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Testing of new rootstocks for drought tolerance targets traditionally rain-fed districts where supplemental irrigation is more frequently needed due to the pressures of global warming. A seasonal evaluation of gas exchange and water-use efficiency (WUE) of cv. Sangiovese grafted to the new drought-tolerant genotype M4 in a dry-down trial against the commercial SO4 stock is reported. The experiment was conducted in 2014 on twelve 2-year-old, non-fruiting potted Sangiovese grapevines grafted on M4 and SO4 stocks and assigned to SO4-WW (well-watered), SO4-WS (water-stressed), M4-WW and M4-WS treatments. Progressive water deficit was imposed by reducing water supply to 70, 50 and 30 % of whole-canopy demand derived from concurrent measurements of transpiration in WW. Unlike SO4, M4 showed slower stress progression, as highlighted by pre-dawn leaf water potential, and retained higher whole-canopy net CO2 exchange rates (NCER) and transpiration rates per unit of leaf area at all replenishment levels as well as exhibiting higher canopy WUE at both 50 and 30 % WW. Although single-leaf assessment was in partial disagreement with data recorded on the whole-canopy basis, robust data were acquired to confirm that the M4 stock performs better than SO4 at any water replenishment level in terms of higher NCER/leaf area and/or canopy WUE. Findings feed expectations that grafting Sangiovese to the M4 rootstock should result in a problem-solving tool for rain-fed areas subject to temporary summer drought.

Background and Aims: Accelerated berry sugar accumulation resulting in wines of excessive alcohol concentration, sub-optimal colour and atypical flavour has become increasingly frequent in warm growing districts, a trend induced by factors that include global warming. The application of a film-forming antitranspirant may be an effective way of reducing early sugar accumulation without affecting colour development. Methods and Results: An antitranspirant emulsion was applied in 2013 and in 2014 on field-grown cv. Barbera vines at pre-flowering (PF), pre-veraison (PV) and at both dates (PFPV), and compared with the unsprayed control. Post-treatment assessment included seasonal gas exchange, yield components, growth of berry organs and must composition. Although all treatments were effective in reducing gas exchange by as much as 46% compared with that of the control, berry growth was not affected. Conversely, whereas PF slightly modified the ripening pattern, PV and PFPV markedly delayed accumulation of sugar in the warm 2013 season (-2.4 and -3.7° Brix, respectively, vs control) without detriment to colour development because the onset of anthocyanins occurred at lower TSS. In the cooler, wet 2014 season, PV and PFPV were again able to delay sugar accumulation without affecting colour development. Conclusions: Pre-veraison application of the antitranspirant alone or in combination with a PF spray proved effective in slowing sugar accumulation while avoiding concurrent delay of colour development. Significance of the Study: The use of antitranspirants is a practical and flexible way of regulating the sugar:anthocyanin ratio under conditions of excessively fast ripening. © 2016 Australian Society of Viticulture and Oenology Inc.

Ground-based proximal sensing of vineyard features is gaining interest due to its ability to serve in even quite small plots with the advantage of being conducted concurrently with normal vineyard practices (i.e., spraying, pruning or soil tilling) with no dependence upon weather conditions, external services or law-imposed limitations. The purpose of the present work was to test performance of the new terrestrial multi-sensor MECS-VINE® in terms of reliability and degree of correlation with several canopy growth and yield parameters in the grapevine. MECS-VINE®, once conveniently positioned in front of the tractor, can provide simultaneous assessment of growth features and microclimate of specific canopy sections of the two adjacent row sides. MECS-VINE® integrates a series of microclimate sensors (air relative humidity, air and surface temperature) with two (left and right) matrix-based optical RGB imaging sensors and a related algorithm, termed Canoyct). MECS-VINE® was run five times along the season in a mature cv. Barbera vineyard and a Canopy Index (CI, pure number varying from 0 to 1000), calculated through its built-in algorithm, validated vs. canopy structure parameters (i.e., leaf layer number, fractions of canopy gaps and interior leaves) derived from point quadrat analysis. Results showed that CI was highly correlated vs. any canopy parameter at any date, although the closest relationships were found for CI vs. fraction of canopy gaps (R2 = 0.97) and leaf layer number (R2 = 0.97) for data pooled over 24 test vines. While correlations against canopy light interception and total lateral leaf area were still unsatisfactory, a good correlation was found vs. cluster and berry weight (R2 = 0.76 and 0.71, respectively) suggesting a good potential also for yield estimates. Besides the quite satisfactory calibration provided, main improvements of MECS-VINE® usage versus other current equipment are: (i) MECS-VINE® delivers a segmented evaluation of the canopy up t

