Genetics of fungicide resistance in Talaromyces flavus

Abstract

Three mutants resistant to the fungicide benomyl and 2 resistant to dicarboximides were developed from a wild-type strain of T. flavus. Based on sensitivity of various isolates to benomyl concentrations, 2 levels of resistance were recognized. One isolate with low resistance (LR) was resistant to 5 .mu.g/ml, but sensitive to 50 .mu.g/ml benomyl; and 2 highly resistant (HR) isolates grew uninhibited at 50 .mu.g/ml. Crosses between resistant isolates and sensitive wild types and between different resistant isolates showed that the 2 levels of benomyl resistance are conferred by different alleles at a single locus. The LR allele pleiotropically brings about slow growth. The dicarboximide-resistant isolates were little affected (mean effective dose (ED50) > 250 .mu.g/ml) by iprodione, vinclozolin, dichlozolinate or Co 6054. Crosses showed that the 2 dicarboximide-resistant isolates carry allelic mutations that can be characterized by the level of osmotic sensitivity pleiotropically conditioned by them. Dicarboximide resistance was not linked to benomyl resistance.