Occurrence of wine yeasts on grapes subjected to different pesticide treatments

As a contribution to the study and preservation of indigenous wine yeast populations, we initiated a programme of isolation and characterization of yeast strains from grapes of the Italian region of Marche. During the 1996 vintage, grape samples were collected from three groups of vineyards differing in the pesticide treatments given. Of the 279 yeasts isolated, thirty-nine were assigned to the speciesSaccharomyces cerevisiae. The majority of the isolates and all thirty-nineS. cerevisiaecame from vineyards which had not been treated with systemic pesticides, indicating that these pesticides may exert a negative effect on the biodiversity of the grape microflora, and in particular on the occurrence ofS. cerevisiaeon grapes. The thirty-nineS. cerevisiaeisolated were subjected to microfermentation mals, in which ten of them showed promising fermentative capabilities.