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The quality traits of a given grapevine cultivar are determined by the combinatorial action of the genotype, and environmental factors such as soil, landscape, and climate. Nonetheless, another critical factor is vineyard management. The forthcoming effects of climate change on viticulture represent a challenge for the application of sustainable practices. The impact of leaf removal at berry set stage on the Greek Vitis vinifera L. cultivars ‘Agiorgitiko’ and ‘Assyrtiko’ (a red- and white-berry cultivar, respectively) was investigated during the 2019 and 2020 vintages. Vine physiology measurements and berry sampling were performed at three phenological stages: green berry, veraison and harvest. Grape berry composition and the expression level of specific genes were analysed during ripening. Defoliation decreased berry weight in Assyrtiko, while no significant effect was observed in Agiorgitiko. The treatment resulted in a significant increase in total soluble solids and reduced acidity compared to the controls in both cultivars, while the effect on total phenols mainly depended on climate conditions. The expression profile of the genes examined was also altered during ripening, whereas the response to defoliation mainly depended on the vintage and the cultivar. Taken together, the results suggest that defoliation is a useful technique for maintaining grape and wine quality.

Rootstocks serve as a strategic tool for grapevine adaptation to specific biotic and abiotic conditions and for managing vine growth, grape yield, and berry composition in commercial vineyards. This study investigates the influences of four different rootstock varieties (101-14 MGt, 3309 C, 110 R, and 140 Ru) on the viticultural performance of ‘Xinomavro’ vines, a prominent Greek red winegrape varietal. By conducting a two-year field experiment using various rootstocks, we assessed parameters related to water status, vegetative growth, yield, and berry composition. Our results revealed that rootstock selection has a significant impact on vine development, especially in terms of berry size and the concentrations of secondary metabolites. Principal component analysis confirmed the complex interaction between rootstock vigor and vine productivity. This study underscores the importance of rootstock variety in manipulating grapevine characteristics, particularly for the ‘Xinomavro’ variety, in response to regional climatic conditions.

A three-year study was conducted to investigate the effects of two timings—at berry set and at veraison—of post-bloom leaf removal (LR) applications from the basal sections of the shoot on the growth, yield, and berry composition of Vitis vinifera L. cv. Xinomavro, the major red winegrape of North Greece. LR at berry set drastically reduced yield by affecting all its components while increasing the ratio of secondary foliage per total leaf area. LR at veraison had a milder effect on growth and yield. Both treatments increased sugar and phenolic compound levels in berries, while early LR increased the contribution of more stable forms of anthocyanins. Additionally, early LR increased the skin-to-pulp ratio, suggesting that it could be an effective viticultural technique for more concentrated red wines. Overall, both LR timings improved most of the berry attributes compared to the non-treated vines; however, the earlier application can be recommended when aiming at the production of deep-colored and richly flavored wines.

Novel monitoring architecture approaches are required to detect viticulture diseases early. Existing micro-climate decision support systems can only cope with late detection from empirical and semi-empirical models that provide less accurate results. Such models cannot alleviate precision viticulture planning and pesticide control actions, providing early reconnaissances that may trigger interventions. This paper presents a new plant-level monitoring architecture called thingsAI. The proposed system utilizes low-cost, autonomous, easy-to-install IoT sensors for vine-level monitoring, utilizing the low-power LoRaWAN protocol for sensory measurement acquisition. Facilitated by a distributed cloud architecture and open-source user interfaces, it provides state-of-the-art deep learning inference services and decision support interfaces. This paper also presents a new deep learning detection algorithm based on supervised fuzzy annotation processes, targeting downy mildew disease detection and, therefore, planning early interventions. The authors tested their proposed system and deep learning model on the grape variety of protected designation of origin called debina, cultivated in Zitsa, Greece. From their experimental results, the authors show that their proposed model can detect vine locations and timely breakpoints of mildew occurrences, which farmers can use as input for targeted intervention efforts.

