steve Striffler, Chicken: The Dangerous Transformation of America’s Favorite Food Alissa Hamilton, Squeezed: What You Don’t Know About Orange Juice James C. Scott, The Art of Not Being Governed: An Anarchist History of Upland Southeast Asia Sara M. Gregg, Managing the Mountains: Land Use Planning, the New Deal, and the Creation of a Federal Landscape in Appalachia Michael R. Dove, The Banana Tree at the Gate: A History of Marginal Peoples and Global Markets in Borneo Edwin C. Hagenstein, Sara M. Gregg, and Brian Donahue, eds., American Georgics: Writings on Farming, Culture, and the Land Timothy Pachirat, Every Twelve Seconds: Industrialized Slaughter and the Politics of Sight Andrew Sluyter, Black Ranching Frontiers: African Cattle Herders of the Atlantic World, 1500–1900 Brian Gareau, From Precaution to Profit: Contemporary Challenges to Environmental Protection in the Montreal Protocol Kuntala Lahiri-Dutt and Gopa Samanta, Dancing with the River: People and Life on the Chars of South Asia Alon Tal, All the Trees of the Forest: Israel’s Woodlands from the Bible to the Present Felix Wemheuer, Famine Politics in Maoist China and the Soviet Union Jenny Leigh Smith, Works in Progress: Plans and Realities on Soviet Farms, 1930–1963 Graeme Auld, Constructing Private Governance: The Rise and Evolution of Forest, Coffee, and Fisheries Certification Jess Gilbert, Planning Democracy: Agrarian Intellectuals and the Intended New Deal Jessica Barnes and Michael R. Dove, eds., Climate Cultures: Anthropological Perspectives on Climate Change Shafqat Hussain, Remoteness and Modernity: Transformation and Continuity in Northern Pakistan Edward Dallam Melillo, Strangers on Familiar Soil: Rediscovering the Chile-California Connection, 1786–2008 Devra I. Jarvis, Toby Hodgkin, Anthony H. D. Brown, John Tuxill, Isabel López Noriega, Melinda Smale, and Bhuwon Sthapit, Crop Genetic Diversity in the Field and on the Farm: Principles and Applications in Research Practices For a complete list of titles in the Yale Agrarian Studies Series, visit yalebooks.com/ agrarian.

Crop Genetic Diversity in the Field and on the Farm Principles and Applications in Research Practices Devra I. Jarvis, Toby Hodgkin, Anthony H. D. Brown, John Tuxill, Isabel López Noriega, Melinda Smale, and Bhuwon Sthapit Foreword by Cristián Samper

New Haven & London

Published with assistance from the Mary Cady Tew Memorial Fund. As of December 1, 2006, the International Plant Genetic Resources Institute (IPGRI) and the International Network for the Improvement of Banana and Plantain (INIBAP) operate under the name “Bioversity International.” The designations employed and the presentations of material in this publication do not imply the expression of any opinion whatsoever on the part of the International Plant Genetic Resources Institute, and the Swiss Agency for Development and Cooperation, concerning the legal status of any country, territory, city, or area or of its authorities or concerning the delimitation of its frontiers or boundaries. The designations “developed” and “developing” economies are intended for statistical convenience and do not necessarily express a judgment about the stage reached by a particular country, territory, or area in the development process. The views expressed herein are those of the authors and do not necessarily represent those of Bioversity International and the Swiss Agency for Development and Cooperation. Copyright © 2016 by Bioversity International. All rights reserved. This book may not be reproduced, in whole or in part, including illustrations, in any form (beyond that copying permitted by Sections 107 and 108 of the U.S. Copyright Law and except by reviewers for the public press), without written permission from the publishers. Yale University Press books may be purchased in quantity for educational, business, or promotional use. For information, please e-mail [email protected] (U.S. office) or [email protected] (U.K. office). Set in Ehrhardt type by Integrated Publishing Solutions, Grand Rapids, Michigan. Printed in the United States of America. Library of Congress Control Number: 2015943897 ISBN 978-0-300-16112-0 (cloth: alk. paper) A catalogue record for this book is available from the British Library. This paper meets the requirements of ANSI/NISO Z39.48-1992 (Permanence of Paper). 10 9 8 7 6 5 4 3 2 1

To the many participants whose names and affiliations may not appear in this volume; numerous farmers, communities, development workers, educators, researchers, and government officials collaborated in the work presented in this work, and it is only through their efforts that this book is possible.

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Contents

Foreword by Cristián Samper  ix Preface xi Acknowledgments xiii chapter 1. Introduction and Overview  1 chapter 2. The Origins of Agriculture, Crop Domestication, and Centers of Diversity  13 chapter 3. Plant Genetic Resources, Conservation, and Politics: A History of International and National Developments Supporting the Conservation and Use of Crop Diversity  35 chapter 4. Diversity and Its Evolution in Crop Populations  64 chapter 5. Measuring Diversity in Crops  91 chapter 6. Abiotic and Biotic Components of Agricultural Ecosystems  126

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chapter 7. Diversity in, and Adaptation to, Adverse Environments OnFarm  154 chapter 8. Who Are the Managers of Diversity? Characterizing the Social, Cultural, and Economic Environments  191 chapter 9. Measuring the Values of On-Farm Diversity  212 chapter 10. Policy and Genetic Diversity On-Farm  232 chapter 11. Farm, Community, and Landscape: Genetic Diversity and Selection Pressures at Different Social, Spatial, and Temporal Scales  255 chapter 12. Strategies for Collaboration and Intervention  283 chapter 13. Conclusions: Traditional Varieties and Agricultural Productivity  313 appendix a. Software Packages Useful for Analyzing Molecular Data  327 appendix b. Geographic Information Systems and Remote Sensing Resources Available on the Internet  329 appendix c. A Selection of PPB Champions Through the Ages  330 Glossary  333 References  351 About the Authors  381 Index  383

Foreword

A

couple of years ago I had a chance to visit some of the indigenous communities in Otavalo, Ecuador. We gathered at a small wooden school at the end of a dirt road to meet with several women and learn about the crops they had in their farms. There was a large table covered with beans and corn, carefully laid out in rows, each of them with a small piece of paper and a name. It was a festival of colors, shapes, and sizes. I spent the next hour learning about each of these varieties, and how each of them had a different life history: some would grow better in dry seasons, others were more resistant to certain kind of insects, others were better to eat. It was several hundred years of knowledge condensed in a small space, kept alive by these farmers and their farming practices through generations. They recognized that crop diversity was important for the production of their agriculture ecosystems and were taking steps to ensure that this diversity continues to be available in their farming systems. The authors of this book are global experts in ecology, crop breeding, genetics, anthropology, economics, and policy who have come together to fill a long-standing gap, namely to place farmer-managed crop biodiversity squarely at the center of the science we need to feed the world and restore health to our productive landscapes. This work is more than a clarion call for biodiversity conservation; it is about using diversity to revitalize agriculture to feed a growing population. It represents nearly twenty years of global research with farmers and communities around the globe that maintain genetic diversity in the form of traditional varieties of a large number

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of crops including those neglected by science. This trans-disciplinary work is the definitive text that puts crop genetic diversity and agrobiodiversity within the scientific stream of evolutionary biology and adaptation to rapid changes in the anthropocene. A clear strength of this book is that it places the focus squarely on farmers and the crop genetic diversity they manage and create. The trans-­ disciplinary scientific documentation is tightly and coherently bound by placing farmers and their livelihoods, their services, and their responses to societal needs and change at the center of the analysis. It supports this approach with tools that document how much and what kind of diversity exists and where and when it is being used. The result is a compelling scientific text that shows students and other concerned readers that the results of farmer interactions with evolutionary process and genetic diversity within agriculture have produced perhaps the most important heritage we possess. As a biologist working in conservation in my own country, a mega­ biodiversity hot spot with its own important agricultural biodiversity, and in global institutions concerned with the ecology of all plants and animals, I am particularly pleased to finally see agricultural biodiversity placed squarely within evolutionary biology and human ecology. This book is an essential tool in training young scientists to produce the information and solutions that will contribute to healthy and resilient ecosystems for future generations. My hope is that it will be widely used in all agricultural schools as well as in training and research institutions concerned with biodiversity conservation, food security, and sustainable rural development. I hope some of you will have a chance to visit Otavalo or other rural communities and to learn from them and support the efforts to use our crop heritage to maintain and improve the production and resilience of rural livelihoods. The world will be richer and people healthier as a result of your work. Cristián Samper Wildlife Conservation Society Bronx, New York, May 2013

Preface

T

his book presents a unique vision, grounded in the experience of researching crop genetic diversity on-farm, as is evident in the plentiful examples and plates the book contains. The vision firmly links research on crop genetic diversity growing in farmers’ fields with conservation of this diversity and its use for sustainable production and for supporting rural livelihoods. The book covers principles and practices for gathering and using data that can come from traditional varieties and traditional farming systems through both participatory diagnostic and empirical approaches. These include methods for identifying ways of supporting farmers who grow these varieties. The book therefore introduces the reader to the several methods and information that the authors see as integral to understanding the extent, distribution, and nature of the genetic diversity still present in traditional varieties in farmers’ fields around the world. The book is an integrated monograph, rather than an edited volume of separately conceived chapters. It emphasizes the importance of bringing together biological (agronomic, ecological, genetic, etc.), social, economic, and cultural perspectives and data using multivariate analyses. For such a broad canvas, the book is a guide to the main motivating concepts (for example, that more diversity improves resilience) and research questions in the assessment, management, and use on-farm of crop genetic diversity. Rather than presenting a comprehensive listing of all the academic literature, or a detailed critical review of specific

xii   preface

subject areas, we refer the reader to a selection of relevant primary literature, which provides an entry enabling the reader to follow up on specific points. In a world of increasing environmental and social change, our view of the conservation and use of crop genetic diversity on-farm is one of dynamic evolution. We give evidence, integrated from several disciplines, that traditional varieties continue to be important to farmers and communities. This diversity can contribute to improving the sustainability of their agricultural production systems. Therefore, the principles and practices linking research to use of traditional varieties are treated within the context of improving the lives of farmers and rural communities. We emphasize the necessity of working together with farmers and rural communities in ways that ensure respect for all those involved. Traditional crop varieties continue to be important to the lives of millions of farmers around the world. They are used and maintained because they play a central role in the livelihood strategies of individual producers and rural communities. The current concerns to improve agricultural sustainability and to meet the challenges of change, especially climate change, suggest that these properties will be crucial for improving rural livelihoods and wider development objectives. Thus, this book offers the tools needed not only to investigate genetic diversity in traditional varieties, but also to support their ongoing conservation and use.

Acknowledgments

T

he work presented here would not have been possible without the time and energy of numerous farmers and their families and rural communities, whose collaboration enabled the core of the content of this volume. The authors thank the government of Switzerland (Swiss Agency for Development and Cooperation) for its generous financial support of this book. Many of the studies presented throughout this book were carried out as part of a global program undertaken by Bioversity International (formerly the International Plant Genetic Resources Institute—IPGRI), with the kind assistance from the governments of Switzerland (SDC— Swiss Agency for Development and Cooperation), The Netherlands (DGIS—Directorate-General for International Cooperation), Germany (BMZ/GTZ—Bundesministerium fur Wirtschaftliche Zusammenarbeit/ Deutsche Gesellschaft Für Technische Zusammenarbeit), Japan ( JICA), Canada (IDRC—International Development Research Centre), Spain, and Peru, as well as from the Global Environmental Facility (GEF) and the United Nations Environment Programme (UNEP), the United Nations Development Programme (UNDP), the Secretariat of the Convention on Biological Diversity (CBD), the Ford Foundation, the Food and Agriculture Organization of the United Nations (FAO), and the International Fund for Agricultural Development (IFAD). This book grew out of an earlier endeavor to create a “scientific basis for in situ conservation on farm,” which began in the mid-1990s and was first

xiv   acknowledgments

compiled in the informal volume, “A Training Guide for In Situ Conservation On Farm,” that was later translated into Russian, Spanish, Arabic, and Chinese for wide dissemination. Many colleagues gave their inputs to the original volume, and continued to do so over the long process of finalizing this book. They include the original members of the IPGRI “in situ family”—Burkina Faso: Didier Balma, Mamounata Belem, Madibaye Djimadoum, Issa Drabo, Omer Kabore, Tiganadaba Lodun, Jean-Baptiste Ouedraogo, Jérémy Ouedraogo, Mahamadi Ouedraogo, Oumar Ouedraogo, Mahamadou Sawadogo, Bernadette Some, Leopold Some, Jean-Baptiste Tignegre, Roger Zangre, Jean-Didier Zongo; Ethiopia: Zemede Asfaw, Abebe Demissie, Tesema Tanto; Hungary: Györgyi Bela, Ágnes Gyovai, László Holly, István Már, György Pataki; Mexico: Luis Arias-Reyes, Luis Burgos-May, Tania Carolina Camacho-Villa, Jaime Canul-Kú, Fernando Castillo-Gonzalez, Esmeralda Cázares-Sánchez, Jose Luis Chavez-Servia, Teresa Duch-Carballo, Jorge Duch-Gary, Víctor Manuel Interián-Kú, Luis Latournerie-Moreno, Diana Lope-Alzina, Fidel Márquez-Sánchez, Carmen Morales-Valderrama, Rafael Ortega-Paczka, Juan Rodriguez, Enrique Sauri-Duch, José Vidal Cob-Uicab, Elaine Yupit-Moo; Morocco: Ahmed Amri, Mustapha Arbaoui, Riad Balghi, Loubna Belqadi, Ahmed Birouk, Abdelaziz Bouisgaren, Mariam El Badraoui, Noureddine El Ouadghiri, Maria El Ouatil, Brahim Ezzahiri, Daoud Fanissi, Lamia Ghaouti, Abouchrif Hrou, Mohammed Mahdi, Hamdoun Mellas, Fattima Nassif, Keltoum Rh’Rib, Mohammed Sadiki, Seddik Saidi, Mouna Taghouti, Amar Tahiri, Bouchta Taik; Nepal: Annu Adhikari, Niranjan Adhikari, Resham Amagain, Jwala Bajracharya, Bimal Baniya, Krishna Baral, Bharat Bhandari, Bedanand Chaudhary, Pashupati Chaudhary, Devendra Gauchan, Salik Ram Gupta, Sanjaya Gyawali, Bal Krishna Joshi, Madhav Joshi, Ashok Mudwori, Yama Raj Panday, Diwakar Paudel, Indra Paudel, Ram Rana, Hom Nath Regmi, Deepak Rijal, K. K. Sherchand, Pitambar Shrestha, Pratap Shrestha, Surendra Shrestha, Deepa Singh, Abishkar Subedi, Anil Subedi, Sriram Subedi, Sharmila Sunwar, R. K. Tiwai, M. P. Upadhyaya, R. B. Yadav; Peru: María Arroyo, Luis Collado-Panduro, Alfredo Riesco, Ricardo SevillaPanizo, Roberto Valdivia; Turkey: Alptekin Karagoz, Ayfer Tan; Vietnam: Nguyen Tat Canh, Pham Hung Cuong, Din Vao Dao, Nguyen Ngoc De, Nguyen Phung Ha, Nguyen Thi-Ngoc Hue, La Tuan Nghia, Nguyen Huu Nghia, Dan Van Nien, Tran Van On, Huynh Quang Tin, Luu Ngoc Trinh, Ha Dinh Tuan, Truong Van Tuyen; IPGRI: Suha Ashtar, George Ayad, Aicha Bammoun, Abdullah Bari, Susan Bragdon, Paola De Santis,

acknowledgments    xv

Carmen de Vicente, Marlene Diekmann, Bernadette Dossou, Jan Engels, Pablo Eyzaguirre, Francois Gerson, Mikkel Grum, Luigi Guarino, Geoff Hawtin, Sara Hutchinson, Valerie Imbruce, Masa Iwanaga, Alder Keleman, Rami Khalil, Amanda King, Helen Klemick, Lorenzo Maggioni, Thomas Metz, Landon Myer, Deborah Nares, Noureddine Nasr, Julia Ndung’u-Skilton, Nicky O’Neill, Abdou Salam Ouedraogo, Stefano Padulosi, Paul Quek, V. Ramanatha Rao, Ken Riley, Percy Sajise, Patrizia Tazza, Awegechew Teshome, Helen Thompson, Judith Thompson, Imke Thormann, Muhabbat Turdieva, Raymond Voduohe, David Williams, Issiaka Zoungrana; other colleagues: Ekin Birol, Stephen Brush, Dindo Campilan, Linda Collette, David Cooper, Erle Ellis, Carlo Fadda, Elizabeth Fajber, Maria Fernandez, Esbern Friis-Hansen, Christina Grieder, Helen Jensen, Peter Kenmore, Liang Luohui, Leslie Lipper, Erika Meng, Christine Padoch, Roberto Papa, Jean Louis Pham, Rene Salazar, Dan Schoen, William Settle, Louise Sperling, Robert Tripp, and Bert Visser. These are followed by the many others who joined the “in situ family” later, including, Algeria: Malek Belguedj; Bolivia: Alejandro Bonifacio; China: Bao Shiying, Chen Bin, Chen Hong, Dai Liyuan, He Chengxin, Huang Yaqin, Huang Yuan, Li Chunyan, Long Chunlin, Lu Chunming, Ma Junhong, Peng Huaxian, Wang Fuyou, Wang Yunyue, Wu Jie, Xu Furong, Yang Xuehui, Yang Yayun, Yu Guo, Yuan Jie, Zhang Enlai, Zhang Feifei; Cuba: Leonor Castiñeiras, Zoila Fundora-Mayor, Tomás Shagarodsky; Ecuador: Catalina Bravo, Hugo Carrera, Jorge Coronel, Polivio Guaman, Carlos Nieto, Jose Ochoa, Juan Pazmino, Carmen Suarez, Cesar Tapia, Danilo Vera, Kyrgyzstan: Kubanichbek Turgunbaev; Mali: Amadou Sidibe; Morocco: Mustafa Bouzidi, Ghita Chlyeh, Selsabil Taoufiki, Nawal Touati, Abdelmalek Zirari; Niger: B. Danjimo; Tunisia: Abdelmajid Rhouma; Uganda: Joyce Adokorach, Grace Atuahire, Enid Katungi, Catherine Kiwuka, Marjorie Kyomugisha, John Wasswa Mulumba, Josephine Namaganda, Michael Otim, Pamela Paparu, Michael Ugen; Uzbekistan: Karim Baymetov; Bio­ versity International: Adriana Alercia, Bai Keyu, Mauricio Bellon, Nadia Bergamini, Evelyn Clancy, Carlo Fadda, Emile Frison, Michael Halewood, Michael Hermann, Deborah Karamura, Prem Mathur, Dunja Mijatovic, Rose Nankya, Paul Neate, Arshiya Noorani, Qi Wei, Marleni Ramirez, Frederik van Oudenhoven, Barbara Vinceti, Zhang Zongwen; and others: Rima Alcadi, Irene Bain, Walter de Boef, Salvatore Ceccarelli, Maria Finckh, Agnes Fonteneau, Barbara Gemmill, Stefania Grando, Hans Herren, Timothy Johns, Richard C. Johnson, Michael Milgroom, David Molden, Tim Mur-

xvi   acknowledgments

ray, Chris Pannkuk, Miguel Pinedo-Vasquez, Massimo Reverberi, Marieta Sakalian, Dan Skinner, Peter Trutmann, Eva Weltzien, John Witcombe, Denise Tompetrini, Leverett Hubbard; and, in addition, the many other development and extension workers, educators, researchers, and government officials who took part in the work that made this volume possible. Our specific thanks go to Daniela Horna for her review and additions to economic issues in Chapters 8 and 9, to David Williams for his review and comments on domestication for Chapter 2, to Alessandra Giuliani for her review and inputs to market chain analysis in Chapter 9, to Tim Murray and Marco Pautasso for their helpful suggestions to improve Chapter 7, to Paolo Colangelo for his inputs on statistical methods in Chapters 5, 6, and 7, to Pablo Eyzaguirre for adding suggestions to strengthen the human management components throughout the book, to Patrick Mulvany for his inputs to Chapter 12 regarding food sovereignty, and to Jan Engels, Christophe Bonneuil, and Marianna Fenzi for their stimulating inputs and views that helped shape Chapter 3. Special thanks also go to Collin McAvinchey for his assistance in searching for references and applying for permission to use published artwork, to Maria Garruccio and Francesca Giampieri for providing library support, to Silvia Ticconi for providing computer support at a moment’s notice, Safal Khatiwada for revising figures at the last minute, and to Bai Keyu, Nadia Bergamini, Michele Bozzano, Nora Capozio, Carmen de Vicente, Carlo Fadda, Yasuyuki Morimoto, Rose Nankya, Stefano Padulosi, Peng Huaxian, Devin R. See, Ambika Thapa, Raymond Vodouhe, Camilla Zanzanaini, and the Bioversity Communications group for their help in rapidly locating high-resolution photos in time for the volume. Our particular thanks to Paola De Santis for her inputs, logistics, and innovative suggestions from beginning to end of the preparation of this book. Raffaella Krista Jarvis assisted in preparing figures for this volume and together with her father and her grandmother, Lillian B. Jarvis, provided encouragement and support to her mother patiently throughout the long writing process. We owe our very special thanks to Linda Sears, for her inspired, precise, and rapid editing of this volume; she took our diverse inputs and styles and ensured that we wove together the final product presented here.

