Abstract:

Adzuki bean, originated from China, is either one of traditional exports or an important crop for agricultural structure adjustment. As the traditional varieties can not meet the demands of modern markets and the genetic bases of the cultivars have been narrow, it is necessary to develop new breeding materials or novel germplasm, to improve varieties of adzuki bean. China has a collection of over 5 000 adzuki bean resources, which is lacking in study and use in breeding. In the paper, genetic diversity of 158 accessions of cultivated and 18 wild types of adzuki beans were analyzed by using 24 pairs of SSR primers. The results showed that 18 pairs of SSR primers were detected to be polymorphic in cultivated adzuki beans and 21 in wild adzuki beans. The average number of allele (NA) per SSR locus for cultivated and wild adzuki beans was 3.0 and 2.6, respectively. The number of accessions used for cultivated and wild adzuki beans differed much, and the NA and genetic diversity index (polymorphic information content, PIC value) showed a higher genetic variation in wild types than in cultivated ones. Both cluster and principal coordinate analysis (PCO analysis) suggested that there was a high genetic differentiation between cultivated and wild adzuki beans, while cultivated adzuki beans from different provinces of China could not be distinguished from each other clearly, suggesting that there is a high rate of the gene exchange among local adzuki beans. The genetic backgrounds of the breeding cultivars revealed by SSRs are almost agreeable with their putative pedigree, indicating that these SSRs can be used to identify the genetic relationships of them, and used in marker-assist-selection (MAS) in breeding. The results also revealed that the adzuki bean germplasms occurred more than once with the same name in the National Germplasm Conservation Centre were different from each other in genetic background and so valuable to be conserved and used individually. The present study not only provides some informations in adzuki bean breeding, but can accelerate the application of SSR markers in diversity analysis, gene tagging and identification of new cultivars.

Key words: Adzuki bean, SSR, Genetic diversity