Aroma composition of Tempranillo grapes as affected by iron deficiency chlorosis and vine water status

Abstract

Water deficit and iron nutritional deficiency (iron chlorosis) are frequent environmental stresses affecting grapevine production in the Mediterranean region. The objectives of this work were (i) to study the combined effects of both stresses on aromatic profile of Tempranillo grapes, occurring simultaneously in the vineyard, and (ii) to evaluate the viability of foliar chlorophyll content at veraison (Chl) to early assess aromatic quality potential of grapes in those conditions. Twenty non-irrigated vineyard subzones (10 m × 10 m each), affected and non-affected by iron chlorosis, were monitored in Ribera del Duero Appellation of Origin (North-Central Spain) during two consecutive seasons. Factorial ANOVA was performed to study the effects of predawn leaf water potential and Chl measured at veraison on the must composition parameters and, specifically, on the concentrations of free and bound aromatic compounds. Water deficit tended to increase color intensity and extractable anthocyanin content of the grapes, whereas the incidence of iron deficiency enhanced total phenolic compound content within subzones with better water status. More water or iron stressed subzones restricted C 6alcohols contents than less stressed subzones. Without significant effects on vine vigor, yield or berry size, the incidence of iron chlorosis increased the concentrations of some specific terpenes, C 13-norisoprenoids, volatile acids and volatile phenols. These results showed that low to moderate iron stress can have positive effects on grape aromatic quality, and demonstrated that Chl can be a useful tool in precision viticulture to map the aromatic potential within rainfed vineyards affected by iron chlorosis.

Relationships between chlorophyll content of vine leaves, predawn leaf water potential at veraison, and chemical and sensory attributes of wine

“…There were significant differences between alcoholic degrees in wines from subzones with low and high Chl (14.4% versus 13.5%, P < 0.05) in 2017 and no differences in 2016. The results on pH and alcoholic degree of wine agree with those obtained in must: 13 the incidence of iron deficiency tended to advance fruit ripening, increasing total soluble solids content and reducing total acidity of the must.…”

“…The factorial ANOVA (Table 2) shows that the incidence of iron chlorosis in the study area had a much greater impact on wine composition and sensory attributes than vine water status at the beginning of fruit ripening. When the musts from the subzones with different LWP were analysed in both seasons, no significant differences in the soluble solids content or total acidity were detected, 13 although an increase in water deficit during the ripening period should tend to enhance the maturity level of the grapes 7,8,11 . Nevertheless, in 2017, low‑ versus high‐LWP subzones had significantly increased extractable anthocyanin content in grapes and potassium content and colour intensity of the must.…”

“…Berry weight had few significant correlation coefficients with chemical and sensory attributes of the wine in the study area (Table 4). It has been proven that the water and iron stress levels registered in the vineyard subzones in 2016 and 2017 did not produce smaller berries, 13 which would have increased skin/pulp ratio and therefore polyphenol and anthocyanin contents in the grapes. Thus, the higher polyphenol content and the improvements on sensory attributes (as colour and flavour intensity), in wines from the more stressed zones, could be mainly associated with an increase in the biosynthesis of phenolic compounds in grapes, caused by moderate iron and water deficits 10,34 .…”

“…These results completely agree with the Chl × LWP interaction on total phenolic content in grapes, detected previously. 13 The increase in red colour, astringency, and persistence of the wine from plants with low Chl might be due to a direct effect of iron deficiency on biosynthesis of polyphenols in grapes through the shikimate pathway, 10 although this effect could be limited in water-deficit conditions.…”

“…10,11 Recent studies in Ribera del Duero Designation of Origin (Spain) have demonstrated that mild to moderate iron deficiency can improve the phenolic content and aromatic potential of Tempranillo grapes. 12,13 It would be interesting to study to what extent these improvements are transferred to the composition and sensory characteristics of the wine. To the best of our knowledge, there are currently no studies on how iron deficiency affects the chemical and sensory qualities of wine.…”