Yevgen Kovalenko,* Marie Nosten, Tyler Abbey, Bartosz Kozak, 
and Simone Castellarin  
*The University of British Columbia, 330 – 2205 East Mall, Vancouver, BC V6T1Z4, Canada (hophmen@gmail.com)

Deficit irrigation of grapes can decrease berry weight and increase concentrations of secondary metabolites, including the volatile organic compounds. This practice is often used in red grape varieties to improve grape and wine quality; however, little work has been done with white grapes, particularly in the Okanagan Valley. The timing of deficit irrigation application can alter the efficacy of the treatment. In this study, field-grown Gewürztraminer under a deficit irrigation regime applied at different periods throughout berry development (well-watered, preveraison deficit, postveraison deficit, and prolonged deficit) were characterized for their ecophysiological, biochemical, and molecular response to the treatments. The hypothesis was that application of deficit irrigation will induce synthesis of quality-determining volatile compounds, with preveraison and prolonged ap-plication of water deficit being more effective than later application. Treatments were replicated on four plots arranged in a randomized block design. Sampling occurred every seven to 14 days starting three weeks after fruit set. Grapevine leaf water potential was monitored using the Scholander pressure chamber at ±1 hr from solar noon. The effect of these treatments on leaf water potential, photosynthesis, vegetative growth, and sugar, acid, and volatile compound concentrations was analyzed. Ecophysiological parameters, sugar concentration, berry weight, and vine yield were significantly affected by deficit irrigation; however, there was a clear effect from timing of application as well. Previously identified genes involved in drought response and central and specialized metabolism will also be analyzed for treatment response. Free and bound volatiles will be quantified using solid-phase micro-extraction gas chromatography mass spectroscopy. The goal of this project is optimize Gewürztraminer grape quality through targeted irrigation practices, as volatile organic compounds are closely tied to the economic potential of winegrapes.

Funding Support: British Columbia Investment Agriculture Foundation, Mitacs, British Columbia Wine and Grape Council