Lauren Marigliano, Nazareth Torres, Runze Yu, Mark Battany, and Kaan Kurtural*
*University of California Davis, 1 Shields Avenue, Davis, CA 95616 (skkurtural@ucdavis.edu)

Climate conditions are expected to increase temperature and water deficits in viticulture regions by the mid-21st century, impacting grapevine physiology and production sustainability. Photoselective overhead shade films (D1, D3, D4, D5) with varying degrees of solar spectra exclusion were installed and compared to an uncovered control (C0) in a randomized complete block design with four replicates. The goal of the experiment was to evaluate the vulnerability of Cabernet Sauvignon grape berry to solar radiation overexposure and optimize the use of shade films for berry development. Results indicated that C0 had significantly greater evapotranspiration than shaded treatments. Consequently, the water footprint (m3/tonnes) of C0 was significantly greater than the shaded treatments with no difference in yield. Through- out berry ripening and at harvest, total skin anthocyanins (mg/g fresh mass) in the shaded treatments were greater than C0 and the molar abundance of kaempferol (%) was lowest in D1 and D3. Relative yield was not different between the control and treatments, although dormant season precipitation was excluded from shaded treatments. Our results indicated that shade films reduced evapotranspiration from the grapevine canopy in the hot climate without reducing yield, while arresting anthocyanin and flavonol degradation relative to exposed grapevines.

Funding Support: University of California Davis Foundation