Abstract
The action of probenazole (Oryzemate®), 3-allyloxy-1, 2-benzisothiazole-1, 1-dioxide), a rice blast controlling agent, on several stages of the life cycle of blast fungus was investigated. Anti-microbial activities against twenty-six species of plant pathogens including the blast fungus in vitro were weak. In contrast, when the inside of the rice leaf sheath was inoculated with conidia suspended in 10ppm of probenazole solution, a high inhibitory effect against the penetration was observed. Also a high inhibitory effect against the appressorial formation and penetration was observed in vitro employing cellophane membrane. Inhibitory effect against the growth of mycelia in a lesion and sporulation were observed more evidently in the experimental system in vivo than in vitro. Therefore, it was quite plausible that the strong controlling effect of probenazole against blast disease by the submerged application is the integrated effect of these inhibitory actions including the strong inhibitory effect against the penetration. The inhibitory actions of the transformed products of probenazole was generally weaker.
