PIWIs’ variation in drought response under semi-controlled conditions 

Uruguay is known for the production of Tannat wines, which is a neutral variety from an aroma point of view, but capable of providing aromatic precursors that are of interest in the production of wines for ageing. The main aromatic precursors present are glycosidic compounds and carotenoids. The contribution of carotenoid degradation by-products such as norisoprenoids to wine aroma is fundamental, as they are associated with pleasant aroma descriptors and very low olfactory perception thresholds. Several factors have been shown to influence carotenoid concentrations in grapes, such as cultivar, climatic conditions, viticultural region, plant water status, exposure to sunlight and ripening stage.

The main challenge faced by viticulture is to improve the quality of the wines, adapting them to the new consumer demands that demand wines with lower alcohol content and greater freshness. In the last 30 years, a clear modification has been observed in the composition of the grape due to climate change

The hot and dry climate of the Demarcated Region of Douro (DRD), Portugal, particularly during the summer, induces soil water deficits that influence the growth and development of grapevines.

Optimizing the use of water and improving irrigation strategies has become increasingly important in most winegrowing countries due to the consequences of climate change, which are leading to more frequent droughts, heat waves, or alteration of precipitation patterns. Optimized irrigation scheduling can only be based on a reliable knowledge of the vineyard water status.

In this context, this work aims at the development of a novel methodology, using a contactless, miniaturized, low-cost NIR spectral tool to monitor (on-the-go) the vineyard water status variability. On-the-go spectral measurements were acquired in the vineyard using a NIR micro spectrometer, operating in the 900–1900 nm spectral range, from a ground vehicle moving at 3 km/h. Spectral measurements were collected on the northeast side of the canopy across four different dates (July 8th, 14th, 21st and August 12th) during 2021 season in a commercial vineyard (3 ha). Grapevines of Vitis vinifera L. Graciano planted on a VSP trellis were monitored at solar noon using stem water potential (Ψs) as reference indicators of plant water status. In total, 108 measurements of Ψs were taken (27 vines per date).

Calibration and prediction models were performed using Partial Least Squares (PLS) regression. The best prediction models for grapevine water status yielded a determination coefficient of cross-validation (r2cv) of 0.67 and a root mean square error of cross-validation (RMSEcv) of 0.131 MPa. This predictive model was employed to map the spatial variability of the vineyard water status and provided useful, practical information towards the implementation of appropriate irrigation strategies. The outcomes presented in this work show the great potential of this low-cost methodology to assess the vineyard stem water potential and its spatial variability in a commercial vineyard.

La prise en compte des paysages viticoles dans le développement durable ou l’aménagement du territoire est un thème non négligeable pour la valorisation de la filière viti-vinicole à l’échelle d’une exploitation ou d’une A.O.C.