Precision viticulture employs various sensors for assessing nondestructively key parameters in vineyards. One of the most promising technologies for this purpose is the laser scanner sensor. Laser scanner uses the LiDAR (Light Detection And Ranging) method for the calculation of the distance from the sensor. However, the number of cultivation operations affects the credibility of sensors such as the laser scanner. The main aim of this study was to assess a laser scanner sensor at different measurement settings for estimating pruning wood parameters on two wine grape cultivars (Sauvignon Blanc and Syrah) that received different numbers of farming interventions. The experiment was conducted in the two vineyards situated in the same farm for two successive years (2014 and 2015). The results indicated that the use of a laser scanner in the Syrah vineyard presented more accurate results (r = 0.966 in 2014 and r = 0.806 in 2015) when compared to the Sauvignon Blanc one (r = 0.839 in 2014 and r = 0.607 in 2015) regarding pruning wood parameters estimation. Different measurement settings and weather conditions had different effects on the accuracy of the sensor. It can be concluded that the laser scanner is a very helpful sensor for estimating pruning wood parameters in vineyards.

The quality characteristics of a certain grapevine cultivar are determined by the combinatorial action of the genotype and environmental factors, such as soil, landscape and climate. Another critical parameter is the viticultural techniques utilised to improve grape berry quality. The influence of two viticultural practices, deficit irrigation and leaf removal, on the Greek Vitis vinifera L. cultivar ‘Xinomavro’ was investigated during the 2019 and 2020 vintages. Physiology measurements and berry sampling were performed at three phenological stages (green berry, veraison and harvest). The expression of specific genes known to control grape colour, aroma and flavour was studied in conjunction with berry growth and composition. All the parameters contributing to final yield, such as berry size, cluster weight and yield/vine, were reduced in non-irrigated and defoliated vines compared to their control (irrigated and non-defoliated) vines. Both treatments showed a significant increase in anthocyanin level, whereas total phenols increased in the deficit irrigation treatment only. Water deficit had no effect on total soluble solids, whereas leaf removal resulted in significantly increased levels compared to the controls. The expression profile of the genes examined was altered during ripening. Although both water deficit and defoliation positively influenced gene expression, there were several diverse responses among the phenological stages that depended on the vintage.

The aim of this study is to analyze the effect of excess boron (B) on the nutrient uptake, growth, and physiological performance of grapevines. Merlot and Cabernet Franc grapevines, either own-rooted or grafted onto 1103P and 101-14 Mgt rootstocks, were exposed in a hydroponic pot experiment to 0.5 mM boron for sixty days. Twenty-five days following the beginning of B treatment, the first symptoms of boron toxicity appeared, including leaf edge and margin yellowing, subsequent necrosis, and cupping of leaf blades. At harvest, sixty days after the start of the experiment, B concentration of the treated vines increased in all parts of the vine in the following order: Leaves > Roots > Trunks > Shoots. Leaf Boron concentration in treated vines ranged from 980.67 to 1064.37 mg kg−1 d.w. Boron excess significantly reduced the concentrations of all macro and micronutrients studied in this experiment. The total leaf chlorophyll (Chl) concentration decreased from 35.46 to 44.45%, thirty and sixty days, respectively, from the beginning of the boron treatments. In addition, an excess amount of boron resulted in a dramatic decrease in net CO2 assimilation rate, stem water potential, and PSII maximum quantum yield, irrespective of vine type (own-rooted or grafted). At the end of the experimental period, the total leaf phenolic content increased by 71.73% in Merlot and by 71.16% in Cabernet Franc due to Boron stress. The tressed vines grafted onto 1103P showed increased shoot and root dry weights, leaf chlorophyll content, CO2 assimilation rates, and Fv/Fm ratio compared to vines grafted onto 101-14 Mgt. It was found that rootstocks play an important role in B toxicity. The results showed that the leaf accumulation of boron was delayed to a greater extent by 1103P rootstock compared to 101-14 Mgt, resulting in the earlier appearance of leaf toxicity symptoms in vines grafted onto 101-14 Mgt rootstock compared to 1103P.