Crop Genetic Diversity in the Field and on the Farm

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chapter 1

Introduction and Overview

Introduction This book is about the crop genetic diversity that is maintained and used in farmers’ fields around the world. In particular, it is about the diversity that is found in the traditional varieties or landraces developed and maintained by farmers over centuries: our crop heritage. The major part of the book describes principles and practices for gathering and using data on traditional varieties and traditional farming systems through both participatory diagnostic and empirical approaches to link research on crop genetic diversity growing in farmers’ fields with conservation of this diversity and its use for sustainable production and for supporting rural livelihoods. Various terms have been used to describe the varieties developed and maintained by farmers over many centuries in their production systems. These include landraces, farmer varieties, and folk varieties. Throughout this book we use the term “traditional varieties” unless the context requires a different term. Over millennia, farmers domesticated plant species and created the crops and traditional varieties we know today. They maintained and modified the genetic diversity found within different plant species through their management of production systems, the farming practices that they used, and the ways in which they maintained and selected crops and varieties to secure their own livelihoods and produce a surplus to help feed the world’s growing population.

   introduction and overview

The past 100–150 years have seen an increasing use of chemical inputs, mechanization, and a dependence on uniform varieties newly developed by professional plant breeders. These changes led to a simplification of many production systems and a reduced dependence on biological diversity, which, in traditional farming systems, provides such benefits as pest and disease control, soil quality maintenance, and organic fertilizers. As agriculture modernized, and as new uniform varieties were introduced, it was widely assumed that traditional varieties would rapidly disappear, given that they were poorly adapted to modern farming practices and often had relatively low yields. While they have been replaced in many farming systems, contrary to expectations they have remained important to many smallholder farmers throughout the world, especially those who farm in less favorable production environments. The value of traditional varieties in many different farming systems was recognized by a number of researchers in the 1980s and 1990s, particularly Altieri and Merrick (1987), and Brush (1995, 1999). The International Fund for Agricultural Development (IFAD) estimates that there are currently about 500 million smallholder farms, often within or close to biodiversity-rich areas. In the developing world, smallscale family farms support almost 2 billion people and produce about 80 percent of the food consumed in Asia and sub-Saharan Africa. The continuing use of traditional varieties by large numbers of such farmers reflects the value of these varieties in low-input farming conditions and their continuing importance as part of the livelihood strategies of poor farmers (see Jarvis et al. 2011 for further discussion of the value of traditional varieties). There is now a growing consensus that many modern agricultural practices are unsustainable, causing environmental damage and a loss of the ecosystem function that underlies agricultural production (MA 2005; Go-Science/Foresight 2011). This has led to a renewed interest in agricultural practices that take greater account of biological processes and maintain or improve ecosystem services (FAO 2012) and in the ways in which biological diversity can be used to improve sustainability and productivity (for example, sustainable intensification, FAO 2012). Climate change also has led to an increased concern with the maintenance and use of the biodiversity in agricultural ecosystems, particularly in crop and livestock diversity. In many parts of the world climate change will lead to changed production environments, and often this will require new and different crop varieties and animal breeds (Zimmerer 2010; Hodgkin and Bordoni 2012).



introduction and overview   

Two other factors favor a continuing interest in the maintenance and use of traditional varieties. First, there is a growing concern that the food we eat should be produced in ways that do not prejudice our health, the health of producers, or the health of the environment (Pollan 2006). Second, there is a developing recognition of the importance of food sovereignty, where those who produce, distribute, and consume food are at the center of food and agricultural systems and policies, rather than solely responding to the demands of markets and corporations that reduce food to internationally tradable commodities (Practical Action 2011). While the increasing recognition of the value of agrobiodiversity and of the importance of traditional crop varieties is important, it is often unsupported by real information about how much and what kind of diversity exists, and where and when it should be used. Over the past 20 years a growing body of work has provided a set of experiences, practices, and procedures that address this lack of information. Work in many countries has explored the maintenance and use of traditional crop varieties, the amounts of diversity present, the ways they are maintained, and the factors that ensure their continued relevance for smallholder farmers. The results of this work are brought together in this book, together with some relevant background so as to provide the information, tools, and methods that can be used to ensure that the diversity found in traditional varieties can be quantified, and its value understood, and its continuing maintenance by farmers supported, where this is their preferred option. This book takes the view that traditional varieties and, more generally, genetic diversity within crop species continue to play an important role in production systems around the world and constitute a relevant component of the changing face of agricultural production. Crop Genetic Diversity and Traditional Varieties Crop genetic diversity includes all the diversity found between and within the different crops and varieties that are grown throughout the world. It includes all the diversity of characters and the variation in the genes that determine their expression. Within any crop, this genetic diversity provides the basis for the development, recognition, and evolution of traditional varieties. One of the best descriptions of traditional varieties (or landraces, as he called them) was given by Harlan (1975), who stated that: “landraces have a certain genetic integrity. They are recognizable morpho-

   introduction and overview

logically; farmers have names for them and different landraces are understood to differ in adaptation to soil type, time of seeding, date of maturity, height, nutritive value, use and other properties. Most important, they are genetically diverse. Such balanced populations—variable, in equilibrium with both environment and pathogens, and genetically dynamic—are our heritage from past generations and cultivators.” Harlan’s brief description captures the essential nature of traditional varieties and many of the issues and questions that lie at the heart of this book. What is the nature or content of the genetic integrity that Harlan identifies? What morphological traits are important to identity, under what conditions for different crops? How consistent is the use of names to confer identity? What is the nature of adaptation and how do farmers balance the different concerns of adaptation to environment, fitting in with different production systems and meeting different needs? Most important, how is the maintenance of genetic diversity balanced against concerns such as maximizing production or ensuring resistance against specific pests or diseases? What is the nature of the balance that maintains both the variability and the equilibrium of the populations that Harlan refers to, and how is it maintained over generations of farmers and cultivators? As noted above, traditional varieties are associated with what is commonly called “low input” agriculture. In comparison with modern varieties developed by plant breeders, they may be low-yielding but appear to offer stability and risk avoidance; that is, they will produce something under adverse conditions and exposure to climatic extremes or disease epidemics. They are the hallmark of subsistence farming, helping to keep farmer and family alive until the next crop and often providing a surplus for sale or exchange. The continued maintenance of traditional varieties in the agricultural production system also meets a wider social need for evolving and adapted materials to meet changing production needs and challenges. As part of an analysis of the ways in which the maintenance and use of traditional varieties for sustainable agriculture might be supported, Jarvis et al. (2011) have reviewed the reasons why farmers maintain traditional varieties. They cite evidence that traditional crop varieties are maintained inter alia, because of their adaptation to marginal or specific agricultural ecosystems and to heterogeneous and variable environments or production conditions, as insurance against environmental and other risks, to meet changing market demands, for pest and disease management, because of their post-harvest characteristics (including their nutritional value), to meet



introduction and overview   

the social and economic conditions of production, and to support cultural and religious practices. They propose that the diversity of traditional varieties, and the diversity within these varieties, allow for the adaptation and evolution needed by farmers to meet the challenges of difficult, uncertain, and changing production conditions. This suggests that key properties of traditional varieties include their ability to produce under conditions of biotic or abiotic stress, their possession of adaptive genes and gene complexes, their genetic heterogeneity, and their local social-cultural value. A further characteristic that is often ascribed to traditional varieties is the favorable interaction of the different components or individuals in a population so that they complement, rather than compete with, each other. There is certainly evidence from many crops that traditional varieties possess useful genes that confer improved performance, resistance to many pests and diseases, and tolerance of abiotic stress (Frankel et al. 1995). In some production environments, traditional varieties have outperformed modern varieties under stress conditions. Experiments conducted with barley (Ceccarelli 1994) have shown that under extreme conditions of drought and salinity, traditional barley varieties performed better than modern cultivars. There is also evidence that the possession of heterogeneity contributes to the disease resistance that can be found in many traditional varieties. Work on mixtures of varieties and on multilines (lines that are near-isogenic except for the resistance gene) has shown that heterogeneity can reduce disease damage and so provide a buffering effect, or “mixture effect” noted by Wolfe (1985:255): “Host mixtures may restrict the spread of disease considerably relative to the mean of their components, provided the components differ in their susceptibility.” Rural communities often maintain a large number of distinct and identifiable traditional varieties, providing another level of heterogeneity important to the production strategies of the communities and farmers. This seems to be most evident in the case of self-fertilized and vegetatively propagated major crops such as rice, potato, and cassava (Rana et al. 2007; Brush et al. 1995; Salick et al. 1997). Where large numbers of varieties are recognized and maintained, each has its own specific characteristics and, as noted by Harlan, they are used by the community in different ways that are complementary—some may be more or less productive staples, others may be used for ceremonies, still others may be adapted to specific fields with cultivation problems or to meet certain seasonality requirements.

   introduction and overview

It also has been suggested that traditional varieties consist of complementary genotypes which in some way “fit together” to form a population of plants that can make best use of limited resources or confront stresses of different kinds and are, because of this characteristic, particularly adapted to low-input farming. This is a much more controversial proposition. Marshall (1977) found little evidence of such interactions in mixtures, although studies on the barley composite cross-populations have suggested that positive interactions may occur (Allard and Adams 1969). Major Crops and Minor Crops Agricultural research and development have focused on major crops to the neglect of the many other crops that are important to human well-being (Mangelsdorf 1966; Kahane et al. 2013). Three crops (wheat, rice, and maize) provide 50 percent of the world’s calorie intake, and 15 crops supply 90 percent of our total food intake (Ceccarelli 2009). Yet, in farming communities where traditional varieties remain important, a wider range of crops often can be found than in agricultural systems dominated by modern varieties. The less important crops have been given various labels such as minor, neglected, underutilized, or even “lost crops.” Minor crops tend to include any that fall outside the group of globally important crops that dominate modern production systems. They may be globally distributed (such as buckwheat), regionally significant such as Lathyrus sativus in India (which contains significant anti-nutritional factors), or very local such as the minor roots and tubers (for example, maca and ulluco) of the Andes. Neglected crops are usually those neglected by modern agriculture while still important to local communities. Examples of such crops would include tef from Ethiopia or fonio from West Africa. Underutilized species (following the description used by the National Academy of Sciences [1975]) include those crops that are believed to have potential for expansion but which are not, for some reason, adapted to modern agriculture or current production practices. The categories often overlap, and there is obviously a continuous gradation from rather well-known crops such as sesame, buckwheat, and bambarra groundnut to those which are extremely local and almost completely marginalized, such as some of the minor millets in southern India (for example, Panicum sumatrense and Paspalum scrobiculatum). In traditional farming systems these crops are important because they

introduction and overview   



contribute directly to local livelihoods and to health and nutrition, provide a source of income, and still constitute a part of the total production system supporting the functionality of the agro-ecosystem (for example, as part of rotations the provision of green manure, or the crops’ ability to produce on the most marginal lands). Often traditional varieties are much less well defined in such minor crops. The amount of genetic diversity present in these crops is also much less well known. Sometimes such small populations are maintained (one or two plants per household in the case of the open-­pollinated sponge gourd in Nepalese mid-hill villages) that they raise interesting questions in their own right about their maintenance and improvement by farmers. The Book’s Contents If traditional varieties continue to be important to farmers and communities and to make definite contributions, and if they are likely to be important in improving sustainability, then we need to understand how to help maintain them within the context of improving the lives of farmers and rural communities and the sustainability of production systems. This book therefore provides tools for identifying ways of supporting farmers who wish to maintain these varieties. It provides principles for gathering and using real data of the kind that can come from traditional varieties and traditional farming systems through both participatory diagnostic and empirical approaches. It emphasizes the importance of bringing together biological (agronomic, ecological, genetic, etc.), social, economic, and cultural perspectives, and of respect for all partners involved. A common theme throughout the book is the way in which traditional varieties are able to adapt to changing conditions. This adaptability involves ensuring the existence of planting materials that will continue to evolve to (1) cope with change (environmental, economic, social), and (2) provide resilience over time under constantly changing conditions. In this regard, an important property of these varieties is their evolutionary capacity. With this in mind, tools centered on deciphering what is involved in maintaining the evolutionary capacity in production systems are presented. This is not a simple task, as when we talk about maintaining evolutionary capacity, we may ask the questions: For what use? For whose use? How does the maintenance and use of traditional crop varieties support food sovereignty and the rights of the farmers and communities who maintain and use these

   introduction and overview

varieties? How much diversity do we need to have to allow for this evolution, be it evolutionary capacity for crop improvement (the genetic makeup of the crops we will need for future conditions), or for the evolving needs of using diversity in the farmers’ production systems for productivity and resilience? Chapters 2 and 3 of this book provide some background information on the origin of today’s crops and on the development of international and national agendas on the conservation and use of their genetic diversity. Chapter 2 describes the processes of domestication, the characters or traits involved, and the genetic changes that occurred during domestication processes. The importance of centers of genetic diversity and centers of origin of crops is also described. Chapter 3 provides a historical picture of the development of work on the deliberate conservation of plant genetic resources. The development and evolution of national programs on plant genetic resources, and the origins and development of an international commitment to plant genetic resources conservation, are examined, and the work of the Convention on Biological Diversity, the FAO Commission on Genetic Resources, and the International Treaty of Plant Genetic Resources for Food and Agriculture is described. The chapter also explores the different ways in which indigenous peoples, rural communities, national programs on genetic resources, and international organizations approach questions on conservation and define use of crop genetic diversity. Chapter 4 presents the basic concepts of genetic diversity and its measurement in plant populations, including how population size and evolutionary forces—selection, mutation, recombination, and migration—affect the extent and distribution of genetic diversity, and the effects of reproductive biology, breeding (mating) systems, pollination, and seed dispersal on genetics are introduced. Chapter 5 aims at providing the reader with tools and methods in which data are obtained and analyzed to understand the extent and distribution of genetic diversity in crops, from agronomic to biochemical to molecular methods. Methods presented include those used when working with farmers to obtain information and data on the extent and distribution of diversity, and on how farmers themselves view and classify diversity. The chapter emphasizes the importance of participatory approaches and of having clear common agreements with the farmer communities and prior consent of all parties concerning data collection and data use. Differences in altitude, slope, aspect, rainfall, temperature, light intensity, wind velocity, and levels of CO2, together with the texture, fertility,



introduction and overview   

and toxicity of the soil, and the pollinators, pests, and belowground organisms all play a role in including the extent and distribution of traditional crop varieties in agricultural ecosystems. Chapter 6 provides basic tools to identify and characterize key environmental factors affecting crop genetic diversity and productivity. These include tools for collecting and analyzing information on farmers’ knowledge of their biophysical environment and the perceptions on the ecological processes that surround them. The chapter also includes introductory information on ecosystem services and the potential role of crop genetic diversity in supporting ecosystem functions. Chapter 7 explores the evolution of crop varieties in stress environments, providing basic principles of adaptation to stress in adverse environments, and genetic variation within and among traditional crop varieties in respect to environmental stresses. The chapter presents basic concepts and tools to measure stress tolerance and stress resistance, and abiotic and biotic stresses, by comparing modern and traditional varieties. The use of a variety deliberately chosen as adapted to a specific environment is distinguished from the use of diversity per se as insurance to maintain productivity in heterogeneous environments, or under changing climates. A more detailed discussion is given on the interrelationship of (1) genetic diversity, (2) reducing current damage, and (3) reducing genetic vulnerability, or reducing the potential of future crop loss from pests and diseases. Culture can be defined as an expression of the interaction over time between communities and their natural, historical, and social environments. These environments not only satisfy people’s material needs for food, fodder, water, medicines, and other natural resources, but also provide the bases for ethical values, concepts of sacred spaces, aesthetic experiences, and personal or group identities derived from the local surroundings. Chapter 8 is about characterizing farmers and farming communities who maintain crop genetic diversity within their social, cultural, and economic environments. Characteristics to consider include age, gender, kinship, education, economic status, relative wealth, social status, ethnicity, and language. Tools for characterizing social relationships and social capital are also fundamental for understanding the role humans play in using and managing their crop genetic resources. Both qualitative and quantitative methods are introduced to analyze how socially, culturally, and economically determined roles shape patterns of crop genetic diversity among farmers and their households, networks, or formal associations of farmers and farming communities. Chapter 9 is geared toward providing tools and methods to value on-

