Tommaso Frioni

One of the major challenges that global warming poses to viticulture is the maintenance of adequate acidity at maturity in white grapes for sparkling winemaking. This issue arises from three main occurrences: (i) with higher temperatures, degradation of malic acid is significantly enhanced; (ii) with a general advancement in grapevine phenology, grape maturity may occur under suboptimal climatic conditions; and (iii) harvesting grapes at “traditional” dates results in overripe fruits for sparkling destinations. In this biennial work, we compared the fruit and must composition of a local, widely grown white grape variety in the Colli Piacentini area (cv. Ortrugo, ORT) with those of a minor autochthonous variety, namely, Barbesino (BRB). Furthermore, we compared the composition, aromatic, and sensory profiles of wines obtained from ORT and BRB grapes picked on the same date and, in addition, of a second Barbesino wine from late harvest (BRB-LH). ORT and BRB had a similar sugar accumulation dynamic, whereas BRB exhibited a delayed loss of titratable acidity. In more details, BRB had lower malic acid degradation rates when malate concentration was <9 g/L. As a result, with comparable yield and total soluble solid content (TSS) (∼20°Brix), BRB had a higher berry titratable acidity and malic acid concentration at harvest than ORT. BRB wines showed the highest titratable acidity (TA), while ORT had the lowest TA and a higher pH, and as expected, BRB-LH had the highest pH and a lower TA than BRB although still higher than those of ORT wine. The aroma profiles of wines were mainly characterized by fermentative aromas, including esters, fatty acids, higher alcohols, and C6 compounds, and BRB-LH wines showed the highest concentration of higher alcohols, while the fermentative esters were higher in ORT wines. Panelists considered BRB significantly fresher and with bigger aroma intensity than ORT, confirming that the higher acidity detected in BRB musts is well preserved in final wines. Our work demonstrates that local minor varieties can be reconsidered in light of the new climate change-related issues impairing viticulture sustainability today. In particular, currently neglected cultivars could help preserve must acidity as compared to traditional varieties having early ripening, maintaining the links with terroir and local traditions at the same time.

Background and Aims. In viticulture, one of the effects of warming trends is the advance of budburst date and the consequent increased risk of spring frost-related damage. In 2021, severe frost events affected a large fraction of European viticulture. In a cv. Barbera vineyard, located in NW Italy, primary bud shoots (PBS), secondary bud shoots (SBS), and suckers (SK) were tagged after the occurrence of freezing temperatures in spring. The goal of the study was to clarify if SBS could partially restore yield loss and analyze their contribution to fruit composition. Methods and Results. The number of developing SBS and SK correlated with the number of killed PBS. While PBS bore 1.44 inflorescences per shoot, SBS had much lower fertility (0.4), with SK at intermediate levels (0.85). The vine yield was 40% of the previous season, with SBS bunches contributing just 17% of the total. SBS produced smaller and looser bunches, as compared with PBS (−28% mass and −27% compactness). At harvest, no difference was found in grape total soluble solids (TSS) among different shoot types. However, the TSS average was notably higher than that observed in the previous season (27.8°Brix vs. 23.3°Brix in 2020). Interestingly, while in PBS and SK, a direct correlation (linear and quadratic, respectively) existed between the leaf area to yield ratio (LA/Y) and grape TSS or total anthocyanins, this did not occur for SBS. Conclusions. In the case of spring frost damage, the number of PBS avoiding fatal injuries will drive agronomic results at harvest since SBS contribution to total yield is modest due to low shoot fruitfulness. The frost-induced increase in vine LA/Y leads to a dramatic rise in grape TSS and phenolics. Significance of the Study. When spring frosts kill a significant number of primary shoots, an altered grape composition at harvest should be expected due to changes in vine balance. Therefore, the vineyard management should be adjusted accordingly early in the season. Further studies are needed to test specific post-frost canopy management strategies ensuring yield, optimal fruit composition, and cane renewal.