Studies on resistance of black spot disease fungus of Japanese pear (Alternaria kikuchiana TANAKA). VII

The isolation of host-specific toxin from the natural lesions, and the chemicals which decrease in toxicity of that toxin

Abstract

The isolation of host-specific toxin from natural lesions attacked the young leaves of Nijisseiki, susceptible variety, by black spot disease fungus of Japanese pear (Alternaria kikuchiana TANAKA) and decrease in toxicity of that toxin with various chemicals was described.
The isolation of K-III fraction (host-specific toxin) from culture filtrate and mycelium of causal fungus was previously reported. The toxin isolated from natural lesions was identified that fraction with thin layer chromatography and plant test, so that the fraction was regarded as vivotoxin.
Toxicity of that fraction was decreased with tannic acid, pyrogallol, hydroxyhydroquinone, pcresol and dimethyl sulfoxide. Effect of tannic acid on toxicity of that fraction was excelled. Toxicity of that fraction (200ppm) was completely inhibited with tannic acid of 10, 000ppm and moderately inhibited with the same substance 1, 000 and 100ppm. The consequent decrease in necrosis on the young leaves was depened upon the relative concentration of both that fraction and tannic acid.