Bunch Zone Research Articles

Temperature variation linked to trellis height: an opportunity for adaptation to climate change?

Temperature is a key factor in vine growth and grape composition (Jones, 2006). Climate change is already having an impact on these parameters in many wine regions, and it is becoming necessary to adapt in order to continue producing quality wines, without strongly altering their typical character (van Leeuwen et al., 2019). One way to adapt could be to modify the vine’s training system. A study of temperature at different heights was carried out in the Bordeaux region to assess whether increasing trunk height could modify the microclimate in the bunch zone (de Rességuier et al., 2023).

Fungitoxic role of endogenous eugenol in the hybrid grapevine cultivar Baco blanc resistant to <i>Botrytis cinerea</i>

Eugenol (2-methoxy-4-(2-propenyl)-phenol), widely spread in various plants, notably clove, basil and bay, is a well-known antifungal and antibiotic molecule that is abundant in the hybrid grapevine cultivar Baco blanc (Vitis vinifera × Vitis riparia × Vitis labrusca). This variety, created by François Baco (19th century), is confirmed in this study as highly resistant to Botrytis cinerea by comparing fruit rot incidence and severity with two Vitis vinifera cultivars: Folle Blanche and Ugni Blanc. According to two major antibiosis modes of action, i.e., direct or volatile, this study demonstrated the efficiency of eugenol in vitro by also investigating precisely the effect on B. cinerea of small concentrations of eugenol, 3 to 4 ppm, corresponding to IC10. Moreover, the vapour-inhibiting effect was shown to be highly powerful. The total eugenol concentration peaked at the veraison stage, exceeding 1000 μg×kg-1 in the skin of Baco blanc berry under our conditions. At this point, leaf removal in the bunch zone induced a significant increase in eugenol (32 %), from 1118 to 1478 μg×kg-1, which was also associated with a significant decrease in B. cinerea infection in the vineyard. Thus, for the first time, eugenol, as an endogenous molecule of Baco blanc, was clearly demonstrated to be an inducible compound in the vineyard. Furthermore, significant intravarietal variability in eugenol concentrations according to the Baco blanc clone was demonstrated to be associated with significant differences in fruit susceptibility to the plant pathogen assessed in biotests. Interestingly, in keeping with fruit ontogenic resistance, a significant negative correlation was established between the technological maturity of berries and the total eugenol content in the berry skin. Finally, the time-progress study of the two biochemical forms of eugenol (bound vs. free eugenol) allowed us to hypothesise the effectiveness against the plant pathogen of some precursor forms of eugenol, and the corresponding biochemical structures are currently being investigated. Thus, eugenol appears to be a key biochemical marker of ontogenic resistance in the hybrid cultivar Baco blanc.

Effects of ultraviolet and infrared radiation absence or presence on the aroma volatile compounds in winegrape during veraison

Light environmental factors have been identified to influence grape aromas greatly. Among them, the effect of non-visible light on grape aroma compounds has scarcely been investigated during grape growth and development. In the present study, ultraviolet (UV) or infrared (IR) radiation was eliminated in the grape bunch zone, and the grape bunches were irradiated with UV or IR light in vitro. The effect of UV and IR radiation on the grape aroma profile of the Cabernet Sauvignon variety was assessed by headspace solid phase microextraction gas chromatography mass spectrometer (HS-SPME GC–MS). A total of 16 aroma compounds were identified in the grape berries under UV radiation absence (UV-) or IR radiation absence (IR-). They were classified into aliphatic alcohols, aliphatic acids, benzenolds, aldehydes, and monoterpenes. A total of 23 aroma compounds were identified in the grape berries under UV radiation presence (UV+) or IR radiation presence (IR+), which were classified into aliphatic alcohols, aliphatic ketones, aliphatic esters, aliphatic acids, monoterpenes, aldehydes, volatile phenols, and other volatiles. Linalool and hexanal aroma compounds were the most responsive to UV- and UV+, according to OPLS-DA analysis. Hexanal was increased by UV- and decreased by UV+, thus was negatively correlated with UV radiation. Benzaldehyde and 2-decanone were also found as the main differing aroma compounds according to VIP scores in the IR- and IR+, respectively. The significant differences of aroma compounds in three UV and IR intensities were also observed by headspace gas chromatography-ion mobility spectrometry (HS-GC-IMS). The content of acetic acid, 2-methylbutanal, and pentanal were reduced with the radiation intensity increase, and the content of 2–3-butanedione, butyl acetate, and 1-hexanol was enhanced, especially with UV radiation. This study improves our understanding of the non-visible light role in volatile aroma compound accumulation and further expands on the useful wavelength for plant growth and development. Our study provides a theoretical basis for non-visible light field management and indoor plant growth applications.