   introduction and overview

farm diversity from an economic perspective. A starting point is differentiating among the private and public values of crop genetic resources in the production systems and the provision of tools to determine what economists call “total economic value.” The chapter discusses “varietal choice” (which varieties to grow) and on what proportions of crop area to grow each variety. Guidance is provided to test relationships between social, cultural, and economic factors and on-farm diversity and to identify external factors that affect farmers’ decision making about diversity. This includes understanding the direct yield effect of crop genetic diversity, which is related to the effect of the use of productive inputs like fertilizer, labor, or seed type and can have a direct effect on the performance of the crop, and the damage abatement effect, related to the effect of the use of control inputs like insecticides, fungicides, or resistant varieties that do not directly increase the output but do reduce the effect of pests or diseases on the crop. Econometric models are introduced to test causal relationships and test them with multiple regression analysis. Chapter 9 also includes tools for understanding the market and nonmarket values of crop genetic diversity and presents principles for creating a market chain approach to the use of crop genetic diversity. Chapter 10 explains how policies and legal frameworks create disincen­ tives or obstacles for farmers to maintain and manage plant diversity and presents an overview of concepts and methods to analyze and develop policy measures oriented toward the creation of incentives for farmers to continue using plant genetic resources on-farm, in line with the concept of farmers’ rights as recognized by the International Treaty on Plant Genetic Resources for Food and Agriculture. The chapter discusses how policy instruments ensure that technologies respond to the purpose of agriculture modernization. These include seed laws, issues of intellectual property rights, and alternative approaches to plant variety protection. The chapter provides a framework for developing a policy process including identifying areas for policy reform, understanding the context in which the policy process takes place, and putting in place participatory tools for policy research and development. The chapter also provides tools for identifying stakeholders to be involved in policy evaluation and formulation. Chapter 11 takes a more detailed look at the processes that continue to shape the structure and evolution of crop diversity from the perspective of crop production. The ways in which different evolutionary forces such as migration, gene flow, and selection can influence diversity at different

introduction and overview   



stages of the crop production process are described. The importance of selection as a major evolutionary force is discussed in a separate section. Seed systems (the processes and practices used by farmers and communities to ensure that seed of traditional varieties is available) are described, as this constitutes a central feature of the maintenance of traditional varieties. A final section considers questions of spatial and temporal scale and the ways in which community management of resources can influence the maintenance of traditional varieties. Developing and carrying out a program that supports the use and conservation of crop genetic diversity in the agricultural production system requires more than resources and the expertise to collect and assimilate research data. It also requires cultivating partnerships among many individuals and institutions and mobilizing community-based organizations for concrete actions. Although collaborative aspects may be easily overlooked, they are a fundamental element of a successful on-farm initiative. Chapter 12 first presents the range of actors, the types of relationships that are necessary, and the ways in which responsibilities and benefits can be shared. Then, the chapter introduces a portfolio approach using the types of information covered in earlier chapters to identify a range of actions to support the conservation and use of traditional crop varieties. The final chapter brings the reader back to the core question of why we need to keep the genetic diversity of our crop heritage in the agricultural production system. Further Reading Altieri, Miguel A. 1995. Agroecology: The Science of Sustainable Agriculture, 2nd ed. Westview Press, Boulder, CO. Brush, S. B. 1999. Genes in the Field: On-Farm Conservation of Crop Diversity. IPGRI/ IDRC/Lewis, Ottawa, ON. FAO. 2012. Save and Grow. FAO, Rome. Frankel, O. H., A. H. D. Brown, and J. J. Burdon. 1995. The Conservation of Plant Biodiversity. Cambridge University Press, Cambridge. Harlan, J. R. 1975. Crops and Man. American Society of Agronomy, Madison, WI. Pollan, M. 2006. The Omnivore’s Dilemma. Bloomsbury, London. Zimmerer, K. S. 2010. “Biological Diversity in Agriculture and Global Change.” Annual Review of Environmental Resources 35:137–66.

Plate 1. Traditional varieties, also termed landraces, farmer varieties, or folk varieties, are crop varieties often harboring some genetic variability, yet with a certain genetic integrity. Farmers recognize a traditional variety’s characteristics, select for traits they desire, and usually give it a name. Upper left: traditional rice varieties from Nepal. Upper right: Moroccan farmer separating seeds of two faba bean varieties. Lower left: traditional taro varieties planted in a local diversity demonstration plot in Hue, Vietnam. Lower right: Burkinabe woman describing her local pearl millet varieties. Photo credits: R. Vodouhe (upper left), B. Sthapit (lower left), D. Jarvis (lower right and upper right).

chapter 2

The Origins of Agriculture, Crop Domestication, and Centers of Diversity

B

y the end of this chapter the reader should have an understanding of:

• The emergence of agriculture and of crops. • The characters or traits associated with domestication. • The processes involved in domestication and the genetic changes that have occurred. • Centers of crop diversity around the world. The first half of this chapter provides an overview of the origins of agriculture and of crop domestication, the processes that were involved, and the changes that occurred in the species that humans chose to domesticate. The diversity present in crops today reflects the processes of domestication and the subsequent history of different crops, as human societies changed and developed and as humans moved around the globe. Certain parts of the world are associated with high levels of diversity, and these “centers of diversity” often seem to have been associated with the domestication of many of our major crops and with the subsequent evolution of the great range of different types found today. The second half of the chapter describes the identification of these centers of diversity and the subsequent development of the concept. The continuing process of domestication and evolution—and the changing ways in which farmers, communities, and societies manage their crops—continue

   origins

to influence the changing patterns of diversity that we see today, both within and outside the accepted centers of diversity. Comprehensive treatments of crop evolution and domestication can be found in Harris and Hillman (1989), Barker (2009), and, from an archaeological perspective, Weiss et al. (2004). More recent treatments that include the information from molecular studies include reviews by Fuller (2007) for Old World crops, Pickersgill (2007) for New World crops, Burger et al. (2008) and Purugganan and Fuller (2009) for the process of domestication, and Miller and Gross (2011) on differences in domestication of annual versus perennial crops. Descriptions of the domestication pathways for individual crops can be found in Sauer (1993) and in Smartt and Simmonds (1995). The Origins of Agriculture and Crops The archaeological record shows that humans ate wild grains at least 20,000–25,000 years ago (Weiss et al. 2004). Foraging began to give way to cultivation about 13,000–11,000 years ago during the Epipalaeolithic and Neolithic periods. In the Americas domesticates appeared not long after the arrival of humans, at least 13,000 years ago. The evidence suggests that hunter-gatherer groups independently began cultivating food plants in as many as 24 different regions of the world. Grain crops were the focus of early cultivation in perhaps 13 different regions (Purugganan and Fuller 2009). Over the next few thousand years, the domestication of many different species occurred in such diverse regions of the world as the Middle East (the Fertile Crescent and the watersheds of the Euphrates and Tigris Rivers), Mesoamerica, the central Andes, sub-Saharan West Africa, East African uplands and Ethiopia, different regions of India, New Guinea and Wallacea (Indonesia and New Guinea), and Central Asia. Table 2.1 summarizes information on crops, area of domestication, and the presumed dates (where known) by which they were domesticated. In the Middle East, the first crops that were domesticated included einkorn and emmer wheat, barley, faba bean, pea, chickpea, and lentil, together with olive and fig. In Asia, domestication of foxtail millet took place in northern China while domestication of japonica rice occurred in the ­Yangtze basin, and Indica rice was probably domesticated in India. Squash and maize domestication has been dated as occurring 10,000–7,000 years ago in Meso­ america, while in South America, Phaseolus vulgaris (common bean), sweet

table 2.1.  where and when some major seed and root crops were domesticated.

Location Eastern North America Mesoamerica

Northern lowland neotropics in South America

Andes

West Africa

East Sudanic Africa East African uplands Near East

Central Asia India

China

New Guinea and ­Wallacea

Crop Chenopodium berlandieri Helianthus annuus—sunflower Cucurbita pepo—squash Zea mays—maize Phaseolus vulgaris—common bean Manihot esculenta—cassava Cucurbita moschata—squash Ipomoea batatas—sweet potato Arapis hypogaea—peanut Chenopodium quinoa—quinoa Solanum tuberosum—potato Oxalis tuberosa—oca Phaseolus lunatus—lima bean Phaseolus vulgaris—common bean Pennisetum glaucum—pearl millet Vigna unguiculata—cowpea Oryza glaberrima—African rice Dioscorea rotunda—yam Sorghum bicolor—sorghum Eragrostis tef—tef Eleusine corocana—finger millet Triticum spp.—durum wheat, bread wheat Hordeum vulgare—barley Lens culinaris—lentil Pisum sativum—pea Cicer arietinum—chickpea Vicia faba—broad bean Malus  domestica—apple Pyrus communis—pear Vigna mungo—black gram Vigna radiata—mung bean Oryza sativa ssp. indica—rice Setaria italica—foxtail millet Glycine max—soybean Oryza sativa ssp. japonica—rice Colocasia—taro Prunus persica—peach Colocasia esculenta—taro Dioscorea esculenta—yam Musa acuminata—banana

Adapted from Purugganan and Fuller (2009) and Miller and Gross (2011).

Date when domesticated (years before present) 4500–4000 4000 10,000 9000–2500 6000 9000–8000 4000 8500 5000 8000 3000 5000 4000 4500 3700 4000 4000? 13,000–10,000

5000 8500–4500 8000 4500? 9000–6000 Uncertain 3000? 7000

   origins

potato, and potato domestication has been dated to about 8,000 years ago with the possible earlier domestication of Phaseolus lunatus (lima bean) and Cucurbita ecuadoriensis (perhaps as early as 10,000 years ago). In Africa, where domestication is likely to have occurred later (between 5,000 and 3,000 years ago), crops such as finger millet (Eleusine coracana), pearl millet (Pennisetum glaucum), and sorghum (Sorghum bicolor) were probably domesticated at the southern margin of the Sahara (Barker 2009). Bottle gourd (Lagenaria siceraria), a container crop rather than a food crop, is indigenous to Africa and may have been domesticated there as much as 10,000 years ago. According to the archaeological evidence, bottle gourd was carried from Asia to the Americas during the late Pleistocene (Erickson et al. 2006), implying that this species was one of the earliest to be brought under domestication (Zeder et al. 2006). The Changes Associated with Domestication A fairly limited number of plant families provide most of our domesticated species. The most important of these include the Gramineae (cereals and sugarcane), Leguminosae (pulses), Solanaceae (potato, tomato, and pepper), Cucurbitaceae (squash, cucumber, melon, and gourd), Umbelliferae (vegetables, herbs, and spices), Cruciferae (vegetables and oilseeds), Rosaceae (temperate fruit trees), and Palmae (coconut, oil palm). Within these families certain genera have proved to be particularly important such as Allium (onion), Brassica (oilseeds and the different vegetables of the cabbage family), Phaseolus (different beans), Dioscorea (true yam), and Gossypium (cotton). Domestication is the selective process by which human use of plant and animal species leads to morphological and physiological changes that distinguish today’s domesticated taxa from their wild ancestors and relatives (Hancock 2004; Purugganan and Fuller 2009). Unraveling the history of domestication in individual crops brings together archaeological and historical evidence with studies on genetics and gene expression, the current patterns of distribution, and the ways in which crops are used in different societies. Domestication has adapted crop species to human cultivation. It has included selection for traits that lead to successful seed germination and growth in disturbed and managed environments. The traits make harvesting easier and increase the amount and availability of the desired product



origins   

(for example, grain, fruit, floral parts, leaves, stems, root, and tuber). Domestication involves both conscious selection for desired attributes and unconscious selection for characteristics associated with the processes of cultivation and harvest (that is, the changing agro-ecological environment in which the plants are grown). The process of domestication continues today, particularly in areas where farmers continue to bring wild plants into their cultivated production systems. Typical changes that accompanied domestication in cereal crops such as wheat, barley, rice, millet, and sorghum were the loss of shattering (free dispersal of seed as it becomes mature) and an increase in grain size. Other trends include the loss of seed dormancy (which gave more uniform germination after sowing), synchronization of tillering, a more determinate growth habit, and more uniform maturity. In maize, a reduction in branching of the plant to generate a single large stem, and a reduction in the number of male and female inflorescences, accompanied these changes. Grain legume crops such as common bean, lentil, chickpea, soybean, and faba bean showed similar changes with a more uniform ripening of pods, an increase in seed size, and a more determinate growth habit. In oilseed crops such as sunflower and oilseed Brassica, similar seed characteristics found favor, although in some of these crops the process of domestication is less complete; for example, pod shattering remains common in sesame and is often a problem in traditional oilseed Brassica varieties. In crops such as cassava, yam, sweet potato, and potato, domestication resulted in significant increases in size of the harvested root or tuber storage organ. In these crops, such selection also led to the partial or complete loss of seed production, with vegetative propagation becoming the norm. Significant increases in size of the particular organ consumed are also characteristic of most vegetable crops—bulbs in onion, leaves in cabbage and lettuce, immature floral buds in cauliflower—and the fruits of squash, pepper, tomato, aubergine, okra, and banana, as well as perennial fruit trees such as apple, pear, olive, date, mango, avocado, and many other fruits. Table 2.2 lists traits associated with domestication, and table 2.3 gives examples of the crops and of changes that occur. In some crops, current crop diversity can be traced to a single place and appears to have involved a single process that has given rise to a single lineage that can be traced to a single gene line. This appears to be the case for maize, sunflower, and einkorn wheat, although these crops may have been

   origins

table 2.2.  traits commonly associated with domestication. Traits commonly associated with domestication Increased reproductive effort Larger seeds and fruit More even and more rapid germination Germination from greater soil depth More uniform ripening Non-dehiscent fruits and seeds Self-pollination Trend to annuality and annual production cycles Increased palatability Color changes Loss of defensive structures Increased local adaptations Increased variability around certain key performance traits

domesticated more than once, with the other lineages dying out or being replaced. This also may have been the case in rice, according to a recent molecular analysis (Molina et al. 2011). In the cases of common bean and squash at least two separate lineages can be identified, indicating separate domestication in different places (see box 2.1 for common bean domestication). In the case of some major crops such as tetraploid wheat and barley, the number of times the crop has been domesticated remains uncertain (Burger et al. 2008). Even where crops eventually developed reproductive barriers with the wild species from which they were derived, there were probably long periods where gene flow between the putative crop and its wild ancestor took place. In many crops, and particularly in fruit trees, domestication involved a number of locations (often different geographic areas) with complex histories of hybridization and selection of new types by different societies. Domestication often has involved changes in the reproductive biology of the crop as compared with its wild ancestor. Many crops such as rice, tomato, and diploid oilseed brassicas (Brassica rapa) are self-fertile, while their wild ancestors and related wild species in the genus are outbreeders. This is also the case for a number of important fruit and nut crops such as almond, grape, and papaya. The production of seed in root and tuber crops



origins   

is often reduced or more or less entirely suppressed, as in the case of yam, cassava, and potato. Cultivated bananas almost never produce seed, which makes crop improvement and the production of new varieties in the crop extremely difficult. Sterility barriers may be complete or partial and appear to have developed over generations through a range of different mechanisms that include physical separation, alterations in flowering time, and cytological changes such as altered levels of ploidy and intra-chromosome rearrangements that prevent successful pairing at meiosis. About four out of five crops are autopolyploid, amphidiploid, or both (Hancock 2004), which provides another isolation mechanism and may well have provided other advantages from the point of view of human cultivation, such as larger size. A classic crop complex in which amphiploidy has played a major role is the Brassica complex, where three amphidiploid crop species (Brassica carinata, B. juncea, and B. napus) are the result of hybridization between three diploid species (B. nigra, B. oleracea, and B. rapa). Domesticated crops generally contain only a limited part of the diversity found in their ancestral species or wild relatives. Often, this has resulted from a single domestication process as in the case of wheat or lentil, or from a limited number of processes, as is likely the case for Phaseolus vulgaris. These occurred in specific locations and involved a limited part of the total gene pool of the ancestral species. This founder effect gave rise to a genetic bottleneck. Thus, in Triticum, it appears that the hexaploid bread wheat has about half the nucleotide diversity found in the wild tetraploid ancestor, whereas durum wheat (also a tetraploid species) appears to have even less diversity than bread wheat has. Many perennial fruit trees have gone through less of a genetic bottleneck and have often have kept a greater proportion of the genetic variation present in their wild progenitors than have annual crops (Miller and Gross 2011). Exceptions to this general observation include rambutan and mangosteen. Most perennial fruit crops have long generation times and are clonally propagated. A single desirable type can be maintained over many hundreds of years, as in the case of some of the European apple and pear varieties, which originated in the eighteenth and nineteenth centuries. One of the consequences of the genetic bottleneck that occurred during domestication is that useful genes still remain in the wild species related to crops. Interest in using crop wild relatives in crop improvement has increased over the past 50 years, particularly for the closest relatives, which

table 2.3.  changes associated with domestication, and examples of annual and perennial crops where these changes have occurred. Trait Breeding system

Mode of reproduction

Wild (ancestral) state

Domesticated (derived) state

Allogamous

Autogamous

Dioecious

Gynodiecious, andromonoecious, hermaphroditic Asexual via parthenocarpy

Sexual

Asexual via nucellar embryony Asexual via propagation by humans (grafting, layering, cuttings) Asexual via roots or tubers Inflorescence

Sterile flowers

Seeds

Few Shattering Smaller size

Sterile flowers become fertile Many Non-shattering Larger size

Lower seed set

Higher seed set

Examples of annual crops Rice, faba bean

Examples of perennial crops Almond, grape, papaya, plum Black pepper, grape, carob Fig, jocote, banana, pistachio, pears Citrus spp. Approx. 75 percent of cultivated perennials

Cassava, yam, potato, sweet potato Cereals Wheat, barley, rice Cereals, sunflower, pulses Most cereals, sunflower, legumes Flax

Fruit

Shell thickness Defensive structure Growth form

Ploidy level

More toxic Low oil content High dormancy Relatively homoge­ neous fruit Smaller size

Less toxic High oil content Low dormancy Increased variation in color, size, and shape Larger size

Low oil content Dehiscent Thick Thin Spines Perennial

High oil content Indehiscent Thin Thick No spines Grown as annuals

Indeterminate growth Large

Determinant growth

Diploid

Polyploid

Adapted from Miller and Gross (2011).

