The antifungal activity against Botrytis cinerea, a pathogen of grape gray mold disease, was validated in vitro for 59 of 225 wild yeast strains isolated from naturally fermented wine samples (69 strains), our university campus plants (129 strains), and commercially available fruits (27 strains). Twenty strains showing strong antifungal activity were identified. The majority of the strains were Saccharomyces cerevisiae (16 of the 20 strains). The S. cerevisiae strains were differentiated by genetic polymorphism analyses with comparisons of their antifungal activities. As a result, it was clarified that each strain type showed different antifungal activity, and that automatic rRNA intergenic spacer analysis was extremely useful for the differentiation of S. cerevisiae strains when compared to other conventional polymerase chain reaction-based methods.

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Microorganisms, including native yeasts, are abundant in vineyard fields. Herein, we studied the possibility of using vineyard-derived wild yeast as a microbial pesticide against Botrytis cinerea, a pathogen that causes grape gray mold disease, to boost the initial alcohol production of spontaneously fermented wine. We identified the Saccharomyces cerevisiae strain KONDO170908, which showed the most effective antifungal activity in an ex vivo yeast dripping experiment on grape berries. This strain was utilized in an in vivo spray test on grape bunches in vineyard fields and was proven to significantly suppress gray mold disease on the grape berries in test plot #16 when the yeast was sprayed during both the flowering and ripening periods (morbidity 11.2% against 15.3% of the control plot, χ2 test, P < 0.0001). However, in test plot #17, spraying the yeast during only the ripening period had no effect (morbidity 16.3%). The grapes from each test plot were also submitted for spontaneous wine fermentation. Alcoholic fermentation of the grapes from test plot #16 provided the most active bubbling of CO2 gas and the highest ethanol production and colony counts over seven days of fermentation. Unique changes in the different strains of S. cerevisiae among the plots were observed throughout the early fermentation stage. Thus, yeast spraying during the flowering period might trigger modification of the entire microbiota and could ultimately contribute to promoting alcohol production in the spontaneously fermented wine.

Microorganisms, including native yeasts, are abundant in vineyard fields. Herein, we studied the possibility of using vineyard-derived wild yeast as a microbial pesticide against Botrytis cinerea, a pathogen that causes grape gray mold disease, to boost the initial alcohol production of spontaneously fermented wine. We identified the Saccharomyces cerevisiae strain KONDO170908, which showed the most effective antifungal activity in an ex vivo yeast dripping experiment on grape berries. This strain was utilized in an in vivo spray test on grape bunches in vineyard fields and was proven to significantly suppress gray mold disease on the grape berries in test plot #16 when the yeast was sprayed during both the flowering and ripening periods (morbidity 11.2% against 15.3% of the control plot, χ2 test, P < 0.0001). However, in test plot #17, spraying the yeast during only the ripening period had no effect (morbidity 16.3%). The grapes from each test plot were also submitted for spontaneous wine fermentation. Alcoholic fermentation of the grapes from test plot #16 provided the most active bubbling of CO2 gas and the highest ethanol production and colony counts over seven days of fermentation. Unique changes in the different strains of S. cerevisiae among the plots were observed throughout the early fermentation stage. Thus, yeast spraying during the flowering period might trigger modification of the entire microbiota and could ultimately contribute to promoting alcohol production in the spontaneously fermented wine.

No abstract