Grape and wine quality of terraced local variety Pinela (Vitis vinifera L.) under different water management

Abstract

Climate change is driving global temperatures up together with a reduction of rainfall, posing a risk to grape yields, wine quality, and threatening the historical viticulture areas of Europe. This issue is particularly challenging in hilly territories. In fact, in these areas, water stress is more severe than in the plains. Moreover, the challenge is even more critical for white grape varieties, since biosynthesis of several aromatic compounds is sensitive to both water and heat stress. Thus, it is important to optimize both water use and production quality.

Our research was carried out on the Pinela, a white local variety grown in the sub-Mediterranean climate of Vipava Valley (Slovenia). The experiment was performed on a terraced vineyard in Šmarje with the aim to evaluate the effects of three levels of water deficit imposed from flowering till harvest on primary and secondary metabolites in grapes, leaves and wines. The DSS Vintel® was used to irrigate the vineyard, targeting three levels of pre-dawn leaf water potential (Ψpd), namely Severe Ψpd – 0.55 MPa, Moderate Ψpd – 0.35 MPa, and Well-Watered Ψpd – 0.2 MPa. The water status of the plants was maintained using a drip irrigation system. Grapes and leaves were sampled four times from veraison to harvest, after which microvinifications were performed for wine chemical and sensory analyses.

First results showed that from the veraison till harvest, under well-watered conditions, berry mass was significantly higher than in moderate and severe treatments. The sugar per berry (sugar loading) was higher for the well-watered treatment during maturation, but not at harvest. On the other hand, differences in pH, °Brix, total acidity, malic acid and YAN were not significant between treatments in grapes during maturation.

As regards the must after pressing, the severe treatment had the highest pH and YAN and the lowest °Brix and total acidity. The moderate water stress had the lowest malic acid concentration, and the highest °Brix and ammonium (however, the last two were not significant as compared to well-watered). It can be concluded that severe stress negatively impacted °Brix, pH, total acidity, and ammonium levels when compared to the other treatments.