Terroir of winter hardiness: bud LT50, water metrics, yield, and berry composition in Ontario Cabernet franc

Abstract

Winter hardiness may be influenced by vineyard terroir-driven factors, and vineyard zones with low water status [leaf water potential (ψ)] could be more winter hardy than vines with high water status (higher leaf ψ). Six Cabernet franc vineyards were chosen throughout the Niagara region in Ontario. Data were collected at fruit set, lag phase, and veraison [soil water content (SWC), leaf ψ], at harvest (yield components, berry composition), and three times during winter (LT50; the temperature at which 50% of buds die) in the 2010–2012 seasons. Interpolation by kriging and mapping of variables was completed using ArcGIS, and statistical analyses (linear correlation, k-means clustering, principal components analysis, multilinear regression) were performed. Spatial trends were observed in each vineyard for SWC, leaf ψ, yield components, berry composition, and LT50. Geographic information systems (GIS) and statistical analysis revealed that leaf ψ could predict LT50, with strong positive correlations between LT50 and leaf ψ values in most vineyards in 2010–2011. In the dry 2012 season, leaf ψ (particularly at veraison; range −1.3 to −1.6 MPa) was positively correlated to LT50, yield, titratable acidity (TA), pH, and Brix and negatively to SWC, color, anthocyanins, and phenols. Overall, vineyards in different appellations (Niagara Lakeshore, Lincoln Lakeshore, Four Mile Creek, Beamsville Bench) showed many similarities. These results suggest that there is a spatial component to winter injury, as with other aspects of terroir. Furthermore, this study allows for means by which to compare winter hardiness to other critical variables to better understand the terroir of the Niagara region.