Cucurbita spp. Flax, sunflower Pulses, rice Chickpea, tomato, chili pepper Pulses, tomato

Pulses

Eggplant Tomato, chili pepper, eggplant Cereals, sunflower, soybean

Dwarf

Durum and bread wheats, peanut

Almond Clove Polaskia (cactus) Apple Most fruit crops, olive, date, grape, pomegranate, apple, plum, mango, banana Olives Kapok Pecan, almond Bottle gourd Olive, plum, kapok

Avocado, coconut, papaya, apple, cherry, peach, pear, plum, citrus Kiwi, breadfruit, sour cherry

Box 2.1. Domestication Pathways in Different Crops A. Sorghum (Sorghum bicolor) Hunter-gatherers appear to have consumed sorghum as early as 10,000 years ago, and its domestication appears to have had its origins in Ethiopia and the surrounding countries, but domestication may have occurred in a number of different locations across Africa including West Africa and the savannah of Central Africa. Disruptive selection seems to have been responsible for the development of different races and numerous varieties in different parts of Africa. Sorghum appears to have reached India about 3,000–3,500 years ago, and it arrived later in the Middle East and East Asia. Domestication was associated with a shift toward larger, non-shattering seed and more compact panicles. Harlan and deWet (1971) recognized five main races of cultivated sorghum based on morphology: (1) Bicolor, widely distributed across the African savannah and Asia; (2) Caudatum, found in central Sudan and surrounding areas; (3) Guinea, which is grown in both East and West Africa; (4) Durra, found primarily in Arabia and Asia Minor, and (5) Kafir, cultivated mainly in southern Africa. Domestication QTLs (Quantitative Trait Loci) have been identified in sorghum and mapped to a number of different regions on the genome. (Sources: Hancock 2004; Smartt and Simmonds 1995.) B. Common Bean (Phaseolus vulgaris) Wild P. vulgaris has a wide distribution in the Americas, ranging from Mexico into Central America and south along the Andes mountains to Peru, Bolivia, and Argentina. The northern populations of wild P. vulgaris from Mexico and Central America are genetically and morphologically distinct from those of the southern end of the species’ range and show incomplete reproductive isolation. Common bean remains do not preserve particularly well, which complicates the development of an archaeological record, but cultivated types of P. vulgaris appear in the Mesoamerican archaeological record around 2,500 years ago, while South American archaeological sites have yielded bean remains that date substantially earlier, to 4,400 years ago. Studies on seed storage proteins and DNA polymorphism suggest that beans were independently domesticated on at least one occasion in both Mesoamerica and the Andes (with southern Peru being the most likely Andean location), rather than undergoing a single domestication event in South America and subsequent dispersal northward to Mexico. This is reflected in current patterns of diversity in the regions and in the partial reproductive isolation of cultivated Mesoamerican and Andean cultivated gene pools. (Sources: Gepts 1998; Kaplan and Lynch 1999; Chacón et al. 2005.) C. Banana (musq spp.) Most edible bananas belong to the Eu-musa section of the genus Musa and are diploid or triploid hybrids from Musa acuminata (A-genome) alone or from hybridization with Musa balbisiana (B-genome). A minor group, including Fe’i bananas, is confined to the Pacific region and is derived from Australimusa species. The first stages of banana domestication appear to have involved the hybridization of geo­ graphically isolated subspecies of M. acuminata by people of Southeast Asia and the Melanesian islands. Archaeobotanic evidence suggests that this occurred some

6,950–6,440 years ago. Domestic parthenocarpic diploids resulted from the human translocation of these so-called cultiwilds outside their range and hybridization with local species, both M. acuminata and M. balbisiena. Linguistic and other evidence suggest there were at least three different contact regions: (1) New Guinea and Java, (2) New Guinea and the Philippines, and (3) among the Philippine islands, Borneo, and mainland southeast Asia. The emergence of triploid bananas with, variously, AAA, AAB, or ABB genomes occurred independently in these different contact areas. Of the numerous triploid subgroups, three are remarkable because they are largely cultivated far from their region of generation: the African AAA “Mutika Lu-jugira,” AAB “African Plantains,” and AAB “Pacific Plantains.” The antiquity of each subgroup is attested to by the extraordinarily large number of cultivated morphotypes, indicative of a long period of somaclonal variation, and by the evidence of Musa phytoliths in central Africa, which have been dated to 2,500 years ago. (Sources: Zeder et al. 2006; Perriera et al. 2011.)

are often the ancestral species of the crop. They have proved to be particularly valuable as a source of disease-resistance genes. For example, over 35 disease-resistance genes originally found in wild Lycopersicon species have been used to improve disease resistance in tomato (Bai and Lindhout 2007). Genes from wild relatives have enhanced both the tolerance of crops to abiotic stresses and the yield-improving genes found in Oryza rupifogon and transferred to the rice crop. Since many crops are inter-fertile with their wild relatives, opportunities remain for the introduction of new traits and for continuing domestication over the centuries. Even today, farmers may allow the products of such crossing to remain in their varieties (Jarvis and Hodgkin 1999), or use wild relatives to select material for new domesticates, as in yam in West Africa (Scarcelli et al. 2006b). While domestication has generally reduced the total genetic diversity present in the crop in comparison with the wild ancestor species, variation in certain characteristics often has increased. As crops spread out and moved into new areas of production, adaptation to different agro-ecological environments occurred. The spread of wheat, barley, lentil, and pea out of the Fertile Crescent appears to have been relatively rapid eastward (to Pakistan) and westward (to Greece and the western Mediterranean). The spread northward beyond the Balkans required adaptation to cooler production conditions and different day lengths. This involved the development of a vernalization response in cereals and of day-neutral types. Crops such as lentil and chickpea did not adapt and remain associated with warmer climates, while appropriate adaptations were developed in barley, wheat, pea, and faba bean (Purugganan and Fuller 2009).

   origins

Domestication is the result of human selection. People’s cultural and social preferences were central to the development of the wide variety of domesticated types that are found today in many crops. Regional variation for hulled as against naked barleys, or for both 2-row and 6-row barleys, persisted for a long time in some parts of Europe owing to local preferences. Other examples of cultural selection associated with local food preferences that are characteristic of a range of crops include the selection for popping and elastic type in maize (Mexico), the fragrant rice traits associated with basmati (India) and jasmine (Thai) rice, and the many different examples of selection for reduced amylase levels in grain starch that give rise to the sticky trait found in modern varieties of at least eight different cereal species (Sakamoto 1996). Over time, different useful characters were favored where the crop was used for different purposes, and visible characters often may have been selected where they could be used to identify a variety (see Chapter 5). Examples include the different types of sorghum, which include selection for sweetness in certain sorghum varieties; the size, shape, and maturity characteristics of different varieties of apple, pear, and other fruit, and the many different forms of potato. A number of vegetable species have given rise to many different crops in different parts of the world, with the different Brassica species perhaps providing the most extreme example. In Europe, B. oleracea has given rise to at least 10 different crop types: kale (marrow stem kale, thousand head kale, curly kale, cavolo nero), cabbage (many—round, pointed, savoy, red), collards, Brussels sprouts, calabrese, cauliflower (many—white, green, romanesco), and kohlrabi as a result of selection for leaf, stem, axillary bud, and floral characters. A similar rich diversity can be found in Chinese B. juncea vegetable crops. The Processes of Domestication Even before the “agricultural revolution,” hunter-gatherer societies came together in communities, as they still do today, and managed both the landscape in which they lived and the plants and animals that were part of that landscape. Indigenous knowledge of biological resources existed (and still exists) within these societies. Yen (1989) has described this environmental management as “domestication of the environment,” which includes both incidental aspects (the accumulation of waste around a center of habitation leading to soil enrichment and changes in local vegetation) and more



origins   

deliberate activities, such as flooding control in valley floors, the use of fire, and the management of vegetation around particularly important resources (especially valuable trees or medicinal plant species). Debate surrounds the drivers of the development of agriculture and domestication. Agricultural development coincided with (and supported) an increased world population as well as the development of states, cities, and an increasingly stratified society in which different groups undertook different tasks (see, for example, Weisdorf 2005). Climate change—­particularly the increasingly drier and warmer climate of the period—also may have played a major role as a driver of domestication. All three factors (increased population, increased food supply through domestication, and climate change) likely worked in concert in elaborate feedback loops. Some investigations (for example, Hillman and Davies 1990) have suggested that domestication occurred over a relatively short period of time and that, for each crop, domestication could have been relatively rapid. This hypothesis views domestication very much as an event in which over a few (or a few tens) of generations a crop changed from being a wild species into something recognizable as a crop by virtue of the acquisition and maintenance of a few key mutations such as the non-shattering trait in cereals. However, archaeological evidence suggests that the change from “wholly wild” to “wholly domestic” took place over a relatively long time. While modeling studies might indicate that non-shattering could evolve in less than 100 years, archaeobotanical studies argue that the fixation of non-­ shattering rachises in barley took about 2,000 years. Similarly this trait has evolved over long time scales in wheat and rice (Purugganan and Fuller 2009). The evolution of seed size also appears to have taken a long period of time (although, at 500–1,000 years in some sites in the Fertile Crescent, significantly less than non-shattering). Another important conclusion from recent analyses has been that large seed size developed significantly before the development of non-shattering and that in this respect the evolution of the different traits associated with domestication was non-synchronous (Fuller 2007). Purugganan and Fuller (2009) suggest that the rate of increase of the non-shattering domesticated forms of barley, wheat, and rice may have occurred at rates of about 0.03–0.04 percent per year, which implies weak selection pressure for this trait. Studies on domestication have tended to focus on major crops and particularly on the major cereal crops that originated in the Middle East, where there is a comparatively larger amount of archaeological evidence than in

   origins

other regions of the world. New evidence from other crops originating in other regions suggests that the process of domestication is much more varied than had previously been thought. Meyer et al. (2012) have reviewed the information available on domestication for 203 major and minor food crops. They argue that many of the “classical” features associated with the few major crops that have been intensively studied (including changes in ploidy level, loss of shattering, multiple origins) are less common when the wider range of crops is considered. Perhaps this reflects the differences that exist in the degree of domestication, but it reminds us that generalization is dangerous and that domestication is a dynamic process. The combination of additional archaeological data with information from molecular analyses is likely to shed new light on the processes of domestication in an ever-wider range of crops, as illustrated by the analysis of the way in which gene mutations and genome ploidy paved the way for successful domestication of modern cultivated wheat varieties (see review by Dubcovsky and Dvorak 2007). Genetic Aspects of Domestication The suite of changes on seed crops characteristic of domestication are sometimes labeled the “domestication syndrome” (Hammer 1984), and the identification of the genes involved in the control of these traits has been a subject of considerable interest for many years. Table 2.4 lists the main traits involved in the domestication syndrome of two crops: wheat and pea. A number of the traits associated with domestication are controlled by only a few genes. Non-shattering in rice is under the control of a single locus, whereas in sorghum, pearl millet, and barley two loci are involved. The genes involved in these examples are all recessive. Determinate and indeterminate growth in maize and common bean are under the control of one or two genes, as is branching in sunflower and sesame (Hancock 2004). Even when traits are thought to be regulated by a larger number of genes, QTL (Quantitative Trait Loci) analysis has often shown that a few loci have a major influence for each trait investigated (see, for example, Koinage et al. 1996 for common bean). The genes that control variation in the different traits associated with domestication are becoming increasingly understood thanks to fine resolution mapping, gene cloning, and other molecular techniques. An increas-

origins   



table 2.4.  some characters associated with the “domestication syndrome” of wheat and pea. Wheat

Pea

Loss of shattering Loss of tough glumes Increase in seed size Reduction in tiller number More erect growth Reduced seed dormancy

Indehiscent pods Increased seed size Reduced plant height Reduced number of basal branches Day-neutral Reduced seed dormancy

Adapted for wheat from Dubcovsky and Dvorak (2007) and pea from Weeden (2007).

ingly diverse and complex picture is emerging. For example, Weeden (2007) concluded that domestication of pea involved a minimum of 15 known genes in addition to a relatively few major quantitative trait loci. The genes differed from those involved in domestication of faba bean, suggesting that there was no common genetic basis to the domestication syndrome in Fabaceae. Vaughan et al. (2007) noted that domestication trait alleles often can be found in populations of wild relatives, that transcriptional regulators involved in domestication often belong to different families of transcriptional regulators, and that gene and genome duplication have been ­important. Molecular characterization, in particular QTLs—multiple genes that affect a particular phenotypic feature—has been used as a major method for understanding the genetic basis of domestication in plants (see Chapter 5 for a further description of molecular methods). Traits that were the targets of selection and the genes that affect them have been called “domestication genes.” One of the first domestication genes studied, teosinte branched 1 (tb1), was found to be the gene that affects apical dominance in maize architecture, allowing maize branches instead of the single dominant stalk of its wild relative teosinte. QTL analysis also allows the detection of genomic regions associated with domestication traits and therefore helps us understand whether changes under domestication are due to many changes of small effects, or a few changes of large effect (larger effects being traits controlled by at least 20 percent of the phenotypic variance in the mapping population). QTLs

   origins

have shown that in annual crops a number of domestication traits come from relatively few changes of larger effect, but that this is not universal (Burger et al. 2008). For example, ten loci control the domestication trait of shattering in maize, three loci in rice, but only one locus in sorghum (Zeder et al. 2006). Centers of Diversity and Centers of Origin In the first decades of the twentieth century, the Russian agricultural botanist N. I. Vavilov and his collaborators undertook a very extensive series of investigations on a wide range of crop plants. Vavilov believed that crop production in Russia (later the USSR) needed the introduction of crop diversity from the widest possible range of environments in order to meet the challenge of developing improved varieties adapted to the range of production environments found in the country. Vavilov’s own expeditions took him first to all the different parts of Russia—especially to the Caucasus and Central Asia—and then to neighboring countries such as Afghanistan and Turkey as well as to other parts of the Middle East, and to the countries of the Mediterranean. He also visited Ethiopia, the Far East (notably China, Japan, and Korea), and South and Central America (Vavilov 1997). These explorations were extended by his colleagues and resulted in the accumulation by the All-Union Institute of Plant Industry (VIR, later the Vavilov Institute) of one of the largest collections of plant diversity that has ever been assembled. From the observations during these travels and studies made in the USSR on the genetic diversity of the materials collected, Vavilov identified areas of the world which he described as centers of genetic diversity. He suggested that these were also centers of origin of major crops (Vavilov 1929; 1945–50). These tended to be in mountainous areas with evidence of ancient civilizations. They included Mexico and northern Central America, Central America, the central Andes, the Mediterranean basin, West Asia (including the Caucasus), Central Asia, the Ethiopian highlands, the Indian subcontinent, Southeast Asia, and China (figure 2.1). Further analyses have revealed a much more complex picture. In some cases centers of origin and diversity do seem to coincide but in others this does not seem to be the case. Recognizing that in some crops diversity was much more widely distributed, Harlan (1971) suggested that there were both centers of diversity



origins   

Figure 2.1. Eight centers of origin of cultivated plants proposed by Vavilov: (1) China; (2) India; (2a) the Indo-Malayan region; (3) Central Asia, including Pakistan, Punjab, Kashmir, Afghanistan, and Turkestan; (4) the Near East; (5) the Mediterranean; (6) Ethiopia; (7) southern Mexico and Central America; (8) South America (8—Ecuador, Peru, Bolivia, 8a—Chile, 8b—Brazil-Paraguay) (from Harlan 1971, reprinted with permission from AAAS)

that were fairly localized and others he termed non-centers that were much more widely distributed across a whole continent, as in the case of sorghum in Africa or banana in Southeast Asia. Molecular genetic analyses of putative ancestral wild relatives and of traditional varieties are beginning to provide new information on the possible location of some of the major domestication events. However, molecular evidence needs to be read cautiously. The archaeobotanic evidence indicates that domestication occurred over a long period of time and was probably accompanied by both many changes in direction and degree of selection, and variations in maintenance practices as communities and civilizations developed or suffered setbacks. The molecular evidence often indicates that the location of the presumed centers of origin of many crops was often at the margins of the apparent centers of diversity identified by Vavilov. The concept of centers of diversity has proved of immense value in helping us to understand observed patterns of diversity, to focus collecting and conser-

   origins

vation efforts, and to look for potentially useful variation or specific traits of potential value to plant breeders. The Movement of Crops Around the World The distribution of genetic diversity in crops is not fixed. Crops and varieties have been transported by farmers and societies throughout history. The Neolithic farming revolution that began in the Fertile Crescent moved through the Mediterranean region and Europe, and evidence of the earliest crop remains in different parts of Europe gives us an idea of how fast this might have occurred and of when agriculture became established in different areas. The earliest sites with the domesticated complex of wheat, barley, lentil, and faba bean found in south Turkey and Syria date from about 10,000 years ago. By 6,000 years ago this complex had reached Greece and then Italy; the crops more adapted to northern climates (wheat and barley) have been found in sites in Britain that date from 3,000 years ago (Zohary and Hopf 1988). Similar movements of individual crops or of crop complexes have been traced for many different species. As crops were moved, new patterns of genetic diversity developed. Often this involved further loss of diversity in new areas occupied by the crop and the accumulation of new mutations associated with the needs of farmers, or adaptation to new production environments. One of the most intriguing features of the distribution of crop genetic diversity is the occurrence of so-called secondary centers of diversity. These are areas of high diversity of particular crop species that can be found far from other centers where the crop seems to have evolved. Ethiopia, for example, appears to be a secondary center of diversity for a number of crops including barley, wheat, and lentil as well as a primary center of diversity for tef and Brassica carinata. The central Andes region, in addition to being a primary center of diversity for potato, is also a secondary center for maize. Human-aided movements of plant and animal species across continents began not long after the establishment of domesticated species in their centers of origin. The Near East crop package of barley, wheat, pea, lentil, vetch, faba bean, flax, and vine fruits spread along the shores of the Mediterranean, the Danube, and down the Rhine, east to northern India and south across Arabia and Yemen and into Ethiopia. By 4,000 years ago, the complex had reached China. Carbonized plant remains excavated in India and dated to approximately 4,600 years ago have been identified as grains



origins   

of millet crops domesticated in Africa on the southern limit of the Sahara (Zeder et al. 2006). The banana, domesticated in Southeast Asia, is estimated to have been introduced into East Africa by at least 3,000 years ago (Zeder et al. 2006). On the other side of the world, manioc, root crops, and maize have been found in Panama in a tropical forest site dating earlier than 5,000 years ago. This crop complex had spread from Brazil over a couple of thousand years (Piperno et al. 2000). In later periods, crops moved across the Eurasian continent following burgeoning trade along the routes of the Silk Road; spices moved from Asia into the Near East and Europe by means of both sea and land routes from early antiquity through the Medieval period. An ancient Indian Ocean trading network linking Africa, Arabia, South Asia, and settlements farther east can be traced through genetic and archaeobotanical research. The early movement of soy is linked to the diffusion of Buddhism throughout China and then from China to other countries in South and Southeast Asia (Du Bois et al. 2008). The major and most rapid movement of crops was associated with the development of links between the Americas and Europe following Columbus’s journeys in what has become known as the Columbian Exchange (Crosby 2003). As noted, some movements and adoptions occurred very rapidly whereas others apparently took longer. This movement of crops led to the establishment of new secondary centers of diversity. For example, the varieties of common bean found in East Africa are extraordinarily variable as a result of the transfer of materials from the two different gene pools in South America and their subsequent mixing, intercrossing, and selection by local farmers. In their new environments, a number of crops developed significantly changed characteristics, and adaptive new mutations were presumably identified and fixed by farmers in the new locations. Thus, while northern European potatoes have relatively low levels of diversity compared with those found in the Andes from where they originated, they possess genes that adapt them to the long day conditions of their new environment. It is interesting how rapidly some crops became established parts of the European (and American) agricultural production systems. In a series of frescos painted by Giovanni da Udine from a design by Raphael in Rome around 1517 (25 years after Columbus’s first journey to the New World), one can already find maize and beans beautifully depicted, although not yet potato or tomato (Caneva 1992).

