New genetic markers for Botrytis cinerea (Botryotinia fuckeliana)

Selenate-resistant (SelR) mutants of Botrytis cinerea were selected by plating conidia or mycelial plugs onto minimal medium amended with selenate and taurine. Ultraviolet irradiation of conidia to give 5% survival increased mutant yield twenty-fold. Mutants could be divided into three classes based on growth in the presence of selenate or chromate and on response to taurine in minimal media. Nitrate non-utilizing (Nit) mutants, generated as spontaneous sectors on minimal media amended with chlorate, behaved as nif1 mutants in growth tests (i.e. putatively defective in nitrate reductase apoenzyme). When nit1 mutants were paired on medium with nitrate as sole nitrogen source some pairings complemented, behaviour attributed to intragenic complementation. Selected crosses of SelR and nit1 mutants with wild-type strains gave 1:1 segregation of both phenotypes and no evidence of linkage to either Mbc1 (benzimidazole resistance) or Daf 1 (dicarboximide resistance) markers; loose linkage was confirmed between Mbc1 and Daf 1. Strains showing the SelR phenotype may result from mutations in different genes; the genotypic symbol Sel 1 is allocated to one of these mutations. Four-point crosses involving the markers at Sel1, nit1, Mbc1 and Daf1 generated progeny with all 16 genotypes. Both Sel1R and nit1 mutants were stable following subculture and retained pathogenicity in a bean seedling assay. Complementation was demonstrated between SelR and nit1 mutants selected from the same parent.