Laboratory assays for selection of <i>Botrytis</i> suppressive microorganisms on necrotic grape leaf discs

Abstract

Isolates of saprophytic fungi (n209) were evaluated for biological control potential against Botrytis cinerea using in vitro dual plate and necrotic grape leaf disc assays Interrupted wetness periods were introduced during the 40day assay to select for disease suppressive saprophytic fungi with a high tolerance to fluctuating dry and wet periods Leaf disc assays were highly reproducible with relative rankings of the test isolates being similar over three assays In the absence of antagonists B cinerea sporulation increased during the 40day incubation to cover over 90 of the leaf disc area in conidiophores However in the presence of antagonists B cinerea sporulation was heavily reduced with the top seven isolates having less than 10 coverage relative to the control Thirteen isolates representing four genera Alternaria spp Epicoccum spp Trichoderma spp and Ulocladium spp have been identified for further laboratory testing prior to selection of a limited number of isolates for field evaluation