The terroir effect refers to the interactions between the grapes and their natural surroundings and has been recognized as an important factor in wine quality. The identification and mapping of viticultural terroir have long been relying on expert opinion coupled with land classification and soil/climate mapping. In this study, the data-driven approach has been implemented for mapping natural terroir units based on spatial modeling of public-access geospatial information regarding the three most important environmental factors that make up the terroir effect on different scales, climate, soil, and topography. K-means cluster analysis was applied to the comprehensive databases of relevant spatial information, and the optimum number of clusters was identified by the Dunn and CCC indices. The results have revealed ten clusters that cover the agricultural area of Drama (Greece), where it was applied, and displayed variable conditions on the climate, soil, and topographic factors. The implications of the resulting natural terroir units on the vini-viticultural management of the most common vine varieties are discussed. As more accurate and detailed input spatial data become available, the potential of such an approach is highlighted and paving the way toward a true understanding of the drivers of terroir.

The Mediterranean basin is regarded as one of the regions the most affected by climate change in the world. Traditionally, viticulture in this region copes with high temperatures, heat waves and drought. Such particularly extreme conditions, which induce severe abiotic stress on plants, are expected to intensify due to the predicted climate changes in the future. Our study focuses on the viticulture of Santorini Island, located in South Aegean (Greece). Vines have been cultivated on Santorini Island for thousands of years on their own roots owing to the phylloxera-free volcanic soil of the island. The vineyards of Mediterranean regions are already encountering difficulties because of ongoing climate change. The aim of this study was to analyse chronological climate data, evaluate the trends in the change of climate parameters and bioclimatic indices and correlate them with viticultural indices. In brief, the average annual temperature has increased in the last 45 years by almost 4 °C and a significant increase in the frequency of days with high temperatures has been recorded. Bioclimatic indicators correspond to warmer climates with warmer nights and longer periods of drought. Finally, it appears that the high temperatures occurring during the critical stages of the development and differentiation of the vine seem to affect production in the following growing season, while earlier harvest dates and higher sugar content than 45 years ago are observed.

A rapid and simple HPLC-DAD analytical method was developed and optimized for the determination of anthocynanins in three red Greek winegrape varieties (Kotsifali, Limnio, and Vradiano). The critical parameters, such as the acidifying solvent and the extraction temperature, which affect the extraction of anthocyanins from the grapes, were studied to find the optimum values. The developed methodology was validated in terms of selectivity, linearity, accuracy, and precision and presented satisfactory results. The limits of quantification (LOQs) ranged between 0.20 mg/kg to 0.60 mg/kg, and the limits of detection (LODs) ranged between 0.06 mg/kg and 0.12 mg/kg. The RSD% of the within-day and between-day assays were lower than 6.2% and 8.5%, respectively, showing adequate precision. The accuracy ranged between 91.6 and 119% for within-day assay and between 89.9 and 123% for between-day assay. Sixteen samples from the main regions of each variety as well as from the official ampelographic collections of Greece were collected during the 2020 growing season and were further analyzed by HPLC-DAD. Notable differences in the anthocyanin content were detected among the cultivars using hierarchical cluster analysis (HCA).

‘Xinomavro’ (the second planted red Greek variety behind ‘Agiorgitiko’) generally produces wines that are light in colour but with increased astringency, possibly related to grape flavonoid amount and composition; although irrigation is accepted as an effective means to enhance grape phenolic maturity, its role has not yet been sufficiently studied in the case of Xinomavro. This study aimed to determine the effect of post-veraison irrigation on berry anthocyanin and proanthocyanidin amount and composition, of field-grown Xinomavro vines (Vitis vinifera L.), under the typical summer conditions of Northern Greece. In a 10-year-old Xinomavro vineyard, two post-veraison watering regimes were applied—irrigation starting 20 days after veraison (mid-ripening irrigation, MRI) and irrigation starting immediately after veraison was completed (after veraison irrigation, AVI)—alongside non irrigated vines (NI), and vines irrigated continuously from berry set through harvest (continuous irrigation, CI). Proanthocyanidin composition was determined in both skins and seeds by employing phloroglucinolysis followed by HPLC-UV and MS detection (high-performance liquid chromatographic with tandem mass spectrometric and ultraviolet absorbance detection), and the anthocyanin profile was identified only in the skin extracts by HPLC-UV (high-performance liquid chromatographic with ultraviolet absorbance detection). Post-veraison irrigation increased yield parameters and reduced anthocyanin levels and the proportion of their stable forms (acylated vs. non-acylated, tri-oxygenated and methoxylated on the B-ring vs. di-oxygenated and hydroxylated), compared to NI vines; however, these effects were more pronounced in the case of early post-veraison irrigation (AVI) than late-season irrigation (MRI). Irrigation also increased the mean Degree of Polymerization (mDP) and prodelphinidin percentage of skin tannins and decreased mDP of seed tannins. In the light of the necessity to control the accelerated ripening under the increasingly hotter and drier climatic conditions, late irrigation (MRI) might provide a solution to avoid excessive sugar levels and allow a slightly higher yield without significant reductions in berry phenolic content. The results suggest that the optimisation of the timing of irrigation could provide an effective adaptation strategy to climate change in Mediterranean viticultural areas.

