Adzuki bean (Vigna angularis (Willd.) Ohwi & Ohashi) breeding

Abstract

Adzuki bean [Vigna angularis (Willd.) Ohwi & Ohashi], an annual pulse crop, belongs to the genus Vigna and subgenus Ceratotrapis. It provides nutritional elements for the human diet and fertilizes soil by nitrogen fixation. It has been traditionally planted and consumed in East and Southeast Asia, especially in China, Japan and Korea, so it came to be called the Asia legume. Adzuki bean was dispersed to other continents for commercial uses in recent decades. Wild adzuki bean (V. angularis var. nipponensis), considered to be the ancestor of cultivated adzuki bean, occurs in East Asia and in the Himalayan Region, which are presumed to be where the domestication of adzuki bean took place. Another wild form, V. nepalensis, called the weedy adzuki bean, is mainly found in Eastern Nepal and around. A large portion of adzuki bean germplasm has been collected and conserved in different gene banks. DNA marker analysis suggests that there are obvious genetic distinctions between different forms, but the diversity among cultivated germplasm is quite low, indicating that the wild forms could be an important genetic resource for breeding. However, the genetic and genomic studies on this species are lagging and include only low-density genetic maps and a few maps of genes. That is the reason conventional breeding of adzuki bean has achieved rapid improvement, while no modern biotechnology has yet been used in breeding.