Fruit Zone Leaf Removal Research Articles

Mechanical Leaf Removal for Improved Botrytis Bunch Rot Control in Vitis vinifera 'Pinot gris' and 'Pinot noir' Grapevines in the Northeastern United States.

Late-season bunch rot can cause substantial yield loss in grapevines grown in humid regions. Fruit-zone leaf removal has been widely used to reduce bunch rot and pesticide applications through improvements in canopy microclimate and grape cluster morphology. In this study, we evaluated whether mechanical leaf removal can be a valid alternative to a labor-intensive manual application by comparing prebloom manual (PB-MA) and mechanical (PB-ME) leaf removal. We also evaluated the effects of the timing of mechanical application, prebloom (PB-ME) versus fruit set (FS-ME), on fruit traits and bunch rot, caused by Botrytis cinerea. Our trials were conducted on two Vitis vinifera 'Pinot noir' and 'Pinot gris' vineyards in the Northeastern United States over two seasons (2017 to 2018). Major findings were overall consistent between cultivars and years. Leaf removal provided reductions in fruit-zone canopy density regardless of method or timing. In general, PB-ME provided similar shifts in cluster morphological traits to PB-MA, including lower number of berries per cluster, cluster compactness, and cluster weight compared with control (no leaf removal) vines. At harvest, both prebloom leaf removal methods equally reduced Botrytis bunch rot severity, whereas Botrytis bunch rot incidence in Pinot noir was lowest for PB-ME in 1 year and PB-MA in the next year. When comparing timing of mechanical leaf removal, FS-ME provided Botrytis bunch rot reductions similar to PB-ME, without effects on cluster weight. Thus, under our growing conditions, FS-ME was considered the best mechanical leaf removal option to help manage Botrytis bunch rot without causing undesirable yield reductions.

Mechanical Fruit-Zone Leaf Removal and Deficit Irrigation Practices Interact to Affect Yield and Fruit Quality of Cabernet Sauvignon Grown in a Hot Climate

Mechanical Fruit-Zone Leaf Removal and Deficit Irrigation Practices Interact to Affect Yield and Fruit Quality of Cabernet Sauvignon Grown in a Hot Climate

Wind speed, sun exposure and water status alter sunburn susceptibility of grape berries.

In the context of climate change, yield and quality losses from sunburn necrosis are challenging grape growers around the world. In a previous review, we identified the role of wind speed, duration of heat exposure, drought stress and adaptation as major knowledge gaps that prevent a better predictability of sunburn events. In this paper we present results of targeted experiments aiming to close these knowledge gaps. The effects of drought stress and adaptation on sunburn susceptibility were investigated in a combined drought stress/ defoliation experiment. Riesling grapevines growing in an arid climate were fully irrigated or drought stressed, and clusters were exposed to sunlight by fruit-zone leaf removal (defoliation) at two developmental stages. Sunburn symptoms were induced using infrared heaters while fruit surface temperature was measured using thermal imaging enabling the establishment of threshold temperatures. The influence of the duration of heat exposure of berries was examined by heating grape clusters to a stable temperature and monitoring the evolution of sunburn symptoms over time. To examine the effects of wind speed on the appearance of sunburn necrosis symptoms, fruit surface temperatures and sunburn severity were measured along an artificially induced wind speed gradient in two cultivars using thermal imaging and visual inspection. Longer durations of heat exposure required lower fruit surface temperatures to induce damage, while the differences in temperature after 60 min and 90 min of exposure were marginal (47.82 ± 0.25 °C and 47.06 ± 0.26 °C). Clusters of vines grown under water deficit were less susceptible to sunburn compared to those of well-irrigated plants following defoliation. The lethal temperature of clusters exposed to sunlight for seven days did not differ from those exposed to sunlight for 28 days, indicating that a full adaptation ocurred within this period. Higher wind speeds led to lower cluster temperatures and reduced sunburn severity. First evidence of a drought priming induced heat tolerance of grapevine berries was found, while adaptation had a more pronounced effect on the susceptibility to sunburn compared to water stress.

