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A field experiment was carried out over three seasons on Vitis vinifera cv. Tempranillo in order to compare pre-veraison and post-veraison water restrictions on vine performance and fruit composition. Rain-fed vines were compared with a treatment named MAX that was constantly irrigated at 75 % of the estimated crop evapotranspiration (ETc). In addition, an early (pre-veraison) water deficit strategy (ED) was applied by withholding irrigation until plant water stress experienced by vines surpassed a threshold value of midday stem water potential of −1.0 MPa. After that, 75 % of ETc was applied. A late season deficit (LD) treatment was irrigated as per the MAX up to veraison, and thereafter, water application was reduced to approximately 37 % of ETc. All irrigation regimes increased vine yield up to 58 % with respect to the rain-fed treatment, and no differences in yield among the irrigated treatments occurred. However, there were differences in berry composition among the different irrigation strategies. The ED strategy was more effective than the LD one in reducing berry growth leading to more concentrated berries in terms of sugars and anthocyanins. The LD water shortage impaired berry sugar accumulation due to the detrimental effect of water stress on leaf photosynthesis. [ABSTRACT FROM AUTHOR]

'Xinomavro' (V. vinifera L.) is an important native red wine grape variety in Northern Greece, particularly in PDO (protected designation of origin) regions. Despite its significance, there is limited research on the effects of pruning type and severity on 'Xinomavro' vine physiology, yield, and berry quality across diverse environmental conditions. This study aimed to address this knowledge gap and provide growers with crucial information for optimizing vineyard management practices. The study was conducted over two consecutive years (2016 and 2017) in a vineyard in Thessaloniki, Northern Greece. Four treatments (B12: 12 buds on 6 spurs, B24: 24 buds on 12 spurs, M12: 12 buds on 2 canes, and M24: 24 buds on 4 canes) combining two bud load levels (12 or 24 count nodes) and two pruning types (short spurs or long canes) were applied to 'Xinomavro' vines in a complete block randomized design. The vine water status, gas exchange, canopy characteristics, yield components, and berry composition were measured. Bud load and pruning type significantly influenced vine canopy development, microclimate, and yield components. Short pruning with high bud load (B24) resulted in denser canopies and higher yields, whereas cane pruning (M12 and M24) led to more open canopies and improved berry quality indicators. Treatment effects on berry composition were inconsistent across years but showed a tendency for higher anthocyanin and total phenol content in cane-pruned vines. This study demonstrates that pruning type (short or long fruiting units) may have a greater impact on vine growth, yield, and berry composition than bud load alone in 'Xinomavro' vines. Cane pruning appears to be a more effective strategy for achieving vine balance and potentially improving grape quality under given experimental conditions. [ABSTRACT FROM AUTHOR]

Grapevine adaptation to drought involves morphological, anatomical, and physiological modifications that could be viewed as a measure of drought avoidance. The main vine responses to drought consist of the regulation of carbon assimilation as a consequence of limited stomatal conductance, which is reflected in changes in plant water status. In this factorial study (2020–2021 growing seasons), two red cultivars, the local 'Aglianico', widely grown in Central-South Italy, and the international 'Cabernet Sauvignon', were used to evaluate how their interaction in three different environments can modify physiological adaptations and how yields and their qualitative traits can be modified. The lowest leaf water potential (−0.68 Mpa) for the two cultivars was registered in Molise, while the most stressed vine was found in Sicily for Aglianico (−1.86 MPa). At least in two of three locations, Molise and Campania, the detected stomatal conductance and the leaf water potential have shown that Cabernet Sauvignon can be classified as a near-isohydric cultivar, whereas Aglianico can be categorized as a near-anisohydric cultivar. The interactions between genotype x environment highlight different levels of adaptability between the two cultivars in different sites during each season. The data presented here contribute to a better understanding of the effects of genotype and environment interactions in progressive dry cultivation and how these interactions can modify the qualitative traits of grapes. [ABSTRACT FROM AUTHOR]

The cultivated grapevine, Vitis vinifera subsp. vinifera, possesses a rich biodiversity with numerous varieties. Each variety adapts differently to varying pedoclimatic conditions, which greatly influence the terroir expression of wine regions. These conditions impact vine growth, physiology, and berry composition, ultimately shaping the unique characteristics and typicity of the wines produced. Nowadays, the potential of the different adaptation capacities of grape varieties has not yet been thoroughly investigated. We addressed this issue by studying two grape varieties, Aglianico and Cabernet Sauvignon, in two different pedoclimatic conditions of Southern Italy. We evaluated and compared the effect of different pedoclimatic conditions on plant physiology, the microbial quality of grapes using Next-Generation Sequencing (NGS) technology, the expression trends of key genes in ripe berries and the concentration of phenolic compounds in grapes and wines by HPLC-MS, HPLC-DAD, NMR and spectrophotometric analyses. Metabolomic and microbiome data were integrated with quantitative gene expression analyses to examine varietal differences and plasticity of genes involved in important oenological pathways. The data collected showed that the phenotypic response of studied grapes in terms of vigor, production, and fruit quality is strongly influenced by the pedoclimatic conditions and, in particular, by soil physical properties. Furthermore, Aglianico grape variety was more influenced than the Cabernet Sauvignon by environmental conditions. In conclusion, the obtained findings not only reinforce the terroir concept and our comprehension of grape's ability to adapt to climate variations but can also have implications for the future usage of grape genetic resources. [ABSTRACT FROM AUTHOR]

