Study on fungicide resistance ofbotrytis cinereaisolates from diseased strawberry plants

Southwestern Spain is one of the main areas for strawberry culture in the world. Large losses are due to grey mould caused by Botrytis cinerea, a plant pathogen that affects a wide variety of crops. Resistance to synthetic fungicides is one of the more important problems that hamper control of grey mould on strawberry. We have characterized the relative response to benzimidazole (benomyl and carbendazaim) and dicarboximide (vinclozolin) among 36 isolates of B. cinerea obtained from different plots in six counties of the province of Huelva during a 2-year period. Three phenotypes with resistance to benzimidazole were detected: (i) BenR1 having phenotype resistant (R) to benomyl and high-resistant (HR) to carbendazim; (ii) BenR2 with phenotype HR to both benomyl and carbendazim; and (iii) BenR3 with phenotype HR to benomyl and R to carbendazim. Strains were either resistant or sensitive to the dicarboximide vinclozolin (DicR or DicS, respectively), but high-resistance to this fungicide (DicHR strains) was not found. The low fitness of the DicHR mutants and the possibility of heterokaryosis indicated by the number of nuclei within fungal conidia indicates that DicHR mutants might not become established in field populations in southwestern Spain.