Chromium toxicity is considered within the most severe and dangerous nutritional disorders, and it can often be observed in crops grown in industrial areas. The present study aims to determine the effects of Cr(VI) toxicity on the growth, nutrition, and physiological performance of grapevines. In a pot hydroponic experiment, own-rooted Merlot and Cabernet Franc grapevine cultivars or cultivars grafted onto 1103P and 101-14 Mgt rootstocks were exposed to 120 μM Cr(VI). Leaf interveinal chlorosis appeared after forty-five days of treatment. Overall leaf chlorosis and brown root coloration after sixty days was reported. A significant effect on the majority of the measured parameters due to the Cr(VI) treatment was observed. Chromium stress increased the total Cr concentrations in all parts of the vines, i.e., leaves, shoots, roots, and trunks. When comparing between the studied plant sections, the roots presented the highest Cr concentrations, ranging from 396 to 868 mg kg−1 d. w., and then, in descending order, the Cr concentrations ranged from 41 to 102 mg kg−1 d. w. in the trunks, from 2.0 to 3.3 mg kg−1 d. w. in the leaves, and from 1.9 to 3.0 mg kg−1 d. w. in the shoots. Between the assessed rootstocks, 1103P was identified to be a better excluder of Cr concentration in the roots and other aerial parts of the vines. Additionally, chromium toxicity negatively affected the concentrations and compartmentalization of the most important nutrients. Leaf chlorophyll (Chl) concentration decreased down to approximately 53% after sixty days of Cr stress. Chromium toxicity significantly reduced the stem water potential (SWP), net CO2 assimilation rate (A), stomatal conductance (gs), and PSII maximum quantum yield in all the cases of grafted or own-rooted vines. At this stage, chromium stress increased the leaf total phenolic content from 46.14% in Merlot vines to 75.91% in Cabernet Franc vines.

Our objective was to investigate the effect of water and nitrogen (N) availability on the carbon isotope composition of leaf blades, canes and ripe berry must (juice) in field grown grapevines. In two consecutive years, the combination of two irrigation treatments [Irrigation (I): 70 % of crop evapotranspiration (ETc) and no irrigation (NI)] and three rates of ammonium nitrate [0 (N0), 60 (N60) and 120 (N120) kg/ha N] were applied to two separate vineyards planted with cv. Xinomavro and cv. Cabernet-Sauvignon respectively in a randomised complete block design. Carbon isotope composition (δ13C) of leaf blades, stem water potential (Ψs), and leaf gas exchange were measured at berry set, bunch closure, veraison and maturity during each growing season. δ13C of bulk berry must at maturity and of dormant canes was also measured. Leaf δ13C and cane δ13C decreased with water supply, but increased with N fertilisation. Must δ13C was lower in the irrigated N0 and N60 vines, whereas irrigation treatments did not differ under the N120 rate. The relative weight of irrigation and fertilisation effect on leaf δ13C varied across samplings: N application accounted for a higher proportion of leaf δ13C variance during the early stages of berry growth, whereas irrigation induced higher variance of leaf δ13C after veraison. The weight of the irrigation effect on cane δ13C was higher from that of fertilisation. Discrimination mechanisms against 13C in grapevine could be mediated by both N fertilisation and irrigation. The well-documented explanation of δ13C variation based on isotopic effects during CO2 diffusion through leaf stomata and carboxylation driven by water conditions may not apply to all cases, since additional discriminating processes against 13C associated with CO2 transfer from the intercellular spaces to the carboxylation sites may be affected by nitrogen supply. The study provides evidence for the first time that carbon isotope composition of leaf blades, canes and berry must is modulated by nitrogen supply. Interpretations of carbon isotope natural abundance in field grown grapevine tissues should therefore consider both water and nitrogen availability.

