Variation in Adzuki Bean (vigna angularis) germplasm grown in China
Adzuki bean [Vigna angularis (Willd.) Ohwi & Ohashi] is cultivated in a wide range of agroecological environments from north to south China. An understanding of the genetic variation for crop adaptation facilitates plant breeding. A core germplasm of 231 accessions (selected from a representative collection of 3908 Chinese landraces) was evaluated at diverse locations in China in 1998 to (i) compare differences among sources of landraces for trait expression, (ii) identify underlying patterns of diversity, and (iii) characterize patterns of genetic adaptation across environments. Three-mode pattern analysis of phenology, yield and yield components, and plant height data identified six accession groups with various levels of cohesiveness. The greatest diversity occurred in the germplasm from the provinces of mid-north China, particularly the lower Yellow River basin, with a partial latitudinal separation of the accession origins in different groups. The most contrasting groups came, respectively, from south China (Sichuan–Anhui), characterized by late maturity and small seed size, and from north China (Liaoning–Heilongjiang), characterized by earliness and short habit. Analysis of the multilocation screening provided genotype x environment characterization of the accession groups and a capability to predict the most suitable groups for specific target environments and breeding objectives, thereby enabling plant breeders to make efficient and effective use of germplasm.