Inactive yeasts as preventive treatments against Botrytis cinerea on grapevine

The demand for alternatives to synthetic fungicides has been increasing due to the rise of pathogens resistant to active principles, consumers and producers consciousness, and EU directives on sustainable farming. Botrytis cinerea is a worldwide distributed pathogen of grapevines causing losses of grape production. In the last years, yeasts and their derivatives have been studied as promising alternatives to fungicides for the management of plants’ pathogens. In this study, a screening of various inactive yeast suspensions from the food industry was performed. The objective of this research was to check several yeast derivates efficacy in plant stimulation and defence activation toward B. cinerea. Grapevine plants, cultivar Merlot grown in pots in a greenhouse, were treated twice using inactive yeast-based suspensions. Stomatal conductance was monitored 48 hours later to assess the plant metabolism. Inoculation of B. cinerea was performed on detached leaves at 72 hours after the second application and extension of the lesions was observed three days later. Results suggest that inactive yeast Saccharomyces cerevisiae grown on exhausted medium of Salvia officinalis efficiently reduce B. cinerea lesions on leaves in comparison to the untreated control. An increase in plants photosynthetic activity has also been observed after the application of the exhausted medium of S. officinalis. Those extracts could offer interesting alternatives to synthetic fungicides. Further in vivo trials need to be conducted to investigate the efficiency of these compounds in protecting Grapevine production.