Katan, T., Department of Plant Pathology, Agricultural Research Organization, Volcani Center, Bet Dagan 50250, Israel
Dunn, M.T., Department of Plant Pathology, Agricultural Research Organization, Volcani Center, Bet Dagan 50250, Israel
Papavizas, G.C., Department of Plant Pathology, Agricultural Research Organization, Volcani Center, Bet Dagan 50250, Israel

Three mutants resistant to the fungicide benomyl and two resistant to dicarboximides were developed from a wild-type strain of Talaromyces flavus. Based on sensitivity of various isolates to benomyl concentrations, two levels of resistance were recognized. One isolate with low resistance (LR) was resistant to 5 μg/mL, but sensitive to 50 μg/mL benomyl; and two highly resistant (HR) isolates grew uninhibited at 50 μg/mL. Crosses between resistant isolates and sensitive wild types, as well as between different resistant isolates, showed that the two 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 μg/mL) by iprodione, vinclozolin, dichlozolinate, or Co 6054. Crosses showed that the two 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.