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Enrichment of Brettanomyces and Other Non-Saccharomyces Fermentative Yeasts from Vineyard Samples in Oregon

Brettanomyces yeasts remain one of the most important spoilage issues facing the global wine industry. Despite their ubiquitous association with wine and wineries from around the world, there is almost no information on the occurrence of Brettanomyces in vineyards. In this study we used enrichment culturing to successfully isolate Brettanomyces yeasts from 12 of 149 grape berry cluster samples obtained from a vineyard in Oregon over two harvest seasons. This low rate of recovery was consistent with another recent study performed in Italy (Oro et al. 2019) and suggests that Brettanomyces is not a prevalent vineyard yeast genus. In addition to Brettanomyces, we recovered non-Saccharomyces isolates from a further 39 samples. These were predominantly from genera infrequently described in the context of vineyards and winemaking fungal communities, such as Nakazawea, Kazachstania, Lodderomcyes, and Ogataea. By evaluating relative growth capacity and direct competitive fitness, we showed that while some vineyard non-Saccharomyces yeasts are likely to be out-competed in enrichment media by Brettanomyces, others can interfere with Brettanomyces recovery. This may partly explain why Brettanomyces vineyard populations are rarely described. Our results pave the way for further studies of Brettanomyces from non-fermentation origins and demonstrate that enrichment culturing can be applied to reveal other rare vineyard yeast populations.