Abstract: The 16S rDNA PCR-RFLP and 16S rDNA sequence analysis were used on genetic and phylogeny of 53 strains isolated from Glycine max, Vicia faba, Pisum sativum and Phaseolus vulgaris of Jiuquan and other regions, Gansu and 9 known strains. Results of 16S rDNA PCR-RFLP indicated that all isolates included 9 reference strains were clustered into 5 branches at 77.5% similarity. Branch I was Sinorhizhobium-Rhizobium, branch II Agrorhizobium-Bradyrhizobium, branch III unknown bacteria branch, branch IV Mesorhizobium, and branch V also unknown branch. Branch I included 2 sub branches at 89.8% similarity：Sub branch 1 included strains CNU1008 and 14 strains witch clustered with Sinorhizobium meliloti LISPA1002^T, Subbranch 2 included 6 strains which clustered with Rhizobium leguminosarum USDA 2370 ^T. Branch II included 3 sub branches：Sub branch 1 included CNU 1041 and other 3 strains witch clustered with 2 strains of Agrobacterium tumefaciens IAM 13129^T and IAM 13569^T together, sub branch 2 included 5 strains which clustered with Bradyrhizobium japonicum USDA 6^T, sub branch 3 included 3 unknown strains. Representative strains were selected in the analysis of 16S rDNA sequencing, and the results show that 16S rDNA PCR-RFLP and16S rDNA sequencing analysis were in good agreement. Strains of Sinorhizobium sub branch of branch I were clustered with S.fredii and S.meliloti at 99% similarity, and their exact system status should be determined by DNA-DNA hybridization. Strains of Rhizobium sub branch of branch I were clustered with R.giardinii at 99% similarity and with R.etli at 98% similarity. So the exact position of the sub branch waited for DNA-DNA hybridization to determine. Strains of Agrobacterium sub branch of the branch II clustered with A.rubi at the similarity of 99%. Strains of Bradyrhizobium sub branch of the branch II were clustered with B.liaoningense at the similarity of 99%.

Key words: Rhizobia, 16S rDNA PCR-RFLP, 16S rDNA sequencing