Bacteria Isolated from Black Rot of Rice Grains

Abstract

In black rot of rice grains a black spot develops on a part of the rice grain, which is formed at the middle or apical part of the grains and rarely at the basal part. Recently, its occurrence has gradually increased in Hokkaido and has been causing serious damage.From both the affected and healthy rice grains, many bacteria and some fungi were isolated. Among them, yellow bacteria were most frequently isolated.Sixty five isolates of bacteria, obtained from both kinds of grains collected from various paddy areas in Hokkaido, were classified into four groups according to some major characteristics. Moreover, group I was divided into three strains on the bases of some minor characteristics. Group II consisting of fluorescent, achromogenic and chromogenic groups named by Iizuka et al.The bacterial isolates of each group were identified as follows;I. A; Enterobacter cloacae, B and C; Erwinia herbicola.II. Fluorescent group; Pseudomonas schulkilliensis and allied species.Achromogenic group; p. sp. (non-fluorescent).Chromogenic group; p. cerealis, p. melanogenum and p. lacunogenes.III. Brevibacterium spp.IV. uncertain.Rice grains did not show any symptom on the surface of them when they were inoculated with E. herbicola through the seed-coat by the injection method before their milky ripe stage. The black rot occurred on the wounded part of grains, whenever they were inoculated with E. herbicola or not, by the needle inoculation method in the milky ripe stage and E. herbicola were re-isolated from both the blackening part of the inoculated and non-inoculated grains. The causal agent of the black rot of rice grains was recoginized as due to the sucking of rice grains by the pentatomid bugs and allied species. Moreover, it was proved that Xanthomonas itoana was synonymous with E. herbicola.