GENETICS OF SEXUAL COMPATIBILITY AND RESISTANCE TO BENZIMIDAZOLE AND DICARBOXIMIDE FUNGICIDES IN ISOLATES OF BOTRYOTINIA-FUCKELIANA (BOTRYTIS-CINEREA) FROM 9 COUNTRIES

Field isolates and laboratory mutants of Botryotinia fuckeliana (Botrytis cinerea) from nine different countries were crossed with reference strains of known mating type, to determine the genetic bases of differences in sexual fertility and in resistance to benzimidazole and dicarboximide fungicides. Most isolates were heterothallic, and carried the MA T1-1 or MA T1-2 mating-type allele. A few isolates were fertile with strains of opposite mating types, due to the presence of both mating-type alleles in heterokaryotic mycelia. The MA T1-1 and MA T1-2 alleles were fairly evenly distributed among the field isolates from most countries. Seventy-six isolates displayed resistance to benzimidazole and/or dicarboximide fungicides due to mutant alleles of the Mbc1 and/or Daf1 genes. Unlike wild-type and low-resistant isolates, those carrying the high-resistance Mbc1HR alleles were sensitive to N-phenylcarbamates. With one exception, isolates carrying the high-resistance Daf1HR alleles were hypersensitive to media of high osmolarity. Heterokaryons containing Daf1HR alleles together with sensitive Daf1S or low-resistance Daf1LR alleles in separate nuclei combined high resistance to dicarboximides with relative tolerance of media with high osmolarity.