   origins

Domestication and the Analysis of Diversity in Traditional Varieties The degree of domestication, or the extent to which any crop possesses all the traits that we regard as representing the most complete expression of domestication, varies significantly from crop to crop. Some cereals such as tef still possess a small seed, which is difficult to manage; many “domesticates” such as different types of cassava still possess toxins injurious to humans that require special treatment prior to use. Indehiscence of seed pods may be absent (as in the case of sesame) or only partial. The degree to which different fruit crops are domesticated is also very variable; some, such as apple, are highly adapted to intensive cultivation over a wide range of environments while others retain many of the characteristics of their wild ancestor. In the case of wheat or rice, some 10,000 generations have elapsed since the original events surrounding their domestication, while in the case of long-lived fruit crops maintained on rootstocks, the number of generations in which selection for their cultivated characteristics has occurred is much less and may be only of the order of tens of generations. Domestication continues today both within and around traditional farming systems and through deliberate breeding efforts to develop new crops. Examples of the former include the continuing selection by West African farmers of yams from the forest margins where wild and weedy species can be found, and the introduction of new fruit trees into home gardens from the wild in Guatemala (Galluzzi et al. 2010). Early farmers probably exerted selection pressure to create more uniform materials, and it is likely that, fairly early in the domestication process, more or less distinct varieties began to emerge. One can hypothesize that early selection of this type focused on use-related properties or traits such as maturity period, which facilitated management and harvesting of the crop. In any event, it is possible that fairly early in the process of domestication, identifiable varieties began to arise. By the time of the first written descriptions of crops (by the Greeks some 2,500 years ago) the concept of varieties was well established and their properties known. The nature and evolution of a crop’s breeding system were likely to be of great importance to the emergence of the early traditional varieties. While fully open outbreeding systems such as self-incompatibility provide for sexual recombination and the generation of diversity, on the other hand they risk the lack of suitable pollination, the security of fruit or seed produc-

origins   



tion, and the production of propagules with predictable performance. Clonal reproduction and self-fertility allow escape from this sexual uncertainty but freeze genotypes completely under clonal reproduction, or partially under selfing. Both of these reproductive mechanisms favor the emergence of distinct lineages or varieties, which have been selected by farmers and can be named and have some durability. Understanding domestication processes and the genes involved in domestication provides important information on the ways in which an analysis of diversity of traditional varieties may best be approached. Knowledge of the existence of different lineages in a crop, of different origins of the history of crop production, and of the genes involved in domestication can help guide investigations on both the maintenance of diversity within farming systems and the improvement of local materials through the introduction of novel variation. Similarly, the identification of centers of diversity has focused attention on the importance of some parts of the world as areas of particular importance for on-farm conservation or as potentially rich sources of useful variation. Further Reading Barker, G. 2009. The Agricultural Revolution in Prehistory. Oxford University Press. Harris, D. R., and G. C. Hillman, Eds. 1989. Foraging and Farming: the Exploitation of Plant Resources. Unwin and Hyman, London. Meyer, R. S., A. E. DuVal, and H. R. Jensen. 2012. “Patterns and processes in crop domestication: an historical review and quantitative analysis of 203 global food crops.” New Phytologist 196:29–48. Miller, A. J., and B. L. Gross. 2011. “From forest to field: perennial fruit crop domestication.” American Journal of Botany 98:1389–414. Pickersgill, B. 2007. “Domestication of plants in the Americas: insights from Mendelian and molecular genetics.” Annals of Botany 100:925–40. Purugganan, M. D., and D. Q. Fuller. 2009. “The nature of selection during plant domestication.” Nature 457:843–48. Smartt, J., and N. W. Simmonds, Eds. 1995. Evolution of Crop Plants, 2nd ed. Longman Scientific and Technical, Harlow.

Plate 2. Domestication is the result of human selection. People’s cultural and social preferences were central to the development of the wide variety of domesticated types that are found today in many crops. The upper left photo shows potato varieties in Ecuador in the Central Andes, while the photo in the upper right shows finger millet varieties (Eleusine coracana, a neglected and underutilized species) in Bangalore in the Karnataka State, India, Southeast Asia. Both the Central Andes and Southeast Asia are considered to be within two of the Vavilov-identified centers of crop genetic diversity. The bottom left photo shows the ongoing process of domestication as a farmer has dug wild yam (Dioscorea minutiflora) out from the bushland to plant in his home garden in Kitui District, Eastern Province, Kenya. The bottom right photo shows a farmer examining a wild apple (Malus sieversii) in the Parkent District, Tashkent Province, Uzbekistan, another Vavilov center. Farmers in Central Asia continue to bring wild relatives of fruit trees into their production systems, for both root stock and grafting materials. Photo credits: J. Tuxill (upper left), S. Padulosi (upper right), Y. Morimoto (lower left), D. Jarvis (lower right).

chapter 3

Plant Genetic Resources, Conservation, and Politics A History of International and National Developments Supporting the Conservation and Use of Crop Diversity

B

y the end of this chapter the reader should have an understanding of:

• The different ideas about conservation of plant genetic resources. • How these ideas affect current international and national policies and approaches to supporting on-farm management and use of crop genetic resources. Nature, Biodiversity, and Genetic Resources In this chapter we review some aspects of the international and national developments in the conservation of crop genetic resources that have shaped the current debates and perspectives on the conservation of traditional crop varieties. The different ways in which indigenous peoples, rural communities, national programs on genetic resources, and international organizations or agreements approach questions on conservation and use are important when developing work to help understand and support the maintenance of crop diversity. Understanding the sometimes contradicting interests and needs of the different actors involved in crop diversity generation, conservation, and utilization is necessary to define and implement sensible measures oriented toward the conservation and sustainable use of crop diversity. There is a marked contrast between the essentially utilitarian view of genetic resources—that is, resources to be managed, deployed, and used to

   resources, conservation, and politics

achieve specific objectives such as higher yield and increased income (this view has characterized much of the efforts of those involved in developing national programs of work on plant genetic resources)—and the views of indigenous peoples or many rural communities. Many traditional societies consider human beings to be an inextricable part of nature, living in harmony with it. For example: “Every seed is awakened and so is all animal life. It is through this mysterious power that we too have our being and we therefore yield to our animal neighbors the same right as ourselves, to inhabit this land” (Sitting Bull). This perspective has led to significant disagreement between indigenous peoples and governments about the ways in which maintenance and use of biodiversity should be approached. As one commentator has noted: The profound cultural, epistemological (ways of knowing), ontological (ways of being) and cosmological (ways of being related to the world) differences between the Culture of the Commercial Seed embedded within Western(ized) societies, and the Cultures of the Native Seed embedded within Indigenous Peoples’ land-place based agricultures, have not been taken, from its inception, into consideration by the trans-­national network System of Agricultural Research, Extension, Education, Science, Knowledge and Technology and their respective dominant, exclusive and assimilationist theories and paradigms of rural/agricultural development. (Tirso Gonzales in Tauli-Corpuz et al. 2010) There have been similar divisions between those involved in conservation of biodiversity. At one extreme, humans are seen as having a responsibility for nature and to be charged with managing it for future generations. At the other extreme are perspectives that see humans as a part of nature as reflected in the perspectives put forward by those who support deep ecology, which argues that the natural world is a subtle balance of complex interrelationships in which the existence of organisms is dependent on the existence of others within ecosystems (Næss 1989). It has been argued that current international agreements such as the Convention on Biological Diversity (CBD), and the ways in which they are implemented, tend to confirm the view that biodiversity is something to be managed and that it can be owned and given an economic value. Crop diversity owes its existence to the intervention, management, and continued selection by humans. In this sense, it might be considered as the result of human dominion over nature. This perspective is reflected in the concept of plant genetic resources, which has framed much of the inter-



resources, conservation, and politics   

national and national effort to conserve crop diversity, although it is not a concept that would be accepted as appropriate by many indigenous peoples. Even among those who are comfortable with the concept of genetic resources—as something created by farmers, pastoralists, and plant breeders around the world—there are substantial differences of opinion with regard to control, ownership, management, and the ways in which benefits from use should be approached. Thus, on-farm conservation of traditional crop varieties sits in an intricate sociopolitical landscape. This chapter summarizes the history of plant genetic resources conservation from an international perspective so as to present some of the major debates and points of disagreement that affect work in on-farm conservation. Biodiversity is a relatively new word or concept—a contraction of biological diversity, which was first used in the 1980s (see box 3.1). In fact, some of the words used to describe the key concepts of conservation of crop biological diversity (like biodiversity, and in situ and ex situ) are relatively new. The term “plant genetic resources” did not exist before the 1960s. The idea of deliberately conserving biological materials either outside their natural habitat or as part of their natural habitat (ex situ and in situ conservation) is also recent. Conservation used in the sense of the maintenance over time of biological diversity is itself a relatively recent concept and, in earlier literature, was used synonymously with preservation, carrying with it the idea of a conservator—someone with responsibility over a domain such as nature. The development of deliberate programs to support the conservation and use of plant genetic resources and traditional varieties has been accompanied by considerable, often acrimonious, debates that have covered a number of different aspects. These include: 1. The way in which agricultural biodiversity is perceived. Is it a part of nature, which includes humankind and all the other elements within the wider landscape (see, for example, the approach of the NGO ANDES: http://www.andes.org.pe/es/), a part of total biological diversity (or biodiversity), or a resource developed by humans for their further management and use (a genetic resource)? 2. The ownership of the materials. Do agrobiodiversity and traditional varieties belong to farmers, pastoralists, forest dwellers, and fisherfolk who have been involved in its development and maintenance over centuries, to the countries in which the re-

Box 3.1. Definitions of Biological Diversity The term “biological diversity” was used first by wildlife scientist and conservationist Raymond F. Dasmann in the 1968 book A Different Kind of Country advocating conservation. The term was widely adopted only after more than a decade, when in the 1980s it came into common usage in science and environmental policy. Thomas Lovejoy, in the foreword to the book Conservation Biology, introduced the term to the scientific community. Until then the term “natural diversity” was common, introduced by the science division of The Nature Conservancy (TNC) in an important 1975 study, The Preservation of Natural Diversity. By the early 1980s TNC’s science program and its head, Robert E. Jenkins, along with Lovejoy and other leading U.S. conservation scientists at the time advocated the use of “biological diversity.” The term’s contracted form—biodiversity—may have been coined by W. G. Rosen in 1985 while planning the 1986 National Forum on Biological Diversity organized by the National Research Council (NRC). It first appeared in a publication in 1988 when entomologist E. O. Wilson used it as the title of the proceedings of that forum.

sources were found (mostly developing countries in the south), or are these resources the natural heritage of mankind, the view expressed by those working on genetic resources conservation in the 1960s? 3. The ways in which farmers, communities, plant breeders, and, today, genetic engineers should be recognized and rewarded for their contributions to the continuing evolution and improvement of crop varieties and the ways in which those varieties can be protected. 4. The importance of individual entities (such as traditional varieties or populations) as things in themselves or as the basis for future selection versus their role as part of functioning agricultural ecosystems which, together with all the other components, provide a range of benefits or services. Plant Hunters and Plant Collectors As noted in Chapter 2, crop plants have moved around the world alongside the movements of people. They spread out from their early centers of domestication, were changed by mixing and intercrossing with new forms, became adapted to new environments, and became part of the development of new cultures adapted to new production practices. Wheat and barley spread through Europe from the Middle East so that by 4,500–



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5,000 years ago they appear to have been grown in central England and, in Roman times, exported to Rome. The Romans brought new crops back to Italy from their conquests around the Mediterranean. Even if the plants themselves were not introduced, they brought back plant products such as myrrh, frankincense, and spices as a result of trade. Later, as Islam spread across the Mediterranean in the eighth and ninth centuries, crops such as aubergine, spinach, and watermelon were introduced into Sicily and Spain. The Great Silk Road provided a route for the transfer of products and seeds from East Asia to Europe over many centuries. In the Americas a similar diffusion of crops took place. Maize, bean, squash, pepper, cacao, potato, and cassava are all examples of crops that spread from the areas where they were believed to be domesticated to a much wider range of environments within the continent (Sauer 1993). A major new diffusion of crops began with the establishment of connections between Europe and the Americas at the end of the fifteenth century. Maize, common bean, pepper, tomato, and, later, cassava began to be grown in the Old World while European crops were carried to the New World by the early explorers and settlers from England, Scotland, France, Spain, and Portugal. The transfer of potentially useful new crops and crop varieties continued with the growth of international trade in the eighteenth and nineteenth centuries. Sometimes this took place as part of a search for new crops for particular environments under the control of the major powers of the day (such as tea in Sri Lanka). Sometimes it was a deliberate attempt to break existing monopolies, as in the case of rubber, some 70,000 seeds of which were taken by Sir Henry Wickham from Brazil to Kew, London, in the 1870s and then distributed to Sri Lanka, Malaysia, and other potential production areas. Most of the attention was focused on potentially high-value plantation crops such as cotton, sugarcane, and oil crops, but there was also a growing interest in ornamentals. Plant breeding and breeding research became increasingly important during the first half of the twentieth century and, as part of this enterprise, plant breeders began to develop collections of some major crops, for example, wheat, barley, maize, and sugarcane. These collections were used to identify desirable traits and as a basis for crossing and selection. Perhaps the greatest practitioners of this approach were Vavilov and his collaborators in the Bureau of Applied Botany in Russia. From hundreds of genetic exploration missions in Russia, the USSR,

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and throughout the world, these collectors brought back samples of a wide variety of crops, which they grew, studied, and used in crossing experiments to develop new varieties. By 1940, the All Union Institute of Applied Botany and New Crops had amassed a collection of over 250,000 accessions of many crops, including 30,000 for wheat alone. These were grown in stations and substations throughout the Soviet Union based on their requirements with the central seed store in Leningrad (now Saint Petersburg). Vavilov used this vast enterprise to develop a geographic understanding of variation in terms of distribution and diversity of genes and alleles, and developed the concept of centers of diversity and origin of crops (see Chapter 2). Detailed descriptions of variation in many major crops were published between 1935 and 1941 (Loskutov 1999). Vavilov’s contemporaries in Europe and America (for example, Stubbe in Germany, Percival and Hawkes in the United Kingdom, Harry Harlan in the United States) were carrying out similar activities and developing sizable collections of material from traditional varieties obtained from around the world. These collections were used both for research on evolution and genetics and as the basis for breeding programs in the different countries of Europe. During the late 1920s and throughout most of the 1930s there appear to have been fairly frequent visits by these research scientists to each others’ institutes and laboratories and the exchange of plant materials. Bateson, L. R. Jones, and Muller from the United States, Hawkes from the United Kingdom, and Frankel from New Zealand all visited Vavilov’s institute during the 1930s, and he continued his own trips to others’ laboratories until prevented by political events in the second half of the 1930s. In addition to providing genetic, archaeological, and evolutionary data, these collecting programs in regions with the richest genetic resources were part of the modernist quest to create improved crop and livestock varieties that, it was argued, would help create a new world and help to build the “new man” (Flitner 2003). The enterprise was firmly utilitarian, aimed at providing new varieties for agriculture in the countries involved. The scale of Vavilov’s enterprise reflected the size and climatic and agricultural diversity of the new Soviet Union and the need for crops and varieties suited to every part of the country. Although the concern of these collectors, researchers, and breeders was for the future and for the ways in which the resources they collected could be used for the future improvement of agriculture and humanity, they were not always unaware of another side to the picture—the potential loss of the



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resources caused by the very success of their enterprise. Harry Harlan had noted as early as 1936 in a monograph on barley: The progenies of these fields with all their surviving variations constitute the world’s priceless reservoir of germplasm. It has waited through long centuries. Unfortunately, from the breeder’s standpoint, it is now being imperiled. When new barleys replace those grown by the farmers of Ethiopia or Tibet, the world will have lost something irreplaceable. (Harlan and Martini 1936) The Second World War interrupted this endeavor, which emerged with renewed urgency after the war in the face of famine in Europe and elsewhere in the world. The perceived need of most countries was to ensure that they possessed the capacity and the resources to place their agriculture on a firm and productive footing. There was substantial state investment in agricultural research throughout the world. The agricultural capacities of the colonies were further developed by the colonizing nations with an emphasis on plantation crops useful to their empires. In Europe there was an emphasis on ensuring that famine never returned, and most countries invested heavily in agriculture. A part of this investment involved the further development of collections. In Eastern Europe and the Soviet Union, collections continued to be developed and maintained although the dominance of Lysenkoist approaches severely limited the ways in which the collections were used. By the 1960s there were important collections in East Germany, Italy, the Netherlands, the United Kingdom, and a number of other countries. Conserving Plant Genetic Resources The Development and Evolution of National Programs on Plant Genetic Resources The 1980s and 1990s saw a remarkable development of countrybased activities to conserve and use plant genetic resources (see box 3.2). As these efforts became more formalized they were recognized as established national plant genetic resources programs or national genetic resources systems—that is, the different components identified as necessary to the maintenance and use of plant genetic resources. These components varied but usually included: an ex situ gene bank, an information system, a research

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program, some identified capacity-building activities, and a management and decision-making procedure that oversaw these activities and was involved in regional or international conservation debates and processes. National programs were usually embedded in the agricultural systems of the country and had little or no relationship with environmental agencies or those involved in biodiversity conservation issues. The national plant genetic resources collections were largely developed within the framework of breeders’ needs and did not have a substantial concern per se with the conservation either of genes or of the varieties collected. They were a basis for the identification of desirable new traits and understanding the inheritance of useful characters, and for use as parents in crossing and selection programs. Gene banks that are closely associated with breeding or research institutes are often major suppliers of their germplasm. Many gene banks are in the public sector and as such are taxpayer-funded. Relationships between gene banks and research or breeding can confer mutual advantages since evaluation data obtained by a breeding institute can easily be made available to an allied gene bank and, in turn, promote the germplasm use. As a consequence, such collections are often used intensively. In some countries, the management of gene bank collections may be highly decentralized and closely linked to a research or breeding institute for particular crops. Such gene bank collections may be more prone to neglect in the longer term unless the government has taken explicit responsibility for continued maintenance of such decentralized collections. In other countries, strong links have been established between (national) gene banks and in situ and onfarm conservation activities. Such arrangements greatly facilitate so-called complementary conservation approaches, strengthen the interface between nature/field on the one side and the users on the other through the services of gene banks and research, and thus promote the use of conserved genetic resources. Nonetheless, the long-term maintenance of these collections was certainly an objective, and many of the collections were maintained over long periods. The story of the maintenance of the genetic resources collections during the siege of Leningrad in the face of the city’s starvation is justly famous, but other collections also were carefully maintained over long periods. For example, the U.K.-maintained Commonwealth Potato Collection was initiated as a result of collecting missions undertaken in 1938 and 1939

Box 3.2. Managing Gene Bank Collections The appropriate procedures for conserving plant genetic resources ex situ have been the subject of a considerable body of research, particularly during the 1980s. The ex situ conservation methodology of germplasm depends on the biological nature of the plant in question. Species that produce so-called orthodox seeds—that is, seeds that can be dried and stored at low temperatures for an extended period— usually will be conserved in seed gene banks. Species that do not produce seeds at all and/or that are vegetatively propagated (and where the genotype needs to be conserved), and/or that produce so-called recalcitrant seeds (that is, seeds that cannot be dried without killing them and thus that cannot be stored), will be either maintained in the field gene bank or stored as tissue, embryo, or even cell suspension in a so-called in vitro gene bank. For some species also, pollen is stored for shorter or more extended periods of time. The objective of ex situ conservation is to maintain the genetic characteristics of the original sample for as long as possible without mutation, genetic drift, or shift. For seed gene banks the process involves: Seed cleaning. The seed should be harvested under the best possible conditions when it is fully mature and then cleaned of unwanted materials with the removal of any damaged or broken seeds. Drying. The next step consists of the drying of the various seed batches at the right speed to avoid cracking, and at the right temperature so as not to affect the longevity of the seeds. In general, oily seeds can be dried down further than starchy seeds—that is, seed moisture contents as low as 1 percent for oily seeds and 3 percent or more for starchy seeds, and drying at temperatures between 15 and 20ºC. Storage. Seed storage is usually carried out in walk-in deep freezers. The actual temperature depends on the objective of the storage; for longterm storage of germplasm (of base collection material) usually –18ºC is used whereas medium-term storage (up to 5–10 years) can be achieved at a temperature of 5ºC or higher. The containers used should be hermetically sealable and not allow the exchange of gases/air during storage (for example, three-layered aluminum foil bags). It has also become standard practice to subdivide the individual accessions into subsamples of an adequate size for later use and/or distribution. For small orthodox seeds as well as for in vitro material, long-term storage is practicable through storage of seeds or cultures at ultra-low temperature, usually by using liquid nitrogen (–196ºC) in cryopreservation. At this temperature, all cellular divisions and metabolic processes are stopped, and, consequently, plant material can be stored without alteration or modification for a theoretically unlimited period (Engelmann 1997). Viability monitoring. A schedule of viability testing has to be developed for the different stored seed accessions. This allows relatively precise predictions of when seed viability starts dropping below established thresholds, thus allowing timely regeneration of the accession.