Prediction of Grape Berry Temperature Using Wireless Dataloggers Contained Within a Grape Mimic

Fruit zone leaf removal effects on grapevine (Vitis sp.) productivity and fruit quality have been widely researched. Many fruit zone leaf removal studies state that grape temperature influences grape composition; however, few studies have quantified grape berry temperature fluctuations over time, likely because of technical challenges. An efficient, simple, and economical way to estimate grape berry temperature would be valuable for researchers and industry. Consistent quantification of grape temperature would allow researchers to compare the effects of leaf removal on grape composition across varying climates and regions. A cost-effective means to quantify berry temperature would also provide industry members site-specific information on berry temperature patterns and guide leaf removal practice. Our goals were to develop a method and model to estimate berry temperature based on air temperature and berry mimics, thereby precluding the need to measure solar radiation or obtain expensive equipment. We evaluated the ability of wireless temperature sensors, submerged in various volumes of water within black or white balloons, to predict berry temperature. Treatments included 0-, 10-, 30-, 50-, and 70-mL volumes of deionized water in black and white balloons and a clear plastic bag with no water. Regression analysis was used to determine the relationship between sensor-logged temperatures and ‘Camminare noir’ berry temperatures recorded with hypodermic thermocouples. Nighttime berry temperatures were close to air temperature in all treatments. Using a piecewise regression model, the 30-mL white- and 30-mL black-balloon treatments predicted berry temperature with the greatest accuracy (R2 = 0.98 and 0.96, respectively). However, during daytime hours only, the 30-mL white-balloon treatment (R2 = 0.91) was more effective at estimating temperature than the 30-mL black-balloon treatment (R2 = 0.78). Housing temperature sensors in balloons proved to be an accurate, practical, and cost-effective solution to estimate berry temperature. Further refinement of this method in different regions, row orientations, training systems, and cultivars is necessary to determine applicability of this approach under a wide range of conditions.

Performance of Early Fruit-Zone Leaf Removal in Cabernet Sauvignon and Merlot in an Arid Climate

<h3>Summary</h3> <h3>Goals:</h3> Our goals were to evaluate how the timing of early fruit-zone leaf removal, done between prebloom and post-fruit set, influenced the risk of reduced fruit set, sunburn, and fruit quality in <i>Vitis vinifera</i> Cabernet Sauvignon and Merlot grown in the hot, arid, and irrigated region of eastern Washington State. <h3>Key Findings:</h3> Fruit set was reduced in <i>V. vinifera</i> Cabernet Sauvignon when fruit-zone leaf removal was completed during bloom. Prebloom and postbloom fruit-zone leaf removal did not reduce fruit set. Sunburn occurred on fruit on the westside of the canopy in both <i>V. vinifera</i> Cabernet Sauvignon and Merlot. Sunburn severity increased with later-timed fruit-zone leaf removal. Overall, the maximum severity of sunburn was 15% of the cluster surface area. Vintage had a greater effect on fruit quality than timing of leaf removal for both varieties. This emphasizes the need to make canopy management decisions that are informed by weather forecasts to achieve desired management goals. <h3>Impact and Significance:</h3> Early fruit-zone leaf removal was traditionally avoided in eastern Washington, in favor of completing the practice after berries have reached pea-size. The later timing of leaf removal, however, can result in sudden exposure of the fruit during the typically warmest and sunniest time of the growing season. Results from this study show that many of the assumed risks associated with early fruit-zone leaf removal, such as extreme reduction in fruit set and sunburn, are not fully realized. This means that early fruit-zone leaf removal could be adopted in this hot, arid climate without a high risk of reduction in fruit quantity or quality.