Aim: This research aimed to: (1) investigate the relationships between harvest dates and berry composition with air temperature during important periods during the growing season, across a range of indigenous and international winegrape varieties grown in wine regions over the majority of Greece; (2) calculate growing degree-days (GDD) from 1st of April until the harvest date of each variety and group the winegrape varieties according to their heat requirements; and (3) predict future harvest dates based upon these heat requirements under different representative emission pathways (i.e., RCP4.5 and RCP8.5) and future time periods (2041-2065 and 2071-2095) using an ensemble projection dataset. Methods and results: The analysis of heat requirements based on GDD from 1st of April to harvest date identified consistent maturity groups of the varieties studied, especially for indigenous Greek varieties. Trend analysis using the basic linear regression model showed that harvest dates have shifted earlier, during the last few decades, due to warmer conditions (especially during the ripening period) in most cases. In addition, trends in potential alcohol (acid) levels were found to be positively (negatively) correlated with maximum air temperatures in the majority of cases. Analysis of future projections using a global multi-climate model ensemble dataset (10 regional climate models) showed that harvest dates are projected to shift earlier up to 40 days in two future time periods (i.e., 2041-2065 and 2071-2095) depending on the variety and the emission pathway. Conclusions: Harvest dates of the early ripening varieties were associated more with the variations in maximum air temperatures during March to July, while mid- and late ripening varieties appeared to be affected more by maximum air temperatures during the ripening period. In addition, late ripening, mostly indigenous, varieties were less impacted by temperature increases compared to international varieties. Significance of the study: The indigenous Greek varieties appear better adapted to the recent and projected future climate of the region, responding less to warming as compared to international varieties in the majority of the study cases.

Our objective was to investigate the effect of water and nitrogen (N) availability on the carbon isotope composition of leaf blades, canes and ripe berry must (juice) in field grown grapevines. In two consecutive years, the combination of two irrigation treatments [Irrigation (I): 70 % of crop evapotranspiration (ETc) and no irrigation (NI)] and three rates of ammonium nitrate [0 (N0), 60 (N60) and 120 (N120) kg/ha N] were applied to two separate vineyards planted with cv. Xinomavro and cv. Cabernet-Sauvignon respectively in a randomised complete block design. Carbon isotope composition (δ13C) of leaf blades, stem water potential (Ψs), and leaf gas exchange were measured at berry set, bunch closure, veraison and maturity during each growing season. δ13C of bulk berry must at maturity and of dormant canes was also measured. Leaf δ13C and cane δ13C decreased with water supply, but increased with N fertilisation. Must δ13C was lower in the irrigated N0 and N60 vines, whereas irrigation treatments did not differ under the N120 rate. The relative weight of irrigation and fertilisation effect on leaf δ13C varied across samplings: N application accounted for a higher proportion of leaf δ13C variance during the early stages of berry growth, whereas irrigation induced higher variance of leaf δ13C after veraison. The weight of the irrigation effect on cane δ13C was higher from that of fertilisation. Discrimination mechanisms against 13C in grapevine could be mediated by both N fertilisation and irrigation. The well-documented explanation of δ13C variation based on isotopic effects during CO2 diffusion through leaf stomata and carboxylation driven by water conditions may not apply to all cases, since additional discriminating processes against 13C associated with CO2 transfer from the intercellular spaces to the carboxylation sites may be affected by nitrogen supply. The study provides evidence for the first time that carbon isotope composition of leaf blades, canes and berry must is modulated by nitrogen supply. Interpretations of carbon isotope natural abundance in field grown grapevine tissues should therefore consider both water and nitrogen availability.