Characterisation of the vertical temperature gradient in the canopy reveals increased trunk height to be a potential adaptation to climate change

Given the important role of temperature in vine development and grape composition, climate change has already impacted wine production. Adaptation strategies are needed in order to sustain the production of wines and maintain their typicity. Several levers of adaptation are possible, including the use of more heat and drought tolerant plant material, relocating the vineyard and adaptations in the cellar. The training system is also a potential lever for adaptation that is relatively easy to implement. Taking that avenue, a study of the vertical thermal gradient in the vine canopy was carried out in order to determine whether trunk height could be an adaptation strategy for manipulating micro-climate in the bunch zone. Temperature was measured at four different heights from the soil (30, 60, 90 and 120 cm) in two adjacent vineyard parcels. One parcel was managed with cover crop and the other by tilling the soil. The results of this study show that increased trunk height is not likely to significantly delay ripeness, but it could minimise the potential damages of both frost and heat wave events. Type of parcel management was found to have an effect: close to the ground, the cover crop parcel generally had lower minimum temperatures and higher maximum temperatures in comparison to the tilled parcel, exposing the vines to an increased risk of both frost and heat wave damage. When investigating the factors driving the vertical thermal gradient, soil moisture and weather type were found to have an impact. Some of these factors, like mean temperature and soil moisture, may exacerbate the vertical temperature gradient of maximum temperature in a climate change context and increase the risk of damages due to extreme temperatures.

Impacts of photoselective bunch zone shading on the volatile composition and sensory attributes for <i>Vitis vinifera</i> L. cv. Riesling

Photoselective shading is a process that modulates the radiation intensity in specific regions of the electromagnetic spectrum. It is a common practice in horticulture to manipulate specific plant physiological responses, but to date has only received minimal attention in viticulture. The potent odorant 1,1,6-trimethyl-1,2-dihydronaphthalene (TDN) is of particular relevance for aged Riesling wine, which are also known to be impacted by the magnitude of bunch zone light exposure during berry development. Hence, in this study, the effect of photoselective bunch zone shading on the formation of TDN in wine was investigated across two consecutive growing seasons. Applying red, black or green shade cloth (SC) to the bunch zone provided unique bunch zone light environments and yielded distinct differences in grape and wine composition compared with the unshaded control. Overall, bunch zone shading through shade cloth was effective in reducing overall photosynthetically active radiation compared to the control and the photoselectivity of the SC treatments differently affected a number of grape and wine measures. Fruit yield was somewhat but not significantly lower under black SC treatments, while juice pH was increased in grapes grown under green and black SC across both vintages compared to the control. Both grape sugar accumulation (P = 0.035) and ammonia nitrogen (P = 0.043) showed evidence of treatment effects, although with low F-statistics (4 and 3, respectively). Measures of hydrolytically released TDN in juice and free TDN concentrations in wine were lower in SC treatments. Unexpectedly, sensory descriptive analysis of the wines demonstrated that increased ‘kerosene-like’ aroma was not consistently associated with free TDN concentrations in wine. In summary, photoselective bunch shading was demonstrated to be an effective method for manipulating grape and wine outcomes and may aid in overcoming viticultural obstacles and quality impacts associated with climate change.