Mechanization of Pruning, Canopy Management, and Harvest in Winegrape Vineyards

<h3>Summary</h3> <h3>Aim:</h3> In winegrape production, pruning, canopy management, and harvest are essential practices that are increasingly being done by machines. How well these practices are executed can substantially affect fruit yield and quality. Mechanization offers timeliness, uniformity, and cost benefits, but most methods available to date are nonselective and optimal execution requires careful attention to vineyard design, management, and machine settings. This review provides information to help growers make the best use of machines for these tasks. <h3>Key Themes:</h3> Vineyard design considerations Winter pruning Canopy management Harvesting <h3>Impact and Significance:</h3> The need to manage large vineyards in a contracting labor market is achievable with mechanization. This review summarizes the best practices in consideration of vineyard design, as well as operation of machines for optimal productivity for the winegrape grower. This review also provides information to help growers effectively incorporate the machines in their vineyards for consistent and economical production of winegrapes including pruning, shoot-thinning, fruit-zone leaf removal, crop load management, and mechanical harvest.

Impact of Fruit Zone Leaf Removal on Fruit Quality and Yield of King’s Ruby Grapes (Vitis vinifera L.)

Impact of Fruit Zone Leaf Removal on Fruit Quality and Yield of King’s Ruby Grapes (Vitis vinifera L.)

Fruit Zone Leaf Removal Timing and Extent Alters Bunch Rot, Primary Fruit Composition, and Crop Yield in Georgia-grown ‘Chardonnay’ (Vitis vinifera L.)

Fruit zone leaf removal is a vineyard management practice used to manage bunch rots, fruit composition, and crop yield. We were interested in evaluating fruit zone leaf removal effects on bunch rot, fruit composition, and crop yield in ‘Chardonnay’ grown in the U.S. state of Georgia. The experiment consisted of seven treatments: no leaf removal (NO); prebloom removal of four or six leaves (PB-4, PB-6), post–fruit set removal of four or six leaves (PFS-4, PFS-6), and prebloom removal of two or three leaves followed by post–fruit set removal of two or three leaves (PB-2/PFS-2, PB-3/PFS-3). Although leaf removal reduced botrytis bunch rot and sour rot compared with NO, effects were inconsistent across the two seasons. Fruit zone leaf removal treatments reduced titratable acidity (TA) and increased soluble solids compared with NO. PB-6 consistently reduced berry number per cluster, cluster weight, and thus crop yield relative to PFS-4. Our results show that post–fruit set fruit zone leaf removal to zero leaf layers aids in rot management, reduces TA, increases soluble solids, and maintains crop yield compared with no leaf removal. We therefore recommend post–fruit set leaf removal to zero leaf layers over no leaf removal if crops characterized by relatively greater soluble solids-to-TA ratio and reduced bunch rot are desirable for winemaking goals.

Utilizing Pruning and Leaf Removal to Optimize Ripening of Vitis riparia-Based ‘Frontenac Gris’ and ‘Marquette’ Wine Grapes in the Northern Great Plains

Experiments were conducted to evaluate the effects of three pruning levels (20, 30 and 40 nodes per vine) and three fruit-zone leaf removal levels (0%, 50%, and 100%) on the yield and fruit quality of Frontenac gris and Marquette wine grapes in a northern production region. The study was conducted at three North Dakota vineyards located near Buffalo, Clifford, and Wahpeton, North Dakota, in 2011 and 2012. Increasing the number of buds retained increased yields and reduced pruning weights in both cultivars. Frontenac gris and Marquette yields were greatest when vines had 50% of the fruit-zone leaves removed due to heavier clusters, suggesting that the 100% fruit-zone leaf removal level was too severe. Individual berries in clusters were also heavier when vines were pruned to retain 40 buds. Frontenac gris fruit quality was similar both years and was not influenced by pruning or leaf removal levels. Marquette fruit total soluble solids content was greater in 2012 due to the warmer and longer growing season. Marquette fruit titratable acidity was lower when 100% of the fruit-zone leaves were removed. These results suggest that for the two cold-hardy hybrid wine grapes used in this study, greater bud retention levels should be investigated. Results also warrant further research into cultivar adaptiveness to northern Great Plains conditions. With further research, it is anticipated that wine grape cultivars and management practices will be identified to produce acceptable yields and fruit quality for commercial wine grape production.