Aim: The aims of this study were to (1) formulate a baseline understanding of the performance of the indigenous Cypriot white grape Xynisteri and the red grape Maratheftiko (Vitis vinifera L.), and (2) compare these varieties to Shiraz and Sauvignon blanc grown in a Cypriot vineyard. Materials and results: The investigation involved multiple dry grown vineyards from the Krasochoria region of Lemesos, Cyprus, during the 2017, 2018 and 2019 vintages. Vine performance measurements, including midday stem water potential, stomatal conductance, chlorophyll content, stomata density, vine phenology and vegetative and reproductive measurements, were taken at flowering, veraison and pre-harvest. Xynisteri had the greatest stomatal density, more shoots, more leaves, heavier bunches, greater yield, higher leaf water potential at harvest, and a stomatal conductance equal to Maratheftiko, but greater than that of both Shiraz and Sauvignon blanc. Maratheftiko had the longest shoots, largest shoot diameter and the greatest chlorophyll content out of all four varieties. Conclusions: This study identified the ability of the indigenous Cypriot grape varieties, Xynisteri and Maratheftiko, to better tolerate hot and dry conditions when compared to more commonly cultivated varieties grown in the same environmental conditions. Significance and impact of the study: The changing climate of wine growing regions worldwide is placing great pressure on the resources for sustainable viticulture. Many vineyards in hot climate zones base their businesses on European grape varieties traditionally grown in regions with abundant water resources. It is therefore necessary for the global wine industry to investigate grape varieties that are indigenous to hot climates. The eastern Mediterranean island of Cyprus is one such place, with more than 10 indigenous grape varieties that grow well in a hot climate without irrigation. Consumer studies have demonstrated that wines made from these Cypriot varieties are equally, if not more, acceptable than wines made from more traditional European grapes; therefore, the potential for their use in other hot wine growing regions is promising.

The world’s changing climate is placing great pressure on the resources for sustainable viticulture. With this, it has become necessary to investigate grape varieties that are well adapted to hot climates. This study investigated whether two Cypriot varieties (Xynisteri and Maratheftiko) responded differently to Shiraz and Sauvignon Blanc grown under different irrigation regimes (full, 50% and 25%). Irrigation trials were established in Cyprus in 2019 and in Australia in 2020/2021. Vine growth and physiology and fruit composition (field trial only) measurements were recorded. The trial in Cyprus in 2019 demonstrated that for all three irrigation regimes, Xynisteri had higher stem water potential, stomatal conductance, chlorophyll and greater biomass than Sauvignon Blanc under all irrigation regimes. In 2020/2021, Xynisteri had a greater biomass than Maratheftiko and Sauvignon Blanc, with Shiraz having the lowest. Under reduced irrigation, Xynisteri and Maratheftiko had higher stem water potential, stomatal conductance and chlorophyll content than Shiraz and Sauvignon Blanc. These results indicate that Xynisteri in particular may possess better cultivar-specific growth traits than Shiraz and Sauvignon Blanc when grown under the same environmental conditions and in turn may be a more appropriate choice in areas where water is limited.

Grapevine phenology is particularly sensitive to temperature variations, with changes in climate shifting events earlier and advancing berry maturation into a hotter part of the growing cycle. Consequently, serious concerns regarding the negative influences of climate change on global wine quality have been raised, with the scientific community focusing on documenting these changes to better understand and address the impacts. This study adds to this knowledge by investigating air temperature and precipitation trends over the last 40 years (i.e., 1980–2019). Over the most recent period of records (i.e., 2000–2019), minimum air temperatures significantly increased at a higher rate than maximum temperatures. On the other hand, precipitation showed the least significant trends over time. In addition, wine quality assessment and identification of the most significant weather variables and climatic indices that correlate with wine quality rating scores have also been performed. To serve this purpose, data of wine quality ratings for nine white (W) and two red (R) indigenous winegrape varieties (Vitis vinifera L., cvs) grown in Greece were obtained from the database of Thessaloniki International Wine and Spirits Competition. The results showed a statistically significant upward trend over the recent past in the majority of the varieties studied. To examine future periods, mixed-effect model outputs for Greek wine-producing regions combining an ensemble dataset using RCP4.5 and RCP8.5 emission pathways during two future periods (i.e., 2041–2065 and 2071–2095) predicts wines of higher quality, especially during the latter time period. These results reveal that Greek wine quality rating variations are mainly driven by higher maximum temperatures and drier conditions during the growing season of the grapevines. However, two important issues need to be more fully explored in Greece and elsewhere; (1) non-linear responses to warming where wine quality could suffer above varietally specific optimum temperature thresholds and (2) a better understanding of how other non-climate-related factors (e.g., canopy management, winemaking innovations) affect wine quality in the face of a changing climate.