Distinctive phenolic accumulation response to temperature-induced by row orientation of two field-grown Vitis vinifera cultivars

PurposePhenolic compounds play a critical role in grape quality, and their content is strongly influenced by bunch zone temperature during the ripening period. The mechanism of responding to temperature was found to highly depend on cultivars. The present study aimed to evaluate the effects of row orientation and canopy side on phenolic content in grape berries.Design/methodology/approachThe authors analyzed the accumulation of phenolic compounds in mature berries of Cabernet Sauvignon and Cabernet Gernischt. They were harvested from various canopy sides of north-south and east-west row orientations, which were NS–E and NS–W, EW–S and EW–N.FindingsDuring the ripening period, mean temperatures of the bunch zones, NS–W and EW–N were respectively higher than NS–E and EW–S. At harvest, the total phenolic, total anthocyanin, tannin and reducing sugar contents were higher in NS–E and EW–S, than in NS–W and EW–N, respectively, indicating a negative relationship with temperature. For both varieties, EW–S had the highest proportion of malvidins anthocyanins. Peonidins, delphinidins, and cyanidins anthocyanins of EW–N showed a higher ratio in Cabernet Sauvignon, while NS–E showed a higher ratio in Cabernet Gernischt.Originality/valueTo improve grape monomeric anthocyanin content, the results indicate that Cabernet Sauvignon of NS–W and Cabernet Gernischt of NS–E can be utilized for an effective strategy. Moreover, the optimal combination planting choices with cultivars would improve wine quality by increasing pigment concentrations linked to the color and antioxidant potential.

Leaf removal effects on light absorption in virtual Riesling canopies (Vitis vinifera)

AbstractLeaf removal is a standard vineyard management technique to influence grape composition or to reduce disease pressure; however, the timing and intensity of leaf removal is a widely discussed issue. The interplay of different goals and effects over time does not make experimental studies any easier. To gain insight into positive and negative consequences of leaf removal on grapevine development, a first step can be to study how leaf removal affects the canopy’s light absorption using a dynamic model approach. Functional–structural plant models combine canopy architecture with physiological processes and allow analysing canopy interaction with the environment with great topological detail. The functional–structural plant model Virtual Riesling simulates Riesling vines in a vineyard set-up depending on temperature and plant management. We implemented leaf removal and applied this method in or above the bunch zone to compare the light absorption in canopies. Leaf removal in the bunch zone led to greater loss of absorbed light, but canopies of both scenarios could compensate for most of the loss during the simulation time frame. Compensation was mainly driven by lateral leaves closing the gaps induced by leaf removal and by leaves in the proximity of the leaf removal zones, re-exposed to light. Results showed similar effects as observed in in vivo studies; hence, we suggest extending these simulations to investigate other effects linked to light distribution such as berry sunburn. Simple modifications of implemented leaf removal techniques also allow for testing different application scopes and their impact on canopy light absorption.

Leaf Removal Applied to a Sprawling Canopy to Regulate Fruit Ripening in Cabernet Sauvignon.

Under the effects of climate change, it is becoming increasingly common to observe excessively fast grape sugar accumulation while phenolic and flavour development are lagging behind. The aim of this research was to quantify the impacts of three different leaf removal techniques on the canopy architecture and ripening of Cabernet Sauvignon trained in a sprawl trellis system. Treatments were performed at veraison (~14 °Brix) and included (i) control; (ii) leaf plucking in the bunch zone; (iii) leaf plucking the top two-thirds of shoots, apical to the bunches; and (iv) shoot trimming. On the date of harvest, no significant difference in total soluble solids was observed between treatments. Other results including the effect of the treatments on fruit acidity, anthocyanins, phenolics, and tannins were somewhat inconclusive. While various other studies have shown the potential of leaf removal to achieve slower grape sugar accumulation without affecting the concentration of anthocyanins, phenolics, and tannins, the results of this study do not indicate a decrease in the rate of grape sugar accumulation as a result of the investigated defoliation techniques. Given the cost of implementing these treatments, the results of this study do not support the use of these methods for the purpose of delaying fruit ripening in a hot Australian climate.

