Matteo Gatti

Early Leaf Removal to Improve Vineyard Efficiency: Gas Exchange, Source-to-Sink Balance, and Reserve Storage Responses

Based on earlier findings showing the effectiveness of preflowering leaf removal at reducing yield in several Vitis vinifera L. genotypes, a 3-year study was carried out on Sangiovese vines to evaluate how the technique also affects vegetative growth, wood carbohydrates reserves, and specific physiological traits such as intrinsic water use efficiency (WUEi) and leaf chlorophyll fluorescence. Early defoliation (D) applied before flowering with elimination of ~80% of the leaf area as compared with a non-defoliated control (C) was confirmed as quite effective in limiting yield per vine, cluster weight, cluster compactness and rot incidence, and berry set and mass in two of three seasons. Defoliation also markedly improved relative berry skin mass regardless of season. Vine vigor (pruning weight, cane diameter, and main leaf area) was significantly reduced in D vines (2008–2009 data), whereas vine capacity as total leaf area per vine was not. The leaf-to-fruit ratio dropped dramatically after defoliation to 1 m2/kg in D vines, which recovered thereafter and had a higher ratio from veraison onward. Intrinsic WUE and tolerance to photoinhibition increased in D vines for both main and lateral leaves, which were formed after leaf stripping and which had reached full maturity by the time measurements were made. Berry sugaring was accelerated in D vines, which also showed, at harvest, higher must Brix and phenolic and anthocyanin concentrations than C vines as well as more stable anthocyanins in the wine.

Effects of Cluster Thinning and Preflowering Leaf Removal on Growth and Grape Composition in cv. Sangiovese

Crop-regulation techniques applied as preflowering defoliation (D), early cluster thinning at preflowering (ECT), and cluster thinning at lag-phase of berry growth (LCT) were tested over three seasons on high-yielding Vitis vinifera L. Sangiovese and compared to non-defoliated, unthinned control vines. Treatment severity consisted of removing primary leaves and any laterals developed from nodes 1 to 6 in D and of thinning 50% of clusters chosen from among distal clusters or those inserted on weak shoots in ECT and LCT plots. Although yield per vine was not as reduced in D (−32%) as in ECT and LCT treatments (−45%) as compared to the control, D vines also had largely improved sugar and total anthocyanin concentrations and the highest total phenolics. Yield components were also markedly affected by treatments: D vines had smaller clusters and berries, leading to improved cluster looseness and to higher relative skin and seed growth. While all crop-regulating treatments led to an increase in the final leaf-to-fruit ratio, parameters of technological maturity were essentially uncoupled, as equally high Brix levels corresponded to the highest titratable acidity in D and, conversely, to lowest titratable acidity and highest pH in ECT and LCT. Overall results showed that different final yield-grape composition patterns can be reached depending on the technique used for crop regulation as a primary consequence of a diversified degree of compensation triggered on single-yield components.

An Improved Multichamber Gas Exchange System for Determining Whole-Canopy Water-Use Efficiency in Grapevine

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.

Postbudburst Spur Pruning Reduces Yield and Delays Fruit Sugar Accumulation in Sangiovese in Central Italy

The influence of pruning date on yield control and ripening rate of spur-pruned Sangiovese grapevines was investigated over two years (2013 and 2014). Winter pruning was applied on 1 or 4 Feb (mid dormancy); 1 or 5 March (late dormancy); 2 or 7 April (bud swell); 2 or 7 May (flowers closely pressed together); and 1 or 6 June (40 to 50% of flower caps fallen), respectively. Vine yield and fruit composition at harvest were not affected by shifting from the standard pruning dates of mid and late dormancy to the bud swell stage. In contrast, the number of inflorescences in compound buds was significantly reduced for vines pruned in early May. No inflorescences were retained on vines pruned at the beginning of June. Early May pruning reduced fruit set and berry weight and slowed fruit ripening compared to the other pruning dates. At harvest, must soluble solids and titratable acidity were 1.6 Brix lower and 1.8 g/L higher, respectively, for the May treatment compared to the standard pruning dates. The early May pruning dates also achieved higher total anthocyanins and phenolic concentrations than the standard pruning dates, indicating that this technique can potentially decouple the accumulation dynamics of these components. Further studies are needed to better calibrate winter pruning date for managing yield and berry maturation rate.

Water use efficiency in Sangiovese grapes (Vitis vinifera L.) subjected to water stress before veraison: different levels of assessment lead to different conclusions

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.

Transcriptional Responses to Pre-flowering Leaf Defoliation in Grapevine Berry from Different Growing Sites, Years, and Genotypes