Flavonol Profile Is a Reliable Indicator to Assess Canopy Architecture and the Exposure of Red Wine Grapes to Solar Radiation.

Exposure to solar radiation is a determining factor of grape composition. Flavonol synthesis is upregulated by solar radiation leaving a fingerprint on flavonol profile. This study aimed to test the factors affecting flavonol accumulation and profile and their potential as an indicator to assess the overall exposure of red wine grape berry to solar radiation. We performed three experiments to study the response of flavonol accumulation and profile to (1) three different solar radiation exclusion treatments during berry development; (2) canopy porosity and leaf area index (LAI); and (3) spatial variability of water status, vigor and ripening and cultural practices in commercial vineyards. Results showed a strong relationship between global radiation, inverse dormant pruning weights or canopy porosity (inversely proportional to LAI) and % kaempferol or % quercetin. Furthermore, the increase in concentration of the above two flavonols was associated with a reduction of % myricetin. Total flavonol content, % kaempferol, % quercetin, and % myricetin had significant correlations with inverse dormant pruning weights, but these were less sensitive to over-ripening or water deficits. Flavonol profile was associated to site hydrology (wetness index) through changes in vigor, and to LAI; and responded to shoot thinning or fruit-zone leaf removal. These results support the reliability of the flavonol profile as an assessment parameter for studies aiming to discuss canopy architecture or the effect of solar radiation on grapevine berries.

Adjusting Product Timing during the Powdery Mildew Critical Window to Improve Disease Management

Summary Goals: This project was designed to answer questions about the timing of different cultural (leaf removal) and chemical (fungicide rotation) disease management practices and how they influence the overall efficacy of a powdery mildew management program. Key Findings: The timing of specific chemical modes of action plays an important role in the overall efficacy of powdery mildew fungicide programs. In this study, programs in which the evaluated products were applied once during the critical window performed as well as programs in which the same products were applied twice (during the critical window and at bunch closure). This finding indicates that disease control depends on application of sprays during the critical window rather than later in the season. As expected, leaf removal significantly improved spray coverage in the fruit zone; however, this improved coverage did not last the entire season. Canopy refill, which occurred as summer laterals developed, reduced fruit-zone coverage later in the season. Leaf removal also did not result in any positive additive effects on overall disease control. Impact and Significance: These findings can be used to aid growers in the selection and rotation of products used for powdery mildew management programs to maximize the efficacy of disease control and minimize the risk of fungicide resistance. While early fruit zone leaf removal did not improve overall disease control in this high-pressure scenario, leaf removal resulted in improved spray coverage, which may enhance disease control when low-volume spray applications or contact-active chemistries are emphasized in a commercial program.

Hand and Mechanical Fruit-zone Leaf Removal at Prebloom and Fruit-set Was More Effective in Reducing Crop Yield than Reducing Bunch Rot in ‘Riesling’ Grapevines

Fruit-zone leaf removal is typically applied in cool and humid regions to improve grape and wine quality, while reducing disease pressure. When fruit-zone leaf removal is applied early in the season, before bloom [early leaf removal (ELR)], it also reduces fruit-set, cluster compactness, and susceptibility to bunch rot, a complex disease that involves fungi (Botrytis cinerea, Aspergillus sp., Penicillium sp.) and bacteria (Acetobacter sp.). Over 2 years (2015–16), we tested whether ELR applied mechanically [mechanical defoliation at stage E-L 18 (MD-I)] would mimic the effects of a hand removal [hand defoliation of the first six basal leaves and laterals at stage E-L 18 (Coombe, 1995) (HD-I)] with respect to ‘Riesling’ (Vitis vinifera) production parameters, canopy density and cluster sunlight exposure, fruit composition, and bunch rot control. We also compared the effects of mechanical defoliation applied either at prebloom (MD-I) or at fruit-set [mechanical defoliation at stage E-L 27 (MD-II)]. In both years, fruit-zone leaf removal, regardless of method and timing, reduced yield, cluster weight, and berries per cluster, while maintaining fruit composition and bud fruitfulness as compared with nondefoliated vines (control, C). In 2015, HD-I vines had a lower percentage of clusters infected by bunch rot as compared with the C and MD-II vines. However, severity of bunch rot was low in all treatments, and there was not significant treatment effect on bunch rot severity in either year. ELR consistently shortened cluster length, offsetting much of the intended cluster loosening effect induced by a lower number of berries per cluster—that would have reduced bunch susceptibility to late seasons rots. Despite removing only half the leaf area of HD-I, MD-I successfully mimicked the canopy improving effects of HD-I in terms of fewer interior clusters and leaves, fewer cluster-shading layers, and greater light available to clusters and leaves as compared with C vines.

