scope:

Preface

Domestication of crops from weeds and the taming of wild animals have been an integral part of human civilization since time immemorial. Herbivorous animals, including prehistoric animals, grazed on leaves and succulent stems of weeds as well as leaves of shrubs and trees. Humans from the Old World tamed herbivorous animals such as horses, cattle, sheep, goats, water buffaloes, elephants, swine, domestic fowl, and various others, depending upon their needs. These animals consume the vegetative parts of cereals and legumes after grains are harvested. However, many crops of grass and of the legume family are used exclusively for livestock feed. These crops are used for grazing or are harvested for green-chop feeding, silage, or hay. Grasses such as bermudagrass and ryegrass are used for turf and forage.

Most of the forages belong to the grass family Poaceae (Gramineae) or the legume family Fabaceae (Leguminosae). Six crops from the grass family (wheatgrass, wildrye grasses, Brachiaria, bahiagrass, bermudagrass, and ryegrass) and three crops from the legume family (alfalfa, birdsfoot trefoil, and clover) have been included in Forage Crops, volume 5 of the series Genetic Resources, Chromosome Engineering, and Crop Improvement. Forage does not include plants cut or chopped and fed to animals such as hay, silage, or freshly cut grass. These are known as fodders. However, in developing countries, green pods are hand-picked from common bean, pea, cowpea, faba bean, chickpea, lentil, mungbean, and azuki bean; green leaves and stems are used as fodder for livestock. Goats love green leaves of pigeonpea-my personal observation while living in my hometown (the village of Sirihara in the state of Uttar Pradesh) in India. Lupin is used for forage in Europe and for grain in Australia. These crops have been covered in Grain Legumes, volume 1 of this series. Volume 2 (Cereals) included chapters on wheat, rice, barley, oat, maize, sorghum, pearl millet, rye, and man-made triticale. These are cultivated for grain. Straw is fed to livestock worldwide. Soybean, groundnut, and sunflower-covered in Oilseed Crops, volume 4 of this series-were initially used as forage crops but are now grown for oil and meal.

The majority of forage crops (alfalfa, clover, birdsfoot trefoil, bermudagrass) were domesticated in the Old World because they were fed to or allowed to be grazed on by tamed animals. By contrast, the New World inhabitants, the American Indians, did not tame herbivore animals. More than two thirds of wheatgrasses and wildrye grasses are native to Eurasia; from 22 to 30 grasses are considered native to North America and these are distributed throughout the vast prairies of the northern Great Plains of the United States and Canada. Bahiagrass originated in tropical South America.

The latter two books are in their sixth editions. However, none of the books mentioned here or elsewhere has attempted to assemble the comprehensive information on genetic resources, gene pools, cytogenetics, and varietal improvement that has been compiled in Forage Crops.

The intensive varietal improvement of forage crops for high yield and improved nutritional quality (or elimination of antinutritional quality) and high palatability are the primary breeding objectives of various national programs (public institutions and private industries). Centro Internacional de Agricultura Tropical (CIAT) has a mandate for collection, maintenance, and varietal improvement of Brachiaria. Most genetic improvement of forage crops has been accomplished by conventional breeding assisted by germplasm resources, cytogenetics, plant pathology, entomology, agronomy, cell and tissue cultures, and molecular biology. Three forage legumes (Medicago truncatula, Lotus japonicus, and Trifolium pretense) are considered model crops for molecular genetics and genome sequencing.

The introductory chapter of this book (Chapter 1) summarizes landmark research done in the nine forage crops discussed in this book. Successive chapters provide a comprehensive account of the origin of each crop, its genetic resources in various gene pools, basic and molecular cytogenetics, conventional breeding, and the modern tools of molecular genetics and biotechnology. Appropriate germplasm collections can be an excellent resource for genetic enhancement of various traits in forage crops and for broadening their genetic bases. The genetic bases of forage crops are extremely narrow. In view of the narrow genetic base of oilseed crops, three gene pools (GPs) have now been identified by scientists for each crop: primary (GP-1), secondary (GP-2), and tertiary (GP-3). The recommendation is to use GP-2 and GP-3 resources in producing widely adapted varieties. The utilization of these resources (wide hybridization) in producing high-yielding cultivars that are resistant to abiotic and biotic stresses and have improved nutritional qualities is discussed in this book.

Eight major forage crops-alfalfa (Chapter 2), wheatgrass and wildrye grasses (Chapter 3), bahiagrass (Chapter 4), Brachiaria (Chapter 5), birdsfoot trefoil (Chapter 6), clover (Chapter 7), bermudagrass (Chapter 8), and ryegrass (Chapter 9)-are included in this book. Other minor grasses and legumes are not included in this volume.

Each chapter has been written by experts in the field. I am extremely grateful to all the authors for their outstanding contributions and to the reviewers of all the chapters. I have been fortunate to know them both professionally and personally, and our communication has been very cordial and friendly. I am thankful to Byron Byrson for identifying several forage crop researchers and encouraging them to contribute their expertise to this book. I am particularly indebted to Govindjee, William Grant, and Joseph Nicholas for their comments and suggestions.

This book is intended for scientists, professionals, and graduate students whose interests center upon genetic improvement of crops in general and major forage crops in particular. This book is also intended as a reference for plant breeders, taxonomists, cytogeneticists, germplasm explorers, pathologists, entomologists, physiologists, agronomists, molecular biologists, food technologists, and biotechnologists. Graduate students in these disciplines who have an adequate background in genetics, as well as other researchers interested in biology and agriculture, will also find this volume a worthwhile source of reference. I sincerely hope that the information assembled here will help in the much needed genetic amelioration of forage crops to feed livestock because an ever expanding global population depends on livestock. I anticipate that this book will enhance awareness of raising livestock in open pastures and feeding them grasses grown in nature rather than meals enriched with hormones and other animal by-products.