Diversity Of Rhizobia Isolated From Astragalus Spp. In West Pleateau Of Sichuan Province

33 rhizobia strains were isolated from the nodules of Astragalus gilviflorus and Astragalusstii comb in the plateau of two different altitudes in the west of Sichuan province. After thenodulation test, the phenotypic characteristics and genectic diversity of these 33 strains and18 reference strains, totally 51 strains, were revealed by using numerical taxonomy andAFLP: BOX-PCR; 16SrDNA-RFLP. The results indicated thatAccording to the numerical taxonomy analysis, these 33 strains were diversephenotypically, and all of them were fast-growers. Moreover, the dendrogram showed that51 strains could be separated into 2 groups at the similarity of 65%. In thephysiological and biochemical tests, 33 Astragalus rhizobia strains showed theirbeing vulnerable in the media which contain antibiotics, and similarly in the extremePH conditions, when compared with reference strains.Based on the dendrograms generated by AFLP and BOX-PCR, all the strains wererepectively divided into 9 and 5 groups at the similarity of 70% and 68%. Notably,most of Astragalus rhizobia strains and the following reference strains: 102F28,USDA1002, USDA1037, USDA205, I66, NZP2234, IAM13129, all of which belongsto Rhizobiaceae fell into the same group at certain similarities. And being identical tothe results to the numerical taxonomy, the strains obtained in the two differentaltitudes were not separated respectively.The 9 genotypes of all the swains obtained by 16SrDNA-RFLP analysis showed that mostof the genotypes Astragalus rhizobia strains were very similar to the following genera:Rhizobium, Sinorhizobium, Agrobacterium, and the genotypes of part of the Astragalusrhizobia strains were completely identical to the following swains: USDA2370yå’ŒUSDA1002, 102F28, USDA4102, strongly suggesting that Astragalus rhizobia swainswere closely related to Rhizobiaceae from the standpoint of phylogeny.However, a lot of previous studies demonstrated that 16SrDNA can exist inmulti-copies in the same cell, which is different, and 16SrDNA also can spontaneouslymutate and recombine. Hence, to get the authentic phylogenetic information,sequencing some orthologous genes would be indispensable.