Leaf Removal Effects on Cabernet franc and Petit Verdot: II. Grape Carotenoids, Phenolics, and Wine Sensory Analysis

The rationale for fruit zone leaf thinning in a humid environment is often driven more by the need for disease management than by anticipated improvements in fruit composition. Fruit zone management is often applied uniformly over climatically diverse regions, with little regard for interaction with ambient temperature or radiation. We evaluated how the timing and magnitude of fruit zone leaf and lateral removal altered fruit composition and wine consumer preference of Cabernet franc and Petit Verdot, with the underlying premise that current fruit zone management recommendations (one to two leaf layers) may be overly conservative in the humid, eastern United States. Three post-fruit set leaf/lateral shoot removal treatments (no removal [NO], removal from opposite the basal primary cluster and the node directly above [MED], and removal from the node directly above the distal primary cluster down to the cordon [HIGH]) and one pre-bloom leaf/lateral shoot removal treatment (removal from the six primary basal nodes [P-B]) were evaluated. P-B more consistently increased total berry phenolics in Petit Verdot than in Cabernet franc, while total berry anthocyanins were unaffected. Carotenoids were quantified due to their importance as aroma precursors. When compared to NO and MED, HIGH and P-B treatments tended to increase carotenoid accumulation more in the preveraison period than in the postveraison period. HIGH and P-B treatments also tended to increase carotenoid degradation more in the postveraison period, particularly for zeaxanthin. Wines made with fruit from P-B plots were ranked higher in color intensity compared to wines made with fruit from MED plots. Fruit zone leaf removal modestly improved fruit composition and wine quality potential, and created a microclimate less conducive to fungal diseases.

Impact of Fruit-Zone Leaf Removal on Rotundone Concentration in Noiret

Rotundone was recently identified as the compound that imparts the black pepper aroma in several winegrape cultivars. This two-year study aimed to identify the presence of rotundone in Noiret (interspecific hybrid of Vitis) and to determine the impact of fruit-zone leaf removal on rotundone concentrations in fruit and wine. The relationship between the intensity of black pepper aroma and rotundone concentration in Noiret wine was also explored. An undefoliated control (CON) was compared to a maintained fruit-zone sunlight exposure (MSE) treatment, where leaves were periodically removed from the fruit-zone. The influence of timing of fruit-zone leaf removal was assessed in a separate experiment by comparing preveraison leaf removal (LR) and postveraison leaf removal (PVLR) treatments. MSE vines had greater fruit-zone sunlight exposure compared to the CON throughout the season in 2015, both at the pre- and postveraison stages, but in 2014, only after veraison. PVLR increased fruit-zone sunlight exposure during ripening compared to LR in 2015 only. Rotundone could not be quantified in Noiret berries sampled before or at veraison (limit of quantitation = 0.16 μg/kg). Rotundone concentrations in harvested fruit and wines did not differ between treatments in 2014, but were significantly higher in MSE than in CON in 2015 (1.98 versus 1.28 μg/kg). PVLR temporarily increased rotundone concentration compared to LR, but differences disappeared by harvest. Black pepper aroma intensity, as determined by a sensory panel, was positively correlated (p = 0.023, r = 0.791) with rotundone concentration in wines made from imposed viticulture treatments, providing evidence that black pepper notes in Noiret are positively related to concentration of rotundone in the wine.

