Pathogenicity of sclerotial fungi of rice plants

Abstract

In artificial inoculation using pot-grown rice plants, pathogenic differences were found in four sclerotial fungi tested. The severity of the pathogenicity was in order of Pelli-cularia sasakii, the most severe; Rhizoctonia oryzae, severe; Sclerotium oryzae-sativae, moderate; and the culture type III-B of Rhizoctonia solani, slight, while there werec ertain pathogenic differences within the isolates of individual fungal species. In paddy field experiments, the pathogenic severity of these fungi was in the following order when the rice plants were inoculated at the stage of panicle formation on August 10:R. oryzae≥the culture type III-B of R. solani>P. sasakii≥S. oryzae-sativae. However, when inoculated at the boot-stage on August 24, the pathogenic severity was in order of P. sasakii>the culture type III-B of R. solani>S. oryzae-sativae>R. oryzae. Thus, it is suggested that the pathogenicity of the sclerotial fungi on rice plants varies according to the growth stage of rice plants at the time of inoculation.