1982 Volume 48 Issue 4 Pages 466-470
This investigation was carried out to determine the appearance of variants in virulence by pairing-inoculation of 2 different pathogenic isolates (races 047 and 303) of rice blast fungus, Pyricularia oryzae Cavara, on both agar media and rice leaves. The mycelium-joining method on media, and the methods of the punch-inoculation of mixed spore suspension and the pairing-inoculation on leaves using the above 2 parent isolates, induced to arise some variants having virulence different from that of the parent isolates. These variants were divided into 2 groups; one contained the isolates (races 337, 317, 313, 137 and 037) that newly acquired the strong pathogenicity for 2 rice varieties, Kanto 51 and Tsuyuake, to which the parent isolates were non-pathogenic, and the other contained the isolates (race 347) that had both pathogenicity of the parent isolates. On the other hand, no variants in virulence appeared from the parent isolates. The race 337 isolate arised in both experiments on agar media and rice leaves. In addition, the variants were divided into 3 groups by the colony type and the color of culture on potato decoction agar medium. Thus, it was suggested that the variants in this experiment might be resulted from the anastomosis of the parent isolates.
