Genetic diversity and phylogeny of soybean rhizobia isolated from the Hilly area of Central Sichuan in China

OBJECTIVE: We investigated the genetic diversity and phylogeny of 28 rhizobial isolates from root nodules of soybean growing in the Hilly Area of Central Sichuan in China. METHODS: We used 16S rDNA PCR-RFLP and phylogenetic analyses of the 16S rDNA, glnII and symbiotic genes (nodC). RESULTS: Five 16S rDNA genotypes among the isolates were distinguished with restriction endonucleases Hae III, Hinf I, Msp I and Taq I. In the 16S rDNA PCR-RFLP analysis, all the isolates are divided into Bradyrhizobium group and Sinonrhizobium group at the 83% level, and Sinonrhizobium strains accounted for 75% of the isolates. The phylogenetic analyses of 16S rDNA, glnII and nodC show that 4 representative strains SCAUs1, SCAUs2, SCAUs7 and SCAUs4 were closely related to S. fredii USDA205(T) while the other 2 representative strains SCAUs3 and SCAUs5 were closely related to B. yuanmingense CCBAU10071(T) and B. diazoefficiens USDA110(T). The 16S rDNA, glnII and nodC sequence similarity of 4 Sinonrhizobium representative strains were 98.3% - 99.9%, 98.2% - 100% and 100%, respectively. CONCLUSION: Soybean rhizobia isolated from the Hilly Area of Central Sichuan in China has rich genetic diversity, S. fredii was the predominant genus.