NATURALLY-OCCURRING ANTIDOTES AGAINST BENZIMIDAZOLE FUNGICIDES

TLC bioautography using precoated glass thin-layer plates impregnated with benomyl or carbendazim (MBC), and Cladosporium herbarum as a test fungus was evaluated as a facil way to detect plant secondary metabol ites antidoting against benzimidazole fungicides. In addition to emodi n and alpha-tocopherol from Polygonum sachalinense, three phenolics, 3 ,5-dihydroxy-4-methylstilbene and 5-methoxy-6,7-methylenedioxyflavone from P. lapathifolium, and 2,6-dimethoxybenzoquinone from P. thunbergi i were isolated and characterized as new benzimidazole antidotes. Emod in exhibited the antidoting activity not only against benomyl but also against carbendazim (MBC), thiabendazole (TBZ), thiophanate-methyl an d nocodazole. Furthermore, emodin showed antidoting activity against M BC in the wild-type Neurospora crassa and against diethofencarb in the mutant of N. crassa resistant to benzimidazole fungicides but highly susceptible to diethofencarb.