Project Title: Characterization of indigenous yeasts associated with wine grapes and early-stage fermentations in Washington State
Project Duration: 2014-2017

Principal Investigator(s): Patricia Okubara
Organization: USDA ARS
Telephone: 509-335-7824

Co-PI(s): Tim Murray
Organization: WSU
Telephone: 509-335-7515

Co-PI(s): Charles Edwards
Organization: WSU
Telephone: 509-335-6612

Co-PI(s): Thomas Henick-Kling
Organization: WSU
Telephone: 509-372-7292

Project Summary:

Production and consumption of wines made solely with native yeasts and bacteria have risen across Europe, USA, and Washington state. Production of alcohol, flavors and aromas during native fermentation is driven by the microbial communities that live on grape berries and in wine production environments (1,2,11,12,17,18,28). However, the lack of predictability of microbial composition in native fermentations poses the risk of vintages with undesirable flavors or aroma. To address a knowledge gap about the native yeasts present on Washington grapes and their persistence during native fermentation, we used advanced DNA sequencing technologies and sequence analysis procedures to determine yeast diversity in Cabernet Sauvignon vineyards and fermentations from two Washington AVAs. The project
complements ongoing studies at the Wine Science Center (23; Piao and Henick-Kling, unpublished), and opens doors to more comprehensive diversity testing and comparisons of yeast diversity among Washington AVAs, vineyards and grape cultivars.

A useful characteristic of certain native yeasts is their ability to suppress grape diseases, including Botrytis bunch rot (15,16,26,27,31). Botrytis bunch rot is a serious yield reducer in wet, cool grape production regions. Biological control offers a complementary tool to fungicides, as the bunch rot pathogen can develop resistance to fungicides (7,9,13,20). In another aspect of this project, we quantified the disease suppressive activities of eleven strains of native yeasts against nine strains of the Botrytis bunch rot pathogen on synthetic medium and on individual grape berries in the laboratory. We also evaluated the virulence of the pathogen isolates on inoculated grape berries.

To monitor specific native yeasts of interest in biocontrol and wine quality studies, we are developing molecular (DNA-based) diagnostic assays (22). The assays can rapidly detect and quantify yeasts in berry, fermentation and environmental samples with a high degree of sensitivity.

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Enology // Yeast //