Comportement de différents clones de Sauvignon blanc dans certains terroirs viticoles du Friuli-Venezia Giulia (Nord-Est de l’Italie)

Climate change presents a significant challenge to grape growing worldwide as increased temperatures lead to wines with increased sugar and pH levels. Manipulation of the exposed leaf area is a powerful lever governing the assimilation and storage of non-structural carbohydrates in grapevines. Reducing the leaf-to-fruit ratio is now considered as a tool for adapting to hotter and dryer grape growing conditions.

Climate strongly affects the geographical distribution of grape varieties, grapevine cultivation techniques and wine organoleptic properties.

In the last decades the growers of the Portuguese Dão winegrowing region (center of Portugal) are experiencing changes in climate that are influencing either grape phenology berry health and ripening. Aiming to study the relationships between climate indices (CI), seasonal weather and grapevine phenology, in this work long-term climate and phenological data collected at the experimental vineyard of the Portuguese Dão research centre between 1958 and 2019 (61 years) for the red variety Touriga Nacional, was analyzed. The trends over time for the classical temperature-based indices (Growing Season Temperature – GST -, Growing Degree Days – GDD, Huglin Index – HI and Cool Night Index – CI) presented a significantly positive slope while the Dryness Index (DI) showed a negative trend over the last 61 years. Regarding grapevine phenology, an average advance of 4.5 days per decade in the harvest day was observed throughout the last 61 years. Consequently, the weather conditions during the ripening period have changed, showing an increasing trend over time in the average temperature (higher magnitude in the maximum than in the minimum temperature) and a decrease in the accumulated rainfall. A regression analysis showed that ~50% of harvest date variability over years was explained by the temperature-based indices variability. These observed effects of climate change on bioclimatic indices and corresponding anticipation of harvest date can still be considered advantageous for the Dão terroir as it allows to achieve an optimal berry ripening before the common equinox rains and, therefore, avoid the potential negative impacts of the rainfall on berry health and composition.

The decision for grape berries to ripen involves a complex interplay of genetic regulation and environmental cues. This review explores the molecular mechanisms underlying the transition from vegetative growth to ripening, focusing on transcriptomic studies and the role of the NAC gene family. Transcriptomic analyses reveal a significant rearrangement of gene expression patterns during this transition, with up-regulation of ripening-related genes and down-regulation of those associated with vegetative growth. A molecular phenology scale providing a high-precision map of berry transcriptomic development, indicates that key molecular changes occur well before the onset of ripening.

The browning index (BI), based on the absorbance at 420 nm, is a common oxidation marker in white wines, typically measured after thermal stress (50–60 °C for 5 up to 12 days) in air-saturated wines.