Influence of timing and intensity of fruit zone leaf removal and kaolin applications on bunch rot control and quality improvement of Sauvignon blanc grapes, and wines, in a temperate humid climate

Leaf removal is beginning to receive consideration for many growers as an important cultural practice for bunch rots control. It is normally applied after veraison and almost only on red varieties because of the high sunburn susceptibility of white grapes varieties under Uruguayan climatic conditions. The aim of this study was to determine the time and intensity of leaves removal impact on bunch rots and grapes quality on Sauvignon blanc. In parallel, the effects of kaolin (Surround® WP) applications in reducing the negative impact of excessive exposure to high temperatures were evaluated. Different intensities and times of defoliation, in combination with kaolin applications, were evaluated over 2006/07, 2007/08 and 2008/09 seasons. All defoliation treatments and mainly those made after fruit set, significantly reduced the occurrence of bunch rots, having a critical impact on those metabolites responsible for the final taste of wines. Early defoliation was significantly more effective controlling Botrytis incidence and improving berry quality than later in the season. Leaf removal had a determining impact over fruit quality and primary and secondary metabolites contents. An increase in soluble solids and glycosides concentrations was observed, while IBMP grape content was reduced, thus affecting the flavor of Sauvignon blanc wines. Kaolin applications significantly reduced berries temperature, sunburn and other berry damages associated with clusters solar exposure.In sum, leaves removal and exogenous kaolin application in Sauvignon blanc showed great potential as Botrytis mitigation strategy because it positively impacts berry quality as a result of many molecular and biochemical changes in key secondary metabolic pathways. Simultaneously reducing berry sunburn.

Pinot noir wine volatile and anthocyanin composition under different levels of vine fruit zone leaf removal

The impacts of fruit zone leaf removal on volatile and anthocyanin compositions of Pinot noir wine were investigated over two growing seasons. Wine volatiles were analyzed by multiple techniques, including headspace solid phase microextraction-GC-MS (HS-SPME-GC-MS), headspace-GC-FID (HS-GC-FID) and stir bar sorptive extraction-GC-MS (SBSE-GC-MS). Fruit zone leaf removal affected the concentration of many grape-derived volatile compounds such as terpene alcohols and C13-norisoprenoids in wine, although the degree of impact depended on the vintage year and severity of leaf removal. Fruit zone leaf removal resulted in greater concentrations of linalool, α-terpineol and β-damascenone but had no impact on other terpene alcohols or β-ionone. Fruit zone leaf removal had no consistent impact on C6 alcohols, volatile phenols, lactones, fermentation-derived alcohols, acids, or most esters. Fruit zone leaf removal increased anthocyanins in final wine.

Efficacy of Biopesticides and Leaf Removal in Grapevine Powdery Mildew Management

Integrating biological-based fungicides into conventional spray programs may help with fungicide resistance management. However, little is known about how to best integrate these products while still maintaining maximum disease control. Programs with as few as one synthetic fungicide or as many as three synthetic fungicides added to a biopesticide-based rotation during the bloom period of Vitis vinifera had significantly better disease control than a biopesticide-only-based program. When integrated with different timings of fruit-zone leaf removal, specific combinations of biopesticide programs and fruit-zone leaf removal enhanced the efficacy of that program to be on par with disease control seen in a program entirely based on synthetic fungicides. This suggests that when designing a fungicide program using biopesticides as a base, the addition of a synthetic fungicide during the window of ontogenic susceptibility in clusters and the adoption of cultural practices such as leaf removal can significantly improve the efficacy of that program. Accepted for publication 11 April 2016. Published 20 April 2016.

