Atiako Acheampong, Lauren Marigliano, Yosepha Shahak-Ravid, and Sahap Kurtural*
*University of California Davis, 1 Shields Avenue, Davis, CA, 95616
(skkurtural@ucdavis.edu)

Partial solar radiation exclusion has emerged as a viable technology to mitigate the effects of global change in winegrape production. A factorially arranged experiment consisting of Opti-Panel and irrigation was conducted in the Napa Valley of California. Treatments consisted of Opti-Panel, a recently developed product of Opti-Harvest, and an uncovered control that were completely crossed with irrigation replacements of 100% and 25% of crop evapotranspiration replacement (ETc) starting at engustment. Opti-Panels consistently maintained ~17% greater net carbon assimilation (Anet) and stomatal conductance (gs), regardless of irrigation treatment or measurement date, than the uncovered control throughout the growing season. Likewise, irrigating with 100% ETc increased Anet and gs ~17% over that of the 25% ETc treatment. Components of yield were not adversely affected by Opti-Panel application, but 25% ETc irrigation reduced berry and cluster mass as well as yield per plant. Berry titratable acidity increased with Opti-Panel application, while irrigating with 25% ETc reduced it. Berry total soluble solids increased when Opti-Panel was not applied, indicating dehydration. Likewise, berry total skin anthocyanins were 21% greater with Opti-Panel application, while irrigating to 100% ETc reduced it by a similar amount, indicating Opti-Panel application was arresting anthocyanin degradation. Berry skin flavonol content increased 45% when Opti-Panel was not applied and increased by a similar amount when 25% ETc was applied, indicating overexposure of the fruit zone. The molar abundance of kaempferol in berry skin, a biomarker for exposure to solar radiation, was ~250% higher in the uncovered control than in Opti-Panel, regardless of irrigation treatment. Results indicated that Opti-Panel was a useful cultural practice and technology that maintained yield without adversely affecting berry composition and increased berry anthocyanin content without having to increase applied water amounts in a hot climate prone to frequent heat waves.

Funding Support: Opti-Harvest Inc.