Regeneration. When the viability of the stored seeds drops below the set minimum threshold, or the stored quantity of the seeds for a given accession has dropped below a minimum amount, the accessions in question will have to be grown out under ecologically adequate conditions to regenerate the germplasm and/or to increase the stored stock. Detailed procedures on seed drying, storage, and viability monitoring for many crop species can be found in the Crop Knowledge Base (http://cropgenebank.sgrp .cgiar.org/). Standards for seed storage in gene banks have been developed and recommended for international adoption by FAO and International Plant Genetic Resources Institute (IPGRI) and are currently being revised and further detailed for seed, field, and in vitro gene bank conservation.

and is kept today by the James Hutton Institute (formerly the Scottish Crop Research Institute). Over the years, national genetic resources programs have begun to take on broad mandates. Animal genetic resources are often included in addition to plant genetic resources. Moreover, national programs look not only at the dynamics of genetic diversity, but also at the interactions between cultivated (sometimes also non-cultivated) species and farm animals, and at the roles of plant and animal species in the general agro-ecological environment. In summary, integrating gene bank activities into a national genetic resources program broadens the perspective, increases gene bank responsibilities, and promotes more balanced and realistic priority-setting. In general, such national programs or systems all aim at providing a coordination platform at the national level for the conservation and sustainable use of genetic resources and thus they provide a critically important foundation for regional and global activities (Spillane et al. 1999). Nonetheless, and despite increasing recognition of agricultural biodiversity by the CBD, the structure and operations of most national programs remain embedded in agricultural agencies and are often poorly connected to other agencies concerned with conservation of wild biodiversity. The Origins of an International Commitment to Plant Genetic Resources Conservation Despite early alarms like those by Harry Harlan at the Division of Plant Exploration and Introduction in the United States (Harlan and Martini 1936), the loss of genetic resources and the need to maintain genetic diversity begin to emerge as international issues only in the mid-1960s. Geneticists and plant breeders seem to have been increasingly aware of the issue during the 1950s, and Jack Harlan drew attention to the loss of this di-



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versity during a symposium on genetic resources at the American Academy of Sciences in 1959 (Harlan 1961). During the 1960s and 1970s this concern was transformed into a series of programs and initiatives that created the basis of an international plant genetic resources endeavor. The Food and Agriculture Organization (FAO), as part of the United Nations, began to be seen as an important focus for activities associated with the conservation and use of genetic resources. In 1957, FAO launched the FAO Plant Introduction Newsletter to encourage circulation of genetic material between different institutes and soon after provided support for countries to collect and create regional centers of plant resources in Turkey, Ethiopia, and Afghanistan. The Technical Meeting on Plant Exploitation and Introduction, held in Rome in July 1961, was the first international event addressing the issue of loss of genetic diversity. This led to the creation, in 1965, of a Panel of Experts in Plant Exploration and Introduction. From 1965 to 1974, this group met regularly to advise FAO on this issue and to set international guidelines for germplasm collection, conservation, and exchange. Following this series of international discussions, FAO established a new Subdivision for Plant Ecology and Genetic Resources within its Plant Production and Plant Protection Division. The International Biological Program (IBP), initiated in 1964 by the International Council of Scientific Unions with the support of UNESCO, was a second arena, existing in synergy and competition with FAO, for the definition of the issue of genetic resources and related solutions. The program included a section named Use and Management of Biological Resources, with a committee on Plant Gene Pools headed by geneticist and plant breeder Otto Frankel. Although IBP was strongly oriented toward ecological and population approaches, this particular part of its program focused very much on practical aspects of conservation and use from plant-breeding perspectives. The third important element was the creation of the International Board for Plant Genetic Resources (IBPGR). The Consultative Group on International Agricultural Research developed a program of action on genetic resources in 1972, which led to the formation of IBPGR in 1974. Although housed in FAO, the Board was, in practice, programmatically and financially independent. Over the subsequent 15 years there developed increasing distance between FAO and IBPGR in their approach to many key issues of plant genetic resources conservation and use, and in 1989 the Board of Trustees of IBPGR agreed to separate fully from FAO. Nearly

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five years later, in 1994, IBPGR became the International Plant Genetic Resources Institute (IPGRI—­now Bioversity International). These international developments, and the various decisions and recommendations made by the different organizations involved, have been described as reflecting a number of dominant values of the time, particularly: 1. Loss of diversity in agricultural production systems (and hence loss of traditional varieties) was an inexorable and necessary consequence of agricultural development. The Green Revolution accelerated the pace of loss and required greater action but was an essential strategy in global efforts to feed the world. 2. Genetic resources were a world heritage on which plant breeders were free to draw at no cost. Varietal innovations were best seen as efforts to rearrange genes that were initially scattered in multiple varieties. Free access to varieties should be facilitated in every way, and international exchanges of improved varieties should also be fostered. 3. Conservation of plant genetic resources should focus on the development of ex situ gene banks in institutions around the world that could be supported internationally and would be able to distribute the materials they held to potential users (seen as plant breeders and the research community).

All of these were to be the subject of debate over the next decades. Policy Debates on Conservation

During the 1970s and into the 1980s there was increasing debate on the developing international approach and its dependence on ex situ conservation in large, relatively well-endowed gene banks that were largely in the north or that formed part of the Consultative Group for International Agricultural Research (CGIAR). In 1979, Patrick Mooney wrote Seeds of the Earth, in which he denounced both genetic erosion and the takeover of resources by northern interests, and in 1984 he founded the Rural Advancement Fund International with Cary Fowler. Several governments of developing countries expressed concern about the development of patents on biotechnology inventions, while genetic resources in developing countries were free, and raised questions about the possibility that intellectual property rights might be obtained on samples from the collections of CGIAR centers. Mooney



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observed that “the Third World is being invited to put all its eggs in someone else’s basket” (Mooney 1979). The issues of genetic resources conservation, seen up to then as largely technical in nature, became increasingly politicized. In 1981, the group of 77 backed a Mexican proposal at the FAO Conference, the highest decision-making body within the FAO (Resolution 6.81 of the twenty-first session of the FAO conference in November 1981), calling for an international convention that would establish a new gene bank system, independent from CGIAR, and that would bring the IBPGR back under FAO control. An international commitment on genetic resources was negotiated in 1983, reaffirming genetic resources as “common heritage of mankind.” The FAO Commission on Plant Genetic Resources was created during that same year in order to better represent developing countries and discuss issues of “farmers’ rights.” IBPGR responded only partially to these criticisms and claims, despite several negotiations between CGIAR and FAO. Although it became increasingly concerned with supporting national program development and capacity building, it remained primarily focused on collecting and on the technical aspects of ex situ conservation. During the 1990s, the International Plant Genetic Resources Institute (IPGRI)—the successor to IBPGR—became increasingly sensitive to policy dimensions of conservation and use of genetic resources and began an extensive program of work on on-farm conservation. Esquinas-Alcázar et al. (2012) identified two major issues that dominated the discussions at that time: 1. Plant genetic resources are found throughout the world, but the greatest diversity is in tropical and subtropical areas, where most developing countries are situated. When seeds are collected and deposited in germplasm banks, often in developed countries, to whom do these stored samples belong? The country where they are collected? The country where they are being stored? To humanity at large? 2. If the new varieties obtained are the result of applying technology to raw material or genetic resources, why are the rights of the providers of the technology recognized (plant breeders’ rights, patents, and so on) and not the rights of the providers of genetic resources? The establishment of the Commission and the signing of the International Undertaking on Plant Genetic Resources for Food and Agriculture

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in 1983 created a framework for the further development of international policies on plant genetic resources. A very real need was seen to develop an approach that reflected the realities of agriculture and the ways in which resources were used in agriculture. There was concern over the CBD’s approach to biodiversity (the Convention entered into force in 1992), which emphasized country responsibilities and sovereign rights, and the potential impact on the use of genetic resources of the Trade-Related Aspects of Intellectual Property Rights (TRIPS) agreement, adopted in 1994 as part of the Agreement Establishing the World Trade Organization. As a result of a long and often difficult set of negotiations, the members of the Commission agreed in 2001 to establish a Treaty on Plant Genetic Resources for Food and Agriculture with provisions that directly responded to some of the particular characteristics of crop diversity and its management and use (see below). In addition to the issues noted above, the Treaty had to deal with the rights of farmers over the genetic resources which they, after all, had developed and maintained over many generations, and with the ways in which global access to genetic resources might be made operational through a multilateral system of exchange that would transcend the CBD’s country-based bilateral approach to exchange of biodiversity. Technical aspects of conservation were also the subject of increasing discussion during the 1980s and 1990s. Even in the early technical discussions in the 1970s a debate persisted about the relative merits of static ex situ conservation approaches and dynamic in situ ones (see Pistorius 1997), but in situ approaches had been largely dismissed, not least on the grounds that traditional varieties were rapidly disappearing as a result of agricultural development and modern plant breeding (Frankel and Soulé 1981). However, in many production systems, traditional crops and varieties clearly persisted for a whole range of reasons, and conservation workers and many NGOs working with farmers and communities began to argue for their value to be recognized and for them to be supported (for further discussion see Altieri and Merrick 1987; Brush 2000). The Convention on Biological Diversity and Ecosystem Perspectives The entry into force of the CBD in 1992 significantly changed the international “rules of the game” with respect to agricultural biodiversity. Article 1 of the Convention states:



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The objectives of this Convention, to be pursued in accordance with its relevant provisions, are the conservation of biological diversity, the sustainable use of its components and the fair and equitable sharing of the benefits arising out of the utilization of genetic resources, including by appropriate access to genetic resources and by appropriate transfer of relevant technologies, taking into account all rights over those resources and to technologies, and by appropriate funding. Thus, while concerned with biological diversity in the broadest sense, the Convention still uses the concept of genetic resources and emphasizes the importance of fair and equitable sharing of benefits arising from use. It replaced the concept of the global heritage of mankind with country sovereign rights over the resources. It envisaged a system whereby countries would regulate access to the resources within their boundaries. Indeed, the CBD recognizes (1) countries’ sovereignty over “biological resources,” including genetic resources (Art. 15), (2) the obligation to share the benefits arising from the utilization of these resources with countries of origin of the resources and local and indigenous communities (Art. 8j and Art. 15), and (3) the existence of, and the need to respect, intellectual property rights over biological material (Art. 16.5). To a great extent, the CBD linked the conservation of biodiversity with the market value of its components, the “biological resources,” which were susceptible to being appropriated through intellectual property rights (Aubertin et al. 2007). The member countries of the CBD recently negotiated a new international protocol that establishes the measures to be adopted for ensuring equitable benefit-sharing with countries that provide access to genetic resources within their territories: the Nagoya Protocol on Access to Genetic Resources and the Fair and Equitable Sharing of Benefits Arising from Their Utilization to the Convention on Biological Diversity, adopted in 2010. Another element of the CBD, important to the conservation of crop diversity, was the explicit recognition it gave to in situ conservation which it described as: “the conservation of ecosystems and natural habitats and the maintenance and recovery of viable populations of species in their natural surroundings and, in the case of domesticated or cultivated species, in the surroundings where they have developed their distinctive properties.” This recognition can be seen as a consequence of the new and comprehensive understanding of biodiversity conservation and at the same time as an event that helped this new understanding to consolidate. During the

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1990s, there was an increasing interest in in situ conservation and a number of national and international research programs were initiated. This approach, which reflects the earlier thinking of Bennett (1970) and others, was concerned with exploring dynamic conservation approaches that emphasized the importance of continuing adaptation and evolution and recognized the importance of the maintenance of the systems in which crop diversity is present and evolves as a result of the interaction between the environment and humans. This new approach required scientists to work in a more multidisciplinary manner than before, combining anthropology, evolution genetics, population genetics, conservation biology, sociology, and economics (Bonneuil and Fenzi 2011/2012). The implementation of the CBD has involved, inter alia, the development of a number of programs of work, which identified the work that countries should undertake in key areas of conservation. The Programme of Work on Agricultural Biodiversity was adopted in 2002. The CBD considers that agricultural biodiversity includes all components of biological diversity of relevance to food and agriculture, and all components of biological diversity that constitute the agricultural ecosystems, also named agro-ecosystems: the variety and variability of animals, plants, and micro­ organisms at the genetic, species, and ecosystem levels, which are necessary to sustain key functions of the agro-ecosystem and its structure and processes (COP decision V/5). It further notes that agricultural biodiversity is the outcome of the interactions among genetic resources, the environment, and the management systems and practices used by farmers. This is the result of both natural selection and human inventiveness developed over millennia. It identifies the following dimensions of agricultural biodiversity: (1) genetic resources for food and agriculture; (2) components of biodiversity that support ecosystem services; (3) abiotic factors; and (4) socioeconomic and cultural dimensions. This places plant genetic resources and their conservation and use in a wider context of the diversity within the agricultural system as a whole and is reflected in the CBD’s own work programs, which include initiatives on pollination, soil biodiversity, and biodiversity for food and nutrition. In its recent decisions on agricultural biodiversity, the CBD has emphasized collaboration with the FAO Commission on Genetic Resources and the development of collaborative programs of work, creating a framework for a developing global consensus on how to treat agricultural biodiversity internationally.

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table 3.1.  biodiversity benefits to agriculture through ecosystem services. Provisioning

Regulating

Supporting

Food and nutrients Fuel Animal feed Medicines Fibers and cloth Materials for industry Genetic material for improved varieties and yields Pest resistance

Pest regulation Erosion control Climate regulation Natural hazard regulation (droughts, floods, and fire) Pollination

Soil formation Soil protection Nutrient cycling Water cycling

Cultural Sacred groves as food and water sources Agricultural lifestyle varieties Genetic material reservoirs Pollinator sanctuaries

Adapted from MA (2005).

