Shifts in the phenolic composition and aromatic profiles of Cabernet Sauvignon (Vitis vinifera L.) wines are driven by different irrigation amounts in a hot climate.

Wine final color, taste and aroma are closely related to the accumulation of secondary metabolites that may be affected by deficit irrigation applied in viticulture. A two-year study was conducted to assess the different fractions of crop evapotranspiration (ETc) irrigation replacement on wine composition, addressing the analysis of flavonoids and volatiles under context of global warming. Irrigating with 100% ETc (full grapevine demand) enhanced wine hue, antioxidant capacity, and some aromas; however, it came with a diminution of flavonoids and a less stable flavonoid profile. Replacing 25 and 50% ETc in wine grape improved wine color intensity, concentration of flavonoids, and shifted the aromatic profiles. These treatments increased some terpenes and esters which may enhance the desirable aromas for Cabernet Sauvignon, and decreased C6 alcohols related to unpleasant ones. Therefore, despite the warming trends in Mediterranean climates, 100% ETc irrigation would be not advisable to improve or maintain wine quality, and 50% ETc was sufficient.

Impacts of leaf removal and shoot thinning on cumulative daily light intensity and thermal time and their cascading effects of grapevine (Vitis vinifera L.) berry and wine chemistry in warm climates.

Leaf removal (LR), shoot thinning (ST) and their combination (LRST) are known to increase berry solar exposure affecting berry composition and consequently improving wine quality and antioxidant properties. We hypothesized that LR, ST or their combination (LRST) would affect flavonoid content during berry ripening by means of changes of the berry microclimate (light and temperature) as well as wine composition, quality, and antioxidant properties. Thermal time and sum of light intensity thresholds were different to achieve the maximum berry anthocyanin and flavonol contents. ST mostly affected wine characteristics by increasing alcoholic content, acidity, hue and phenolic substances. Wine antioxidant capacity decreased in ST wines likely by decreases in catechin and quercetin contents. ST and LRST increased proanthocyanidin polymerization and decreased monomeric flavan-3-ols, which may reduce wine bitterness and enhance astringency. Therefore, the management of canopy should take into account the warming trends in viticulture regions, rather than being applied preemptively.

Impact of insecticide-manipulated defoliation by Japanese beetle (Popillia japonica) on grapevines from vineyard establishment through production.

BACKGROUND: Japanese beetle (JB), Popillia japonica Newman, is a severe pest of grapes in the southeastern USA where viticulture is a growing industry. This study evaluated the impact of foliar injury from JB field populations on growth, fruit ripening, berry composition and yield of young vines of six cultivars from vineyard establishment through the first year of production. Three spray regimes, carbaryl applied every 7 or 14 days, or no insecticide, were used to manipulate levels of defoliation by JB. RESULTS: Cultivars varied in susceptibility and response to defoliation by JB. Some (e.g. Norton) showed reduced vine growth and delayed post-veraison increase in total soluble sugars and pH, as well as reduced cluster number and weight, berries per cluster and yield. Others (e.g. Concord) showed little or no measurable impact from JB. Notably, the biweekly spray regime was as effective as weekly sprays in mitigating the impacts of defoliation. CONCLUSION: Foliar loss from JB feeding can set back establishment and productivity of young grapevines. Nevertheless, many growers can reduce spray frequency without compromising the benefits of JB management. Even susceptible cultivars can tolerate low to moderate (<20%) levels of defoliation, and some are resistant enough to be grown without treating for JB.