UAV and ground-based imagery analysis detects canopy structure changes after canopy management applications

Aim: To analyse unmanned aerial vehicle (UAV)-based imagery to assess canopy structural changes after the application of different canopy management practices in the vineyard.Methods and results: Four different canopy management practices: i–ii) leaf removal within the bunch zone (eastern side/both eastern and western sides), iii) bunch thinning and iv) shoot trimming were applied to grapevines at veraison, in a commercial Cabernet-Sauvignon vineyard in McLaren Vale, South Australia. UAV-based imagery captures were taken: i) before the canopy treatments, ii) after the treatments and iii) at harvest to assess the treatment outcomes. Canopy volume, projected canopy area and normalized difference vegetation index (NDVI) were derived from the analysis of RGB and multispectral imagery collected using the UAV. Plant area index (PAI) was calculated using the smartphone app VitiCanopy as a ground-based measurement for comparison with UAV-derived measurements. Results showed that all three types of UAV-based measurements detected changes in the canopy structure after the application of canopy management practices, except for the bunch thinning treatment. As expected, ground-based PAI was the only technique to effectively detect internal canopy structure changes caused by bunch thinning. Canopy volume and PAI were found to better detect variations in canopy structure compared to NDVI and projected canopy area. The latter were negatively affected by the interference of the trimmed shoots left on the ground.Conclusions: UAV-based tools can provide accurate assessments to some canopy management outcomes at the vineyard scale. Among different UAV-based measurements, canopy volume was more sensitive to changes in canopy structure, compared to NDVI and projected canopy area, and demonstrated a greater potential to assess the outcomes of a range of canopy management practices. Significance and impact of the study: Canopy management practices are widely applied to regulate canopy growth, improve grape quality and reduce disease pressure in the bunch zone. Being able to detect major changes in canopy structure, with some limitations when the practice affects the internal structure (i.e., bunch thinning), UAV-based imagery analysis can be used to measure the outcome of common canopy management practices and it can improve the efficiency of vineyard management.

Recent advancements in understanding the terroir effect on aromas in grapes and wines

Terroir is about the link between wine and its origin. It has long been understood by sensory evaluation that the taste of wine from a given variety can be related to its origins. Specific organoleptic characteristics of wine are influenced by environmental factors such as soil and climate. By deconstructing the effect of measurable soil and climate parameters on grape and wine aroma compounds, the terroir effect on wine typicity can be better understood. Climate influences on vine development and grape ripening are mainly associated with temperature, radiation and rainfall, while soil influences are primarily associated with water availability and nitrogen supply. Significant advances have been made over recent years in understanding wine aromas and their molecular basis and influences of climate and soil on a wide range of molecules responsible for wine aroma expression. This article aims to review these recent research advances to obtain a more comprehensive understanding of how terroir influences wine typicity. The effect of terroir on wine quality and typicity is sometimes considered intangible and difficult to explain on a scientific basis. By combining agronomic, analytical and sensory approaches, however, this review shows that the terroir effect is mediated by measurable factors that can easily be monitored in the vineyard. Assessment of the results compiled by this review allows the suggestion that terroir expression at specific sites might be maximized by choosing appropriate plant material in relation to soil and climate, by acting on manageable parameters like vine water and nitrogen status, or by implementing canopy management to modify microclimate in the bunch zone.

Evaluation of South African Chenin Blanc Wines Made From Six Different Trellising Systems Using a Chemical and Sensorial Approach

There are many ways of manipulating the components of grape berries and one of these is the implementation of a specific trellising system. This will affect light exposure in the bunch zone, air flow through the canopy, crop load, etc., and consequently the primary metabolites that contribute to the production of secondary compounds in wine. The aim of the present study was to characterise the grape musts and wines of Chenin blanc made from grapes of different trellising systems, using chemical fingerprinting of the samples and the check-all-that-apply method, combined with a quality scoring test. The results indicate that, while the wines could not be separated according to treatment from an aroma point of view, the grapes produced by different trellis systems resulted in wines characterised by differences in taste and mouthfeel. The present study shows that trellising systems can influence amino acids, yeast assimilable nitrogen, phenolic content and aroma compounds, as well as sensory characteristics. In this case study, wine quality was not affected by the trellising systems, with one exception. Fingerprinting using high-resolution mass spectrometry proved to be a successful tool to separate the samples according to the systems.

