Genetic diversity and phylogeny of soybean bradyrhizobia isolated from south and north region of China
我国南北大豆产区慢生大豆根瘤菌的遗传多样性和系统发育研究

Studies on genetic diversity and phylogeny of soybean bradyrhizobia isolated from south and north region of China were investigated through 16S rRNA gene PCR RFLP, 16S rRNA gene sequencing and 16S-23S rRNA IGS PCR RFLP assays. Results of 16S rRNA gene PCR RFLP and 16S rRNA gene sequencing analysis reveal that strains tested are ascribed into Bradyrhizobium japonicum and B. elkanii species. B. japonicum is the dominant species and accounts for 91% of strains tested, but B. elkanii just up to 9%, which shows poor genetic diversity. Results of 16S-23S rRNA IGS PCR RFLP assays reveal that strains belonged to B. japonicum can be divided into Group I and Group HIIat the 69 similarity. Group I consists of strains from northern China, and Group 1I consists of strains from southern China, which demonstrates geographical effect on genetic diversity of bradyrhzobia. Results of 16S-23S rRNA IGS PCR RFLP further reflects that strains of Group I and Group II are phylogenetically different with type or representative strains USDA6, USDA110 and USDA122 of B. japonicum.