Diversity And Phylogeny Of Rhizobial Strains Isolated From Root Nodules Of Lespedeza Michx In Arid-hot Valley Of JinSha River

The diversity and phylogeny of 86 rhizobial strains,which were isolated from the root nodules of Lespedeza Michx in arid-hot valley of JinSha river,were investigated by the numerical taxonomy,BOXAIR-PCR fingerprinting,16S rDNA PCR-RFLP,16S rDNA,and GSⅡsequences.The results demonstrated that a high biological diversity existed among these root nodule bacteria of Lespedeza Michx.The strains tested were divided into 6 groups at the similarity of 85.6%through the numerical taxonomy,and most(68.6%) was Bradyrhizobium.these revealed that there was a great phenotypic diversity among the isolates.The strains tested could grow normally at up to 60℃or in culture solution with pH＜4.0.However,they could not grow when the temperature was lower than 10℃or in culture solution with pH＞9.0,and they were not salt tolerant.The same strains used in numerical taxonomy were analyzed by 16S rDNA PCR-RFLP with four kinds of restriction endonucleases including HaeⅢ,MspⅠ,HinfⅠand Taq I.The strains have 15 genotypes and 9 of them are unique genotypes different from the reference strains.Based on the dendrograms generated by BOX-PCR, the strains could be divided into 37 groups with the similarity of 82%.Many strains were in different phenons in BOXAIR-PCR although they belonged to the same phenon in 16S rDNA PCR-RFLP,which indicated that there was a great diversity in genes among these stains.The results of 16S rDNA and GSⅡsequences analysis indicate that the six representative strains could be classified into four groups of genus Bradyrhizobium,Rhizobium,Sinorhizobium,and Mesorhizobium,respectively.But 16S rDNA sequencing homology was higher than GSⅡsequencing homology.GSⅡsequencing homology and 16S rDNA sequencing homology among the six representatives of strains are between 79.4%～89.8%and 87.5%～99.5%,respectively.As a contrast, GSⅡsequencing homology and 16S rDNA sequencing homology between the representative strains and phylogenetically closest reference stains are respectively from 88.9%to 99.6%and from 99.9%to 100%,respectively.