Diversity And Phylogeny Of Rhizobia Isolated From Dumasia DC. In Jingshajiang Dry Heat Valley

Forty-three rhizobia isolated from Dumasia truncata Sieb.et Zucc.in jingshajiang dry heat valley were studied together with the reference strains of some recognized rhizobial species by numerical taxonomy,BOXAIR-PCR finger-printing,16S rDNA PCR-RFLP and 16S rDNA sequence.The result of numerical analysis showed that there is a great phenotypic diversity among the isolates.All tested strains were divided into 13 groups and the reference strains of different recognized rhizobial species can be distinguished basically at a similarity level of 83%.Compared with the reference strains,most of the new isolates have different phenotypic characteristics and fall into new clusters respectively.The slow-growing and fast-growing strains of rhizobia in jingshajiang dry heat valley were obviously different from each other,they were divided into 2 groups at a similarity level of 66%.Furthermore,there is a great phenotypic diversity among the new strains.The same strains used in numerical taxonomy were analysed by BOXAIR-PCR Finger-printing.All tested strains were clustered into 24 groups at the similarity level of 84%.Compared with the result of numerical taxonomy,strains belonged to one phenon in numerical taxonomy always distributed into several BOXAIR-PCR groups,most of reference strains come from one recognized rhizobial species were not grouped together.As a result,BOXAIR-PCR finger-printing is appropriate as a method of revealing genetypic diversity within a rhizobial species and strains.For another,the result above showed that there is a great genotypic diversity among the isolated rhizobial strains.Based on the results of numerical taxonomy,16S rDNA PCR-RFLP were applied to 43 representatives and 19 typical strains of some recognized rhizobial species.All strains tested were divided into 21 groups at the similarity level of 87%. They were in good agreement with the grouping of numerical taxonomy at the similarity level of 83%.The result above showed that there is a great genotypic diversity and phylogenetic diversity among the isolated rhizobia in jingshajiang dry heat valley.In order to analyze the genetic position of these type strains:SCAU181,SCAU187 and SCAU206,the 16S rDNA was sequenced.It was found that those strains belong to Rhizobium,Agrobacterium and Bradyrhizobium separately.On homology level,the variability between SCAU187 and the nearest reference strain IAM13569 was about 1.8%,compared with SCAU181 and SCAU206,whose variability were less than 1%.In summary,the paper disclosed a great diversity of the strains isolated from jingshajiang dry heat valley in the aspects of phenotypic and genotypic characteristics,and phylogenetic relationship.The gene stock of rhizobial diversity was enriched.The rhizobial resources were provided on breeding excellent strains. The base was also established on further studying taxonomic position of rhizobia isolated from Do truncata in jingshajiang dry heat valley.