Leaf removal is a grapevine canopy management technique widely used to modify the source–sink balance and/or microclimate around berry clusters to optimize fruit composition. In general, the removal of basal leaves before flowering reduces fruit set, hence achieving looser clusters, and improves grape composition since yield is generally curtailed more than proportionally to leaf area itself. Albeit responses to this practice seem quite consistent, overall vine performance is affected by genotype, environmental conditions, and severity of treatment. The physiological responses of grape varieties to defoliation practices have been widely investigated, and just recently a whole genome transcriptomic approach was exploited showing an extensive transcriptome rearrangement in berries defoliated before flowering. Nevertheless, the extent to which these transcriptomic reactions could be manifested by different genotypes and growing environments is entirely unexplored. To highlight general responses to defoliation vs. different locations, we analyzed the transcriptome of cv. Sangiovese berries sampled at four development stages from pre-flowering defoliated vines in two different geographical areas of Italy. We obtained and validated five markers of the early defoliation treatment in Sangiovese, an ATP-binding cassette transporter, an auxin response factor, a cinnamyl alcohol dehydrogenase, a flavonoid 3-O-glucosyltransferase and an indole-3-acetate beta-glucosyltransferase. Candidate molecular markers were also obtained in another three grapevine genotypes (Nero d’Avola, Ortrugo, and Ciliegiolo), subjected to the same level of selective pre-flowering defoliation (PFD) over two consecutive years in their different areas of cultivation. The flavonol synthase was identified as a marker in the pre-veraison phase, the jasmonate methyltransferase during the transition phase and the abscisic acid receptor PYL4 in the ripening phase. The characterization of transcriptome changes in Sangiovese berry after PFD highlights, on one hand, the stronger effect of environment than treatment on the whole berry transcriptome rearrangement during development and, on the other, expands existing knowledge of the main molecular and biochemical modifications occurring in defoliated vines. Moreover, the identification of candidate genes associated with PFD in different genotypes and environments provides new insights into the applicability and repeatability of this crop practice, as well as its possible agricultural and qualitative outcomes across genetic and environmental variability.

Distinct transcriptome responses to water limitation in isohydric and anisohydric grapevine cultivars

BackgroundGrapevine (Vitis vinifera L.) is an economically important crop with a wide geographical distribution, reflecting its ability to grow successfully in a range of climates. However, many vineyards are located in regions with seasonal drought, and these are often predicted to be global climate change hotspots. Climate change affects the entire physiology of grapevine, with strong effects on yield, wine quality and typicity, making it difficult to produce berries of optimal enological quality and consistent stability over the forthcoming decades.ResultsHere we investigated the reactions of two grapevine cultivars to water stress, the isohydric variety Montepulciano and the anisohydric variety Sangiovese, by examining physiological and molecular perturbations in the leaf and berry. A multidisciplinary approach was used to characterize the distinct stomatal behavior of the two cultivars and its impact on leaf and berry gene expression. Positive associations were found among the photosynthetic, physiological and transcriptional modifications, and candidate genes encoding master regulators of the water stress response were identified using an integrated approach based on the analysis of topological co-expression network properties. In particular, the genome-wide transcriptional study indicated that the isohydric behavior relies upon the following responses: i) faster transcriptome response after stress imposition; ii) faster abscisic acid-related gene modulation; iii) more rapid expression of heat shock protein (HSP) genes and iv) reversion of gene-expression profile at rewatering. Conversely, that reactive oxygen species (ROS)-scavenging enzymes, molecular chaperones and abiotic stress-related genes were induced earlier and more strongly in the anisohydric cultivar.ConclusionsOverall, the present work found original evidence of a molecular basis for the proposed classification between isohydric and anisohydric grapevine genotypes.

Long-Term Effects of Mechanical Winter Pruning on Growth, Yield, and Grape Composition of Barbera Grapevines

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 (~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.

Double-Pruning Grapevines as a Management Tool to Delay Berry Ripening and Control Yield

Sangiovese vines mechanically spur-pruned during dormancy in February were manually finished either immediately or post budburst to test the potential of a ‘double-pruning’ approach to delay fruit sugar accumulation and limit yield. The treatments were applied in 2014, 2015, and 2016 at BBCH-0 as standard hand-finishing on dormant buds (SHF), and as late (LHF) and very late (VLHF) hand-finishing at BBCH-14 and BBCH-19, i.e., when the two apical shoots on the mechanically-shortened canes were ~10 and 20 cm long, respectively. While yield per vine was drastically reduced in the VLHF treatment (−43% versus SHF) due to high incidence of unsprouted (blind) nodes, lower shoot fruitfulness, and berries per cluster, yield reduction in LHF was −22% versus SHF due only to the incidence of unsprouted nodes. While the fruit ripening profile was not significantly modified in VLHF compared to SHF, in data pooled over three seasons, LHF delayed basic fruit composition at harvest, producing fruit with less total soluble solids, lower pH, and greater acidity, but more phenolics than SHF. Overall, LHF proved to be effective at reducing yield per vine to a level that did not require expensive cluster thinning. By reducing berry sugar accumulation, it has the potential to produce wines with lower alcohol and higher phenol content. Noteworthy too is its potential to delay harvest date or increase crop hanging time under specific vineyard conditions.

Effects of Early Shoot Trimming of Varying Severity on Single High-Wire Trellised Pinot noir Grapevines

Amid growing concerns over global warming and available management strategies to reduce cluster temperature and prevent overheating and sunburn damage, there is increasing interest in sprawling, nonpositioned canopies as an alternative to traditional vertically positioned ones. However, management of sprawling canopies requires adjustments to maintain a mostly erect growth pattern during the season. A three-year study (2009–2011) was carried out to investigate the performance of 15-year-old Pinot noir grapevines trained to a single high-wire trellis subjected to prebloom shoot trimming to retain seven (T7) or eleven (T11) main stem leaves. There were significant year × treatment interactions: with a low crop and weather conducive to posttrimming lateral regrowth in 2010, trimmed vines had higher leaf area, soluble solids concentration, pH, total anthocyanins, and cluster rot incidence than control vines, whereas in 2009 and 2011, the overall must compositional pattern was reversed due to suboptimal leaf-to-fruit ratios in the trimmed plots. The effects linked to this necessary operation are highly dependent on unpredictable weather occurring after shoot trimming; hence, the milder trimming severity (T11) may more successfully balance the need to induce a still mostly erect canopy while retaining sufficient vine leaves to buffer possible weak lateral formation after trimming. This paper provides new and useful knowledge for improved canopy management in trellises with free shoot growth due to the absence of foliage wires.