Coupling Tempranillo grape phenolic and technological ripeness by forcing vine bud regrowth

Abstract

Global warming is causing early harvests because of the fast grape total soluble solids accumulation. This results in a decoupling of phenolic and technological ripening, negatively affecting wine quality. In this trial, carried out in cv. Tempranillo under the temperature-warm and semi-arid conditions of eastern Spain, we evaluated the effects on must composition of two types of pruning that force the regrowth. The treatments, applied during the 2016 growing season, were: a) winter pruning (Control); ii) pruning to 6 buds in anthesis; iii) pruning to 6 buds 23 days after anthesis; iv) pruning to 2 buds in anthesis; v) pruning to 2 buds 23 days after anthesis. All the treatments applied were successful in forcing vine regrowth and delayed the harvest date at least 45 days compared to that of the Control. Nevertheless, they also reduced yield by 80% on average. Must composition was considerably modified, lowering total soluble solids and pH values and increasing titratable acidity due to increments of tartaric and malic acids concentrations. In addition, the berries of forced treatments were smaller with significantly higher total polyphenol index. The obtained results are satisfactory in terms of grape composition but the yield penalty obtained was too drastic. The experiment is in due course in order to adjust the forcing date and the number and type of of buds to leave after pruning to achieve an adequate yield while grape ripeness is recoupled. Possible carry over effects of consecutive applications of vine forcing also need to be investigated.