Effect of Regulated Deficit Irrigation on Malbec and Syrah Grape Volatiles
Fang Yuan, Michael Qian,* Yanping Qian, and
Krista Shellie
*Department of Food Science and Technology, Oregon State
University, Corvallis, OR 97331 (michael.qian@oregonstate.edu)
The concentrations of volatile compounds and precursors in grape berries are highly influenced by viticultural practices. Among these cultural practices, regulated deficit irrigation to improve water use efficiency and reduce canopy vigor is an important practice for sustainable agriculture, especially in arid and semi-arid areas. Imposing a water deficit to the vine during berry development is also an important vineyard management strategy to alter grape and wine quality. Previous studies showed that water deficit influenced physiological parameters of the vine, changed berry composition, and improved sensory attributes of wines by increasing fruity aromas and decreasing vegetal aromas. The objective of this study was to determine the effect of water stress on grape secondary metabolites and its implications for wine quality. Four irrigation regimes (70% ETc from fruit set to veraison, 35% ETc from veraison to harvest [70/35]; 70% ETc sustained from fruit set to harvest [70/70]; 35% ETc from fruit set to veraison, 70% ETc from veraison to harvest [35/70]; and 35% ETc sustained from fruit set to harvest [35/35]) were applied to the vines with two irrigation frequencies (1x = one event per week and 3x = the same irrigation amount apportioned into three irrigation events per week). In 2013, the 35/35 treatment with 1x frequency resulted in the greatest trans-β-damascenone concentration in Malbec grapes, but no significant difference was observed in Syrah grapes. The 35/35 treatment at 1x frequency also resulted in more vitispirane and TDN in Malbec grapes but not in Syrah. Syrah had higher concentration of C6 compounds than Malbec. The effect of irrigation on grape volatile composition may depend on variety. In 2014, wine was made from the trial grapes and wine volatile composition was analyzed. The concentration of trans-3-hexen-1-ol was highest with the 70/35 and 70/70 treatments in both Malbec and Syrah wines compared to the 35/70 and 35/35 treatments.
Funding Support: USDA-CSREE-NWSFR
