Comparative Resistance Patterns of Fludioxonil and Vinclozolin in Botryotinia fuckeliana

Fludioxonil is a new non-systemic phenylpyrrole fungicide. It is a derivative of the antibiotic pyrrolnitrin and is highly active against Ascomycetes. Basidiomycetes and Deuteromycetes. In the present study we determined the baseline sensitivity of B. fuckeliana for fludioxonil in comparison to the dicarboximide vinclozolin. Subsequently these baselines were compared with the sensitivity of dicarboximide-resistant field isolates and with resistant laboratory strains selected on media amendedwith vinclozotin or fludioxonil, respectively. Additionally, sensitivities of genetically homogeneous ascospore progenies of sexual crosses of sensitive isolates with dicarboximide-resistant field isolates or resistant laboratory strains were compared to, the baselines. Baseline ECst, values for the inhibition of germination ranged from 0.07 to 0.20 μg ml-1 of vinclozolin and for mycelial growth from 0.003 to 0.016 μg ml’ of fludioxonil and from 1.7 to 2.0 μg ml-1 of vinclozolin and for mycelial growth from 0.003 to 0.016 μg ml-1 of fludioxonil and from 0.13 to 0.27 μg ml-1 of vinclozolin. Sensitivity to fludioxonil of all dicarboximide-resistant field isolates did not differ from their baseline. However, resistant laboratory strains that were selected either on media amended with fludioxonil or vinclozolin showed decreased sensitivities to both active ingredients. All sexual progenies of the crosses described above were of the parental phenotypes. We found no independent segregation of the resistance markers.