Post-budbreak pruning changes intra-spur phenology dynamics, vine productivity and berry ripening parameters in Vitis vinifera L. cv. ‘Pinot Noir’

Late pruning is an emerging cultural technique aimed at deferring ripening kinetics and reducing the negative effects of warming trends on grape maturity. It relies on the inhibition of basal nodes and on the postponement of the progression of phenological stages. As a consequence, late pruning is capable of maintaining at harvest a moderate sugar concentration and an adequate acidity level in grapes. This work was intended to deepen the effects of late pruning, focusing on the intra-vine phenology variability and progression as well as on the interactions existing between the changes in vine balance and the ripening time shift. Two experiments were conducted over two consecutive years in different vineyards located in Abruzzo (central Italy), comparing late pruning (LP) applied when unpruned canes had shoots with two/three leaves already unfolded (phenological stage BBCH 12/13) with standard winter pruning executed at dormancy (WP). LP shifted phenology and led to a significant variability in the development stages detected on shoots arising from the different nodes of the spurs, whereas in WP vines shoots arising from count-nodes developed in synchrony. LP successfully delayed ripening, but the outputs of the two experiments were different: LP postponed sugars accumulation and the decrease of acidity in both experiments (-2° Brix and +2.5 g/L at harvest, as an average of the two experiments) though the yield was negatively affected only in the first experiment (-47% as compared to WP). Late spur-pruning confirmed its efficacy in spreading grapes maturity and maintaining higher acidity along with a reduced sugar concentration. The delaying effect seems to be quite independent from the seasonal vine balance given as leaf area-to-fruit ratio. The study provided further clarification of the physiological bases underlying vine response to delayed winter pruning and indicated robustness of its effects regardless environmental conditions and degree of vine balance