Abstract
Aims: The aim of the present study was to analyse the impact of different water regimes on the physiological and agronomical behavior of an aromatic white grapevine (cv. Arvine) by means of various levels of irrigation. The consequences of the plant water status were evaluated by carrying out a chemical (aromatic precursors) and sensorial analysis of the resulting wines.Methods and results: Adult vines of Vitis vinifera L. cv. Arvine 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 [pre-dawn leaf (ΨPD) and stem (ΨSTEM) water potentials and carbon isotope composition (d13C) in the must]. Gas exchange (net photosynthesis AN and transpiration E), stomatal conductance (gs), 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 analysed over a period of 8 consecutive years (2009-2016) in the Agroscope experimental vineyard in Leytron under the relatively dry conditions of the Rhône valley in Wallis, Switzerland.In the non-irrigated vines, the progressively increasing water deficit observed over the season reduced the leaf gas exchange (AN and E) and gs. The intrinsic water use efficiency (WUEi, A/gs) increased over the season and was greater in the vines that had suffered water restriction than in the irrigated vines. The rise in WUEi was correlated with an increase in d13C 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. The G-G values for berries increased with rising water stress in the non-irrigated vines. The wines from the plants subjected to water stress and to yeast available nitrogen deficiency (non-irrigated vines during hot and dry seasons) had a less distinctive typicity, and developed a lower aromatic expression with a more bitter taste, than the wines from the non-stressed plants. Overall, and compared with the stressed vines, the organoleptic characteristics and quality of Arvine wines from vines which had not undergone restrictions in water and nitrogen during the growing season were appreciated more.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.
Highlights
The vine water status derives from numerous pedoclimatic factors (soil properties, soil water reserves, mesoclimate (Seguin, 1975), from the rootstock’s genetic characteristics and grape variety, and from cultivation practices, including irrigation in some cases
By limiting water flux in the plant and canopy development, the plant is able to maintain its water status and stabilizes the leaf water potential above the threshold required for avoidance of hydraulic rupture in cases of high water stress (Tyree and Sperry, 1988)
Vines should not be exposed to a water deficit that is too severe (Choné et al, 2006; Deluc et al, 2009) which may result in a loss of aromatic compounds and wine quality (Reynolds et al, 2010; Reynard et al, 2011; Verdenal et al, 2012)
Summary
The vine water status derives from numerous pedoclimatic factors (soil properties, soil water reserves, mesoclimate (Seguin, 1975), from the rootstock’s genetic characteristics (root density, for example) and grape variety (drought sensitivity), and from cultivation practices (cover crop, leaf-fruit ratio), including irrigation in some cases. For the elaboration of high-quality white wines, it is well known that vines should experience no mineral nutrient deficiencies, nitrogen deficiencies (Bell and Henschke, 2005; Lacroux et al, 2008) For this reason, vines should not be exposed to a water deficit that is too severe (Choné et al, 2006; Deluc et al, 2009) which may result in a loss of aromatic compounds and wine quality (Reynolds et al, 2010; Reynard et al, 2011; Verdenal et al, 2012). The Arvine grape variety, cultivated mainly in the Swiss canton of Wallis, is well appreciated for the character and the complex fruity and floral bouquet of its wines (Spring et al, 2014) This aromatic typicity arises from sulphur compounds of the thiol family and in particular 3-mercaptohexanol (Fretz et al, 2005), whose aromas are evocative of grapefruit, lemon, rhubarb and exotic fruits. The influence of the water regime on the vine physiology (gas exchange, plant vigor, leaf and berry mineral nutrition) and agronomical behavior (yield components) and the quality of the resulting wines was observed in adult vines of the cultivar Arvine over a period of eight consecutive years on the experimental Agroscope vineyard, which is located in a relatively dry alpine region of Switzerland (Valais)
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