In the present paper a series of WUE expressions, including the physiological and agronomical, were compared in potted cv. Sangiovese (Vitis vinifera L.) grapevines which were either well watered (WW) or subjected to progressive post-veraison water stress (WS) by supplying decreasing fractions (i.e. 70%, 50% and 30%) of daily canopy transpiration (Tc) concurrently recorded via a plant-enclosure gas exchange system. While single-leaf intrinsic water-use efficiency (WUEi) increased with water stress severity, seasonal whole-canopy WUE were similar at pre-stress, 70% Tc, and upon rewatering but dropped during severe water stress. WUE calculated as mass of dry weight stored in annual biomass (leaves, canes and clusters) per liter of water used, did not differ on a seasonal basis, whereas WW and WS showed similar grape composition despite the latter suffered a 25% yield reduction. Results confirm that whole-canopy WUE is a much better index than single-leaf based WUE parameter for extrapolation to agronomic WUE and actual grape composition. Under our specific case study, due to high reactivity of Sangiovese to early yellowing and shedding of basal leaves, it can be recommended that post-veraison water supply to Sangiovese vines should not be lower than 70% of daily vine water use

Several recent papers have shown that in grapevine (Vitis vinifera L.), interpretation of responses to drought can differ depending upon the parameter chosen to express water use efficiency (WUE). In the present paper, a series of WUE expressions, including physiological and agronomical, were compared in potted grapevines (Vitis vinifera L. cv. Sangiovese) that were either well-watered (WW) or subjected to progressive drought before veraison (WS) by supplying decreasing fractions (i.e. 70%, 50% and 30% of daily vine transpiration (Trd) determined gravimetrically before vines were fully rewatered. Although single-leaf intrinsic and instantaneous WUE increased with water stress severity, seasonal and whole-canopy WUE were similar to that before stress, at 70% Trd and upon rewatering, but dropped during severe water stress. WUE calculated as mass of DW stored in annual biomass (leaves, canes and bunches) per litre of water used did not differ on a seasonal basis, whereas WS plants showed lower must soluble solids at harvest, and unchanged colour and phenolic concentration in spite of smaller berries with higher relative skin growth. Results confirm that whole-canopy WUE is a much better index than any single-leaf based WUE parameter for extrapolation to agronomic WUE and actual grape composition. In our specific case study, it can be recommended that water supply to drought-stressed Sangiovese grapevines before veraison should not be lower than 70% of daily vine water use.

Here, we describe a novel device for programming and replenishing water transpired by potted plants. To test the robustness of the system, vines were subjected to progressive water stress (WS), the severity of which was maintained in relation to transpiration (Tc) of well-watered (WW) plants. Throughout the 40-day experiment, water supply in the WS treatment was progressively lowered to 70, 50, and 30% of WW Tc prior to rewatering. During the same stages, mean Tc of WS plants was 74, 48, 28, and 93% that of WW plants. Linear relationships between vine transpiration and water supply during the 40-day experiment (R2 = 0.95 for WW and 0.94 for WS) confirmed the reliability of the system in providing a water supply that closely tracked measured transpiration. The emptying volume of the cylinder t ank was set at 265 m L and proved to be adequate for daily water losses, which ranged from ~300 to 2300 mL. In addition to relieving operators of laborious and time-consuming manual irrigation, the system provides the ability to adjust water supply to actual water use as measured concurrently in a grapevine-enclosure system and enables customization of the water supply according to the size and transpiration potential of each vine.

