In its 2018-19 fiscal year, the Oregon Wine Board of Directors granted $437,500 to researchers for nine projects with the potential to advance quality grape growing and winemaking in Oregon. The update below is part of a series to let you know about the status of these projects.

Dr. Jeremy Weisz is an associate professor in the Department of Biology at Linfield College. His research focuses on understanding interactions that plants and animals have with their microbiomes, the microbes that live on and in them. He has been studying microbiomes on wine grapes since 2014 and has prepared the update below.

Examining the impacts of environmental variations and farming practices on wine grape microbiomes

Project objectives:
The goal of this project was to better understand how the microbiome—the associated microbial community—of wine grapes is influenced by geography and viticulture practices. Specifically, we investigated:

  1. How AVA influences the bacterial and yeast communities on Pinot noir grapes; and
  2. How Biodynamic vs. non-Biodynamic viticulture practices influence the bacterial and yeast communities on Pinot noir grapes.

Importance to the Oregon wine community:
Winemakers spend significant time and money marketing their wines based on terroir. Given that much of this terroir is really microbial terroir, understanding what factors make their bacterial and fungal communities unique is important for understanding and marketing why their wines are unique. Winemakers and viticulturists are increasingly interested in understanding what microbial processes are happening in their vineyards and how management practices impact these processes. Our research is key to understanding this important but poorly understood aspect of the wine industry.

Progress so far:
In 2018, we sampled 12 vineyards in the Willamette Valley across five AVAs. In each AVA, one sampled vineyard was certified Biodynamic, while one vineyard was more conventionally farmed, though almost all were LIVE certified.

Looking first at the bacterial communities, we found significant differences between Biodynamic and “conventional” vineyards. When we examined the bacterial community data by AVA, only the Eola-Amity Hills AVA was found to be significantly different from the other AVAs. Thus, bacterial communities among our samples are shaped much more by farming practices than by geography.

Samples were also analyzed for fungal community diversity, which includes yeasts. The data for these samples were markedly different than the data for the bacterial communities. Looking at the fungal data, there were no differences between Biodynamic and other vineyards. However, there was much more variation between AVAs in the fungal data, with only the Dundee Hills and Eola-Amity Hills AVAs showing any significant overlap.

Overall, these results suggest that grape-associated bacterial communities are influenced by farming practices, while grape-associated fungal/yeast communities are influenced by geography.

Next steps:
For the 2019 vintage, this project has been expanded in several ways. Dr. Krista McGuire, a collaborator from the University of Oregon, has been added to the team. She brings experience and expertise in soil microbiology. This larger team will examine vineyards across the state, including samples for vineyards in AVAs in Southern Oregon, the Columbia Gorge, and a wider sampling in the Willamette Valley. We will also be sampling more than just grapes, including samples of soil, bark and leaves. In addition, for a subset of locations, we will sample must and juice at multiple times during fermentation. This wider sampling will allow us to start to understand how vineyard microbiomes directly influence the final wine.