Fungal and bacterial communities of ‘Pinot noir’ must: effects of vintage, growing region, climate, and basic must chemistry

Authors: Steenwerth, Kerri; Morelan, Ian; STAHEL, RUBY - US Department Of Agriculture (USDA); FIGUEROA-BALDERAS, ROSA - University Of California, Davis; CANTU, DARIO - University Of California, Davis; Lee, Jungmin; RUNNEBAUM, RON - University Of California, Davis; Poret-Peterson, Amisha

Submitted to: PeerJ
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/4/2021
Publication Date: 2/4/2021
Citation: Steenwerth, K.L., Morelan, I.A., Stahel, R.J., Figueroa-Balderas, R., Cantu, D., Lee, J., Runnebaum, R.C., Poret-Peterson, A.T. 2021. Fungal and bacterial communities of ‘Pinot noir’ must: effects of vintage, growing region, climate, and basic must chemistry. PeerJ. 9. Article e10836. https://doi.org/10.7717/peerj.10836.
DOI: https://doi.org/10.7717/peerj.10836

Interpretive Summary:

Technical Abstract: The geographic and temporal distributions of bacterial and fungal populations are poorly understood within the same wine grape cultivar. In this work, we describe the microbial composition from ‘Pinot noir’ must with respect to vintage, growing region, climate and must chemistry across the states of California and Oregon, USA. We sampled ‘Pinot noir’ clone 667 clusters from 15 vineyards existing in a latitudinal gradient spanning nearly 1200 km in California and Oregon for two vintages (2016 and 2017). Regions included five American Viticultural Areas (AVA). In order from southern California to Oregeon, these AVAs were Santa Barbara, Monterey, Sonoma, Mendocino and Willamette Valley. Uninoculated grape must was analyzed after three days of cold soaking. To assess the composition of microbial communities, we conducted 16S rRNA gene and ITS-1 amplicon sequencing. We also measured grape maturity metrics to further characterize grape must samples. Finally, to describe regions by precipitation and growing degree days, we queried the Parameter-elevation Relationships on Independent Slopes Model (PRISM) spatial climate dataset. Most of the dominant bacterial taxa in must samples were in the family Enterobacteriaceae, notably the lactic acid bacteria or the acetic acid bacteria groups, but some, like the betaproteobacterial genus Massilia, belonged to groups not commonly found in grape musts. Fungal communities were dominated by Hanseniaspora uvarum. We detected relationships between covariates (e.g., vintage, precipitation during the growing season, pH, titratable acidity, and total soluble solids) and bacterial genera Gluconobacter, Sphingomonas, Tatumella, Lactobacillus, and Massilia, as well as fungal genera Kazachstania, Alternaria, Erysiphe, Hanseniaspora, Lachancea, Torulaspora, and Udeniomyces. Fungal Hellinger distances (i.e. community dissimilarities) were significantly correlated with geographic distances, but this was not observed for bacterial communities. Climate varied considerably across regions and vintages, with growing season precipitation ranging from 11 mm to 285 mm and growing degree days ranging from 1245 to 1846. Using culture-independent methods to characterize grape must microbial communities, we determined that 1) bacterial beta diversity (as determined by NMDS of Bray-Curtis dissimilarity matrices) is structured by growing season precipitation, 2) fungal beta diversity reflects growing season precipitation and growing degree days, and 3) microbial differential abundances of specific genera vary with vintage, growing season precipitation, and fruit maturity metrics. Further, the correlation between fungal community dissimilarities and geographic distance suggests dispersal limitation and the vineyard as a source for abundant fungal taxa. Contrasting this observation, the lack of correlation between bacterial community dissimilarity and geographic distance suggests that environmental filtering is shaping these communities.