Combined effect of crop forcing and reduced irrigation as techniques to delay the ripening and improve the quality of cv. Tempranillo (Vitis vinifera L.) berries in semi-arid climate conditions

In Mediterranean vineyards, high temperatures and scarce water resources affect the quantity and quality of harvests. Crop forcing (F) is a novel approach that consists of inducing the bud burst of buds developed during the current season in order to modify the phenology of the vine and shift berry ripening to a period of moderate temperatures. The aim of this work is to evaluate the effect of F on cv. Tempranillo grapes in the semi-arid conditions of Extremadura (Spain) under different water regimes. A field experiment was carried out from 2017 to 2019 in a vineyard of cv. Tempranillo with three pruning treatments: winter pruning only (NF) and two F treatments, in which, in addition to winter pruning, forced pruning was carried out at two different phenological stages, after flowering (F1) and after fruit set (F2). These treatments were subjected to two watering regimes: irrigation covering the vines' water requirements (I) and deficit irrigation (DI) with moderate water stress during the preharvest period. The average delay in harvest of the F treatments compared to NF was 32 and 56 days in F1 and F2, respectively, with a decrease in the average temperature during ripening (veraison to harvest). Yield was lower in F1 and F2 than in NF regardless of water regime, although yield levels were more stable between seasons in these treatments. Titratable acidity, malic acid content, total polyphenol content and total anthocyanin content increased in the F treatments, and the combined application of F and DI improved grape composition but also resulted in a higher yield penalty.