Pin-Jui Chen,* Joshua VanderWeide, Christopher Mark, and Simone D. Castellarin
*Wine Research Centre, University of British Columbia, 2205 East Mall, Vancouver/ BC/ V6T 1Z4, Canada (pj0508@student.ubc.ca)

Several grape cultivars are characterized by a rich assortment of volatile terpenoids (mono- and sesqui-), a class of secondary metabolites that affect grape and wine aroma. Intra-vineyard factors that affect volatile terpenoids are not well known, despite potentially affecting the quality of grapes and wines. This study aimed to assess the relationships between grape volatile terpenoids and other vine parameters within vineyards. Two commercial vineyards (Riesling and Gewürztraminer) in the Okanagan Valley (British Columbia, Canada) were considered. To assess intra-vineyard variation, 40 and 48 plots distributed within the Riesling and Gewürztraminer vineyards, respectively, were selected. Three random vines per plot were used for all measurements. These included plant water status (stem water potential), leaf area, and leaf gas exchange (CO2 assimilation, transpiration, stomatal conductance), measured at bloom and veraison. At the same stages, normalized difference vegetative index (NDVI) and normalized difference red edge index (NDRE), calculated from remote sensing-based multispectral drone images and ground-based measurements, were used to estimate vine vigor. Vine nutrient status was determined by petiole analysis at veraison. Yield, berry technological quality (total soluble solids, pH, and titratable acidity), and volatile terpenoids were determined at harvest. The content of grape volatile terpenoids correlated positively with leaf area, NDVI, NDRE, and yield in Riesling, and with petiole nitrogen content, NDVI, NDRE, and yield in Gewürztraminer. Our study confirms that remote sensing-based NDVI and NDRE correlate positively with petiole nitrogen content, leaf area, and yield, and indicates that these parameters could predict variation in grape volatile terpenoids within vineyards. Our results also suggest that, in the Okanagan Valley, promoting vine vigor can improve grape aroma, and remote sensing-based vegetative indices could serve as a cost-efficient and time-saving approach to estimate vine vigor within a vineyard.

Funding Support: MITACS/ Investment Agriculture Foundation