Summer pruning encompasses a series of operations typically performed on the grapevine during the growing season. This review provides an update on the research conducted over the last 20 years on the modalities and strategies of main summer pruning operations, which include shoot positioning and thinning, shoot trimming, leaf removal, and cluster thinning, with a special focus on their adaptation to climate change occurring in Mediterranean areas. Three main novelties emerged from the survey. First, due to a common need to shelter clusters against overheating and sunburn-related damages, shoot thinning and leaf removal are practices that are now being applied in a much more cautious and conservative manner. Second, the meaning of summer pruning is evolving because operations are being used as precious tools to direct ripening toward a desired direction rather than being received passively. Third, some operations, such as leaf removal, have disclosed very high plasticity, which means that, depending on the timing and modalities of the intervention, yield can be either increased or decreased and ripening anticipated or postponed. In an era where economic and environmental sustainability have to find a good compromise, cluster thinning is increasingly being depicted as an extraordinary operation that should be left to occasional occurrences of overcropping. Moreover, summer pruning is a tool through which growers can, to an extent, exploit the potentialities offered by climate change. For instance, the crop-forcing technique, under the different configurations of single and double cropping within the same season, has been trialed promisingly in several regions and cultivars. The principle of forcing is to unlock the dormant bud during the first year by removing at least the young organs present on the shoot within a time window between the end of the flowering and pea-size stages. In particular, when it is applied in a double-cropping mode, the preliminary results related to Pinot noir, Grenache, Tempranillo, and Maturana tinta indicate that two harvests separated by 30-50 days can be obtained, with the latter having superior quality in terms of a lower level of pH and higher levels of acidity, anthocyanins, and phenolics. [ABSTRACT FROM AUTHOR]

Several studies have revealed that fruit-zone leaf removal could change the microclimate of grapevine growth, thereby causing complex effects on fruit composition. This study analyzed the profiles of volatiles in Cabernet Sauvignon (Vitis vinifera L.) grapes exposed to leaf removal treatment at different phenological periods in three continuous years. The treatments (leaf removal before flowering, after flowering, and veraison) were applied to Cabernet Sauvignon grapevines grown in Yantai (Shandong, China). Berry samples were harvested at maturation to determine the chemical composition, including total soluble solids, phenols, and volatiles. Leaf removal (particularly before flowering) could increase total soluble solids and phenols (anthocyanins, flavonols, and tartaric esters). Volatiles greatly changed in the different years, and leaf removal before flowering could increase the concentration of amino acid-derived volatiles and isoprene-derived volatiles compared with leaf removal after flowering or at veraison. This research provides a basis for further studies on optimizing Cabernet Sauvignon aroma and breeding in vineyards. [ABSTRACT FROM AUTHOR]

Elevated temperatures during berry ripening are detrimental to grape quality. The crop forcing technique (summer pruning that 'forces' the vine to start a new cycle) increases must acidity and malic acid concentration at harvest by delaying the date of veraison. However, little information is available on the sensitivity to water stress of forced vines. A 3-year trial was conducted to test three irrigation strategies in forced vines: a minimum threshold of mid-day stem water potential (Ψs) of −0.75 MPa before forcing (DI), a minimum Ψs threshold of −1.2 MPa only after veraison (RDI), and the combination of both treatments (DI + RDI). Results were compared to a non-forced treatment with a minimum Ψs threshold of −1.2 MPa after veraison (C-RDI). Must acidity increased, and pH decreased in the forced treatments. However, yield was reduced by 35% and irrigation requirements increased by 20% when comparing forced and unforced treatments. As a result, water use efficiency was reduced in forced treatments. Only after a dry spring did the, DI (11%) and DI + RDI (30%) treatments, save water compared to the C-RDI treatment. Moreover, although Ψs before forcing never fell below −0.75 MPa, a significant negative correlation (R2 = 0.76) was found between the integral of water stress before the vines were forced and the number of forced bunches per vine. Post-veraison water stress in forced vines reduced the polyphenol content of the wine. Our findings suggest that forced vines are extremely sensitive to even mild water stress. [ABSTRACT FROM AUTHOR]

The size and number of the berries and the rachis length are the main elements that define bunch compactness in grapevine (Vitis vinifera L.). This trait is of scientific and commercial interest because it strongly influences phytosanitary status and quality of the fruits. In this work, we investigated the effect of different canopy management strategies based on apical shoot and/or leaf removal applied at the early stage (pre-bloom) in altering the key determinants of bunch compactness. Specifically, we compared apical defoliation (removal of the first half of the shoot leaves from the top), basal defoliation (removal of the second half), and shoot trimming (removal of the apical half of the shoot) to untreated controls. The work was carried out in two red varieties ('Aglianico' and 'Casavecchia') that have contrasting bunch compactness (compact and loose, respectively). We measured relevant morphological traits, photosynthetic rates, fertility, fruit set, bunch architecture, and fruit main compositional parameters. This study demonstrates that the position of the removed shoot leaves along with the shoot trimming differentially modified fruit set, the number of berries per bunch, and berry fresh weight and composition at harvest. Nonetheless, the influence on bunch compactness was limited mainly because of photosynthetic and morphological factors strongly associated with the cultivar. [ABSTRACT FROM AUTHOR]

