Nature of Procymidone-Tolerant Botrytis Cinerea Strains Obtained in Vitro

Abstract

Tolerance of plant pathogens to fungicides was not a serious problem when mainly non-systemic conventional fungicides were used. These fungicides have been called “multi-site inhibitors” because they non-selectively inhibit several biologically important functions of living fungal cells. The nature of their fungitoxic mechanisms implies that there is little possibility for the development of tolerant mutants because mutation of a single gene cannot overcome the lethal effect of their multisite activity. On the other hand, we have seen emergence of tolerant pathogens with the recently introduced systemic fungicides. Since these systemic fungicides can easily penetrate into plant tissues, they must be selectively toxic to pathogens at concentrations that do not produce phytotoxic effects. Therefore, systemic fungicides have been understood to be “specific-site inhibitors” as they affect biochemically restricted regions of fungal cells. This intrinsic nature of systemic fungicides accelerated the selection of the fungicide-tolerant pathogens that appeared through mutation of a single gene.