Understanding how water use efficiency (WUE) changes under drought is crucial for interpreting adaptive responses of species and cultivars to such abiotic stress. Several recent papers have concluded that in grapevine these responses and the guidelines stemming therefrom can differ, depending upon the parameter chosen to express WUE. In the present paper a complete set of WUE expressions, including the physiological and agronomical, were compared in potted, fruiting cv. Montepulciano (Vitis vinifera L.) grapevines which were either well watered (WW) or subjected to progressive pre-veraison drought (WS) by supplying decreasing fractions (i.e. 70%, 50% and 30% of daily vine transpiration, Tg) determined gravimetrically before vines were fully rewatered. While single-leaf intrinsic water-use efficiency (WUEi) increased with water stress severity, seasonal and diurnal whole-canopy WUE were similar at pre-stress, 70% Tg, and upon rewatering but dropped in WS during severe water stress. Agronomic WUE calculated as mass of dry weight stored in annual biomass (leaves, canes and bunches) per L of water used, was also lower in WS, whereas WS had similar must composition with WW despite a 37% reduction in the yield per vine. Results warn that whole-canopy WUE is a much better index than any single-leaf based WUE parameter for extrapolation to agronomic WUE and actual grape composition. Under our specific case study, it can be recommended that, to avoid significant profit loss, water supply to drought stressed Montepulciano at pre-veraison should not be lower than 70% of daily vine water use.

A multichamber whole-canopy gas exchange system coupled with an automatic pot weighing device was tested for continuous 24 hr recording over 50 days in a trial comparing cv. Sangiovese vines subjected to progressive reduction of total transpiration water supply to well-watered vines. The system ran smoothly under regular maintenance for the entire period and gravimetric vine water loss was highly correlated with chamber-derived vine transpiration (r = 0.95) for data pooled over treatments. Seasonal and diurnal whole-canopy net CO2 exchange rate (NCER) and transpiration (Tc) showed that supplying 50% and 30% of daily gravimetric vine water loss (Tg) consistently corresponded to a NCER more than proportionally limited as compared to Tc, hence leading to lower canopy water-use efficiency (WUE) expressed as NCER/Tc ratio. Conversely, canopy WUE did not differ between treatments at 70% Tg restitution and rewatering. Similarly, during the most limiting water supply periods, the WUE difference between treatments was greatly reduced during cloudy days with lower vapor pressure deficit and higher diffuse-to-direct light intensity ratio. Data sets taken over different time frames on whole-canopy WUE provide a scenario different from that which might derive from traditional single-leaf assessment, reporting in almost all cases that intrinsic WUE increases under stress and suggests that the methodology used can mask or alter conclusions about adaptive response of grapevine cultivars to water stress. © 2014 by the American Society for Enology and Viticulture. All rights reserved.

Background and Aims: Global warming is inducing a general earliness in the onset of grapevine phenological stages including ripening, a phenomenon that occurs often in the hottest seasons and which leads to unbalanced wines. Our aim was to assess the physiological basis of late leaf removal applied above the bunch area as a tool for delaying ripening. Methods and Results: Potted cv. Sangiovese grapevines were subjected to leaf removal treatments applied preveraison (DEF-I) and postveraison (DEF-II) by pulling out six to seven primary leaves and laterals, if any, above the bunch zone; untouched vines served as the control. Whole-canopy net CO2 gas exchange was monitored seasonally from 9 days before DEF-I to 35 days after DEF-II. Concurrently, single-leaf gas exchange was assessed, and at harvest yield components, grape composition and the leaf-to-fruit ratio were determined. The seasonal carbon/yield ratio did not differ between treatments because of the high capacity for photosynthetic compensation shown by the DEF treatments and quantified as about a 35% higher net CO2 gas exchange per unit of leaf area per day. While ripening was temporarily retarded in both DEF treatments, with sugar content being lower and titratable acidity higher, a week later both treatments had fully or partially recovered; phenolic ripening was unaffected at either harvest date. Conclusions: Defoliation above the bunch zone applied at lag-phase and postveraison (average 12°Brix) was effective in temporarily delaying technological ripeness without affecting colour and phenolics. This result depended upon the high compensation capacity for photosynthesis shown by vines in both treatments. Significance of the Study: The data provide a preliminary yet robust physiological background for targeting better field application of the technique.

