抄録
Kasugamycin-resistant strains of rice blast fungus, Pyricularia oryzae, were isolated with a high frequency from the samples collected from those districts where kasugamycin had been used consecutively as a sole anti-blast fungicide, whereas no resistant strain was found in the samples collected from the districts where kasugamycin had been used by mixing with fthalide or alternately with organophosphorus fungicides. Resistant strains occur in conidia formed on lesions with a frequency below 1/105 by spontaneous mutation irrespective of kasugamycin application and their population density becomes higher under the selection pressure of kasugamycin.