Over the years, the decisions of CBD conferences have increasingly emphasized the importance of ecosystem perspectives. This reflects in part the importance of the frameworks developed and put forward in the Millennium Ecosystem Assessment. This Assessment, published in 2005, was a key moment in the linking, under the global “ecosystems services” cate­gory, of wild and crop biodiversity and, increasingly, climate (MA 2005). Crop genetic diversity has thus recently become considered as essential in the provision of ecosystem services (table 3.1), contributing not only to provisioning services (food, fodder, fuel, medicines, etc.) but also to supporting, regulating, and cultural services. Ecosystem services and ecosystem function are regarded as increasingly important to improving the sustainability of agricultural systems and a response to climate change. Agrobiodiversity at the gene, species, and agro-ecosystem levels increases adaptability and resilience to the changing climate. Promoting agrobiodiversity therefore remains crucial for local adaptation and resilience of agro-ecosystems (Ortiz 2011). Bonneuil and Fenzi (2011/2012) have suggested that it is possible to identify two different paradigms that are operating with respect to the conservation and use of crop plant diversity. The first (which was operational for most of the twentieth century) saw crop diversity essentially as a resource. Plant genetic resources were considered a reserve of genes of inter-

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est to agriculture and other industries such as pharmaceuticals or textiles. This paradigm was associated with an emphasis on the use of ex situ gene banks for conservation of diversity, the view that genetic resources were the common heritage of humankind, constituting a global public good, and an increasing importance of professionals in managing, maintaining, and using diversity. The more recent paradigm, they argue, views genetic diversity as a component of a dynamic biological system and a part of a changing and evolving set of ecosystems. There is a concern with in situ conservation and with maintaining the situations in which evolution and adaptation can continue to occur within the production system. Farmers, rural communities, and indigenous peoples are recognized as playing a key role in conservation, and participatory approaches to conservation and use are emphasized. This paradigm also recognizes national sovereignty over genetic resources and the possibility of developing forms of protection that codify ownership with identified rights and responsibilities: the connections that exist (in terms of evolution, gene flow, and selection) between wild relatives. The FAO Commission on Genetic Resources for Food and Agriculture (CGRFA), the International Treaty on Plant Genetic Resources for Food and Agriculture (ITPGRFA), and the Developing Global System The CGRFA was established in 1983 as the Commission on Plant Genetic Resources (see above) to deal with the policy challenges of the time and to create an international forum for addressing plant genetic resources issues. Later, it expanded its remit to include animal, forest, and aquatic genetic resources. It now oversees the production of reports on the state of the world’s genetic resources for these different components of agricultural bio­diversity and is the forum for developing internationally agreed programs of work to support their conservation and use (see www.fao.org/ cgrfa). The ITPGRFA entered into force in 2004 and has been ratified by over 125 countries. It attempts to create a global framework for collaboration on plant genetic resources and to ensure their conservation and use for the benefit of all. The Treaty is likely to provide the international legal framework that supports on-farm conservation and, since most countries have ratified it, is likely also to provide a relevant national framework. However, national



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implementation is still very patchy, and few countries have so far carried out the various provisions required to put the Treaty into effect at national levels. Important provisions of the Treaty include Article 5, which requires countries to establish both ex situ and in situ (including on-farm) programs of conservation; Article 6, which is concerned with sustainable use of plant genetic resources; and Article 17, which foresees the establishment of national and international information systems. A crucial article, Article 9, recognizes the rights of farmers to benefit from the genetic resources they have maintained. The Treaty also established a multilateral system of exchange and benefit-sharing which is, at present, limited to some 35 major crops and over 50 forage species described as being of importance to global food security (see www.planttreaty.org). The ITPGRFA can be seen as the latest element in a developing global system of conservation and use of plant genetic resources. This system can be thought of as including all the different elements that support conservation internationally. Table 3.2 lists the different elements of this developing global system as described by Hodgkin et al. (2012). On-farm conservation efforts can be considered to derive an international legitimacy from this global system, and some elements directly support it. The most recent Global Plan of Action for Plant Genetic Resources agreed to by CGRFA contains a section devoted to supporting on-farm conservation and improvement of plant genetic resources. ITPGRFA provides funding to a number of country-based projects that support on-farm conservation. Increasingly, CBD decisions and programs are taking account of agricultural perspectives, as the importance of conservation within and around agricultural environments is recognized. Thus Aichi Target 13 explicitly recognizes the importance of agricultural species and states: “By 2020, the genetic diversity of cultivated plants and farmed and domesticated animals and of wild relatives, including other socioeconomically as well as culturally valuable species, is maintained, and strategies have been developed and implemented for minimizing genetic erosion and safeguarding their genetic diversity.” Similarly, CGRFA has moved from a simple concern with securing specific resources to taking account of ecosystem function and services and sustainability, thus reflecting ecosystem perspectives in its work. However, the CBD and ITPGRFA still occupy very different conceptual worlds. The ITPGRFA has a significant concern with ex situ conservation and with the importance of efficient maintenance of individual accessions. It explicitly recognizes the importance of the international gene banks of the CGIAR

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table 3.2.  elements of a potential global system supporting conservation and use of plant genetic resources. Element *International agreements *Food and Agriculture Organization’s (FAO) Commission on Genetic Resources for Food and Agriculture (CGRFA)

*International Treaty on Plant Genetic Resources for Food and Agriculture (ITPGRFA)

*International Code of Conduct for Plant Germplasm Collecting and Transfer

Convention on Biological Diversity’s (CBD) Programme of Work on Agricultural Biodiversity

Aims and notes

The Commission strives to halt the loss of PGRFA and to ensure world food security and sustainable development by promoting their conservation, sustainable use (including exchange), and the fair and equitable sharing of the benefits arising from their use. It covers animal, fish, forest, and microbial genetic resources as well as crosscutting issues and ecosystem perspectives. The Commission has developed a multiyear program of work to guide its efforts. Its objectives are the conservation and sustainable use of PGRFA and the fair and equitable sharing of the benefits arising out of their use. The Treaty aims at recognizing the enormous contribution of farmers to the diversity of crops that feed the world, and at establishing a global system to provide farmers, plant breeders, and scientists with access to plant genetic materials and ensuring that recipients share benefits they derive from the use of these genetic materials with the countries where they have originated. It aims to promote the rational collection and sustainable use of genetic resources, prevent genetic erosion, and protect the interests of both donors and collectors of germ­ plasm. It sets out minimum responsibilities of collectors, sponsors, curators, and users of collected germplasm in the collection and transfer of plant germ­plasm. It was adopted by the FAO conference in 1993 and was negotiated through the CGRFA, which also has the responsibility of overseeing its implementation and review. These programs aim to promote the positive effects and mitigate the negative impacts of agricultural practices on biodiversity in agro-ecosystems and their interface with other ecosystems, and to work toward the conservation and sustainable use of PGRFA and the fair and equitable sharing of benefits arising out of the utilization of these genetic resources. The CBD Programme of Work on Agri­ cultural Biodiversity was last reviewed in 2008. Decision no. X/34 at the tenth Conference of the Parties (COP-10)

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Element

Aims and notes drew attention to the importance of work on crop wild relatives, and the parties agreed on collaboration with the CGRFA, the ITPGRFA, and the FAO on identified activities. At COP-10, parties agreed to adopt the Nagoya Protocol on Access and Benefit Sharing.

*Regional agreements in Asia, Africa, South America, and Europe Regional networks

*Crop networks

*Thematic networks

International fora and associations with interests in PGRFA Regional fora and associations with interests in PGRFA

*Global Information and Early Warning System on PGRFA

This division includes about 18 regional and subregional networks identified in the second Report on the State of the World’s Plant Genetic Resources. The objectives are usually to support all work on a particular crop. They often have a strong emphasis on genetics and breeding. They include, for example, Crops for the Future, which is concerned with underutilized species; the International Union for the Conservation of Nature’s (IUCN) specialist group on crop wild relatives; and Botanic Gardens Conservation International. Such fora include, for example, Diversitas, the IUCN, and the Global Forum on Agricultural Research’s Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services. These exist for each region although with somewhat differing structures and organizations, and concerns for PGRFA. They include the Forum for Agricultural Research in Africa (FARA), the Asia-Pacific Association of Agricultural Research Institutions (APAARI), the Forum for the Americas on Agricultural Research and Technology Development (FORAGRO), the Central Asia and the Caucasus Association of Agricultural Research Institutions (CACAARI), and the Association of Agricultural Research Institutions in the Near East and North Africa (AARINENA). Its mandate is to keep the world’s food supply/demand situation under continuous review, issue reports on the world’s food situation, and provide early warnings of impending food crises in individual countries. For countries facing a serious food emergency, the FAO, the Global Information and Early Warning System, and the World Food Program also carry out joint crop and food security assessment missions (CFSAMs). continued

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table 3.2.  continued Element *State of the World’s Plant Genetic Resources for Food and Agriculture GENESYS

*International Fund and Financial Mechanism for Plant Genetic Resources

*Global Crop Diversity Trust

Global Environment Facility (GEF)

*International Network of Ex Situ Collections (including the CGIAR in-trust collections, CATIE, and the International Coconut Genetic Resources Network) *Network of in situ conservation areas

Aims and notes It assesses the state of plant genetic diversity and capacities at the local and global levels for in situ and ex situ management, conservation, and utilization of PGRFA. GENESYS is currently being developed to improve global information exchange of PGRFA in the attempt to secure and enhance biodiversity throughout the world. It aims to give breeders and researchers a single access point to information on approximately one-third of the world’s gene bank accessions. The objective of this funding strategy is to enhance the availability, transparency, efficiency, and effectiveness of the provision of financial resources to implement activities under the ITPGRFA. The aims of the funding strategy are, among others, the development of ways and means by which adequate resources are available for the implementation of the Treaty, in accordance with Article 18 of the Treaty. The trust is raising funds from individual, foundation, corporate, and government donors for an endowment fund that will support the conservation of key crop collections in perpetuity. An independent financial organization, it provides grants to developing countries and countries with economies in transition for projects related to biodiversity, climate change, international waters, land degradation, the ozone layer, and persistent organic pollutants. Although it mostly supports country projects, the GEF has an agreed global strategy and strategic objective on mainstreaming conservation, which is relevant to the conservation and use of PGRFA. The UN Environment Programme’s GEF has provided over $100 million in support of multinational projects over the past ten years. In 2006, in accordance with Article 15 of the ITPGRFA, the centers placed their ex situ gene bank collections under the ITPGRFA. The Article 15 agreements replace the former agreements concluded between the centers and the FAO in 1994.

Two relevant networks that already exist are the Globally Important Agricultural Heritage Systems and the Man and Biosphere Programme.

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Element Svalbard Global Seed Vault

Global Partnership Initiative for Plant Breeding Capacity Building (GIPB)

*Global Plan of Action (GPA) for the Conservation and Use of Plant Genetic Resources for Food and Agriculture

National collections placed under the MLS

International nongovernmental organizations

International research efforts

Aims and notes It is designed to store duplicates of seeds from seed collections around the globe. Many of these collections are in developing countries. If seeds are lost—for example, as a result of natural disasters, war, or simply a lack of resources—the seed collections may be reestablished using seeds from Svalbard. Its mission is to enhance the capacity of developing countries to improve crops for food security and sustainable development through better plant breeding and delivery systems. The longer-term vision of success of this initiative is the improvement in crop performance and food security based on the establishment of enhanced sustainable national plant-breeding capacity. It might also be classed as an agreement but is placed here because of its emphasis on the actions that need to be undertaken to support global conservation objectives. The GPA’s main objectives are to: ensure the conservation of PGRFA as the basis of food security; promote sustainable use of PGRFA to foster development and reduce hunger and poverty; promote the fair and equitable sharing of the benefits arising from the use of PGRFA; assist countries and institutions to identify priorities for action; strengthen existing programs; and enhance institutional capacity. Included here to emphasize the point that national collections are as much a part of the global system as international collections and, once placed under the MLS, become an effective global resource. These organizations include the IUCN, the Botanic Gardens Conservation International, as well as civil society organizations with a commitment to specific objectives in regard to PGRFA’s conservation, such as the European Topic Centre on Biological Diversity, GRAIN, Practical Action, and so on. Includes the research and breeding activities of the CGIAR and other international and regional centers.

Note: There are a number of international agreements that affect the use of PGRFA through their effect on the release, availability, and distribution of crop varieties and seeds. These include the UPOV, the Rotterdam Convention, world trade regulations, and a range of seed-certification schemes which operate internationally and regionally. Although they are not usually regarded as part of the global system of PGR conservation and use, their effect on PGR use and on the amount of diversity likely to be found in production systems may be significant. * Included in FAO’s description of the Global System. Adapted from Hodgkin et al. (2012).

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and the work of the Global Crop Diversity Trust. The CBD remains primarily concerned with ecosystem perspectives and with in situ ­conservation. The Use of Genetic Resources for Plant Breeding In its primitive form, plant breeding started after the invention of agriculture, when human beings switched from a lifestyle of hunter-­ gatherers to sedentary producers of selected plants and animals. It is difficult to identify when crop-improvement techniques led to the development of new plant varieties that previously did not occur in natural populations, but archaeological records indicate that the Assyrians and Babylonians artificially pollinated date palm at least 2,700 years ago. Important developments from the sixteenth century onward included descriptions of cultivated plants in the herbals of the sixteenth century, the description of sexual reproduction in plants by R. J. Camerarios in 1694, the first systematic studies on plant hybridization by Joseph Koelreuter from 1760 to 1766, and the classification of plants developed by Carolus Linnaeus during the second half of the eighteenth century. Plant breeding as a commercial endeavor became increasingly important during the nineteenth century. Seed companies selected specific strains that they sold with identified names. The numbers of varieties of many crops that were available to farmers grew rapidly, and seed catalogues from the end of the nineteenth century and the beginning of the twentieth century often list a very large number of varieties, which were frequently reselections of specific types by individual seedsmen. The twentieth century saw the rediscovery of Mendel’s works on inheritance (originally published in 1865) and the gradual development of plant-breeding programs based on genetics and theories of selection. The value of F1 hybrids for maize and other outpollinated crops was recognized and their production became the norm, not only in maize but also in sunflower, tomato, and many vegetable crops. Breeding programs became larger as the importance of using large numbers of progeny from planned crosses was recognized. From the mid-twentieth century until the 1980s, the state often played a major role in the development of new varieties, particularly after the Second World War in Europe, where the need to expand production as a response to postwar food shortages was of paramount importance. The development of ways of protecting new varieties, particularly during the second half of the twentieth century, played an important part in stimu-



resources, conservation, and politics   

lating investment in plant breeding by the private sector (see Chapter 10 for further discussion). Another important development in breeding major crops was the establishment of the international agricultural research system, which dates back to 1940, when the United States and Mexican governments requested support from the Rockefeller Foundation for research on basic food crops. As a result, a special unit focusing on maize, wheat, bean, and soil management was established in the Mexican Ministry of Agriculture. Following the Mexican example, in the 1950s India and Pakistan established technical assistance programs. In 1960, the International Rice Research Institute (IRRI) was opened in Los Baños, Philippines. The genetic improvement of rice at IRRI followed the already formalized model of pedigree breeding, international collaborative trials, and sharing of germplasm and information that had earlier been adopted by the wheat system in Mexico. The development of the first high-yielding semi-dwarf varieties of wheat by the Mexican program and of rice by IRRI, and the rapid expansion of both of these innovations through the international nursery networks, stimulated the origin of the Green Revolution. Traditional varieties provided the starting material for the selection of the first modern varieties developed by public- and private-sector breeding programs. As these new varieties became more widely distributed and adopted, traditional varieties were replaced. This was accompanied by an overall reduction in the diversity present in the areas of adoption. While modern varieties were significantly more productive under the conditions of high-input agriculture, they often did not meet the needs of low-input farming systems in environmentally variable areas, where traditional varieties continued to be grown. The varieties developed through established breeding programs were increasingly uniform and genetically homogeneous. In self-pollinated crops, pedigree breeding programs led to the development of homozygous lines with the desired traits of the new variety. In outpollinated crops the demand for uniformity was met through the development of F1 or double cross hybrids. Increasing use of highly selected materials adapted to modern farming techniques led, in some cases, to a steady reduction in diversity in production systems and a tendency for varieties to be developed from a narrow genetic base. Plant breeders preferred to use already improved materials wherever possible, rather than materials such as traditional varieties that would necessitate several cycles of additional selection to re-create

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the desired phenotype and characteristics required in modern varieties. Of course, if the desired trait was present only in such traditional materials, their use, and the additional work involved, were accepted. As noted above, the transition from traditional varieties to modern varieties was accompanied by an overall loss of genetic diversity. However, once the transition had occurred, the loss of diversity was much slower and in some crops seemed not to have been very significant. A meta-analysis of changes in diversity over time has suggested that rather little had changed over the period 1930– 1990 (van de Wouw et al. 2010), except for a 6 percent reduction during the 1960s that appears to have been followed by some recovery. During the past few decades, some plant breeders have begun to test and adopt innovative approaches to crop improvement that are closer than conventional plant breeding to farmers’ traditional practices of crop diversity management and that take plant breeding back to farmers’ fields. Evolutionary plant breeding was first introduced in the 1950s based on “a broadly diversified germplasm, and a prolonged subjection of the mass of the progeny to competitive natural selection in the area of contemplated use” (Suneson 1956). Participatory plant breeding (PPB) is the process by which farmers are routinely involved in a plant-breeding program with opportunities to make decisions throughout (see Chapter 12). By adopting these two techniques and, sometimes, by combining both, breeders aimed at providing farmers with more diverse varieties and populations, with better capacities to adapt and perform in different environments in the absence of externally supplied inputs. Conclusions—A Continuing Debate The political debates surrounding plant genetic resources conservation continue, although their intensity and nature vary depending on the national and international policy-making fora where they take place. The debates change and evolve with changing political perspectives and new appreciation of the importance of genetic resources to different sectors of society. Some of the elements of current discussions that need to be taken into account include: 1. While the initial concern with on-farm conservation emphasized the conservation benefits, there is increasing awareness of the socioeconomic and cultural dimensions and a concern with wider livelihood benefits from the maintenance of traditional varieties.



resources, conservation, and politics   

2. Climate change is creating an increasing interest in adaptability and resilience in production systems, and with it the importance of ensuring that diversity is present to provide these properties. It is also creating an increased interest in the resources themselves by plant-breeding companies and a recognition of the importance of ensuring a continuing supply of new better-adapted varieties. 3. The interface between the CBD, ITPGRFA, Commission on Genetic Resources, and wider international policy decisions like TRIPS is becoming more complex and is increasingly constraining the decisions of countries. This can be desirable in that, for example, the Treaty places clear obligations on countries to support on-farm conservation. However, it also results in increasing consciousness of property perspectives, ownership, and intellectual property considerations around the development of new varieties. 4. Traditional varieties are dynamic and changing (see Chapter 11), and most national and international conservation and use programs are poorly equipped to cope with this aspect. Even the most advanced legislation that supports the maintenance of traditional varieties sees them as essentially static entities with stable characteristics. 5. The growth of active NGOs and social movements around a common concern with food and food sovereignty is likely to strengthen recognition of the importance of on-farm maintenance of traditional varieties. At the same time, strengthened agricultural development programs often remain antagonistic to the maintenance of such materials in favor of new uniform varieties. The increased demand for agricultural land (as seen in recent “land grabs”) also threatens local approaches to sustainable development that make use of traditional varieties. 6. Plant breeding has become increasingly commercialized over the past 50 years or so and dominated by large transnational seed companies. Their interest in traditional varieties is as potential users of the traits found in them as part of the process of producing new high-yielding varieties. This can be met through ex situ germplasm collections, allowing seed companies to encourage replacement of traditional varieties in production systems.

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Contrasting approaches to crop improvement based on PPB are being tested around the world but, apart from the International Center for Agricultural Research in the Dry Areas (ICARDA) barley breeding program, which has involved countries in the Middle East and North and East Africa, these are small programs involving only a few crops. Pressures reflecting these different issues and the opposing views held by different actors will undoubtedly continue to affect on-farm conservation activities and the work of those involved. Further Reading Bonneuil, C., and M. Fenzi. 2011/2012. “Des ressources génétiques à la biodiversité cultivée.” Revue d’anthropologie des connaissances 5:206–33. Chiarolla, C. 2011. Intellectual Property, Agriculture, and Global Food Systems. Edward Elgar Publishing, UK. Esquinas-Alcázar, José, Angela Hilmi, and Isabel López Noriega. 2012. “A brief history of the negotiations on the International Treaty on Plant Genetic Resources for Food and Agriculture.” Pp. 135–49 in Crop Genetic Resources as a Global Commons: Challenges in International Law and Governance (M. Halewood, I. López Noriega, and S. Louafi, Eds.). Routledge, NY. Gepts, Paul. 2004. “Who Owns Biodiversity, and How Should the Owners Be Compensated?” Plant Physiology 134 no. 4:1295–307. Hodgkin, T., N. Demers, and E. Frison. 2012. “The evolving global system of conservation and use of plant genetic resources for food and agriculture.” In Crop Genetic Resources as a Global Commons: Challenges in International Law and Governance (M. Halewood, I. López Noriega, and S. Louafi, Eds.). Routledge, NY. Moore, Gerald K., and Witold Tymowski. 2005. Explanatory Guide to the International Treaty on Plant Genetic Resources for Food and Agriculture. IUCN, Gland, Switzerland. Pistorius, Robin. 1997. Scientists, plants and politics: a history of the plant genetic resources movement. Bioversity International (IPGRI & INIBAP), Rome. Tauli-Corpuz, V., L. Enkiwe-Abayao, and Raymond De Chavez, Eds. 2010. Towards an Alternative Development Paradigm: Indigenous Peoples’ Self-Determined Development. Tebtebba Foundation, Baguio City, Philippines. Thrall, P. H., J. G. Oakeshott, G. Fitt, S. Sotherton, J. J. Burdon, A. Sheppard, R. J. Russell, M. I. Zalucki, M. Heino, and R. F. Denison. 2011. “Evolution in agriculture: the application of evolutionary approaches to the management of biotic interactions in agro-ecosystems.” Evolutionary Applications 4:200–215. Tilford, D. S. 1998. “Saving the blueprints: The international legal regime for plant resources.” Case Western Reserve Journal of International Law 30:373–446.

