Chapter 8 - Yard-long bean

Abstract

Yard-long bean [Vigna unguiculata ssp. sesquipedalis (L.) Verdc], belonging to family Fabaceae, is a distinctive subspecies of cowpea [Vigna unguiculata (L.) Walp.], characterized by its climbing growth habit and long draping pods. It is cultivated for its tender pods relished as vegetable, a good source of vitamin A and C, protein, fiber, and other minerals. South East Asia is considered as the center of diversity of this crop. It is cultivated as a sole crop as well as an integral part of intercropping and sequential cropping systems. Lack of improved varieties, inadequate extension services, poor market price, and incidence of pests and diseases are some of the constraints to yard-long bean production. The primary breeding objective is to increase the pod yield per hectare by increasing the number of pods per plant and to improve other attributes namely earliness, determinate and less viny growth habit, photo-insensitivity, resistance/tolerance to biotic stresses, terminal drought tolerance, and wide adaptation to different agroclimatic conditions. With the advent of molecular markers, detailed scanning of yard-long bean genome led to the refined mapping of various agronomic traits to the respective linkage groups. A recent study reported a 632.8Mb genome assembly (549.81Mb non-N size) based on the whole-genome shotgun sequencing strategy wherein a total of 42,609 protein-coding genes as well as 3579 nonprotein-coding genes were reported. Detailed studies on the molecular physiology of abiotic stress tolerance will potentially identify the key genes or proteins that can provide a more simple and efficient strategy to improve the breeding process for the development of tolerant lines.