Rice bean (Vigna umbellata (Thunb.) Ohwi & Ohashi)

Abstract

Rice bean (Vigna umbellata (Thunb.) Ohwi & Ohashi) is a legume crop widely distributed throughout South and South-east Asia, and other parts of the world. It is a nutritionally rich legume crop and plays a crucial role in securing food and nutritional requirements in traditional farming systems. Its grains are a rich source of quality protein (18–32%) and minerals such as Ca (68–230 mg/100 g), P (209–370 mg/100 g), Mg (9–16 mg/100 g), K (8–1122 mg/100 g) and Fe (2.61–6.4 mg/100 g). Rice bean grain contains vitamins such as thiamine (0.5–1.09 mg), riboflavin (0.18–0.5 mg) and niacin (2.0–3.6 mg). The crop is grown in diverse agro-climatic conditions by diverse ethnic groups for food, fodder, cover crop, living hedges, etc. More importantly, the species is relatively free from pests and diseases. Therefore, it is being utilized as a donor species in pre-breeding programmes for trait introgression and genetic base broadening of V. radiata, V. mungo and V. angularis. Even though the crop has several beneficial traits and plays a crucial role in local nutritional and food security, rice bean improvement has been relatively inadequate. Therefore, the crop remains an orphan legume, and the area under crop production has continued to decline amid competition from more profitable similar crops such as mung bean, urd bean and cowpea. Nevertheless, a substantial amount of rice bean crop diversity has been collected and conserved to avoid any risk of losing it. National and international project-based initiatives are reviving, improving and introducing crop cultivation in its original habitats and new areas. Recently, significant genetic and genomic resources have been generated, which will help in crop improvement programmes.