Berry primary and secondary metabolites in response to sunlight and temperature in the grapevine fruit zone

The chemical composition of berries at harvest, which will affect wine styles, is determined by complex physiological processes occurring from set through the fruit’s lifetime to maturity, and this is closely intertwined with environmental and crop management factors. Among those factors, climatic conditions within the fruit zone (i.e. microclimate), such as light and temperature, are well-known to affect the physiology of the fruit at the skin, pulp and seed levels. This article will present the potential of leaf thinning in the bunch zone to modify cluster microclimate and berry composition.

Bunch Microclimate Affects Carotenoids Evolution in cv. Nebbiolo (V. vinifera L.)

This study investigates the impact of bunch microclimate on the evolution of some relevant carotenoids in Nebbiolo grapes. Four bunch-zone microclimates, defined by different vineyard aspect and vine vigor, were characterized by radiation and temperature indices. Berry samples were collected from green phase up to harvest, during two consecutive seasons and carotenoid determination was assessed by High-Performance Liquid Chromatography (HPLC). High carotenoid concentrations were highlighted in Nebbiolo. Lutein and neoxanthin contents (μg berry−1) varied similarly in both seasons achieving a concentration peak after veraison especially in the cooler plots while a variety effect on the lutein seasonal trend was presumed. Conversely, β-carotene content remained generally constant during ripening, with the exception of the south plots showing dissimilar evolution between the seasons. Furthermore, higher temperature in the less vigorous and south facing vineyards led to lower amounts of carotenoids, both during ripening and at harvest. Bunch zone temperature and light condition may affect both synthesis and degradation of grape carotenoids determining their amount and profile at harvest. These findings add further knowledge about the influence of climate changes on grape aroma precursors, and are useful to adapt cultural strategies and preserve grape quality consequently.

Grape Flavonoid Evolution and Composition Under Altered Light and Temperature Conditions in Cabernet Sauvignon (Vitis vinifera L.).

The evolution of flavonoids under altered temperature and light conditions in the fruit zone was followed in Cabernet Sauvignon (Vitis vinifera L.) grapes during ripening. The study was conducted over two consecutive seasons in 2010/2011 and 2011/2012 comprising two main treatments in which the light quantity was manipulated in the bunch zone: (1) standard (STD) with no lateral shoot or leaf removal and (2) leaf removal west (LRW) treatment with leaf removal on the western side of the bunch zone. Furthermore, the light quality was altered by installing ultraviolet B-suppression sheets within the bunch zone in both seasons. Tannin evolution was dependent on the prevailing light quality/quantity and temperatures during berry development in a particular season. Grape seed tannin accumulation coincided with seed development and commenced at the early stages of berry development. Seed proanthocyanidin composition was not influenced by the treatments. The largest impact on proanthocyanidin accumulation and structure in the skin was due to seasonal variations highlighting the complex interaction between light quality and/or quantity across the two growing seasons and eventually the complex interaction with temperature. Flavonol accumulation was significantly influenced by the light quality, which is known to be the main abiotic driver of flavonol biosynthesis regulation. Anthocyanin concentration and content were largely dependent on the temperature and light quality in a particular season. Anthocyanin composition was altered by the season rather than the treatment.

Defoliation of the vines before or after berry set: Physiological consequences and qualitative factors

Defoliation of the vines consists of eliminating the leaves in the grape bunch zone in a more or less intensive manner. It is a long-proven prophylactic technique that has seen a renewed interest in the current context of the reduction of phytosanitary inputs. However, several questions remain. Which is the optimal period? What is the ideal intensity? What are the risks? Is the mechanization of this process a feasible option? Agroscope has been undertaking defoliation trials in Switzerland since 2010 in order to shed light on these questions.

