Pectolytic and Cellulolytic Enzymes of Dicarboximide-sensitive and Resistant Strains of Botrytis cinerea1

Starting in 1979 the pathogenicity of dicarboximide-resistant and sensitive strains of Botrytis cinerea was regularly examined in greenhouse tests using grape plants. In these tests the proportion of resistant strains with low or nearly no pathogenicity was always higher than that of sensitive strains. This led to comparative studies on the enzyme activities of sensitive and resistant field isolates. Pectolytic and cellulolytic enzymes were chosen because of their importance in the infection process of B. cinerea. The results of these studies indicated that no correlation could be found between the activity of these enzymes and the pathogenicity of the tested isolates, and that resistant strains tended to have higher enzyme activities than sensitive ones. Comparison of the enzyme activities of laboratory-adapted isolates and the original sensitive ones gave similar results. Since enzyme activities do not seem to play an important role in explaining the general observations on the slow increase and spread of resistant strains in vineyards, other factors must be considered, such as the stability of the dicarboximide resistance, which apparently is very low.