Polyphasic Taxonomy Of Rhizobial Isolated From Robinia And The Effect Of Root Exudate

40 unknown strains of rhizobia isolated from robinia in Yangling. They were analyzed by polyphasic taxonomy (phenotypic and genetic analysis such as numerical taxonomy, 16S,23S rDNA PCR-RFLP,IGS PCR-RFLP,etc.) and phylogenic study (the sequence analysis of 16S rDNA gene and nodulation gene nodA).The 105 physiological and chemical characteristics of all isolates were tested and the result indicated that there was difference in the features of carbon and nitrogen source, resis- tance to antibiotics and chemical dye, endurance to salt alkali among strains isolated from robinia. 42.5% strains had properties resistant to 3.0% NaCl, 17.5% of strains can grow in YMA medium with pH12.All the test isolates were divided into 3 distinctive groups by numerical taxonomy. Both cluster 1 and cluster 2 had 10 strains, CCNWYC119 was the central strain of cluster 1, and CCNWYC129 was the central strain of cluster 2. Cluster 3 had 7 strains and CCNWYC147 was the central strain. 16S rDNA PCR-RFLP analysis show that these strains were different from the reference strains of recognized species in the related genera, which was good agreed with those of numerical analysis. The result of 23S rDNA PCR-RFLP,IGS PCR-RFLP analysis of 38 rhizobal were more diverse than those of numerical taxonomy and 16S rDNA PCR-RFLP analysis, and divided these strains into 5, 4 genotypic clusters, respectively.The 16S rDNA full sequence analysis of the center strains CCNWYC119,CCNWYC129, CCNWYC147 were performed. The genetic distance of 16S rDNA full sequence between CCNWYC119 and the other reference were fast relatively. Strain CCNWYC129 located in the Rhizobium-Agrobacterium branch in the phylogenetic positions. The similarities of 16S rDNA full sequence between CCNWYC129 and Ag. Tumefaciens, Ag. rubi, Ag. Albertimagni were 92.8%, 97.4% and 96.8% respectively. Strain CCNWYC147 located in the Mesorhizo- bium branch in the phylogenetic positions. The similarities of 16S rDNA full sequence between CCNWYC147 and M. thiogangeticum, M. septentrionale, M. amorphae, M. huakuii, M. plurifarium were 97.5%, 99.9%, 100%, 99.6% and 99.6%, respectively.nodA sequence analysis of the center strains CCNWYC119, CCNWYC129, CCNWYC 147 were performed. The nodulation genes nodA analysis existed discrepancy with 16S rDNA...