Impact of irrigation regime on berry development and flavonoids composition in Aragonez (Syn. Tempranillo) grapevine

In the present study, field grown Aragonez (Syn. Tempranillo) grapevines (Vitis vinifera L.) were subjected to three irrigation regimes (conventional sustained deficit irrigation (DI), regulated deficit irrigation (RDI) and non-irrigated (NI)) during two successive seasons (2007–2008). An integrative study was performed in grape berry skin tissues at four phenological stages of grape berry (pea size, véraison, mid-ripening and full maturation). The accumulation of flavonoid compounds, the profile of accumulation of abscisic acid (ABA) and jasmonic acid (JA) hormones were analysed during grape ripening. The non-enzymatic antioxidant capacity was also characterised. Principal component analysis followed by a between group analysis (PCA–BGA) showed a clear separation already at early stages of grape berry development between the three treatments in both years. The main compounds affected by water availability were proanthocyanidins and flavonols, which increased with irrigation at all phenological stages. In both years, concentrations of anthocyanin at full maturation were observed to be higher in the skin of berries belonging to DI and RDI vines than in NI ones. ABA accumulation was also regulated by the intensity of water stress since early stages of berry development. However, no differences in sugar accumulation were observed between treatments. The present study also shows that climatic conditions, namely temperature, play an important role in the ripening process of grape berries. This was clearly observed in NI vines during both years, in which a decrease in the quality parameters in grape skins is presumably related to high temperature and excessive cluster sunlight exposition more marked in 2007, the hotter year. This supports the crucial role of irrigation in maintaining the cluster microclimate in an optimum range, thus enabling a balanced synthesis of the compounds relevant to wine quality.