Vine performance was tested over five years (2005-2009) on Vitis vinifera L. cv. Barbera either manually spur-pruned (HP) or mechanically hedged with light (SMP-LF) or severe (SMP-SF) hand follow-up. Although mechanical treatments retained 2- to 2.5-fold higher count nodes per vine than did HP, yield per vine (similar to 5 kg) was almost identical between treatments due to the strong offsetting effect of reduced budbreak. Weak compensation and no compensation were seen for cluster weight and bud fruitfulness, respectively. Except for a slight reduction in anthocyanin concentration, overall grape composition was similar among treatments throughout the trial. As minor differences in vine vigor and capacity were found and the leaf-to-fruit ratio (vine basis) was unaffected by treatments, the slightly lower anthocyanin berry content in the SMP vines may have derived from increased shoot density and, hence, more shade cast in the fruiting area. Winter pruning was performed in less than 25 hr/ha in the hedged vines, thereby cutting labor demand from 54 to 70% compared with HP. Thus, if all other vineyard operations are also mechanized, a single high-wire Barbera vineyard with a mostly erect canopy can be maintained in less than 70 worker hr/ha. Such a performance, coupled with overall unchanged yield and grape composition, represents a solid and reliable approach in a wine market that demands greater efficiency and competitiveness.

Aims: Competitiveness in modern viticulture requires that vineyard management techniques used for crop regulation, besides being economically viable, would assure stable grape composition improvement across variability of genotypes and seasons. Pre-flowering basal leaf removal has previously been shown as an effective tool in controlling yield primarily through a reduced fruit-set. This study aims to evaluate the impact of early leaf removal on the differential growth of the various berry organs (skin, flesh and seeds) as well as the constancy of such effects across season variability and their impact on final grape composition. Methods and results: Pre-bloom defoliation (D) of the first six basal leaves on main shoots was applied to the field-grown Barbera cultivar (Vitis vinifera L.) from 2006 to 2008 and compared with non-defoliated (ND) controls. Over a three-year period, defoliation induced a 34% average reduction in berry number as compared to ND, which led to a notable decrease in fruit-set (-7.6 %), cluster mass (-34%) and yield per shoot (-30%). The berry mass showed a significant relationship with the year factor, as berry size in D shoots was larger, similar and smaller than ND in 2006, 2007 and 2008, respectively. In both treatments, skin mass was closely correlated with berry mass and, within each season and berry mass category, D had relative skin mass values higher than ND. Although the effects were milder in 2007, D induced a significant increase in soluble solids, anthocyanins and phenolics, whereas total acidity was unaffected. Conclusion: These results indicate that, regardless of final berry size, a pre-flowering defoliation favors skin development, which results in higher relative skin mass than ND vines. This effect appears to predominate over variations due to specific weather and cultural conditions along the season and leads to a marked improvement in final grape composition. Significance and impact of study: Repeatability of results implies