Plate 3. The development of programs to support the conservation and use of plant genetic resources and traditional varieties has been accompanied by considerable, often acrimonious, debates on such issues as how agricultural biodiversity is perceived, the ownership of the materials, and the ways in which farmers, communities, plant breeders, and, today, genetic engineers should be recognized and rewarded for their contributions to the continuing evolution and improvement of crop varieties. Some plant breeders have begun to test and adopt innovative approaches to crop improvement that are closer than conventional plant breeding to farmers’ traditional practices of crop diversity management, and that take plant breeding back to farmers’ fields. The upper left photo shows a panel discussion during the 146th Session of the FAO Council in Rome. The conservation and use of plant genetic resources have been a recurrent element in the agenda of this intergovernmental body. The upper right photo shows the International Institute of Tropical Agriculture (IITA) ex situ gene bank cowpea collection located in Nigeria. Each of the bottom photos shows a different method of evolutionary participatory plant breeding. On the left, a farmer and researcher are carrying out mass selection on maize. On the right, breeders and farmers are jointly selecting rice plants in Nepal. Photo credits: ©FAO/Alessia Pierdomenico (upper left), IITA (upper right), D. Jarvis (lower left), B. Sthapit (lower right).

chapter 4

Diversity and Its Evolution in Crop Populations

B

y the end of this chapter the reader should have an understanding of:

• Basic concepts of genetic diversity and its measurements in plant populations; • How population size, evolutionary forces, and reproductive biology affect the extent and distribution of genetic diversity. The treatment of population genetics is introductory, for those who are not familiar with the subject. Interested readers may complement and extend their knowledge by consulting textbooks such as Gillespie (2004), Hedrick (2004), Hartl and Clark (2007), Hamilton (2009), Frankham et al. (2010), or other standard texts on population genetics. The Nature of Diversity Diversity describes the nature and extent of variation that occurs in a system, or in relation to a set of entities. Three levels of biodiversity are usually distinguished—ecosystem, species, and genetic (Frankel et al. 1995). Ecosystem diversity describes the variety or number of ecosystems in an area (ultimately the entire biosphere), while species diversity is concerned with the numbers and frequencies of species. Genetic diversity is the result of the genetic variability among or between a set of individuals of a variety, a population, or a species. It arises from the differences in the DNA sequences of different individuals.



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In crop plants, genetic diversity is most commonly seen as differences between varieties of a crop. The individual plants of a particular named variety may approach uniformity, as in the case of exclusively self-pollinated crops such as rice, or in clonally propagated crops such as potato or apple (for example, the differences between apple varieties such as Red Delicious and Granny Smith). Partially or wholly cross-pollinated crops may show large amounts of variation within varieties as well as between varieties. For example, crops such as maize, pearl millet, or cabbages can show considerable plant-to-plant variation within any one open-pollinated variety of the crop. The amount of diversity present in plant species, populations, or varieties reflects the amount of DNA sequence variation present, which results in differences in genes. Genes are sequences of DNA that are responsible for a discrete hereditary characteristic, usually corresponding to a single protein or RNA. DNA sequences are organized into chromosomes in cell nuclei or are found in cell organelles such as chloroplasts and mitochondria. The genetic constitution provides the first basis for a description of the properties of a plant. A genetic locus may have alternative forms, called alleles. A locus is the place on a chromosome where an allele resides. In a diploid organism, such as rice, each chromosome will carry an allele of the same gene, occupying the same position (or locus) on each member of the homologous pair of chromosomes. If the two alleles at any one locus are the same, the individual is said to be homozygous with respect to that gene. If the alleles are different, the individual is described as heterozygous. Often a locus appears to have only two alleles in the population (for example, the round and wrinkled peas studied by Mendel). However, a locus may also have a number of alternative alleles. This is frequently the case with biochemical or molecular variation such as seed proteins, isozymes, or microsatellites described below. Within a population of plants or a traditional variety, there can be one, two, or more alleles, or versions, of the gene. A genotype is the totality of the genetic constitution of an individual, referring either to the set of alleles at a particular limited number of loci, or to all the loci in the genome. A phenotype is the sum of physical characteristics of a plant and results from the interaction between the genotypic status of an individual and environmental conditions. Not all differences in DNA sequence result in a physical difference in the plant. In fact, much of the sequence variation in many species is cryptic and may result in no visible difference in plant characteristics. Variation that can be detected includes obvious differences in specific qualitative

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table 4.1.  kind of data: phenotypic examples and genetic examples. note that both phenotypic and genetic data can be metric, ordered, or unordered. Kind of data Metric or measurement traits Count or qualitative data—ordered Count or qualitative data—unordered

Phenotypic examples Plant height, seed weight Seed number per legume Major-gene disease resistance, seed color

Genetic examples DNA sequence divergences SSR or microsatellite alleles RAPD, AFLP

traits such as flower color, and variation in quantitative characteristics such as height, time to maturity, and seed weight (table 4.1). It also includes variation in performance-related traits such as resistance to pests and diseases, biochemical differences in the production of specific enzyme forms or secondary metabolites, and differences in DNA sequence. This last has become an increasingly important and useable method of analyzing diversity over the last decade. Various different procedures are now available to detect different kinds of DNA variation among individuals (see Chapter 5). Crops, Varieties, and Populations: Population Structure An important aspect of on-farm maintenance and use of crop diversity is gaining an understanding of the amount and distribution of genetic diversity present in crops in farmers’ fields. The quantification and analysis of patterns of genetic diversity allow one to answer questions such as: How genetically variable are the varieties of a crop, or different populations of one variety currently growing in a village or on-farm? How much do varieties differ from one another in the kind and amount of variation they harbor? Do some varieties contain unique characteristics (singly or in combination) that are absent from other varieties? Answering such questions involves plant population genetics, a discipline that has three aims: (1) to describe the genetic diversity within and between the populations of a plant species, (2) to estimate the nature and strength of the evolutionary forces that shape these observed patterns of diversity, and (3) to develop models that predict the stability and change

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in these patterns. Plant population genetics underpins decisions such as how many different populations or varieties in an area provide an adequate sample of the diversity of a crop for different objectives such as meeting the needs of farmers and communities, providing adaptability, limiting vulnerability, or meeting overall conservation targets. A population is a group of plants of one crop or species that are growing together in a specified locality. In the case of traditional varieties, different farmers commonly maintain separate populations, and the individual populations that they maintain constitute their unit of management of the varietal diversity. In a specified area, the population structure of a crop species can be complex and can compose several levels in a hierarchy. At the highest level are the number of varieties and proportionate acreage planted to each variety of that species. Next, each variety may be planted as several distinct populations in various farms and different fields of the community or region. The final level of structure may be evident within a local population as distinct subpopulations, such as age-related cohorts of a perennial fruit tree, or plants growing in distinct microhabitats defined by local variation in soil, exposure, or moisture conditions. Again, the number and size of sub­ populations specify the structure. Size The size of a population is the number of individuals growing in that population in a given area. Depending on the population and species, this could be the number of plants in a single field, or the number of plants of a variety in a specified area. While in any one generation not all individual plants of a single population actually mate and exchange genes with all others, they potentially can do so. In the case of self-pollinating or clonally propagated species, the local population tends to fragment into many different lineages that would be genetically isolated except for rare outcrossing. In many field crops propagated by seed, the number of individuals in a single population is very large, with farmers growing many thousands of individuals in a field. Crops grown in home gardens usually have much smaller population sizes, with only a few individuals growing in any one home garden of crops like pepper, sponge gourd, or fruit trees. The size of a population is one factor that affects its genetic composition, especially when there are large changes in size due to random or cat-

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astrophic events. Small populations tend to have less genetic diversity and a larger number of homozygous loci than large ones. A reduction in population size results in the loss of some individual alleles and the fixation of others within the population. Some changes in population size may occur because of normal management practices, as when farmers select a small number of plants as parents for the next generation. However, changes can also occur because of the spread of a serious disease or flooding, hurricanes, or other similar event (see Chapter 7). Two parameters that are useful to describe the abundance or size of a population for comparison are frequency and density. Frequency refers to the proportion of spatial units in an area that contains the members of the population, such as the proportion of fields, or of area on a farm, or in a landscape that contains a particular variety. Density is the number of individuals per unit area such as per field or farm. A particular fruit tree variety may be grown by every household in a village and have a high frequency but a low density, assuming the farmers grow only one of each variety on each farm. Even in natural plant populations, not all individuals in a population will produce the same number of progeny in the next generation. In crop populations, farmers often select a limited number of plants or seed heads to provide next year’s seed, but even without this, the seeds actually sown will usually come from a small number of plants of the previous crop. The “effective” size of a population is, at most, the number of individuals that actually contribute gametes to the next generation. It is likely to be less than this if the fecundity of each parental plant varies a great deal, such as when most of the seeds stem from only one plant. In such cases, the effective size is usually much smaller than the actual population size. As well as depending on farmer decisions on the number of seed parents, the effective population size will reflect any previous founder effects, bottlenecks in size, the crop’s breeding system, and variation in plant fecundity. Maturity, Perenniality, and Structure As noted above, differences in maturity of the plants in a population can have a significant effect on the structure of a population. Plants that flower at different times will not intercross, and this may lead to the divergence into different subpopulations maturing at different times. Of course, this can assist farmers in ensuring continuity of supply of a crop, as

diversity and its evolution   



is the case for many fresh vegetables. Differential flowering times are also important in the isolation of different varieties, such as in maize, helping to keep them distinct by lessening the chance of crossing between them. Determinacy refers to the tendency of the plants in a population for coordinated flowering and ripening at the same time. Determinacy may be under heavy selection pressure in the farmer’s field, for seed production and harvest. The plants may differ substantially in age and maturity, but still have a long period (over many years) of possible overlap in flowering and fruiting times. In populations of perennial plant species it is the timing of flowering events within a year rather than maturity per se that will affect population structure. Perennial crop species, such as fruit trees and date palms, may have complex age structure on-farm. Farmers may have chosen different geno­ types when planting new cohorts or replenishing losses. This leads to opportunities for affecting mating system, fruit yield, and gene exchange between age-cohorts. In wild plant populations, an important cohort of age structure is the dormant seed bank in the soil. Discarded seed of fruits and local seed banks are analogies in horticultural and field crop populations. Connectedness Connectedness refers to the links between the spatially distributed elements between plant populations and involves both the spatial isolation of populations and the frequency of migration (of seed or pollen) between populations or subpopulations. The term “gene flow” applies when the donor and the recipient populations differ in allele frequency. Several theoretical models are available for analyzing connectedness between populations such as the continent-island model, the multiple island model, and the stepping-stone model (see Hamilton 2009 for further information). The metapopulation concept (or “population of populations”) stands at one extreme of the “connectedness” spectrum. The primary dynamics of a metapopulation are the extinction of distinct populations in the system to leave “niches” temporarily vacant, later to become reoccupied or colonized by dispersal. The concept emphasizes the population ecological processes of local extinction and recolonization rather than the genetic ones of cross-pollination, migration, or seed admixture. The metapopulation concept seems relevant to situations where a single variety is grown in different fields around a landscape. Occasionally the variety may be lost from

   diversity and its evolution

one farm or field and, subsequently, the farmer may replace fresh seed from another external source. The way in which metapopulation approaches can be helpful in understanding genetic structure of traditional varieties will be discussed in Chapter 11. In situations where farm or field size decreases, or where new refined modern varieties extend over increasing areas of land, the area growing a particular traditional variety may shrink to a smaller size. Ultimately, the sampling inherent in such processes might give rise to recognizably new variants, particularly in combination with a farmer’s choices. Some crop varieties may continue to exist for a long time in very small populations grown by only one or two farmers, while others rapidly disappear, but whether this is related to their small population size or to other reasons (for example, the farmer finds a better alternative variety) is difficult to establish. Small populations of rare varieties of partially or completely outbreeding crops are likely to suffer the loss of allelic variants and inbreeding depression. Minimum Viable Populations The size, life history, connectedness, and breeding system (see below) of a population form the framework for the concept of a minimum viable population. This is the size of a population needed to have a level of genetic diversity that will ensure the persistence of a population for a specific time, usually at a specified probability (see Frankel et al. 1995 for further discussion). In crop plants, the concept may be most relevant in relation to the maintenance of small populations of large perennial species—such as fruit trees—or home garden crops—such as spices, chili peppers, or vegetables. However, given the essentially managed nature of crop varieties and the importance of farmers’ decisions in determining the continued existence of a variety, the concept of minimum viable population is difficult to apply to crop conservation, although a useful concept in assessing observed population sizes. Population Genetic Structure So far, we have been discussing populations in terms of the numbers of individuals without any particular reference to their genetic makeup. Analysis of population genetic structure turns the attention to the genetic characteristics of populations—the genes and allelic variants and their fre-

diversity and its evolution   



quencies in a population—and how these vary within and among populations in space and time. As noted above, a considerable range of different methods has been developed to determine the extent and distribution of diversity within and between populations. These include analysis of variation as found using morphological characters, quantitative performance-related variables, biochemical traits, and DNA markers. Many countries and laboratories around the world now have the capacity to generate molecular data from Amplified Fragment Length Polymorphism (AFLP), microsatellites, Single Nucleotide Polymorphism (SNP), and Expressed Sequence Tags (ESTs). Sequencing capabilities have developed rapidly over the last de­ cade and it is now realistic to talk in terms of generating DNA sequences of specific loci of large numbers of plants, or even of generating full-sequence data for significant numbers of plants of a species (see Chapter 5). However, managing and analyzing the data from such procedures still presents significant problems. Despite the extraordinary development of DNA analysis capacities, it is worth remembering that much useful information can still be obtained from quantitative data or even simply from data on variety distribution, provided it is collected and analyzed in ways that inform the specific questions to be addressed. Even the most comprehensive set of DNA data ultimately needs to be connected in some way to the morphological, agronomic, and other useful traits in which farmers and producers are interested. Richness and Evenness Richness and evenness are two key notions or parameters of diversity of particular importance to studying and maintaining crop diversity. Richness is the total number of different alleles, or genotypes, or distinct types present in a specified sample. Evenness refers to the similarity in frequency of the different types (alleles or genotypes) and the lack of one or a few types greatly outnumbering all other co-occurring types (Frankel et al. 1995). The concepts of richness and evenness can be applied to molecular data such as microsatellite allele numbers, haplotypes, identifiable allelic states (for example, seed colors or biochemical markers). They apply also to the frequencies of individual crop varieties or to the numbers of crops or species present in a production system. Most commonly, qualitative data are used to estimate richness and evenness, but quantitative data can also provide estimates (table 4.2).

   diversity and its evolution

table 4.2.  the measurement of richness and evenness. Richness Quantitative or metric data

Qualitative or count data

Range (depends on sample size) After classifying, the number of classes Number of types Number of alleles per locus Number of multi-locus genotypes, clones, haplotypes

Evenness Coefficient of variation, skewness, kurtosis Variance components Similarity in frequency of types Gene diversity index (Nei) Nei index of genetic diversity, Shannon-Weaver Index. Note: these indexes combine both evenness and richness.

Table 4.3 presents an example of richness and evenness of sorghum varieties from Yambasse in Burkina Faso. The results from a survey of eight different farmers show that they grew a total of six different varieties on areas that ranged from 5,000 m2 to 17,500 m2. The most common variety (Belko) was grown on 38 percent of the land used, while the least common (Bura pelga) was grown on only 3 percent of the land. Individual farmers grew from one to three varieties on areas that varied from about 2,500 m2 to about 10,000 m2 (1 ha). From the data it was possible to calculate richness and evenness for each farmer and for the community sampled (richness = 6; evenness calculated as the Nei index of genetic diversity [or panmictic heterozygosity He ] = 0.72). It was also possible to estimate the divergence—the proportion of additional diversity to be found in different areas of varieties, maintained by the different farmers in the sample (community He − mean farmer He / community He = 0.36). Jarvis et al. (2008) investigated the diversity of traditional varieties of 27 crops from eight countries (figure 4.1). They recorded variety names and the areas the varieties occupied in three communities in each country by talking with farmers from over 2,000 households in 26 communities in the different countries. The researchers found that richness and evenness were closely related, at both farm and community levels. In some cases, high dominance occurred, with much of the variety richness held at low

table 4.3.  richness and evenness of sorghum varieties for a single site in yambasse, burkina faso. Sorghum variety names Farmer name Bouda, Laurent Mare, Salamata Ouedraogo, Marcelline Ouedragog, Hamidou

Total area (m2) 17,500 5000

Belko

5000

1.00

17,500

0.29

5000

Ouedraogo, Inoussa

7500

0.67

Dakissaga, Boukare

17,500

0.57

Total cultivated land to sorghum of sampled HH

5000

Kara Wanga

0.50

0.14 0.50

0.29

Sampelga, Barahissa

Dakissaga, Bintou

Gambre

Zulore

0.14

Household richness

Household Simpson (1-sumsq)

0.57

3 2

0.57 0.50

1

0.00

0.57

3

0.57

2

0.50

0.33

2

0.44

0.29

3

0.57

2

0.50

2.25

0.46

Zugilssi

0.50

0.50 0.14

0.50

Bura pelga

0.50

80,000 Mean HH richness and Simpson

Area covered by each variety in the community (%)

Community richness (total number of varieties in the community) 0.38 0.09 0.09 0.06 0.34 0.03

6

Community Simpson (based on percentage of area covered by each variety at community level) Divergence (= Community simp—mean HH Simp/Community Simp) Source: Sawadogo et al. (2005b).

0.72 0.36

   diversity and its evolution (a)

(b)

(a) Relationship between farm evenness and farm richness, both on a logarithm scale. Black circle = main staple; gray circle = non-main staple; 2  2 contingency x (p = 0.03). (b) Relationship between farm area and divergence, both on a logarithm scale. White circle = outcrossing; semi-filled circle = partial outcrossing; gray circle = inbreeding; black circle = clonal. Graph excludes farms with