Genetics, Genomics and Breeding of Cool Season Grain Legumes PDF

Preface to the Volume

Cool season grain legumes (pea, faba bean, lentil, chickpea and grass pea) constitute a set of important leguminous species mainly for food as dry seeds, traditionally valued for their content of protein and carbohydrates. Nowadays, they are also valued for their low content in fats and high content in dietary fi ber, thus contributing to healthy nutrition. Crop legumes have been traditionally classifi ed into cool season and warm season legumes, refl ecting their origin and agroecological requirements. Cool season legumes are included in two tribes, Vicieae (pea, faba bean, lentil and grass pea) and Cicereae (chickpea). A sister tribe to these two tribes is Trifolieae which includes the model legume species Medicago truncatula (barrel medic), the closest reference for comparative genetics and genomics for these crop species. As other legumes, cool season grain legumes enrich the soil by fi xing atmospheric nitrogen in symbiosis with root nodule bacteria, and therefore are a traditional component of agriculture in temperate climates, generally in rotation with cereals and other crops. These fi ve species were domesticated in the Fertile Crescent among other fi rst domesticated plant species such as wheat and barley. The oldest archaeological remains are dated around 10,000 BP in aceramic Neolithic layers. The crops spread fi rst to Europe, the rest of Asia and North Africa with the expansion of agriculture and were introduced into America and Australia after 1500 AD. They are mostly consumed as dry seeds, but immature pods and seeds of faba bean and pea are also consumed as vegetables. Although none of these species is individually included in the list of main crops on which human diet depends, their joint contribution to human nutrition is signifi cant, and even more so considering that they are mainly consumed directly by humans. In fact they constitute, together with other pulses, one of the cheapest and healthiest sources of food proteins. According to FAOSTAT, the 2009 world production of these crops reached approximately 19 million tons for pea (dry and green), 9.8 for chickpea, 4.1 for faba bean and 3.6 for lentil. No individual record is available for grass pea. In spite of their traditional cultivation and consumption during millennia, some of these crops can be considered as neglected and underutilized species. However, many neglected and underutilized species are extremely important for food production in low-income food countries. The general tendency in the last decades for these cool season legume species is a slow increase in production and yield.

The genetics and genomics knowledge as well as the breeding advances in these species are unequal. Plant breeders have used traditional or conventional techniques to improve these species. In comparison with old classical early-domesticated crops, systematic breeding research started later. The exception is pea, which was the pioneering species in genetic research and was bred since the XIX century. The interest in these crops has increased in the past decades and research and the application of modern breeding techniques have increased recently. This volume, as others in the Series, deals with recent advances in cool season grain legume research and breeding, including genome mapping, molecular breeding and genomics and intends to bridge the gap between traditional breeding research and modern molecular developments. As can be seen in the different chapters, the "state of the art" for each individual crop differs; however, their phylogenetic proximity to M. truncatula, a legume model species, justifi es their joint study, since most of the knowledge obtained in one species is useful to speed up the research and breeding in the other ones.

There are 12 chapters in total. The fi rst fi ve chapters are each devoted to a species (pea, faba bean, lentil, grass pea and chickpea, respectively), while the remaining chapters are devoted to horizontal common aspects which affect all these crops. When information from one chapter is needed or relevant for completing another, cross references are provided. Likewise, cross references within chapters are provided. The fi rst fi ve chapters introduce the basic knowledge of each species, then, describe classical genetics and traditional breeding, genetic mapping efforts and linkage map construction, identifi cation and tagging of genes (both quantitative and qualitative), major biotic and abiotic threats, and the genomics advances, and their breeding applications as they exist. Chapter 6 reviews the functional genomics of cool season food legumes, though many insights into the biology of a specifi c legume derive from so-called model plants; describes the complex worlds of transcriptomics and some of the techniques frequently used in the study of these species. Because of the limited availability of large-scale genome sequences in cool season grain legumes, Chapter 7 focuses on comparative mapping between the most important cool season grain legumes at the macrosynteny level. Results achieved so far suggest that the knowledge gained from comparative mapping may have considerable utility to solve basic and applied agronomic questions of importance in the crop species. Comparative studies are particularly relevant in this set of related species. Chapter 8 focuses on proteomic and metabolomic techniques that have been successfully adopted for systems biology approaches especially in Medicago. Furthermore, applications of these novel strategies in the fi eld of cool season legumes research is described. The studies on regeneration and genetic transformation in cool season legumes are described in Chapter 9. It summarizes the hurdles being faced in the effi cient recovery of transgenic plants and presents a comparative account of explants used, mode of regeneration, gene delivery techniques and recovery of transgenic plants in these crops.

Legume nitrogen fi xation plays a key role in the maintenance of crop production worldwide. However, this property is often not considered in new cultivar selection programs. Chapter 10 reviews the effectiveness and effi ciency of the process and the structural and functional genomic studies on plant-bacteria interactions. The identifi cation of symbiotic genes in legumes has been speed up by the use of model legume species and functional genomic technologies such as map-based gene cloning, transcriptomics, proteomics and metabolomics. The chapter also stresses the importance of breeding for enhancing nitrogen fi xation. In legume breeding programs, more attention should be directed at understanding and evaluating plant mechanisms that control root nodule formation and activity, otherwise biological nitrogen fi xation may be compromised. Chapter 11 is devoted to broomrape. Broomrapes are annual or perennial obligate parasitic plants which represent a major threat to cool season legumes and other crops in many temperate areas, and are one of the main limiting factors to crop legumes around the Mediterranean basin, one of the major traditional areas of production and consumption of these crops. Traditional plant breeding has failed to produce stable resistance; although genetic resistance exists and has been used in cool season legume breeding. Molecular mapping of broomrape resistance QTLs together with the development of MAS techniques are promising approaches to rapidly improve crop resistance. With the emergence of large-scale genomic tools, the combination of genetic mapping with gene expression studies, can offer an integrated approach to study resistance to parasitic plants. Finally, Chapter 12 summarizes the current status of genetic and genomic research and points to future developments and applications.

Each chapter has been written by several experts who have worked thoroughly in compiling the information available in their area of expertise. We are indebted to all of them for the dedication and effort devoted towards producing the book. We hope that this book is useful for researchers and breeders interested in cool season crop legumes, in particular those interested in a broader spectrum of legumes and crop plants.