Diversity and phylogeny of rhizobia isolated from root nodules of Sesbania cannabina in Jinshajiang arid river valley

Abstract:

[Objective] To study the diversity and phylogeny of Rhizobia strains from Sesbania cannabina in Jinshajiang arid river valley in Sichuan province, China. [Methods] We used numerical taxonomy, 16S rDNA PCR-Restriction fragment length polymorphism(RFLP), sequences analysis of 16S rDNA and Glutamine synthetaseⅡ(GSⅡ)genes. [Results] Based on the dendrograms generated from numerical taxonomy, the strains were clustered into 6 groups 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. The results of 16S rDNA PCR-RFLP were in good agreement with that of numerical taxonomy, only two separated groups showed some differences. 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% respec-tively. GS II sequence analysis revealed that SCAU176 and SCAU144 were clustered together, and the homology coeffi-cient with the nearest type strains R. tropici was below 90%. [Conclusion] Rhizobia of Sesbania cannabina in Jinshajiang arid river valley are highly diverse, they are closely related to Rhizobium, Sinorhizobium and Agrobacterium.