Production of Anti-Fungal Substance(s) in the "Sekiguchi Lesion"Induced by Pyricularia oryzae Infection on Rice cv.Sekiguchi-asahi

The anti-fungal substance(s) were isolated from the "Sekiguchi lesion" formed on rice cv. Sekiguchi-asahi by Pyricularia oryzae infection. These substance(s) were partially purified by silica gel column chromatography. Although spore germination of P. oryzae was completely inhibited in solution of the anti-fungal substance(s) at concentrations of 0.1-2.5 mg/ml, but that of Bipolaris oryzae was not. When a spore suspension of P. oryzae was inoculated to inner surface of rice leaf-sheaths which had been pre-treated with the solution of 0.5- 2.5 mg/ml of the anti-fungal substance(s) for 24 hr, penetration and hyphal growth were significantly inhibited. The same phenomenon was also observed in B. oryzae infection at the concentration of 0.5 and 1.0 mg/ml of the anti-fungal substance(s). However, phenomena associated with anti-fungal substance-induced resistance such as inhibition of penetration and hyphal growth disappeared within 24 hr after removal of the anti-fungal substance(s). Further, inhibitive effect was not observed in thermal-treated sheaths before the treatment of the anti-fungal substance(s). These results suggest that the anti-fungal substance(s) isolated from the "Sekiguchi lesion" have two biological activities; one is direct effect to the pathogens such as inhibition of spore germination and another is indirect effect to the plants such as induction of disease resistance.