金沙江干热河谷区田菁根瘤菌多样性与系统发育

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

【目的】揭示金沙江干热河谷区这一特殊地理环境下田菁根瘤菌的多样性和系统发育地位。【方法】采用了数值分类、16S rDNA PCR-RFLP、16S rDNA和GSⅡ序列分析方法。【结果】数值分类结果表明:在93%的水平上,待测菌株分布于6个群,其中4个群分别与R.tropici、R.etli、S.saheli、A.rubi的参比菌株聚在一起,两个群没有参比菌株与之聚群。16S rDNAPCR-RFLP结果与数值分类基本一致,只有两个独立群有所差异。16S rDNA序列分析表明:两独立群中心菌株SCAU176和SCAU144与R.huautlense聚在一起,与该种同源性分别为100%和98.9%。GSⅡ序列分析中SCAU176和SCAU144单独聚在一起,与最近的参比菌株R.tropici的同源性系数在90%以下。【结论】金沙江干热河谷区田菁根瘤菌具有较为丰富的多样性,在系统发育地位上分布于Sinorhizobium、Agrobacterium和Rhizobium三个属。

[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 synthetase Ⅱ （GS Ⅱ）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% respectively. GS II sequence analysis revealed that SCAU176 and SCAU144 were clustered together, and the homology coefficient 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.