Background: Climate change results in warmer air temperatures and an uncertain amount and distribution of annual precipitations, which will directly impact rainfed crops, such as the grapevine. Traditionally, ancient autochthones grapevine varieties have been substituted by modern ones with higher productivity. However, this homogenization of genotypes reduces the genetic diversity of vineyards which could make their ability to adapt to challenges imposed by future climate conditions difficult. Therefore, this work aimed to assess the response of four ancient grapevine varieties to high temperatures under different water availabilities, focusing on plant water relations, grape technological and phenolic maturity, and the antioxidant capacity of the must. Methods: The study was conducted on fruit-bearing cuttings grown in pots in temperature-gradient greenhouses. A two-factorial design was established where two temperature regimes, ambient and elevated (ambient + 4 °C), were combined with two water regimes, full irrigation and post-veraison deficit irrigation, during fruit ripening. Results: There were significant differences among the ancient varieties regarding plant water relations and fruit quality. Conclusion: This research underlines the importance of evaluating the behavior of ancient grapevine varieties that could offer good options for the adaptation of viticulture to future climate conditions. [ABSTRACT FROM AUTHOR]

Climate change scenarios are predicting an increase in temperature as well as more scarce and torrential rainfall episodes. Due to this, an imbalance between grape technological and phenolic maturity is being observed, which detrimentally affects the grapes' composition. In semi-arid areas, irrigation management is a main field practice used to influence grape ripening. The goal of the present study was to investigate the influence of vine irrigation on the aroma composition and sensory characteristics of La Mancha Chelva wines. Volatile compounds were studied by gas chromatography–mass spectrometry (GC/MS). A total of 75 aroma compounds were identified and quantified in Chelva wines elaborated with grapes of irrigated and non-irrigated vines. The results show that the application of irrigation during vine cultivation produced small changes in the concentration of wine volatile compounds. Nevertheless, it increased, in general, the intensity of the attributes of the main aroma sensory profile of the wines. According to the results, the vine irrigation of Chelva cultivated in the La Mancha region can be used as a method to increase the aroma of wines. [ABSTRACT FROM AUTHOR]

Xylem vessels are essential pivotal organs in bulk hydraulic flow through the whole woody plant. However, environmental constraints generate disagreements in xylem structures, which are characterized by air emboli and occlusions formations, compromising water conductivity in grapevines. The aim of this work was to explore xylem morphology dynamics through the xylem sap flow of five Tunisian grapevine cultivars during the natural bleeding sap periods of 2019, 2021, and 2022. In fact, Sakasly, Khamri, Hencha, Razegui1, and Razegui2 rain-fed grapevine cultivars revealed differential responses towards xylem sap movement. The results demonstrated that the xylem sap flow was significantly more abundant in 2019 than 2021 and 2022 bleeding sap campaigns. A variation was revealed between the cultivars regarding the xylem sap flow. In fact, Sakasly gave the best xylem flow during the three campaigns. Razegui1 and Razegui2 registered approximately similar xylem sap flow, while Hencha and Khamri present the lowest sap fluxes during the three campaigns. Moreover, several vascular occlusions forms were identified from stem cross sections using environmental scanning electron microscopy (ESEM), including tyloses, gels, starch, and gum deposits. The highest occlusion number was observed in Sakasly, Razegui1, and Razegui2 cultivars. Among different biogenic calcium shapes, several were observed for the first time in grapevine, including multi-faceted druse, cubic, crystalline sand, styloids, spherical, or drop-like structures. Considering their lower flow and totally blocked vessels, both Hencha and Khamri confirmed their susceptibility to environmental constraints. However, Sakasly, Razegui1, and Razegui2 cultivars presented higher tolerance according to their sap flow and xylem morphology. [ABSTRACT FROM AUTHOR]

This study aims to analyze the effects of non-limiting irrigation (I) vs. rainfed (R) through two different shoot densities, high-load (H) and low-load (L), on vegetative growth, agronomic parameters, flavonoid and non-flavonoid polyphenol substances of cv. Tempranillo grown in a semi-arid climate during three consecutive seasons (2014–2016). Under these conditions, in the 2015 and 2016 seasons, irrigation showed significant increases in berry weight (14.7% and 13.4% in H and L, respectively, in 2015, and 35.6% and 23.5% in the same treatments in 2016) and yield (66.7% and 48.5 in 2015; 27.9% and 177.5% in 2016). Additionally, a general decreasing trend is observed in anthocyanins with the exception of peonidin derivates, almost all flavonol compounds, cinnamic acid and resveratrol values with different degrees and statistical significance depending on the shoot density of the vines. A slight variation is observed in 2014 in these parameters. On the other hand, no general trends are established either in flavanol compounds or hydroxybenzoic acid. Thus, the effect of irrigation depends on the parameter considered, the shoot density of the vine and the season considered. [ABSTRACT FROM AUTHOR]

