Climate change projections to support the transition to climate-smart viticulture

AIM: Agiorgitiko (Vitis vinifera L. cv.) is the most cultivated red grapewine variety in Greece1 located mainly in Nemea region, the largest PDO zone in Greece2. Although Agiorgitiko is considered as one of the most interesting red grape varieties, not only in Greece3, but also at international level4,5, however, there is a lack of knowledge

Current climate change is increasing inter- and intra-annual variability in atmospheric conditions leading to grapevine phenological shifts as well altered grape ripening and composition at ripeness. This study aims to (i) detect weather anomalies within a long-term time series, (ii) model grape ripening revealing altered traits in time to target specific ripeness thresholds for four Vitis vinifera cultivars, and (iii) establish empirical relationships between ripening and weather anomalies with forecasting purposes. The Day of the Year (DOY) to reach specific grape ripeness targets was determined from time series of sugar concentrations, total acidity and pH collected from a private company in the period 2009-2021 in North-Eastern Italy. Non-linear models for the DOY to reach the specified ripeness thresholds were assessed for model efficiency (EF) and error of prediction (RMSE) in four grapevine cultivars (Merlot, Cabernet Sauvignon, Glera and Garganega). For each vintage and cultivar, advances or delays in DOY to target specified ripeness thresholds were assessed with respect to the average ripening dynamics. Long-term meteorological series monitored at ground weather station by means of hourly air temperature and rainfall data were analyzed. Climate statistics were obtained and for each time period (month, bimester, quarter and year) weather anomalies were identified. A linear regression analysis was performed to assess a possible correlation that may exist between ripening and weather anomalies. For each cultivar, ripeness advances or delays expressed in number of days to target the specific ripening threshold were assessed in relation to registered weather anomalies and the specific reference time period in the vintage. Precipitation of the warmest month and spring quarter are key to understanding the effect of climate change on sugar ripeness. Minimum temperatures of May-June bimester and maximum temperatures of spring quarter best correlate with altered total acidity evolution and pH increment during the ripening process, respectively.

The objective of this study was to determine the influence of four soils with contrasting chemical and physical properties on vine growth parameters and wine chemistry in a Paso Robles, California Cabernet Sauvignon vineyard

Wine lees are the sediment that settles at the bottom of wine barrels, tanks, or bottles during the winemaking process and represent the second most significant by-product of wineries.

I performed my PhD in grapevine physiology under the supervision of Dr. H. Medrano, standing in the vineyards from pre-dawn to sunrise during many hot, wet and sunny days with my colleagues J.M.E. and J.B. I also spent many days and nights facing ticks year-round working in Mediterranean macchias with J.Gu. and M.M. Later I was able to supervise PhD students on grapevines – like A.P. and M.T. – and on Mediterranean vegetation – like J.Gal. With the incorporation to the group of M.R.-C. ‘the puzzle’ was completed and, combining the aforementioned studies, we could conclude (more than 20 years ago) things like: (1) stomatal conductance is the best proxy for ‘water stress’ in studies on photosynthesis; (2) steady-state chlorophyll fluorescence retrieves photosynthesis under saturating light; (3) photoinhibition is not a major photosynthetic limitation under water stress; (4) mesophyll conductance instead is; and (5) mesophyll conductance is a major driver of leaf water use efficiency.