Forcing bud growth by double-pruning as a technique to improve grape composition of Vitis vinifera L. cv. Tempranillo in a semi-arid Mediterranean climate

In temperate-warm terroirs, climate change is causing early harvests resulting in wines with high alcohol, low polyphenol concentration and color intensity. This is the result of a decoupling of phenolic and technological berry ripening. Aiming to palliate these effects on grape composition, double-pruning that forced bud growth during spring and sununer were applied to displace berry ripening towards cooler periods of the season. Three field trials were carried out in Vitis vinifera cv. Tempranillo under the semi-arid conditions of eastern Spain, testing different types and dates of forcing. In the first season, short and cane double-pruning at anthesis and 23 days after it were compared with simple winter pruning (Control). In the second season, a single date of forcing application was carried out in vines that were either forced or unforced the previous season. In addition, some vines that were forced during the first and second seasons were treated as Control in the subsequent seasons to quantify the possible carry-over effects. All the double-pruning treatments were successful in forcing bud growth, delaying phenology and thus the harvest date at least in 49 days compared to Control. Berries from forced treatments showed lower pH and higher titratable acidity than the Control at similar TSS. This was due to increments of both tartaric and malic acids concentrations. In addition, the ratio anthocyanin to TSS was significantly higher in the berries from the forced treatments. Indeed, the double-pruning technique improved grape potential for wine making but, on the other hand, it drastically reduced yield, both in the season of application and in the subsequent. This may be due to depletion in wood reserves, which in turn modified vine phenology. Therefore, adapting viticultural practices to double-pruning technique should be further investigated for maintaining yield while improving grape composition under warmer conditions.