Weather trend and impact on sugar accumulation in Montepulciano grapes in a viticultural area of central Italy

The increase in temperatures and frequency of drought summers is reshaping viticulture, favoring cooler and higher-altitude areas while challenging traditional wine-growing regions. This study examines the relationship between climatic variables and sugar accumulation in Montepulciano grapes in Villalfonsina (Abruzzo, Italy) over the period 1998-2022, using data from a cooperative winery and a regional weather station.Results show a significant rise in seasonal temperatures since 2010, with growing degree days (GGDs) increasing by 7.5%, from 1,988 (1998-2009) to 2,135 (2010-2022). High-temperature events (above 30°C and 35°C) doubled and quintupled, respectively, leading to photoinhibition, leaf necrosis and berry dehydration. The day-night temperature range also increased by 40%, negatively affecting metabolic processes such as sugar transport.Harvest dates were highly variable, with 50% of the grapes harvested between September 29 and October 16. Sugar concentrations ranged from 17.3°Babo (2014) to 20°Babo (2022), with recent vintages consistently exceeding 19°Babo, enabling wines with alcohol levels between 13.3% and 13.8%.This research emphasizes the importance of adapting vineyard practices and choosing harvest dates to reduce climate stress and maintain wine quality as the climate continues to change.