Starmerella bacillaris grape treatment as a sustainable approach to manage Botrytis cinerea during the withering process

Abstract

Growing concerns over the environmental and health risks posed by chemical pesticides have highlighted the need to reduce their use in the agri-food sector. The fruit post-harvest management is a critical stage for implementing strategies to prevent pesticides from reaching the consumers table. A promising alternative seems the use of microorganisms as biocontrol agents.

This study explored the biocontrol activity of the yeast Starmerella bacillaris, applied on drying grapes, against the spoilage fungus Botrytis cinerea. Two different grape varieties were tested: Garganega and Raboso. During the withering process, the trend of the population of S. bacillaris released on grapes and the growth dynamics of B. cinerea have been monitored by real-time quantitative PCR (qPCR) to evaluate the impact of the treatment. Additionally, DNA metabarcoding was employed to compare the microbial biodiversity associated with grapes surface and to assess how it was influenced by the treatment. At the end of the withering process, grapes were pressed and the must was fermented to evaluate the effect of S. bacillaris on alcoholic fermentation.

The development of a successful qPCR-based method for the identification and quantification of the selected S. bacillaris strain provided evidence of its persistence on the grape surface until the end of the withering process. DNA metabarcoding showed that the application of S. bacillaris on the surface of the Raboso grapes caused an increase in the biodiversity of fungal communities and a decrease in the proportions of filamentous fungi, such as B. cinerea. This result was confirmed also by qPCR results which confirmed that the application of S. bacillaris effectively inhibited the growth of B. cinerea on Raboso grape bunches.