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A survey of wine- and vineyard-associated yeast and fungal populations at a British Columbian winery Martiniuk, Jonathan Todd

Abstract

Wine is produced by one of two methods: inoculated fermentation, where a commercially produced, single Saccharomyces cerevisiae yeast strain is used; or the traditional spontaneous fermentation, where yeasts on grape and winery surfaces carry out the fermentative process. Spontaneous fermentations are characterized by a diverse succession of yeasts, ending with one or multiple strains of S. cerevisiae dominating the fermentation. In wineries using both fermentation methods, commercial strains may dominate spontaneous fermentations. In addition to S. cerevisiae, other vineyard-associated yeast and fungi affect grapevine crop health and impact wine quality, particularly in spontaneous fermentation. Grape fungal community composition – both S. cerevisiae strains and other fungal populations – varies regionally, and community differences may correlate with wine metabolite composition and sensory profile, suggesting a microbial role in shaping a wine’s terroir or regional character. Over two vintages, we characterize the S. cerevisiae and other fungal populations found in three closely situated vineyards and spontaneous fermentations of a British Columbian winery, elucidating the impact of the winery environment and commercial strain use on S. cerevisiae population structure in spontaneous fermentations. Winery fermentations were not dominated by commercial strains, but by a diverse number of strains with genotypes similar to commercial strains, suggesting a population of S. cerevisiae derived from commercial strains is resident in the winery. Commercial and commercial-related strains were identified at a lower frequency in the three study vineyards. There is low genetic differentiation and S. cerevisiae population structure in vineyards that may be driven by commercial strains. Genetically distinct S. cerevisiae populations unrelated to commercial strains were also identified. We lastly examined the fungal communities on the surface of grape berries, crushed grapes, and during fermentation. Spatiotemporal fungal community structure was evident among grape berry surface, crushed grape and fermentation samples from the three vineyards, with each vineyard retaining a community signature across vintages and throughout fermentation. This study, which is the first to profile Canadian vineyard-associated fungal populations, suggests that fungal populations may be a defining contributor to small-scale or ’micro’ terroir, having significant implications for ’single vineyard’ wine production.

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Attribution-NonCommercial-NoDerivatives 4.0 International

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