Characterization of phenolics and VOCs in wines obtained from Malbec vineyards of the UCO Valley submitted to high-altitude solar UV-B, water restriction and abscisic acid sprays

ALONSO R.; BUSCEMA F.; FONTANA A.; BOTTINI R.; BERLI F.; PICCOLI P.

Oregon

Congreso; XI International Terroir Congress; 2016

Southern Oregon University

The Uco Valley, ca. 1100 m and 1500 m asl, is a high altitude grape growing area in Mendoza (Argentina) in which well reputed wines are produced. The drip-irrigated vineyards receive relatively high levels of solar ultraviolet (UV)-B during summer days (irradiances up to 0.40 W m−2 at noon hours). Restriction in water supply (D) to the vines has become a usual practice to enhance fruit quality in many wine regions of the world, but little is known about their interaction with UV-B radiation. Abscisic acid (ABA) is a plant growth regulator that modulates many physiological and biochemical acclimation processes, some of them common to different stress conditions and/or environmental signals. It is known that ABA biosynthesis in grapevine is induced by D and high UV-B, and that ABA is involved in berries maturation. We previously analyzed at physiological and biochemical level the effects of UV-B, D, ABA applications and their combinations on vegetative growth and berry development of Vitis vinifera cv. Malbec. In the present work we aimed to continue the characterization of the Uco Valley region by assessing phenolics and volatile organic compounds (VOCs) in the wines obtained from grapevines of cv. Malbec in a high altitude vineyard (1450 m asl), and to evaluate the interaction of UV-B, D and ABA applications. Two UV-B treatments (ambient solar UV-B, +UV-B; or reduced UV-B, −UV-B) from budbreak, two watering treatments (well watered, +D; or moderate D, −D) from veraison and two ABA treatments (no ABA, −ABA; and sprayed ABA, +ABA) were given alone and combined in a factorial design. Wines from grapevines under +UV-B had a greater (17.2 %) content of low molecular weight polyphenols (LMWP) than wines −UV-B, being quercetin the LMWP with the highest increase. UV-B interacted with ABA, where +UV-B and +ABA additively augmented polydatin. Also significant interactions between UV-B and D were observed, in which wines +UV-B/+D presented the higher content (additive effect) for astilbin. Regarding resveratrol, a triple interaction amongst the three factors was observed, and the combination of +UV-B, +D and +ABA had a synergistic effect. Wines +ABA showed a marked increases of total anthocyanins (non-acylated, acetylated and p-coumaroylated forms), respect to −ABA wines. The anthocyanins peonidin and delphinidin were additively increased by +ABA and +UV-B. Twenty six VOCs were identified and quantified by gas chromatography-mass spectrometry (GC-MS). D was the main factor influencing the aromatic profile of wines. Some VOCs were reduced by +D (independently of combination with another factor) while for other VOCs, antagonistic or additive effects were observed in combination with +UV-B. In summary, D and ABA sprays can modify the effects of UV-B in high altitude vineyards of the Uco Valley, being reflected in the phenolic and VOCs profile of the wines. It was also found that some UV-B effects previously observed in berries remain in the wine obtained, such as higher content of LMWP.