Abstract
After treating rice plants by submerged application with probenazole no changes were noted in the siliciferous cells in the leaves, no morphological changes in the leaf tissue and no anti-fungal activity in leaf exudates were detected. When rice plants were treated by submerged application of probenazole and subsequently inoculated with the blast fungus (Pyricularia oryzae CAVARA) peroxidase activity (oxidation of phenolic substances) increased and an anti-conidial factor in the rice leaf increased. Also the increase of the factor was observed in rice plants treated by the chemical but not inoculated. A part of the appearance of induced resistant characteristics were thought to be similar to a reaction of resistant rice plant. The induction of resistant characteristics were largely inhibited by a heat shock upon rice plant indicating that the event was host mediated reaction. Probenazole (submerged application) appears to control the blast disease in rice by a combination of the events, such as inhibiting sensitive stages in the life cycle of the blast fungus and also activating the host defence.
