Potential use of the yeast Starmerella bacillaris as a sustainable biocontrol agent against gray mold disease in viticulture

Abstract

Pest biocontrol strategies are gaining attention as eco-friendly alternatives to the use of synthetic pesticides, including in viticulture.

The yeast Starmerella bacillaris strain FRI751 was previously proven in vitro and in vivo to exhibit antagonistic activity against Botrytis cinerea, the etiological agent of gray mold disease in grapes. The study presents the first evaluation of the biocontrol potential of this strain against B. cinerea, as a defense treatment in vineyards.

S. bacillaris was sprayed on Pinot gris grapes during the pre-bunch closure, veraison, and pre-harvest phenological stages. Trends of S. bacillaris and B. cinerea on grapes surface were monitored through qPCR. Each application of S. bacillaris established an initial estimated population that was one to two logs lower than the concentration of the sprayed culture, with a subsequent decline over time. B. cinerea growth was detected in untreated bunches but was absent in those treated with S. bacillaris. The use of conventional antibotrytic pesticides showed, instead, a slight reduction in detected B. cinerea over time.

Metabarcoding analysis of the whole ITS region on grape surface fungal communities further supported the biocontrol effect of S. bacillaris. Additionally, S. bacillaris was still present in the must derived from sprayed grapes, and the wine produced from this must exhibited a higher glycerol content and a similar acetic acid content compared to controls, supporting the known positive contributions of this yeast during fermentation.

This study highlights the potential of S. bacillaris FRI751 as a sustainable option for grape protection from gray mold disease and for improving wine quality.