Abstract
Several colony type variants of Xanthomonas campestris pv. oryzae developed during subculture of the pathogen on PSA medium. These variants were easily distinguished from the wild type of large-waxy yellow (Lw) colonies and were divided into five types according to their colony size and appearance, i. e., large-halo (Lh), large-dark yellow (Ld), large-white (Lwh), small-transparent (St) and small-mucoid (Sm). The variants of St and Sm types did not develop during 2 months of subculture, but after that, their populations increased with increase of subculture period. The frequency of development of small colony variants from large colony types varied depending upon isolates or clones. All of the Lw clones and most of the Lh variants belonged to serovar A. On the other hand, a part of the Lh and most of the Ld variants belonged to serovar B-I and all of the St and Sm type variants belonged to serovar B-II. Both serovars B-I and B-II were lacking in antigen “a”. From serological point of view, the colony types Lh, Ld and Lwh were considered to be the intermediates of variation from Lw to St or Sm. A close correlation was observed between autoagglutination in 1% CaCl2 solution and serovars.
