Tess Snyder, Jacob Martin, Bjarne Bartlett, James Osborne, and Chris Curtin*
*Oregon State University – Department of Food Science and Technology, 100 Wiegand Hall, Corvallis, OR, 97331 (christopher.curtin@oregonstate.edu)

The apiculate yeast genus Hanseniaspora has appeared frequently in enological research for over a century, mostly focused upon the species Hanseniaspora uvarum because of its notable capacity to cause spoilage. Recently, there has been more research into the potential benefits of other Hanseniaspora species, such as Hanseniaspora vineae, in producing more complex wines. Furthermore, large-scale, DNA sequencing-based (metabarcoding) vineyard ecology studies have suggested that Hanseniaspora species may not be evenly distributed. Does this mean that fruit from different vineyards could yield spoiled or complex wines depending on which Hanseniaspora species are present? To address this, we sampled extensively from 12 vineyards within the Willamette Valley AVA, across two sub-AVAs (Eola and Yamhill). We then used metabarcoding to assess the contribution of Hanseniaspora to the grape berry fungal community and their relative abundance in cold-soak and early stages of fermentation.

Our results show that while six of the 23 recognized Hanseniaspora species were present on Pinot noir grapes in the Willamette Valley AVA, differences between vineyards were driven by the abundance of H. uvarum. On the other hand, fungal community differences between sub-AVAs were not related to Hanseniaspora species. We observed significant positive correlation between the amount of H. uvarum present in must and at cold-soak, and then cold-soak to early fermentation. While intuitive, it is worth noting that no prior studies have observed this across so many grape samples from different vineyards. Our results provide clear evidence that the amount of H. uvarum on grapes may be an important predictor of potential effects on wine quality, particularly if performing cold-soak, which acts as an enrichment step. H. uvarum isolates have been recovered from almost every must sample for whole genome sequencing and are being evaluated for genetic and phenotypic differences to determine whether vineyard and/or sub-AVA populations vary.

Funding Support: Oregon Wine Research Institute, Agricultural Research Foundation and Oregon State University