BACKGROUND In monsoonal climates, grape anthocyanin and proanthocyanidin (PA) accumulations are unsatisfactory for producing optimal wine. Agronomical practices are often considered to be effective means for regulating fruit components. However, there is a lack of quantitative information on the effects of deficit irrigation (DI), basal leaf removal (LR) or their combination of deficit irrigation and leaf removal (DILR) on the characteristics of anthocyanin and PA compositions and their implications on the resulting wine quality. In this study, the dynamics of grape anthocyanin and PA accumulation were investigated in DI, LR and DILR during grape ripening, and the resulting wine profile was assessed. RESULTS: The contents of reducing sugar and total anthocyanins in Cabernet Sauvignon berries were significantly increased by DI, LR and DILR, while titratable acidity, total flavan‐3‐ols and tannins levels were generally decreased. Notably, the levels of 3′5′‐substituted anthocyanins, such as malvidin and its derivatives significantly increased, and 3′‐substituted anthocyanins decreased in both grape and wine under DI and DILR strategies. Skin PAs were sensitive to water deficits, whereas they were insensitive to LR. In resulting wine, PAs content and the proportion of 3′‐hydroxylated PAs, such as (+)‐catechin, (−)‐epicatechin and (−)‐epicatechin‐3‐O‐gallate units were significantly decreased under DI and DILR, while molecular mass and the proportion of 3′5′‐hydroxylated units of PAs were increased in response to DILR. CONCLUSION: The DILR was the most favorable for the repartitioning of anthocyanin and PA metabolites, and promoted the accumulation of tri‐substituted forms contributing a higher color intensity, mouthfeel persistence, structure, and astringency of wine. This information provides an important strategy for modulating the anthocyanin and PA compositions by agricultural practices and achieving the desired quality of grapes and wines in monsoonal climates. © 2021 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Bunch rot is a fungal disease and causes significant yield loses to grapes yield every year. Fruit Zone Leaf Removal (FZLR) is a canopy management technique that provides a cost-effective and high-quality grape yield. In order to boost grape quality and minimize disease incidence in the King's Ruby variety, FZLR was used for two seasons in a row. Total leaf removal was used before bloom, during full bloom, and four weeks after bloom, and was compared to an untreated control (non-defoliated). In all leaf removal treatments, titratable acidity and bunch rot incidence decreased significantly, while total soluble solids, total phenolic content, total sugars, and reducing sugars increased significantly when compared to regulation. In comparison to the other treatments, the growth of lateral shoots was significantly higher in the control. At bloom and four weeks after bloom, FZLR increased the fruit's quality attributes. The proper penetration of light and air in the plants, as a result of leaf removal, decreases the occurrence and severity of bunch rot to less than 5%. This method is extremely useful for maintaining grape quality and quantity without the use of chemicals to combat disease. As a result, this strategy is both environmentally and health-friendly. In Pakistan, we consider using leaf removal therapy to treat grape bunch rot disease because it is the least expensive. [ABSTRACT FROM AUTHOR]

BACKGROUND Small berry size is normally associated with quality wine production. However, the contribution of grapevine variety and environment to sensory quality has not been well established. In this study, genotypes from two intra‐specific hybrid populations were categorized by size according to berry diameter and weight: small (< 13.5 mm, <1.5 g), and large (>16 mm, >2 g). Chemical and sensory attributes of wines produced in two consecutive vintages (2017 and 2018) from each size category were characterized. Perceived intrinsic wine quality was judged by 20 wine professionals. RESULTS: Wines obtained from small berry genotypes consistently displayed higher proportions of phenolic compounds and deeper color and were judged higher in quality regardless of genetic background and vintage. Perceived quality was positively correlated with anthocyanin and phenolic content. Wines presented high sensory variability in both vintages. Small berry size genotypes produced sweeter, fruitier wines with greater astringency; whereas wines from larger berries were perceived as more alcoholic and with lower positive aroma intensities. Berry size influenced color and phenolic compounds more than genotype or environment. CONCLUSION: Small berry‐size genotypes were related to high quality judgements in both years, thus providing a predictor of wine categories, which could be used to meet different market demands. © 2020 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Optimal water supply is one of the most important factors in quality wine making. However, water availability is limited in several wine regions and water shortage is getting even worse due to climate change, especially under arid climate conditions. Therefore, proper water management of the vineyards, the amount and the timing of irrigation will play a crucial role in sustainable viticulture in the near future. In this study, the effect of timing of moderate water deficit on berry texture characteristics and phenolic maturity were investigated. 'Kékfrankos' grapevines were submitted to different water regimes: moderate water deficit from berry set until veraison (WD1), moderate water deficit from veraison until harvest (WD2), no water deficit (C). Concentration of the phenolic components of the grape berry skins and berry mixture for the Glories indices were measured by spectrophotometer (UVmini-1240 CE UV-VIS, Shimadzu, Japan). Cell and seed maturity indices (CMI%, SMI%) were also calculated. Berry texture characteristics were monitored by a TA.XT Plus Texture Analyser (Stable Micro System, UK). Berry skin and seed texture properties were affected by water regimes. Skin and seed hardness of WD1 were significantly lower than those of WD2. Significant differences were found in berry hardness between the treatments (C>WD1>WD2). Berry gumminess, resilience and chewiness of WD2 were lower compared to C and WD1. Anthocyanin extractability was higher when plants were not subjected to post-veraison water limitations (WD1). Furthermore, the seed maturity index was lower when water deficit occurred between berry set and veraison. Pre-veraison water deficit resulted in delayed ripening, softer seeds and thus higher phenol extractability compared to WD2 and C. Late seasonal water deficit resulted in thicker skins, which was accompanied by lower anthocyanin extractability than in WD1 and C. It seems that anthocyanin extractability is influenced by the actual water status of the grapevine rather than skin textural properties. However, there are some connections between skin texture parameters and maturity indices. [ABSTRACT FROM AUTHOR]

