Abstract
In Japan, epidemic occurrence of a destructive blight of pine trees has been reported as very serious problems on forest pathology. In the course of pathological studies on the causal agent, it was found that cut branch of Japanese red pine was wilted with culture filtrate of Botrytis cinerea isolated from the pine tree. This fungus was frequently used for cultivation of a pine wood nematode, Bursaphelenchus xylophilus, because the nematode is mycophagous. The phytotoxicity of culture filtrate was proven by a cytotoxic test using pine tissue culture, and abscisic acid and unidentified cytotoxic compounds were chemically isolated from the toxic fraction. The lethal effect of abscisic acid to the cultured pine cells was not observed at the level below 500 ppm, but the growth inhibition occurred above 125 ppm. Although the wilting effect of abscisic acid to seedlings of the Japanese red pine was not confirmed, their water consumption was strongly inhibited.