Geographical distribution and genetic diversity of Bradyrhizobium spp. isolated from Korean soybean root nodules

This study investigated the distribution and genetic diversity of the indigenous Bradyrhizobium spp. in the Korean agricultural field. A total of 254 Bradyrhizobium strains were isolated from 97 soybean samples (9 cultivars) collected in 14 regions. B. elkanii dominated in the southern regions, while B. diazoefficiens dominated in most central and northern regions. Through non-parametric multidimensional scaling (NMDS) analysis, we confirmed the possibility that environmental factors such as annual average temperature and soybean cultivars might affect the distribution of Bradyrhizobium spp. in some regions. The DNA fingerprint using repetitive DNA sequences showed the genetic diversity among the Bradyrhizobium strains isolated from the different regions. Clustering the strains based on the genetic diversity indicated that Bradyrhizobium spp. grouped into different clusters depending on geographic location. This study suggests that the Korean indigenous Bradyrhizobium spp. distribute differently according to the geographical feature, and the high genetic diversity of each strain attribute to the geographic location.