Water availability is arguably the most important environmental factor limiting crop growth and productivity. Erratic precipitation patterns and increased temperatures resulting from climate change will likely make drought events more frequent in many regions, increasing the demand on freshwater resources and creating major challenges for agriculture. Addressing these challenges through increased irrigation is not always a sustainable solution so there is a growing need to identify and/or breed drought-tolerant crop varieties in order to maintain sustainability in the context of climate change. Grapevine (Vitis vinifera), a major fruit crop of economic importance, has emerged as a model perennial fruit crop for the study of drought tolerance. This review synthesizes the most recent results on grapevine drought responses, the impact of water deficit on fruit yield and composition, and the identification of drought-tolerant varieties. Given the existing gaps in our knowledge of the mechanisms underlying grapevine drought responses, we aim to answer the following question: how can we move towards a more integrative definition of grapevine drought tolerance? [ABSTRACT FROM AUTHOR]

The relationships between differences in plant water status, induced by spatial variability in soil texture, and the changes in berry and wine composition were investigated in an irrigated Cabernet Sauvignon (Vitis vinefera L.) vineyard for 2 years. A stratified and an equidistant grid were overlaid on the vineyard to characterize the soil texture by proximal sensing, soil sampling, and grapevine physiological and berry chemical development. Based on the mid-day stem water potential (Ψ stem ) integrals, the vineyard was divided into two functional homogenous zones: Zone 1 with higher water stress and Zone 2 with lower water. Zone 1 consistently had lower Ψ stem , net carbon assimilation, and stomatal conductance in both years. Berry weight and titratable acidity were lower in Zone 1 at harvest. Zone 2 reached 26 and 24°Bx total soluble solids (TSS) at harvest in Years 1 and 2, respectively, with higher TSS values of 30 and 27°Bx in Zone 1. Ravaz index did not vary spatially. Fruits were harvested differentially in both years and vinified separately from the two zones. In Year 1, all berry skin anthocyanin derivatives, tri-, di- hydroxylated, and total anthocyanins concentrations were higher in Zone 2. However, in Year 2, only malvidin, tri-hydroxylated, and total anthocyanins were higher in Zone 1. There were no differences in wine flavonoids in Year 2 when harvest commenced earlier. In both years, Ψ stem , berry weight, and TSS were directly related to soil bulk electrical conductivity (EC). Our results indicated vineyard variability stemmed from soil texture that affected long-term plant water status which does not affect spatial variability of Ravaz Index. In conclusion, our work provides fundamental knowledge about the applicability of soil bulk EC sensing in the vineyards, and its potential directional utilization by connecting proximal soil sensing to spatial distribution of whole-plant physiological performance together with berry and wine chemistry. [ABSTRACT FROM AUTHOR]

Western Carpathians are historically the northern range traditional grapevine growing areas since the Middle Ages. The mean anual temperature has increased by about 1.1oC during the last century in Slovakia. Elevated temperature impacted the growing conditions of grapevine. Together with the increased temperatures, higher frequency of drought periods and parameters are evident. Traditional grape producing areas are facing new challenges. Except for the accelerated grapevine phenology, pathogene infection pressure and occurence of pests including new ones, as well as the quality of grapes influencing wine quality, are changing. In order to evaluate the drought impact on the quality parameters of grapes the locality of the Cultivar Testing Station in Dolné Plachtince which belongs to the Central Slovakian grape producing region was chosen. Interanual variability of the drought impact on the grape quality was evaluated according to Palmer drought severity index (PDSI). The 1990-2014 period was used as a basis for evaluation. The period with the phenological phase crucial for the grape quality formation was determined. Two groups of cultivars with different ripening periods were selected. Pinot Gris, Muscat Ottonel Weiss, Müller Thurgau represented the early ripening cultivars (OIV earliness code 4 and 5), whereas Grüner Veltliner, Riesling, Welschriesling represented the late ripening cultivars (OIV code 8 and 9) were used. The cumulative values of PDSI for the crucial periods were calculated. The PDSI values as well as the sugar and acid contents were correlated to find the strength of relation between them. Short drought periods did not influence the grape quality significantly, while long drought periods caused a decrease of the acid content and an increase of the sugar content. Though the tendency was clear, the correlation level was mostly low. The most sensitive period in this sense was July--September; however, it was influenced by the ripening term of individual cultivars. The results suggest the necessity of a thorough approach to cultivar selection, taking into account its vitality and ability to preserve a satisfactory acid content in grapes by the harvest date. [ABSTRACT FROM AUTHOR]