The effects of training systems established as vertically shoot-positioned spur-pruned low cordon (SPC), single high-wire cordon (HW), single Guyot (SG), and vertically split double Guyot (DG) were tested over five years (2003–2007) on Vitis vinifera L. cv. Barbera vines planted at 2.5 m interrow and at 0.9 m, 1.2 m, and 1.5 m within-row spacings. In the spur-pruned (SPC and HW) systems, total shoots per count node were about three-fold the values recorded in SG and DG, while vine capacity as total leaf area throughout the trial was highest in SPC (6.48 m2) and lowest in SG (2.93 m2), although the latter bore the most vigorous shoots. Vine capacity measured as leaf area decreased linearly with increasing within-row spacing. Yield per meter of row decreased by ~20% at 1.5 m as compared to 0.9 m vine spacing. No significant differences were found in the yield per vine across training systems, as higher shoot number in SPC and HW was offset by higher shoot fertility and cluster weight in the cane-pruned systems. Must composition at harvest was similar among SPC, HW, and SG, while DG produced grapes of overall inferior quality. Vine spacing had no effects on grape composition. Results indicate that in Barbera similar crop potential and quality expression can be achieved in either cane- or spur-pruned training systems when properly managed. Vine spacing at 0.9 m within-row is advisable as it ensures 20% higher yield per hectare at very similar grape quality across training systems.

Background and Aims: Little work has been conducted on the effects that summer pruning operations have on the relative growth of grapevine berry parts. Our paper studies whether pre-bloom leaf removal is able to modify the proportions of seed, skin and flesh in ripe grapevines berries and the related effects on must composition. Methods and Results: Pre-bloom defoliation (D) of the first six basal leaves on main shoots was applied to the field-grown cvs Barbera and Lambrusco salamino (Vitis vinifera L.) in Italy's Po Valley and compared with non-defoliated controls. D showed reduced fruitset, hence yield per shoot, and concurrently improved must soluble solids and total anthocyanins in both cultivars as a likely result of increased leaf-to-fruit ratio (+3.4 cm2/g and +5.2 cm2/g for Barbera and Lambrusco, respectively) and improved relative skin mass (from 6.0 to 9.0% in Barbera and from 8.1 to 10.4% in Lambrusco). In both cultivars, skin and seed mass were highly correlated with total berry mass and changes in relative skin mass were generally not related to berry size. Conclusions: These results indicate that berry size per se is not the primary factor in determining final grape composition, which instead seems to depend upon factors differentially affecting the growth of the various berry components. Significance of the Study: Pre-bloom D induced a consistent, site and cultivar-independent increase in relative skin mass suggesting this effect being strongly physiologically regulated.

The effects of early season leaf removal on 'Barbera' and 'Trebbiano' cluster morphology and grape quality were examined under potted and field conditions. Potted, non-defoliated 'Barbera' vines (A) were compared to treatments in which the basal portion of the shoot (nodes 1 to 8) was defoliated at a 50 or 100% level pre-anthesis (B, C), post-anthesis (D, E) or 50% both times (F). Treatments A, C, E and F were also replicated in the field using 'Barbera' and 'Trebbiano' grapevines. Fruit-set was reduced by all treatments resulting in looser clusters than the control. The minimum and maximum reduction in cluster weight was 29 and 48% for treatments B and F, respectively, in the pot study. It was 47 and 69% for treatments F and C, respectively, in the field for 'Barbera' and 44 and 56% for treatments F and C, respectively, for 'Trebbiano'. In all cases cluster size reduction was due to reduced berry number rather than smaller berry size. Sugar concentration increased for all defoliation treatments as a result of lower yield per shoot and leaf area to fruit weight ratios (shoot basis) either similar or higher than those of controls. The amount of sugar produced per unit leaf area (shoot efficiency) did not differ significantly among treatments in the potted study or for 'Trebbiano' in the field. Shoot efficiency was reduced in the C treatment for 'Barbera' in the field. These data demonstrate the potential of early season leaf removal for crop control and improvement of fruit characteristics at medium-to-high vigor sites. Work in progress will evaluate carry-over effects and feasibility of mechanical leaf removal in the vineyard.