Development of a method for measuring oil content in oil palm mesocarp using a single-outlet piston press: a feasibility study

In this paper, we proposed a mechanical extraction method using a newly designed single-outlet piston press for measuring oil content in oil palm mesocarp. The aim of this study was to evaluate the feasibility of the proposed method, which was expected to help facilitate and fulfill the development of other methods for assessing oil palm ripeness and, in some scenarios, to be directly used at oil palm trading sites. The six steps of the proposed method include sampling, drying, shredding, digesting, pressing, and interpreting. A prototype of a single-outlet piston press was constructed and integrated with other equipment to form a prototype of a measurement system. The effects of two factors, including bunch zone and sample form, were studied. Bunch zones were equatorial zone and apical zone, while sample forms were chopped mesocarp and capillaceous mesocarp. A full factorial design of experiments having four treatments was used in the study. For each treatment, we established a calibration equation that related the oil content measured by using the proposed method to the oil content measured by using a standard soxhlet extraction method. The study revealed that only the factor of sample form significantly affected the calibration equation. It suggested that higher measurement precision could be achieved by using capillaceous mesocarp. In this case, the maximum standard deviation of the predicted oil content within the range of predicted value from 50 to 82% was calculated to be 2.66%, which was approximately 3.2% of the maximum predicted value in the studied range.

The influence of temperature and solar radiation on phenols in berry skin and maturity parameters of Vitis vinifera L. cv. Riesling

Aim: This research was undertaken in the context of climate change and understanding how rising temperatures may interact with viticultural practices, used to manage fruit exposure in Riesling. An experimental system was designed to passively warm the bunch zone and separate the factors, heat and indirect heat by solar radiation.Methods and results: Field experiments were conducted in 2016 and 2017 at an experimental site located near Rüdesheim in Germany. To increase bunch exposure compared to non-defoliated controls (CON), around 75% of the leaves were removed manually from the bunch zone in an early defoliation treatment at pea size (DEF_E; E-L 31) and later defoliation at véraison (DEF_L, E-L 35). An open heating system (OHS) was installed from pea size stage (E-L 31) onwards. Temperature, light penetration and canopy characterization were determined. Maturity measurements included determination of berry fresh weight, total soluble solids, available primary amino acids (N-OPA), pH, titratable acid and organic acids. For determination of the phenols, berry skin was freeze dried, extracted and analysed by HPLC-PDA.Compared to the same position in the control vine rows, the temperature was more than 10 °C warmer inside the chamber, around 5 °C warmer at the opening of the chamber and at the upper end of the bunch zone, up to 3 °C warmer on a day with high solar radiation. On overcast days there was no temperature difference between these treatments.The OHS treatment affected the ratio of malic and tartaric acid as well as the ratio of glucose and fructose, and produced smaller berries compared to both CON and DEF treatments. Phenols (flavanols, hydroxycinnamic acids, flavonols) in the berry skin were mostly affected by the defoliation. In both years, DEF_E had the highest amount of phenols, followed by the DEF_L. In 2016 OHS had nearly the same concentration of phenols compared to CON. In 2017, the concentrations of phenols were higher in OHS compared to CON.Conclusion: Under future scenarios of increasing temperature conditions, strong changes will be expected for berry maturity parameters. It was found that using an experimental setup to passively heat the bunch zone, malic acid was reduced, smaller berries were produced, and the glucose/fructose ratio changed. For the defoliation treatments, phenol concentrations in berry skin were strongly affected by defoliation and to a lesser extent by higher temperature. Basic maturity parameters were relatively unaffected by defoliation.Significance and impact of the study: Riesling is known for its fruity character and the importance of the sweetness and acidity balance for determining wine style. Under warmer temperature conditions the acidity content will decrease through faster malic acid respiration, impacting the wine´s profile. Higher phenol content could lead to an astringent taste and together with higher protein content, may provide a risk of haze in wine. Neither effect is desirable. In this study, increased bunch exposure following defoliation had a greater effect than temperature alone on phenols. Therefore, the vineyard and canopy management practice will need to be adapted.

