INTERMEDIATES ACCUMULATION AND INHIBITION SITES OF CARPROPAMID IN THEMELANIN BIOSYNTHESIS PATHWAY OF PYRICULARIA-ORYZAE

Carpropamid yl)ethyl]-1-ethyl-3-methylcyclopropanecarboxamide} strongl y inhibited pigmentation in shaking culture as well as in agar plate c ulture of Pyricularia oryzae and Verticillium dahliae. White crystals were isolated from the extract of the cultures of wild type strains of P. oryzae and V. dahliae treated with carpropamid. Analytical data of the crystals obtained from a spot at Rf 0.36 on the TLC plates coinci ded with those of scytalone. A large amount of scytalone and a small a mount of vermelone accumulated in the culture treated with 10 mu g/ml of carpropamid, while 2-hydroxyjuglone was not detected in these analy ses. When scytalone was added to the shaking culture of albino mutants of P. oryzae (P-2-alb), it promptly disappeared from the culture and the culture was pigmented to light brown. But scytalone remained in th e culture if treated with carpropamid. Scytalone and vermelone adminis tered beside the colony of P-2-alb on the agar plates were converted t o black pigments but the pigmentation was inhibited by carpropamid. Th ese results suggest that carpropamid inhibits dehydration of scytalone and vermelone in the fungal melanin biosynthesis.