Heatwave Frequency Affects Gewürztraminer Leaf Physiology and Grape Cuticular Wax Profile
Josh VanderWeide and Simone D. Castellarin*
*The University of British Columbia, 2205 East Mall,
Vancouver/British Columbia/V6T 1Z4, Canada
(simone.castellarin@ubc.ca)
Heat stress events (heatwaves) significantly impair grapevine leaf physiology and berry quality. The prevalence and frequency of heatwaves are predicted to increase in the coming decades, even in moderate climates. Despite this, the effects of heatwave frequency on grapevine physiology remains largely unstudied. We researched heatwave frequency by subjecting potted Gewürztraminer grapevines to a single heatwave event (SHW) at mid-ripening or a double heatwave event (DHW) at both veraison and mid-ripening, and compared them to untreated vines. Leaf gas exchange was measured before, during, and after the heatwave events, while chlorophyll fluorescence was also recorded afterward to evaluate stress recovery. Additionally, berry shriveling was analyzed in accordance with the berry cuticular wax profile and berry transpiration. Photosynthesis was reduced drastically during the heatwave events, but rebounded immediately post-heatwave in both SHW and DHW. In contrast, fluorescence was initially reduced by both SHW and DHW following the events. At harvest maturity, both photosynthesis and fluorescence were significantly reduced only by DHW, suggesting long-term damage to leaves. Berry shrivel was greater in heatwave treatments compared to their respective controls; however, shriveling was not greater in DHW than in SHW. This was attributed to a significant increase in total berry wax (11.8%) and total contents of triterpenes (11.7%) in DHW. As a result, berry cuticular transpiration was reduced by DHW, which correlated strongly with an increased ratio between the two most abundant wax and triterpene compounds, oleanolic acid and ursolic acid. We conclude that 1) grapevines are less resilient to a double than to a single heatwave event, and 2) the ratio of oleanolic to ursolic acid may be an important target for mitigation strategies to reduce berry shrivel. Future work will explore techniques to mitigate heat stress effects on grapevine physiology and quality.
Funding Support: This work was financially supported by the NSERC Discovery program (AWD-000128 NSERC 2020).
