Genetic And Phylogenetic Diversities Of Agrbacterium Isolated From Nodules

Althouthgh Rhizobium and Agrobacterium have different mechanisms to infect plants, they got very close phylogenetic relationship, and the reclassification of agrobacterium has become a recurrent issue in the last several decades. Recent study showed that agrobacterium could occupy in the nodules, which make the study of agrobacterium isolated from noduls become very meaningful. A group of agrobacterium-like strains has been isolated from different kinds of legumes in our lab, 77 strains agrobacterium-like bacteria have been chose to study the diversitiy of agrobacterium isolated from noduls. In this thesis, numerical taxonomy, 16S rDNA PCR-RFLP, IGS PCR-RFLP, BOX-PCR and 16S rDNA gene seqencening were applied to study the diversity of this group of agrobacteria.The result of 16S rDNA PCR-RFLP showed that all the agrobacteria-like starins studied has 3 different genotype. 57 strains could be cassifeid into genotype 2, and 7 strains could be grouped into genotype 1, 7 strains could be grouped into genotype 3, which showed that there were less diversity in the level of 16S rDNA PCR-RFLP. Phylogenetic tree derived from full length 16S rDNA sequence showed that 6 strains of bacteria are agrobacterium tumefaciens, And 127 and 519, which form an outlying line in the phylogenetic tree, could be a potential novel species or bionovel.All the agrobacteria-like strains could be grouped together in the similarity of 20% in IGS PCR-RFLP, which has 20 genotypes. In the similarity of 80%, all the studied strains could be classified into 6 groups. The result of IGS PCR-RFLP showed high diversity of agrobacteria isolated from nodules.BOX-PCR showed a similar result as IGS PCR-RFLP. 30 genotypes were found in BOX-PCR, which showed that the studied agrobacteria has a high diversity in the genome level.The biochemical and physiological tests showed that all the tested strains clusted together with IAM13129, which is type strain of genus agrobacterium, in the similarity of 90.4%, the results of this experiment showed that this group of bacteria were agrobacterium tumefaciens.