Genetic diversity of Japanese strains of Ralstonia solanacearum.

The genetic diversity of 74 Japanese strains of Ralstonia solanacearum was assessed by pathogenicity tests and the repetitive sequencebased polymerase chain reaction (rep-PCR) fingerprint method. Based on their genomic finger prints, biovar N2 strains were divided into two distinct groups, one consis ting of potato isolates belonging to race 3, and the other consisting of to mato, eggplant, pepper, and tobacco isolates belonging to race 1. Biovar 3 strains had low average similarity and were divided into five groups that d iffered in original host or pathogenicity. Biovar 4 strains consisted of on ly one group at the 80% similarity level. Comparative analysis of the rep-P CR fingerprints of 78 strains, including six biovars from Japan and various countries, revealed two main clusters. Cluster 1 comprised all biovar 3, 4 , and 5 strains, biovar 1 strains from Reunion, and some biovar N2 strains from Japan. Cluster 2 included most of the biovar 1, 2, and N2 strains. The fingerprints showed low average similarity with biovar N2 strains from Jap an and Brazil.