Phylogenetic and serological analyses reveal genetic diversity of Agrobacterium vitis strains in Japan

Twenty-eight strains of Agrobacterium vitis, including both tumorigenic and nonpathogenic phenotypes involving 26 isolated in Japan and strains NCPPB 3554^T and NCPPB 2562 isolated in Australia and Greece, respectively, were characterized by means of a slide agglutination test (SAT) using antisera prepared against somatic antigens. Phylogenetic analyses were also carried out, using the results of repetitive sequence-based polymerase chain reaction and the partial nucleotide sequences of pyrG, recA and rpoD. The A. vitis strains separated into four serogroups (A to D) based on the SAT reactivity. The phylogenetic analyses showed A. vitis strains separated into four tumorigenic groups (A to D) and one nonpathogenic group (E). Serogroups A to C corresponded exactly to genetic groups A to C, respectively, whereas serogroup D further divided into two distinct genetic groups, D and E. Genetic group E was isolated in Okayama Prefecture, Japan, and all strains of it have been found to coexist with tumorigenic strains belonging to the other groups within the same galled grapevine tissues. These results suggest that A. vitis strains are genetically heterogeneous and can be separated into several genetic groups. The differences between the nucleotide sequences of pyrG, recA and rpoD of the genetic groups will enable the development of a simple and convenient monitoring method, which will increase understanding of the dynamics of each genetic group of A. vitis in the natural environment.