Toward a Vineyard Model for Low-Alcohol Wines: Severe Shoot Trimming Drastically Reduces Grape Sugar Concentration

The increasing demand for low-alcohol wine products calls for effective vineyard strategies to reduce grape sugar concentration, while climate change is exacerbating sugar accumulation through warmer growing conditions. In this context, severe shoot trimming applied at specific phenological stages may represent a promising approach to induce sustained source limitation. A field experiment was conducted in 2025 on Vitis vinifera L. cv. Ortrugo to evaluate severe shoot trimming performed at the onset of berry softening. Vine growth, yield components, grape composition, and seasonal total soluble solids (TSSs) were monitored. Vine carbon reserves and shoot fruitfulness were assessed to evaluate carry-over effects. Experimental wines were produced to determine alcohol and fermentative aroma. Severe trimming markedly reduced leaf area and vine balance, leading to a sustained reduction in sugar accumulation. At harvest, grape TSSs decreased by 4.1 °Brix (17.6 vs. 21.7 °Brix) and the final wine alcohol concentration was lower by 3.4% (v/v). Yield was unaffected and no substantial negative effects on wine fermentative aroma were observed, while titratable acidity slightly increased. Even if trimming reduced winter starch concentration in roots, no reduction in shoot fruitfulness was observed in the subsequent spring. Severe trimming successfully reduced grape sugar and wine ethanol without compromising yield, aroma, or vine performance, supporting its potential for low-alcohol wine production and reduced-impact dealcoholization.