FUNGITOXICITY OF LEAF EXCRETIONS AS RELATED TO VARIETAL RICE RESISTANCE TO BLAST

Twenty two cultivars of rice (Oryza sativa L.), differing in their ver tical resistance to blast, were studied. Diffusates from healthy leave s and especially from infected leaves during the first three days afte r inoculation inhibited the germination of pathogenic spores. Diffusat es from the resistant plants produced stronger inhibition than the sus ceptible cultivars. Superoxide dismutase suppressed antifungal diffusa te properties, indicating participation of the superoxide radical in t he mechanism of fungitoxicity. A chemical assay (oxidation of adrenali ne) revealed superoxide formation in diffusates, especially in resista nt cultivars. Pathogen suppression by active oxygen forms generated by the plants was suggested to contribute to the varietal resistance of rice to blast.