The influence of vine water regime on the leaf gas exchange, berry composition and wine quality of Arvine grapes in Switzerland

Aim: The aim of the present study was to analyze the impact of different water regimes, by means of various levels of irrigation, on the physiological and agronomical behavior of an aromatic white grapevine (cv. Arvine). The consequences of the plant water status were followed through to chemical (aromatic precursors) and sensorial analysis of resulting wines. Methods and results: Adult vines of Vitis vinifera L. cv. Arsine grafted onto 5BB were subjected to different water regimes (various levels of irrigation) during the growing season. Physiological indicators were used to monitor the plant water status [the predawn leaf (Psi(PD)) and stein (Psi(STEM)) water potentials and the carbon isotope composition (delta C-13) in the must]. Gas exchange (net photosynthesis A(N) and transpiration E), stomatal conductance (g(s)), yield parameters, berry composition at harvest, analysis of potential grape aromatic properties (glycosyl-glucose G-G, precursor 3-mercaptohexanol P 3-MH) and the sensorial quality of wines were analyzed over a period of 8 consecutive years (2009-2016) on the Agroscope experimental vineyard in Leytron under the relatively dry conditions of the Rhone valley, in Wallis, Switzerland. In non-irrigated vines, the progressively increasing water deficit observed over the season reduced the leaf gas exchange (A(N) and E) and g(s). The intrinsic water use efficiency (WUEi, A/g(s)) increased over the season and was greater in vines that had suffered water restriction than in irrigated vines. The rise in WUEi was correlated with an increase in delta C-13 in the must sugars at harvest. A decrease in plant vigor was observed in the water stressed vines over multiple years. Moderate to high water stress during fruit ripening lowered the contents of total and malic acidity in the musts and the content of yeast available nitrogen (YAN). On the other hand, contents in sugar and the aromatic precursor (P-3MH) in berries were not influenced by the vine water status. Values of G-G in berries increased with rising water stress in non-irrigated vines. Wines from plants subjected to water stress and to yeast available nitrogen deficiency (non-irrigated vines during hot and dry seasons) presented a less distinctive typicity, and developed a lower aromatic expression with a more bitter taste, than wines from non-stressed plants. Overall, and compared with stressed vines, the organoleptic characteristics and quality of Amine wines coming from vines where no restrictions in water and nitrogen had been suffered during the growing season were better appreciated. Conclusions: The vine's physiological behavior (leaf gas exchange, plant vigor) and agronomic parameters (yield, berry composition), together with the quality of white aromatic Arvine wines, were strongly influenced by vine water regimes during the growing season. Significance and impact of the study: Vine water status and must nitrogen contents are key factors in grape composition and in the sensorial quality of resulting aromatic white wines.