Delaying berry ripening of Bobal and Tempranillo grapevines by late leaf removal in a semi-arid and temperate-warm climate under different water regimes

Background and Aims Climate change is advancing grape ripening and decoupling sugar and phenolic maturity, impacting wine typicity. The aim of this study was to test whether late leaf removal (LLR) under different watering regimes delayed harvest of two Spanish red cultivars in a semi‐arid and temperate‐warm climate. Methods and Results In two trials carried out in eastern Spain with the Bobal and Tempranillo cultivars, vines were partially defoliated above the bunch zone shortly before veraison under rainfed and deficit irrigation conditions during two seasons. The rate of grape ripening in both cultivars was significantly affected by LLR under either watering regime, consequently delaying harvest. Vine water status and leaf photosynthetic rate were improved by LLR. The reduction in leaf area‐to‐fruit ratio resulting from the LLR treatments was found to be more limiting for the accumulation of anthocyanin than for TSS. Consequently, LLR negatively affected wine colour intensity. In addition, yield was constrained by LLR in Tempranillo due to a reduction in bunch and berry mass. Conclusions The reduction in the rate of accumulation of grape TSS provoked by LLR did not necessarily result in a more balanced berry maturity. The effectiveness of the LLR technique appears to depend on its final impact on leaf area‐to‐fruit ratio and vine water status, the cultivar photosynthetic compensation capacity and the environmental conditions. Significance of the Study Late leaf removal might not be effective for coupling anthocyanin and TSS in berries under moderate water stress conditions, given the observed reductions in red wine colour.

Row Orientation and Defoliation Effects on Grape Composition ofVitis viniferaL. Agiorgitiko in Nemea (Greece)

Vineyard row orientation and canopy side exert a significant role in determining grape microclimate. The latter can be further manipulated by selective defoliation in the bunch zone. The aim of this study was to investigate the combined effects of row orientation and basal leaf removal on grape ripening of Vitis vinifera L. cv. Agiorgitiko in Nemea, Southern Greece. The experiment was conducted in 2017, on two adjacent vineyard blocks planted in 1990 on a flat site with two row orientations, North-South and East-West. Both blocks were grafted onto 41B rootstock and trained on a double cordon vertical trellis with uniform vineyard operations. Defoliation treatments included full leaf removal in the bunch zone performed at berry set and a non defoliated control, replicated three times in both blocks. Grapes were sampled at three time points from veraison to harvest from all canopy sides (i.e. E and W on North-South oriented rows and N and S on East-West oriented rows) and defoliation treatments and were analyzed for yield components and berry chemical composition. In addition, approximately 5 kg of grapes were collected from all plots and processed according to a standard winemaking protocol. Total yield and berry mass were lowest in the W-exposed and in the defoliated grapes. Must sugar and acid content, as well as wine alcohol and acidity did not depend on either factor. Skin anthocyanins and phenolics generally increased with defoliation. Skin anthocyanins and total berry phenolics were highest for north-south oriented rows, in the grapes of the cooler canopy side (E). Wines made from grapes of the E and W canopy sides showed the highest wine color, phenolic richness and the lowest pH. No interaction between row orientation and defoliation was detected for any of the measured parameters. According to the results, the E-facing grapes on the north-south oriented rows showed generally a superior grape and wine composition for Agiorgitiko variety, under the semiarid conditions of the Nemea area.

Effect of Seasonal Canopy Management on the Performance of Chenin blanc/99 Richter Grapevines

The effect of seasonal canopy management on the performance of a Chenin blanc/99Richter vineyard with excessive vegetative growth and trained onto a Lengthened Perold trellising system, was studied. No canopy management (shoots growing in all directions) resulted in over-exposure of the bunch zone directly above the cordon, whereas sunlight reflection from the soil was drastically reduced. In contrast, canopy management led to a much more balanced penetration of sunlight into the bunch zone - here, shoot positioning played a big role. Air flow through the canopy was highest when partial defoliation, in combination with suckering and shoot positioning, was applied; these practices had the highest impact on canopy microclimate and appearance. Canopy management reduced the incidence and severity of Botrytis/sour rot - shoot positioning in particular seemed critical. Highest yields were obtained by applying shoot positioning and defoliation or topping. Although suckering was labour intensive and reduced yields, it resulted in significant labour savings for critical time-dependent actions such as pruning and harvesting. Total grape quality and wine typical flavour were improved by seasonal canopy management.