Bunch compactness (or density) is a grapevine specific trait that affects the commercial quality and sanitary status of wine and tablegrapes. Compact bunches are more susceptible to diverse pests and diseases such as Botrytis bunch rot and their berries ripen more heterogeneously, causing important economic losses through a reduction in crop yield and grape and wine quality. Bunch compactness is determined by the fraction of the morphological volume of the bunch that is filled by berries, but this simple definition contrasts sharply with the difficulty to measure it. While there are several objective and quantitative methods available to measure bunch compactness, the lack of a consistent approach between researchers makes comparing measurements difficult. The complexity of bunch compactness initially arises from the several bunch and berry traits that influence it, and from the distinct effects that these traits may cause in different cultivars. In addition to this genetic effect, diverse environmental signals impact on bunch compactness by affecting those primary factors that contribute to the solid component of the bunch (berry number, berry size) or to its spatial arrangement (rachis architecture). Last, several viticultural approaches, including agronomic techniques and growth regulators, have also proven to affect bunch compactness in different ways. This review aims to discuss present knowledge about this relevant grapevine trait. [ABSTRACT FROM AUTHOR]

Background and Aims Irrigation is an important management practice in viticulture. Irrigation scheduling established by previous researchers was based mainly on the irrigation level for optimal berry composition and size at harvest. Because eventual berry size and composition depend on the accumulation of daily growth, a more precise study must be implemented to establish the soil water potential (ψsoil) threshold to trigger irrigation at different development stages of the berry. Methods and Results Photogrammetry, 13 C isotope labelling and other techniques were applied to study the relationship between ψsoil and real-time change of berry expansion, net photosynthetic rate, and the distribution of photosynthetic products in 3-year-old Kyoho grapevines. The diurnal variation of berry size presented a regular pattern, shrinking in daytime and expanding at night. Analysis of a time series model revealed a close correlation between berry growth and ψsoil. With the decline in ψsoil, berry growth presented four phases of change: high speed growth phase, rapid growth phase, slow growth phase and shrinking phase. Conclusions The optimal ψsoil threshold to trigger irrigation at different berry developmental periods was established: −10 k Pa after berry setting (berry diameter < 10 mm), −15 k Pa during berry pea size (berry diameter 10-20 mm) and −20 k Pa after veraison (berry diameter > 20 mm). Significance of the Study The established ψsoil threshold in this study has significant value for the implementation of precision irrigation, which favours normal berry expansion and composition while saving water. [ABSTRACT FROM AUTHOR]

Background and Aims Interactions are the main causes of complexity in field experiments; however, no studies have combined water and temperature regimes in field-growing vines. Here we assessed grape and wine attributes from a field trial where these factors were directly manipulated. Methods and Results The experiment consisted of Shiraz vines grown in a 22 factorial experiment with two temperature (control and heated) and two water regimes (deficit and irrigated) during two seasons (2010/11 and 2011/12). The sensory and compositional characteristics of grapes and wines were assessed in both seasons, whereas a detailed profile of the phenolic substances was determined by spectrophotometry in 2011/12. We found additive effects (i.e. lack of interaction) between temperature and water for berry mass and components, fruit composition (titratable acidity and pH), grape phenolic substances (12.5% ethanol-extracted and most of the 70% acetone-extracted), wine phenolic substances (chemical age 2), and wine sensory traits (floral aromas and berry flavours). Significantly, previously unrecorded interactions between temperature and water were found for grape phenolic substances (70% acetone-extracted skin and seed tannins and total phenolic substances per berry), wine phenolic substances (colour density, tannins and phenolic substances) and wine sensory traits (floral aromas, cooked fruit flavours and tannin structure). Conclusion The effect of water deficit leading to colourful and flavoursome wines rich in phenolic substances may not be held under high temperature. Significance of the Study Our study anticipates the drier and hotter climate of the Barossa Valley, and provides industry with indications of a shift in wine profiles that would require technological innovation to maintain the identity of Barossa Shiraz. [ABSTRACT FROM AUTHOR]

