Breeding perspectives of snap bean (Phaseolus vulgaris L.)

Abstract

Snap bean (Phaseolus vulgaris L.), a type of common bean whose fresh fleshy tender pods with reduced fibre content in pod-wall, is an important legume vegetable usually used for cooking or canning. Common bean has originated in southern Mexico to Central America (Mesoamerica) and Ecuador-Peru-Bolivia region is the secondary centre of origin, while snap bean is developed from Andean genetic resources in the southern Europe during 19th century. More than 260000 accessions of different species of Phaseolus are being maintained in >245 gene banks of various countries, moreover CIAT Colombia has the mandate for global germplasm collection and conservation of Phaseolus species and hosts the world’s largest and most diverse collections. Globally, the breeders mainly focus on development of varieties having high yield potential; wider adaptability; earliness, better pod quality (bright and uniform colour, non-stringy, slender, long and straight, cylindrical, smooth, small seeded, less inter-locular cavitations and more flavour); tolerance to heat stress, particularly high night temperature; and resistance to major diseases such as bean common mosaic virus, bean golden mosaic virus, common bacterial blight, halo blight, Sclerotinia rot, anthracnose, angular leaf spot and root knot nematode. The favourable genes and QTL for various traits of economic importance are scattered across cultivated and wild populations in the primary, secondary, tertiary and other gene pools of common bean, and the efforts are being made to integrate two- or multi-tiered breeding approaches for broadening the genetic base, and introgressing and pyramiding the resistance genes and QTL.