Study on genetic diversity and phylogeny of soybean rhizobia in China

Fifty-two soybean rhizobia isolated from root nodules of nine soybean cultivars from soil samples collected from seven different sites in China were studied comparing with twenty three type strains of rhizobia by phenotypic characteristics, host specificity, 16S rDNA PCR-RFLP, 16S rDNA sequencing, REP-ERIC-PCR and DNA-DNA hybridization. Results of phenotypic characteristics indicated that twenty nine fast-growing strains could be distinguished with Sinorhizobium xinjiangense CCBAU110 and twenty three slow-growing strains with Bradyrhizobium elkanii USDA76, respectively. The similarities of some slow-growing strains corresponded to geographical sampling sites. All strains could be divided into two types by host specificity. Results of 16S rDNA PCR-RFLP, 16S rDNA sequence analysis, REP-ERIC-PCR and DNA-DNA hybridization revealed that twenty nine strains of fast-growing rhizobia were all clustered together with Sinorhizobium fredii USDA205 and S. xinjiangense CCBAU110. Similarly, twenty three strains of slow-growing rhizobia were highly related with B. japonicum and B. liaoningense.