Compatibility of adzuki bean (Vigna angularis) and Bradyrhizobium USDA strains, and geographical distribution and community structure on indigenous adzuki bean-nodulating bradyrhizobia in Japan

We investigated the compatibility between adzuki bean and Bradyrhizobium USDA strains and the relation between the genetic diversity of indigenous adzuki bean-nodulating bradyrhizobia and their geographical distribution in Japan. Six Bradyrhizobium USDA strains were used in the inoculation test, and B. elkanii USDA 94 showed higher symbiotic efficiency than other strains. Two adzuki bean cultivars were used to isolate indigenous adzuki bean-nodulating bradyrhizobia. Their genetic diversity and community structure were analyzed by restriction fragment length polymorphisms of PCR amplicons to target the 16S-23S rRNA gene internal transcribed spacer region, using 11 USDA Bradyrhizobium strains as reference strains. Furthermore, we performed diversity analysis, non-metric multidimensional scaling analysis based on the Chao index, and polar ordination analysis to explain the relation between community structure and geographical distribution of the adzuki bean-nodulating bradyrhizobia. The major clusters were Bj123 in Hokkaido and Kyoto, Bd110 in Fukushima and Shimane A, Be76 in Shimane B and Fukuoka, Bj6 in Miyazaki, and Bj6 and BeOK in Okinawa. Japan's indigenous adzuki bean-nodulating bradyrhizobial community was strongly and significantly correlated with latitude, longitude, annual mean temperature, and electrical conductivity. This result suggests that the adzuki bean-nodulating bradyrhizobial community is influenced by multiple environmental factors.