Screening of Ampelomyces strains as candidate agents for the biological control of grapevine powdery mildew

Powdery mildews are among the most important plant diseases worldwide. These diseases, caused by biotrophic, epiphytic fungi belonging to Erysiphales, account for the greatest part of the fungicides used in European agriculture and especially in vineyards. An attractive and environmentally safe alternative to fungicide application is the use of biocontrol agents (BCAs), including Ampelomyces spp., a group of hyperparasitic fungi affecting several powdery mildews of different cultivated and wild plants. This work was carried out within the EU-funded project “BCA-grape”, aimed at developing new biocontrol agents for powdery mildew on grapevines. Eighteen strains of Ampelomyces belonging to the culture collection of the Plant Protection Institute of the Hungarian Academy of Sciences, Budapest, were investigated for their ecological requirements and biological characteristics in order to identify candidate BCAs for grapevine powdery mildew. Mycelium growth rate, production of picnidia, and germination of conidia were determined in vitro under different environmental conditions. The mycoparasitic activities of the strains were tested in both controlled and natural environments using potted and field-grown grapevine plants, respectively. In these experiments, Ampelomyces strains were applied to powdery mildew colonies at different colony growth stages. Statistically significant differences were found among the strains and, interestingly, among some of these strains and the commercial product AQ10, which contains A. quisqualis. The preliminary results from this work are promising in that they demonstrate substantial potential for control of grapevine powdery mildew by Ampelomyces spp.