Lucy Joseph* and Linda Bisson
*Department of Viticulture and Enology, University of California, Davis, CA 95616 (cmjoseph@ucdavis.edu)

Using spontaneous fermentations for wine production is increasingly popular with many wineries and wine consumers. However, it is unknown whether such fermentations are being carried out by an autochthonous (indigenous) strain of Saccharomyces, by a commercial strain, or by an autochthonous-commercial hybrid. To help answer this question, we collected yeast primarily from hardwood trees in wine regions of California that are remote from commercial yeast sources. The sites were at least five kilometers from wineries, breweries, or bakeries. Samples were enriched in grape juice medium and organisms responsible for fermentation were selected and identified using 26s rDNA sequence analysis. A variety of different yeast species were isolated including twelve Saccharomyces cerevisiae and one possible Saccharomyces paradoxus. Other isolates included seven Lachancea thermotolerans, five Zygosaccharomyces pseudobailii, two Pichia galeiformis, one Torulaspora delbrueckii, one Cryptococcus diffluens, one Rhodospiridium diobovatum, four Metschnikowia, and three Candida species. Microsatellite DNA analysis was used to compare our isolates to commercial strains and determine whether there is a pattern characteristic of Saccharomyces that are native to western North America. The microsatellite system used 10 primer sets in 10 genes over eight chromosomes labeled with three fluorescent dyes. An extensive database of allele fragments and sizes is available online for this set of primers. This data set allowed us to compare our isolates to strains from other regions of the world and to commercial strains. We could determine whether strains in the culture collection and from spontaneous fermentations are related to commercial strains or are autochthonous. Commercial and North American Saccharomyces strains were distinct by cluster analysis. This ability could help us define California microbial terroir and could potentially help winemakers produce wines with more distinct regional character.

Funding Support: UC Davis Department of Viticulture and Enology