Phenology, Canopy Aging and Seasonal Carbon Balance as Related to Delayed Winter Pruning of Vitis vinifera L. cv. Sangiovese Grapevines

Abstract

Manipulating or shifting annual grapevine growing cycle to offset limitations imposed by global warming is a must today, and delayed winter pruning is a tool to achieve it. However, no information is available about its physiological background, especially in relation to modifications in canopy phenology, demography and seasonal carbon budget. Mechanistic hypothesis underlying this work was that very late winter pruning (LWP) can achieve significant postponement of phenological stages so that ripening might occur in a cooler period and, concurrently, ripening potential can be improved due to higher efficiency and prolonged longevity of the canopy. Variability in the dynamics of the annual cycle was created in mature potted cv. Sangiovese grapevines subjected to either standard winter pruning (SWP) or late and very late winter pruning (LWP, VLWP) performed when apical shoots on the unpruned canes were at the stage of 2 and 7 unfolded leaves. Vegetative growth, phenology and canopy net CO2 exchange (NCER) were followed throughout the season. Despite LWP and VLWP induced a bud-burst delay of 17 and 31 days vs. SWP, the delay was fully offset at harvest for LWP and was reduced to 6 days in VLWP. LWP showed notably higher canopy efficiency as shorter time needed to reach maximum NCER/leaf area (22 days vs. 34 in SWP), highest maximum NCER/leaf area (+37% as compared to SWP) and higher NCER/leaf area rates from veraison to end of season. As a result, seasonal cumulated carbon in LWP was 17% higher than SWP. A negative functional relationship was also established between amount of leaf area removed at winter pruning and yield per vine and berry number per cluster. Although retarded winter pruning was not able to postpone late-season phenological stages under the warm conditions of this study, it showed a remarkable potential to limit yield while improving grape quality, thereby fostering the hypothesis that it could be used to replace time-consuming and costly cluster thinning. This preliminary study indicates that proper winter pruning date should be timed so as not to exceed the stage of two unfolded leaves.

Post‐budburst hand finishing of winter spur pruning can delay technological ripening without altering phenolic maturity of Merlot berries

“…Considering that the reduction of yield components of our Merlot vines occurred from the first year of the trial and remained almost constant over the following seasons, it appears that fewer berries per bunch and the fewer bunches per vine were not affected by inflorescence induction and differentiation in the previous year. Therefore, our results suggest that only the last stages of flower differentiation were negatively influenced by the potential depletion of storage reserves which may have reduced the number of flowers as well as causing a reversion of developing inflorescence to tendrils (Gatti et al 2016. Delaying pruning until BBCH18, however, reduced yield to an unacceptable level (<1 kg/vine in each year) and therefore, this treatment is not recommended commercially .…”

“…In the last decade, many studies have aimed to slow down sugar accumulation by limiting photosynthesis at the beginning of ripening. Leaf removal of the apical part of the shoots, trimming or spraying the same part of the canopy with anti‐transpirants reduced sugar accumulation without detrimental effects on phenolic substances (Poni et al , Palliotti et al ,b, Filippetti et al , Gatti et al ).…”

“…In the last few years, many studies have showed the effects of post‐budburst spur pruning on red wine cultivars and it was reported that the phenological stage at which vines were pruned had a substantial effect on yield and final TSS concentration (Frioni et al , , Gatti et al , , Moran et al , , Palliotti et al , Petrie et al , Silvestroni et al ). It was also demonstrated that this technique, if applied appropriately, was able to delay sugar accumulation and increased the concentration of phenolic substances of berries while not affecting anthocyanin (Palliotti et al , Silvestroni et al ).…”

Delaying winter pruning, after pre-pruning, alters budburst, leaf area, photosynthesis, yield and berry composition in Sangiovese (Vitis viniferaL.)

“…Recently, techniques aiming to ‘control canopy efficiency’ (Naor et al , Lanari et al , Palliotti et al , Silvestroni et al ) or to delay phenology (Friend and Trought , Frioni et al , Gatti et al , Palliotti et al ) were imposed on vines, and their effects on yield and grape composition were assessed.…”

“…By delaying winter pruning, budburst of basal buds is inhibited, along with subsequent phenology and ripening. In unpruned canes, distal buds on canes exert a correlative inhibition, or acrotony, along the cane and the basal buds do not burst (Frioni et al , Gatti et al ). Mechanical pre‐pruning in winter on cordon‐trained vines is a common practice in Central Italy.…”