ABSTRACT
Legumes come across a number of diseases that are controlled by quantitative trait loci (QTLs) including ascochyta blight (chickpea, faba bean, lentil, and pea), molds (common bean), powdery mildew (pea), rusts (groundnut, pea, lentil, and faba bean), wilt (common bean, pigeonpea, and pea), root, or stem rots (pea, soybean). For most of the important legumes different linkage maps have been developed using different types of molecular markers to study the linkages between different genes with different traits of interest among legumes. The availability of molecular markers on linkage maps are of great value for QTL mapping studies and marker assisted programs in disease resistance legume breeding. QTLs mapping essentially requires knowledge of inheritance pattern of the diseases and segregation nature of molecular markers, along with use of suitable statistical tools. QTL detection is highly influenced by several factors such as type and size of mapping population, effect of QTLs involved (major/minor), heredity of QTLs, density of linkage map, and the technique used for QTL detection. The mapping is more accurate and decisive when diseases are scored using different parameters (components, pathogen strains, different organs, or stages of plants life cycle) in multiple environments. The consistent expression of QTLs by different parameters in multiple environments proves their usefulness for marker assisted breeding. In this chapter, we have reviewed the QTLs detected for different diseases, their causing organism, type and size of mapping population, type of molecular marker, and its further use in marker-assisted selection (MAS) of disease resistance QTLs in legumes.