Both water deficit and elevated temperature are likely to accelerate shrivelling in Shiraz berries with consequences for fruit yield and quality. The process of shrivelling is partially related to mesocarp cell death and it has been proposed that enhancement of berry flavour and aroma also correlates with mesocarp cell death. However, the combined effects of water deficit and elevated temperature on berry shrivelling, mesocarp cell death and berry sensory traits are unknown. We tested the hypotheses that (1) the effects of water deficit and elevated temperature on the dynamics of mesocarp cell death and shrivelling are additive, and that (2) faster cell death, as driven by warming and water deficit, negatively contributes to grape sensory balance. Using open-top chambers to elevate day and night temperature, we compared heated vines against controls at ambient temperature. Thermal regimes were factorially combined with two irrigation regimes, fully irrigated and water deficit, during berry ripening. The dynamic of cell death was characterised by a bilinear model with three parameters: the onset of rapid cell death and the rate of cell death before and after the onset of rapid cell death. Statistical comparison of these three parameters indicated that there was not interaction between water and temperature on the dynamics of berry mesocarp cell death. Warming advanced the onset of cell death by ~9 days ( P = 0.0002) and water stress increased the rate of cell death in the period post onset ( P = 0.0007). Both water stress and elevated temperature increased the proportion of cell death and shrivelling at harvest. An interaction between water deficit and elevated temperature was found whereby the onset of berry net water loss was advanced by elevated temperature under water deficit but not in the fully irrigated treatment. Sensory traits typical of ripened berries were associated with higher cell death; however, warming and water deficit hastened ripening and altered the balance of berry sensory traits. [ABSTRACT FROM AUTHOR]

Compact bunches have been often associated with higher susceptibility to Botrytis cinerea and therefore reduction in berry quality in grapevine. The objective of this study was to evaluate three management methods (early leaf removal, gibberellic acid, and their combination) for reducing bunch compactness in Vitis vinifera cv. Pinot gris trained in two different training systems with contrasting vigor (Guyot and pergola). Treatments were applied at BBCH 62 or BBCH 65 and yield components, total soluble solids, fruit set, and bunch compactness parameters were evaluated. Both treatments individually reduced berry number, mean bunches weight and bunches compactness as well as yield per vine when compared to control-untreated vines. However, no major differences were observed when both the treatments were applied in combination for Guyot or pergola although a higher reduction in yield was detected for Guyot and a significant increase in total soluble solids was observed in pergola. Our study suggests that intense leaf removal and gibberellic acid applied at early flowering can help reducing bunch compactness in Pinot gris and showing it in two training systems. In particular, leaf removal represents a valuable alternative to plant growth regulators (i.e., gibberellic acid) as applicable in organic viticulture. [ABSTRACT FROM AUTHOR]

The high phenolic compound content of grapes makes them an important source of natural antioxidants, among other beneficial health properties. Vineyard irrigation might affect berry composition and quality. Regulated deficit irrigation (RDI) is a widely used strategy to reduce the possible negative impact of irrigation on grapes, improving grape composition and resulting in water savings. Monastrell grapevines (Vitis vinifera L.) grown in eastern Spain were subjected to two water regime strategies: rainfed (non-irrigation) and RDI. The content of anthocyanins, flavonols, flavanols, hydroxybenzoic and hydroxycinnamic acids, and stilbenes was determined by HPLC and was related with total phenolic content and three antioxidant activity methods (ABTS, DPPH, and ORAC). The study aimed to evaluate and compare the phenolic composition and antioxidant potential of Monastrell grapes. The rainfed regime concentrated grapes in terms of phenolic compounds. Thus, total content of anthocyanins, flavonols, flavanols, hydroxybenzoic acids, and total phenols were higher in the rainfed grapes than in the RDI ones. Besides, the rainfed grapes doubled their antioxidant potential with respect to the RDI grapes with the ORAC method. Total phenolic content and antioxidant activity by ORAC assay positively correlated with most of the total phenolic compounds analyzed. This study demonstrates how field practices can modulate final grape composition in relation to their antioxidant activity. [ABSTRACT FROM AUTHOR]

Water availability is endangering the production, quality, and economic viability of growing wine grapes worldwide. Climate change projections reveal warming and drying trends for the upcoming decades, constraining the sustainability of viticulture. In this context, a great research effort over the last years has been devoted to understanding the effects of water stress on grapevine performance. Moreover, irrigation scheduling and other management practices have been tested in order to alleviate the deleterious effects of water stress on wine production. The current manuscript provides a comprehensive overview of the advances in the research on optimizing water management in vineyards, including the use of novel technologies (modeling, remote sensing). In addition, methods for assessing vine water status are summarized. Moreover, the manuscript will focus on the interactions between grapevine water status and biotic stressors. Finally, future perspectives for research are provided. These include the performance of multifactorial studies accounting for the interrelations between water availability and other stressors, the development of a cost-effective and easy-to-use tool for assessing vine water status, and the study of less-known cultivars under different soil and climate conditions. [ABSTRACT FROM AUTHOR]

Climate changes lead to a rise in air temperature, which significantly increases the water needs of plants. Maintaining crop productivity will increasingly require the use of plant irrigation. The aim of this study was to assess the water needs of grapevines cultivated in the western provinces of Poland. The calculations were made on the basis of temperature and precipitation measurements collected at three meteorological stations in the period 1981–2010. Water needs were calculated as crop evapotranspiration, which was estimated by crop coefficients and reference evapotranspiration, determined using the Blaney–Criddle formula. The rainfall deficit was assessed by Ostromęcki's method. The tendency to increase the water needs was observed in each subsequent decade of the thirty-year period, both in the whole growing season (May–October), as well as in June–August and July. The highest values of the linear correlation coefficient for the trend of time variability in water needs occurred from June to August. An analysis of water needs and rainfall deficits indicates the need for the additional irrigation of vineyards in western Poland, especially in very dry years and in June–August. Current research results are helpful in designing vineyard irrigation systems and allow an economical and efficient planning of grapevine irrigation. [ABSTRACT FROM AUTHOR]

