Occurrence of wine yeasts on grapes subjected to different pesticide treatments

As a contribution to the study and preservation of indigenous wine yeast po pulations, we initiated a programme of isolation and characterization of ye ast strains from grapes of the Italian region of Marche. During the 1996 vi ntage, grape samples were collected from three groups of vineyards differin g in the pesticide treatments given. Of the 279 yeasts isolated, thirty-nin e were assigned to the species Saccharomyces cerevisiae. The majority of th e isolates and all thirty-nine S. cerevisiae came from vineyards which had not been treated with systemic pesticides, indieating that these pesticides may exert a negative effect on the biodiversity of the grape microflora, a nd in particular on the occurrence of S. cerevisiae on grapes. The thirty-n ine S. cerevisiae isolated were subjected to microfermentation trials, in w hich ten of them showed promising fermentative capabilities.