Alexander Levin*
*Oregon State University, Southern Oregon Research and Extension Center, 569 Hanley Rd., Central Point, OR 97502 (alexander.levin@oregonstate.edu)

Despite increasing Pinot noir acreage in warmer and more arid growing regions, cultivar-specific drought responses remain poorly described in the literature. A multi-year field experiment was established with eight irrigation treatments designed to alter vine water status either pre- or postveraison. Irrigation was scheduled based on applying water at fractions of estimated crop evapotranspiration (ETc) ranging from 25 to 100%. Vine water status was monitored with regular measurements of midday stem water potential (Ψstem) throughout the growing season. At harvest, fruit were analyzed for yield and quality characteristics. The treatments significantly altered vine water status both pre- and postveraison, giving rise to four levels of water stress at both times. Berry size correlated negatively with water deficits at both times. Berry primary metabolism (Brix, pH, and TA) was less responsive to water deficits than secondary metabolism (polyphenolics). Total anthocyanins increased with water deficit both pre- and postveraison. The response was more sensitive preveraison, but the differences were not significant across treatments. In contrast, tannins and iron-reactive phenolics (IRPs) in skins and seeds were significantly impacted by the treatments. Skin tannins and IRPs increased with preveraison water deficits, but decreased with postveraison water deficits. Seed tannins and IRPs increased with preveraison water deficits, but were not affected by postveraison water deficits. In general, berry secondary metabolism was more sensitive to preveraison water deficits. However, postveraison water deficits resulted in higher concentrations of secondary metabolites overall. While wine sensory analyses have yet to be completed, the results suggest that postveraison water deficits may be more effective at improving Pinot noir fruit quality without a yield penalty than preveraison deficits.

Funding Support: Oregon Wine Board