Section 7
Chapter 6,331

Restoration of appressorial penetration ability by melanin precursors in pyricularia oryzae treated with anti penetrants and in melanin deficient mutants

Chida, T.; Sisler, H.D.

Journal of Pesticide Science 12(1): 49-56


ISSN/ISBN: 1348-589X
Accession: 006330289

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The capacity of Pyricularia oryzae appressoria to penetrate onion epidermal walls was lost in an albino mutant or in wild type strains treated with melanin biosynthesis inhibitors, cerulenin, fthalide and tricyclazole. Melanization and penetration ability of cerulenin treated wild type or untreated albino mutant appressoria were restored with scytalone or 1,8-dihydroxynapthalene (1,8-DHN). Fthalide or tricyclazole nullified the restoration by scytalone, but not by 1,8-DHN. Penetration ability of wild type appressoria treated with 0.1 .mu.g/ml of fthalide or tricyclazole was restored by 1,8-DHN, but was not well restored in appressoria treated with 1 or 10 .mu.g/ml of these inhibitors unless cerulenin was also present. This investigation indicates that blocking melanin biosynthesis pathway by fthalide or tricyclazole leads to two mechanisms of antipenetrant action (1) interference with melanin synthesis (2) accumulation of inhibitory metabolites. The latter mechanism, which may operate concomitantly with former, is nullified in the presence of cerulenin.

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