Submitted to: American Journal of Enology and Viticulture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 11, 2013
Publication Date: June 1, 2013
Citation: Shellie, K., King, B.A. 2013. Kaolin particle film and water deficit influence red winegrape color under high solar radiation in an arid climate. American Journal of Enology and Viticulture. 64:214-222. Interpretive Summary: Red-skinned wine grape cultivars are often intentionally grown under a water deficit to control vine vigor and to enhance berry composition for red wine production. Many studies in field and controlled environments have shown that color development in red-skinned grapes is sensitive to temperature and light. An increased incidence of heat and or solar injury has been observed in warm growing regions with high solar radiation when vines are maintained under a water deficit, particularly on western-facing fruit in north-south oriented rows and south-facing fruit on east-west oriented rows. Foliar application of clay-based particle films have been shown to mitigate radiation stress in a number of crops. The objective of this research was to determine whether a foliar application of particle film alleviated water-deficit-induced, high radiation stress during berry development in the winegrape cultivars Cabernet Sauvignon and Malbec. One of the most noteworthy findings from this study was the increase in total anthocyanin concentration of berries from vines with particle film in two out of three years. We observed an increase in berry anthocyanin concentration in response to increased water deficit severity in both cultivars in each year of the study, but the water-deficit-induced increase in anthocyanin concentration was accompanied by a decrease in berry fresh weight and therefore a reduction in yield. An increase in berry anthocyanin concentration of equal or greater magnitude was achieved under less severe water deficit without an accompanying decrease in berry fresh weight in two out of three years when particle film was applied to the vine canopy. This finding is of commercial and economic interest because berry anthocyanin composition predetermines the color potential of the resulting red wine.
Technical Abstract: Main and interactive effects of a kaolin-based particle film and water deficit severity on vine and berry attributes were evaluated in the warm, semi-arid climate of southwestern Idaho over three growing seasons in the cultivars Cabernet Sauvignon and Malbec. Berry concentrations of total anthocyanins increased with increasing severity of water deficit in both cultivars in all three study years; however, the water-deficit-induced increase was accompanied by a decrease in berry fresh weight. Foliar application of particle film to vines under mild water deficit increased total anthocyanin concentrations an equal or greater amount as more severe water deficit, in two out of three years, without an accompanying decrease in berry fresh weight. The responsiveness of stomatal conductance to leaf temperature was influenced by the particle film and the severity of water deficit, and differed by cultivar, suggesting that mechanisms of stomatal control can override the beneficial reduction in absorbed incident radiation provided by the film. Under the climatic conditions of this study, the combination of particle film and mild water deficit provided the greatest net increase in anthocyanin concentration. The differences we observed between cultivars in response to the particle film indicate that applicability of results from this study should be limited to cultivars with similar response to drought as Cabernet Sauvingnon and Malbec.