Jeremy Weiss*
*University of Arizona Cooperative Extension, 1140 E South Campus Dr, PO Box 210036, Tucson, AZ, 85721-0036 (jlweiss@arizona.edu)

As temperatures continue to trend higher, winegrape growers in warm-climate viticul­tural regions will increasingly be challenged by the many effects that temperature has on fruit composition. Warmer ripening conditions in recent years for such growing regions around the world have resulted in higher sugar concentrations, less acidity from declines in malic acid, and higher pH. Precipitation during ripening can influence winegrape composition by interacting with effects caused by temperature. As such changes in the fruit make unbalanced composition more likely, there is increasing industry concern over the effects of climate on winegrape production. Detrimental changes in fruit composition due to variations and changes in climate also are an is­sue for Arizona viticulture, as most vineyards in the state are located in warm-climate growing areas. However, how recent climate conditions in Arizona potentially have affected winegrape composition is unknown. Here, we quantify relationships between elements of fruit composition and exposure to temperature and precipitation during the ripening season. Our hypothesis is that more heat and moisture correlate with less-balanced composition values. For data, we use measures of Brix and pH at har­vest for several varieties across multiple vintages from vineyards in each of the three state American Viticultural Areas, along with those of temperature and precipitation from station and gridded sources. By determining how exposure to heat and moisture during ripening potentially has influenced fruit composition in recent vintages, our work provides an initial model for growers and winemakers in warm-climate viticul­tural regions, with which to predict impacts of climate conditions in future growing seasons and to consider vineyard and winery adaptations to produce quality fruit and balanced wines under continued regional warming.

Funding Support: Funding for this presentation was made possible by the U.S. Department of Agriculture (USDA) Agricultural Marketing Service through grant SCBGP-FB21-19.