A Guide to Sorghum Breeding

A Guide to Sorghum Breeding Second Edition Leland R. House January 1985 ICRISAT International Crops Research Institute for the Semi-Arid Tropics ICRISAT Patancheru P.O. Andhra Pradesh 502 324, India CONTENTS Foreword vii Morphology of Sorghum 12 About This Book viii Roots 12 Acknowledgments ix Culms 13 SECTION 1. THE SORGHUM PLANT: USES, Leaves 13 CHARACTERISTICS, DISTRIBUTION Infloresence 14 Sorghum Uses 1 Panicle 14 Basic Characteristics 2 Raceme 14 Yield Potential 2 Adaptability 2 SECTION 3. GENETICS Fertilizer Response 2 Basic Genetics 27 Water Relations 2 Biological Variation 27 Temperature Relations 2 Basis of Heredity 28 Plant Protection 2 Mitosis 29 Current Production Data 3 Process of Mitosis 29 Sorghum Domestication 3 Meiosis 29 Origin 3 Process of Melosis 31 Early Geographic Spread 4 Gametogenesls and Fertilization 33 Taxonomy 4 Fertilization 33 Species Classifications 4 Single-Factor Inheritance 33 Cultivated Sorghum 7 Basic Laws 33 Wild Sorghum 9 Symbols 36 References 9 Alleles 36 Intermediate Phenotypes 37 SECTION 2. THE SORGHUM PLANT: GROWTH STAGES AND MORPHOLOGY Segregation 37 Growth Stages 11 Test Cross 37 Vegetative Phase 11 Reduction of Heterozygosity by Selfing 38 Germination and Seedling Backcrossing 38 Development 11 Reproductive Phase 11 Independent Assortment 40 Inflorescence Development Dlhybrid Segregation 40 and Fertilization 11 Dihybrld Test Cross 41 Maturation Phase 12 Linkage 42 Seed Development 12 Linked Genes 42 Crossing Over 42 SECTION 4. SORGHUM IMPROVEMENT: Chromosome Mapping 42 METHODS AND PROCEDURES Plelotropic Ger.es 44 Some Basic Working Concepts 73 Two-Factor Inheritance 44 The World Collections of Sorghum and Milllets 75 Mutation 46 Background 75 Chromosome Mutations 46 Remaining Considerations Gene Mutations 46 for Study 76 Induced Mutation 47 Types of Collections Recommended Ploldy 47 for Development 77 Aneuploids 47 Pedigree and Cultivar Nomenclature 78 Euplolds 48 Pedigree Systems 78 Inheritance in Polyploids 49 Basic Uses and Notations 78 Quantitative Inheritance 49 Nomenclature When Crossing Is Involved 84 Variation Due to Environment 49 Backcrosslng 84 Variation Due to Genotype 49 Crossing as a Source from Additive, Dominance, Which to Select New Lines 85 and Epistatic Gene Action 51 Crossing as Part of a Population Genetics: Gene Frequency Hybrid Program 87 and Equilibrium 52 Nomenclature for Lines Gene Frequency 52 and Hybrids to be Released 87 The Hardy-Weinberg Law 53 Breeding Objectives and Procedures 89 Factors That Change Gene Pedigree Breeding 89 Frequency 55 Selection 57 Pollination Procedures 89 Mutation 61 Pedigree Selection 90 Joint Effects of Selection Procedures for Taking Notes 90 and Mutation 62 Selection 91 Subdivision and Migration 62 Crossing InSorghum 93 Small Populations and Effective Choosing Parents Population Size 63 for Crossing 93 Summary 64 Factors Influencing Time Genetics of Sorghum 64 from Sowing to Flowering 94 The Genetics of Maturity 64 Choice of Field 95 Effect of Photoperlod Sowing Rate 95 on Flowering 65 Crossing without the Use The Genetics of Height 69 of Male-Sterility 95 Other Genetic Characters Emasculation by Hand 96 of Interest 70 Equipment Required 96 References 72 The Floral Structure 9" it' The Emasculation Operation 97 Environmental Factors Emasculating with the Hot Water Affecting Grain Quality 141 and Plastic Bag Technique 102 Field Support Techniques 142 Pollination 102 Crop Management 142 Field Records 103 Field Layout 143 Crossing Block for Making Hybrid Seeds Record Books 144 on Male-Sterile Female Parents 112 Row Tags 149 A, B, and R Lines 112 Field house 149 Obtaining Adequate Quantities References 150 of Hybrid Seed 113 Organizing Decisions 113 SECTION 5. THE SEED INDUSTRY: ROLE, Developing New Male-Sterile ORGANIZATION, AND DEVELOPMENT Seed Parents 115 The Role of a Well-Organized Crossing In Large Isolated Seed Industry 152 Open-Pollinating Blocks 116 What is a Seed Industr/? 152 Seed Production 116 Seed Production 153 Flowering Records 118 Industry Organization 154 Composites 118 A Quality Seed Production Symbolic Designations and Distribution Program 155 of Sorghum Populations 119 Implementing the Basic Requirements 156 Selection Techinques 120 References 161 Breeding for Insect Developing A Seed Industry 162 and Disease esistance 126 Responsibilities of Government 163 Mode of Inheritance and Breeding Procedures 126 Responsibilities of Seed Producers 164 Ease of Trait Identification 129 Intensity of Selection 129 APPENDIX I Environmental Factors 131 The Seed Law 167 Screening Procedures 131" DevelopmentSeed Law of167 a Model Insect Resistance 131 Seed Law Enforcement Agency 168 Diseases 133 Official Seed Board 168 Striga 134 Official Seed Testing Stand Establishment 135 Laboratory 168 Breeding for Food Quality 136 