Effect of Early Fruit-Zone Leaf Removal on Canopy Development and Fruit Quality in Riesling and Sauvignon blanc

Canopy management is vital for quality winegrape production. During the 2012 and 2013 growing seasons, the timing of fruit-zone leaf removal (FZLR) was evaluated in two commercial vineyard blocks (<i>Vitis vinifera</i> Riesling and Sauvignon blanc) located north of Prosser, WA. Three different timings of manual FZLR were evaluated with a no-removal control. Leaf removal consisted of complete removal of all leaves and lateral shoots in the fruit zone on both sides of the canopy at prebloom, bloom, and four weeks postbloom. Each vine received the same treatment in both years. No negative implications were observed in total fruit set in either year. When leaf removal was performed, regardless of timing, the fruit zone of the canopy had less lateral shoot development and canopy refill than the control. Leaf removal also improved spray coverage in the fruit zone in Riesling, but the effect was related to the timing of leaf removal relative to the timing of the spray. In 2013, prebloom leaf removal significantly reduced Botrytis bunch rot severity in Sauvignon blanc (<i>p</i> = 0.01) below that of the control and four weeks postbloom leaf removal treatments. In 2013, prebloom leaf removal in Riesling increased terpene concentrations in the harvested juice (<i>p</i> = 0.03). In 2012, postbloom leaf removal in Riesling reduced concentrations of acids below those of the prebloom treatment (<i>p</i> = 0.04) in juice.

Kaolin over sun-exposed fruit affects berry temperature, must composition and wine sensory attributes of Sauvignon blanc

Under humid climatic conditions, crop loss due to bunch rot can be as high as 100% in a given year and, in many cases, it becomes the main factor determining harvest. Although the effectiveness of fruit zone leaf removal depends on initial fruit microclimate, it is generally extremely effective at reducing bunch rots. The impact of leaf removal on Sauvignon blanc must composition and wine sensory attributes, is in general considered detrimental. High temperature achieved as a result of excessive bunch exposure may negatively affect primary and secondary grape metabolites responsible for its typical wine style. The main objective of this work was to determine, if kaolin application over clusters, reduce sunburn and other berry damage associated with excessive fruit exposure. Three treatments were evaluated: untreated control (C); fruit zone leaf removal (LR); and fruit zone leaf removal plus kaolin application (LR+K). Kaolin application significantly reduced berry temperature, sunburn and other berry damage associated with excessive fruit exposure. Wines from the LR+K treatment had the highest sensory scores of all three treatments and were related more to a high intensity of fruity and tropical notes rather than to the absence of green notes as a consequence of leaf remova.

Effects of Severity of Post-flowering Leaf Removal on Berry Growth and Composition of Three Red Vitis vinifera L. Cultivars Grown under Semiarid Conditions

The effects of the severity of post-flowering leaf removal on the growth and phenolic composition of berry skin and seeds were studied in three Vitis vinifera L. genotypes over two consecutive seasons, 2007 and 2008. The study was conducted in a commercial vertical shoot positioned (VSP)-trained nonirrigated vineyard of northern Greece, planted with cultivars Merlot, Cabernet Sauvignon, and Sangiovese. Three different severities of leaf removal in the fruit zone were applied manually at berry set: nondefoliated (ND), removal of the lateral shoots of the first six basal nodes (LR), and full removal of the total leaf area (main leaves and lateral shoots) of the first six basal nodes (FR). Grape samples were obtained at commercial harvest. Leaf removal decreased yield per vine and cluster weight in Merlot and Sangiovese. Cluster compactness was reduced with the severity of defoliation only in Merlot, due to a decrease in berry number per cluster; berry fresh weight was unaffected in both cultivars. On the contrary, in Cabernet Sauvignon, yield was unaffected but berry size was restrained by leaf removal. Skin and seed mass followed variations in berry mass (except for seed mass in Sangiovese). Fruit zone leaf removal did not affect must soluble solids and increased titratable acidity only in Merlot. Defoliation increased skin anthocyanins in Merlot and Cabernet Sauvignon in the order FR > LR > ND but significantly reduced seed flavan-3-ols mainly as a result of the reduction in catechin and epicatechin amount. For these varieties, FR had lower seed flavan-3-ols than ND in both varieties, whereas LR had intermediate values. However, in Sangiovese, the highest seed phenolic content was recorded in LR. The results showed that post-flowering leaf removal improved the overall berry composition in Merlot and Cabernet Sauvignon but had limited effect in Sangiovese.