Genetic basis of resistance to benzimidazole and dicarboximide fungicides in Botryotinia fuckeliana (Botrytis cinerea)

The genetics of resistance to benzimidazole and dicarboximide fungicides in B. fuckeliana was investigated by analysing ascospore progeny of sexual crosses. Field isolates (11 resistant to benzimidazoles, 6 resistant to dicarboximides, 38 resistant to both fungicides) collected from naturally infected plants in two regions of Southern Italy, and 22 laboratory-induced mutants with high resistance to dicarboximides were studied. The results showed that benzimidazole resistance and dicarboximide resistance are each encoded by a single polymorphic major gene, neither of which is linked to the MAT1 mating type gene. Three classes of alleles at each locus have been recognized. Mbc1S, Mbc1LR and Mbc1HR alleles confer sensitivity, low and high resistance to benzimidazoles; the Mbc1HR alleles cause a substantial increase in sensitivity to N-phenylcarbamates. Daf1S, Daf1LR and Daf1HR alleles confer sensitivity, low and high resistance to dicarboximides; the Daf1HR alleles cause a substantial increase in sensitivity to media of high osmolality