Efficient and accurate methods to monitor crop physiological responses help growers better understand crop physiology and improve crop productivity. In recent years, developments in unmanned aerial vehicles (UAV) and sensor technology have enabled image acquisition at very-high spectral, spatial, and temporal resolutions. However, potential applications and limitations of very-high-resolution (VHR) hyperspectral and thermal UAV imaging for characterization of plant diurnal physiology remain largely unknown, due to issues related to shadow and canopy heterogeneity. In this study, we propose a canopy zone-weighting (CZW) method to leverage the potential of VHR (≤9 cm) hyperspectral and thermal UAV imageries in estimating physiological indicators, such as stomatal conductance (Gs) and steady-state fluorescence (Fs). Diurnal flights and concurrent in-situ measurements were conducted during grapevine growing seasons in 2017 and 2018 in a vineyard in Missouri, USA. We used neural net classifier and the Canny edge detection method to extract pure vine canopy from the hyperspectral and thermal images, respectively. Then, the vine canopy was segmented into three canopy zones (sunlit, nadir, and shaded) using K-means clustering based on the canopy shadow fraction and canopy temperature. Common reflectance-based spectral indices, sun-induced chlorophyll fluorescence (SIF), and simplified canopy water stress index (siCWSI) were computed as image retrievals. Using the coefficient of determination (R2) established between the image retrievals from three canopy zones and the in-situ measurements as a weight factor, weighted image retrievals were calculated and their correlation with in-situ measurements was explored. The results showed that the most frequent and the highest correlations were found for Gs and Fs, with CZW-based Photochemical reflectance index (PRI), SIF, and siCWSI (PRICZW, SIFCZW, and siCWSICZW), respectively. When all flights combined for the given field campaign date, PRICZW, SIFCZW, and siCWSICZW significantly improved the relationship with Gs and Fs. The proposed approach takes full advantage of VHR hyperspectral and thermal UAV imageries, and suggests that the CZW method is simple yet effective in estimating Gs and Fs. [ABSTRACT FROM AUTHOR]

The influence of leaf area and various variants of manual defoliation on the phenolic profile of the Prokupac variety grape berry were investigated in the agroecological conditions of southern Serbia. The following four trial variants of manual defoliation were assessed: Early defoliation—variant I (flowering stage, 50% open flowers); early defoliation—variant II (grape size 3–5 mm); late defoliation—variant III (onset of grape ripening, veraison); and control (no defoliation). The first six leaves of each primary shoot were removed from all defoliated vines. The greatest assimilation area of primary and lateral shoots during the study was observed in the control, i.e., the trial variant with no defoliation. Defoliation significantly decreased the grape yield of the all three defoliated variants in regard to the control. The phenolic profile of the three variants and control was established by analyzing the grape seeds and skin. Based on the collected results for the Prokupac variety, significant differences between the trial variants were established regarding the content of phenols and total polyphenols, as well as radical scavenging activity. Defoliation variants showed a significant effect on the total phenols content of grape skin. In all defoliation variants, as well as in the control, high amounts of ellagic acid were measured. Resveratrol was identified only in grape skin samples of the control variant. The removal of leaves increased the concentration of phenolic compounds in variants where early defoliation was applied. The highest total anthocyanins content was found in 2015 in variant I, where leaves were removed during the full flowering stage. [ABSTRACT FROM AUTHOR]

Vitis vinifera L. has been highlighted by its many positive effects on human health, including antibacterial, anti-inflammatory and antioxidant activity due to its rich phytochemical content. Removing six basal leaves has great potential to influence the production of phytochemicals. The purpose of this study was to determine the impact of different terms of defoliation on the antioxidant and antibacterial activity of grape skin extracts of the Blaufränkisch and Merlot varieties. The total phenolic concentration, total and individual anthocyanin concentration, antioxidant activity and antibacterial activity on gram-positive and gram-negative human pathogens have been determined. The study was conducted on three treatments (control treatment without defoliation, defoliation immediately after bloom and defoliation before the start of the véraison phase). The results showed statistically significant enhancement of the total phenolic concentration as well as the antioxidant and antibacterial activity in both studied cultivars. Defoliation just after blooming was the preferable defoliation term in the Merlot variety for achieving the highest total anthocyanin concentration, antioxidant activity and significant increase of antibacterial activity against all four investigated bacteria. Defoliation before the start of the véraison phase was the preferable defoliation term for achieving the highest total anthocyanin concentration in the Blaufränkisch variety. In general, treatment of defoliation immediately after bloom was more beneficial compared with the defoliation before the start of the véraison phase. [ABSTRACT FROM AUTHOR]