Diversity And Phylogeny Of Rhizobia Isolated From Root Nodules Of Sesbania Cannabina In Jinshajiang Arid River Valley

To study the diversity and phylogeny of rhizobia from Sesbania cannabina in JinShaJiang arid river vally in Sichuan,48 rhizobia was isolated,nodulated,and studied by numerical taxonomy,BOXAIR-PCR,16S rDNA PCR-RFLP,sequences analysis of 16S rDNA and GSâ…¡.Numerical taxonomy results showed:at the similarity of 93%,four groups were closely related to type strains of R.tropici,R.etli,S.saheli,A.rubi respectively,and two groups were separated with type strains.BOXAIR-PCR fingerprint analysis showed:at the similarity of 92%,the tested strains were clustered to 11 groups,close to the geographical distribution.Some strains with same genetic type of 16S rDNAPCR-RFLP had more differences,indicating that the tested strains are more differences in genome.The results of 16S rDNA PCR-RFLP were in good agreement with that of numerical taxonomy,only two separated groups showed some differences.11 strains in group 2 were made up of subgroup 3I and group 4 in the numerical taxonomy.29 strains in group 3 were made up of subgroup 3â…¡in the numerical taxonomy.SCAU176 and SCAU144 representing the strains of two separated groups were selected for sequence analysis.The results of 16S rDNA sequence indicated that SCAU176 and SCAU144 were related to type strains R.huautlense,and the homology Coefficient with R.huautlense was 100%and 98.9%respectively.SCAU144 is likely to be new species in Rhizobium.GSâ…¡sequence analysis revealed that SCAU176 and SCAU144 were clustered together,and the homology Coefficient with nearest type strains R.tropici was below 90%. Phylogenetic position of SCAU144 had not been fixed,(G + C)%and gene sequence of nifH,nodA,GSI will be studied to determine it.