Abstract
Studies were carried out with the efficacy of 1-(3, 4-dichlorophenyl)-2-acetylhydrazine (I) and 1-(4-chlorophenyl)-2-acetylhydrazine (II), which showed the strongest and the most consistent effect on rice blast control among β-acylchlorophenylhydrazine derivatives, in suppressing developing mycelia and germination of spores of Pyricularia oryzae in vitro, on leaves and in tissues of rice plant.
Compounds I and II were found to possess complete sporostatic property at 125ppm on the slide glass, and both I and II at 175ppm and above prevented the mycelial growth in shaking culture. While mycocidal action of these compounds were stronger than sporocidal action.
On the leaves of rice plant, both I and II at 1000ppm did not prevent sufficiently spore germination and appressorium formation, but suppressed markedly the mycelial development in the host tissues as well as blasticidin S, a therapeutic agent.
These results suggested that the principal locus of inhibition of β-acylchlorophenylhydrazines against rice blast fungus in the protective and the therapeutic tests was at the stage of mycelial development in the tissues, and not at the stage of spore germination and appressorium formation upon leaves of rice plant.
