Effects of calibrated delayed winter pruning on Vitis vinifera L. ‘Pinot Noir’ grapevines in relation to different training systems

Warming trends are challenging viticulture worldwide. The rise of temperatures recorded in most of traditional and new wine regions can be particularly detrimental for the production of sparkling wines, requiring moderate alcohol level and sustained acidity. The postponement of spur-pruning after bud-break has recently been proposed as a simple and inexpensive technique to delay ripening, exploiting the natural acrotony of the grapevine. A three-year trial was conducted in central Italy to assess if late pruning can successfully delay ripening in grapevines according to different training systems. Mature vines cv. Pinot Noir were subjected to the following treatments: winter spur pruning (WSP), delayed spur pruning (DSP), winter cane pruning (WCP), and delayed cane pruning (DCP). Delayed pruning was performed when shoots growing on apical nodes of unpruned canopies reached the stage of 3 unfolded leaves, as an average. During the season, phenological stages were monitored twice a week for both spurs and fruiting canes. Ripening kinetics were characterized from veraison until the end of the season. DSP and DCP significantly delayed bud-break and early phenological stages. Similarly, sugar accumulation was postponed and the drop of titratable acidity was successfully shifted by 12 and 7 days, respectively. At technological maturity of WSP and WCP vines, corresponding to the achievement of ~20° Brix, DSP and DCP significantly reduced total soluble solids (-4.6 and -1.6°Brix, respectively) and maintained higher acidity (+5.2 and +2.9 g L-1). Accordingly, a 46 and 32% yield loss were recorded. In both training systems, delayed winter pruning can be a simple technique suitable for preserving must compositional characters required for sparkling wines.