Official Inspectors 168 Grain Molds 137 Financial Requirements 168 Evaluation of Food Quality 137 Guidelines for Establishing Grain Traits Affecting Food a Seed Certification Agency 168 Quality and Acceptance 137 Functions of the Seed Selection Criteria Certification Agency 169 for Rotl Quality 140 Long-Term Seed Policy 171 4f Major Responsibilities of the Central Government 171 Major Responsibilities of the District Province, or State Governments 171 Role to be Played by the Seed Industry 171 The Variety Release Committee 172 The Foundation Seed Stocks Agency 172 APPENDIX 2 Sorghum Descriptors 175 Accession Identifier 175 Field Collection Data 175 Taxonomic and Morphological Evaluation Data 176 Agronomic Evaluation Data 179 Pest Resistance Evaluation Data 183 Disease Resistance Evaluation Data 186 Others 187 GLOSSARY 189 INDEX 203 FOREWORD Through the ages sorghum has been a vital source of food for millions of people; In the semi-arid tropics (SAT), it is often the principal means of survival. In recent years, steadily expanding populations have brought Increased demands for this dependable staple, but in the SAT, where more than half the world's sorghum is grown, environmental conditions severely limit production. The small farmer is the first to feel these pressures ol increased demand and limited supply. Cereal scientists have made substantial advances in crop yields of rice and wheat with new varieties and technology-but most of that progress has been made where growing conditions are favorable. Improve ment of sorghum yields is a more difficult task. It is often grown on poorer soils by farmers who have little control of moisture or availability of fertilizers and other inputs that will boost yields. But as a crop sorghum offers proven versatility, hardiness, dependability, and stability of yield under very adverse conditions. Because it has demonstrated its adaptability over such a wide range of cultures and climates, it offers great potential for supplementing the world's food resources. Millions of people now eat sorghum as a staple food (chapatior roti in India, iniera in Ethiopia, tortillas in Latin America, etc.). It also is used as feed for animals and is an industrial raw material. Other uses include processing for beer and preparation of other local drinks; its stalk provides fodder, fuel, shelter, sugar, and syrup. Because of its importance as a staple cereal for million3 of the poorest people of the semi-arid tropics and because of its potential for vastly increased production to help feed the undernourished of developing nations, sorghum is one of the five crops that ICRISAT has a mandate to improve. In compiling this book on Sorghum bicolor (L.) Moench, Dr. Leland House, former principal sorghum breeder and program leader at ICRISAT, and presently manager of the SADCC/ICRISAT Cereals Improvement Project for southern Africa, has utilized the knowledge and experience gained from some 25 years' work with this crop with numerous experts and organizations worldwide. It Is our hope and expectation that this book will be a valuabie guide, particularly to young scientists and senior technicians, in enhancing improve ment of this crop so important to the health and well-being of millions. L.D. Swindale Director General ABOUT THIS BOOK The content and organization of this guide have been developed through several years of field use in draft form; it has been modified and expanded based on this experience. No claims are made for speedy, spectacular performance, nor are there fixed formulas for successful sorghum production. Rather, the main objec tives are to guide in problem identification and basic descriptive analysis, with working examples of breeding theory applied in the field. A systematic breed ing approach is recommended. Intended readers are the crop specialists, field technicians, scientists, and students interested in field-oriented sorghum improvement. It is hoped that these readers, and others at national program planning levels, will also find a broader perspective for analyzing and structur ing their overall crop improvement work. Five general topics are covered: Section 1 is mainly descriptive, providing background on the current status of sorghum and some of its basic characteristics. Some of its earlier history is outlined, and sorghum's classification systems are listed along with informa tion showing its worldwide distribution. Section 2 focuses on the sorghum plant, its growth stages and morphology. Here emphasis is on how the plant develops from seed to maturity. Special characteristics of the sorghum plant are noted, with particular attention to the interests of the sorghum breeder. Section 3 provides a relatively detaikd look at plant genetics from a field technician's

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