Mating behaviour and genetics of fungicide resistance ofBotrytis cinereain New Zealand

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Abstract
The mating type of strains of Botrytis cinerea (teleomorph Botryotinia fuckeliana) from a diverse range of hosts and locations throughout New Zealand was determined by crossing with tester strains of known mating type. Most isolates were hetero‐thallic, 24 carrying the MAT 1–1 allele and 17 the MAT1–2 allele, but 9 were homothallic. The mating type alleles were widely distributed with respect to host, district, and fungicide resistance genes. Fungicide resistance phenotypes segregated as distinct characters consistent with the presence of the previously recognised genes Mbcl, conferring resistance to benzimidazole fungicides, and DafI, conferring resistance to dicarboximide fungicides. A new allele is recognised, DafIUR, encoding ultra‐low level dicarboximide resistance not associated with abnormal osmotic sensitivity. Pairing of single ascospore strains on malt extract agar amended with 0.68M NaCl demonstrated a mycelial incompatibility system in this fungus.