Study On The Diversity Of Rhizobia Isolated From Leguminous Plants In Panxi Region

Forty-three rhizobia isolated from leguminous plants in Panxi region were studied together with the reference strains of some recognized rhizobial species by numerical taxonomy, BOXAIR-PCR fingerprinting and 16S rDNA PCR-RFLP.The result of numerical analysis showed that there is a great phenotypic diversity among the isolates. All tested strains were divided into 14 groups and the reference strains of different recognized rhizobial species can be distinguished basically at a similarity level of 80%. 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 Panxi region were obviously different from each other, they were divided into 2 groups at a similarity level of 66.4%. Furthermore, there is a great phenotypic diversity among the new strains isolated from the same host. Different groups consisted of the new strains from the same host, some were Rhizobium, some were Bradyrhizobium, such as the new strains isolated from leguminous plants of AMkora (Roxb.) Prain, Trifolium repens Lam, Aeachynomene Mica L, Indigofera bungeana Steud.The same strains used in numerical taxonomy were analysed by BOXAIR-PCR fingerprinting. All tested strains were clustered into 47 groups at the similarity level of 50%. 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 fingerprinting is appropriate as a method 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 15 representatives and other of new rhizobial stains and 7 typical strains of some recognized rhizobial species. The 16S rDNA PCR-RFLP analysis resulted in 20 different genotypes by four kinds of allozyme (Haelll^ Msp I ^ Dde I and Rsa I), except CCBAU61224 andR.leguminosarwn, CCBAU61303 and A.twnerfaciense had the same genotypes, the other strains tested had their own unique genotypes. According to the dendrogram derived ftom 16S rDNA PCR-RFLP, all strains tested were divided into 15 groups at the similarity level of 94.2%. They were in good agreement with the grouping of numerical taxonomy at the similarity level of 80%. The result above showed that there is a great genotypic diversity and phylogenetic diversity among the isolated rhizobia in Panxi region.In summary, the paper disclosed a great diversity of the strains isolated from Panxi region 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 leguminous plants in Panxi region.