Aim: The aim of this study was to determine and compare anthocyanin content and profile under variable irrigation regimes in four red grape cultivars (Vitis vinifera L.), the Greek indigenous cvs Agiorgitiko and Xinomavro, alongside Syrah and Grenache noir. Methods and results: Three irrigation treatments were applied in a 6 year-old vineyard comprising all four varieties in a block design, starting at bunch closure (E-L 32) through harvest of 2012 and 2013: full irrigation (FI) at 100% of crop evapotranspiration (ETc), deficit irrigation (DI) at 50% of ETc and non-irrigated (NI). The identification of the compounds was performed by HPLC. Results showed that, under the hot summer conditions of the Greek climate, the four cultivars had a similar response regarding vigor and yield parameters, increasing values with water supply. Anthocyanin concentration was maximized under non irrigated conditions in all cultivars, but anthocyanin profile and relative distribution of individual anthocyanins among irrigation treatments showed a strong cultivar effect. Conclusion: Xinomavro seemed to favor the synthesis of more stable forms of anthocyanins under limited water supply (acylated over non-acylated and tri-oxygenated & methoxylated on the B-ring over di-oxygenated & hydroxylated) while Agiorgitiko had an opposite behaviour, which might imply a need for a different irrigation strategy. Significance and impact of the study: To the best of our knowledge, this is the first comparative report of anthocyanin composition and profile in berry skin, under contrasting water status, for the two most important red winegrapes of Greece.

Plants are exposed to numerous abiotic stresses. Drought is probably the most important of them and determines crop distribution around the world. Grapevine is considered to be a drought-resilient species, traditionally covering semiarid areas. Moreover, in the case of grapevine, moderate water deficit is known to improve the quality traits of grape berries and subsequently wine composition. However, against the backdrop of climate change, vines are expected to experience sustained water deficits which could be detrimental to both grape quality and yield. The influence of water deficit on two Greek Vitis vinifera L. cultivars, ‘Agiorgitiko’ and ‘Assyrtiko’, was investigated during the 2019 and 2020 vintages. Vine physiology measurements in irrigated and non-irrigated plants were performed at three time-points throughout berry development (green berry, veraison and harvest). Berry growth and composition were examined during ripening. According to the results, water deficit resulted in reduced berry size and increased levels of soluble sugars, total phenols and anthocyanins. The expression profile of specific genes, known to control grape color, aroma and flavor was altered by water availability during maturation in a cultivar-specific manner. In agreement with the increased concentration of phenolic compounds due to water deficit, genes of the phenylpropanoid pathway in the red-skinned Agiorgitiko exhibited higher expression levels and earlier up-regulation than in the white Assyrtiko. The expression profile of the other genes during maturation or in response to water deficit was depended on the vintage.

Aim: The aim of this study was to determine and compare anthocyanin content and profile under variable irrigation regimes in four red grape cultivars (Vitis vinifera L.), the Greek indigenous cvs. Agiorgitiko and Xinomavro, alongside Syrah and Grenache noir. Methods and results: Three irrigation treatments were applied in a 6-year-old vineyard comprising all four varieties in a block design, starting at bunch closure (E-L 32) through harvest of 2012 and 2013: full irrigation (FI) at 100% of crop evapotranspiration (ETc), deficit irrigation (DI) at 50% of ETc and non-irrigated (NI). The identification of the compounds was performed by HPLC. Results showed that, under the hot summer conditions of the Greek climate, the four cultivars had a similar response regarding vigor and yield parameters, with values increasing with water supply. Anthocyanin concentration was maximized under non-irrigated conditions in all cultivars, but anthocyanin profile and relative distribution of individual anthocyanins among irrigation treatments showed a strong cultivar effect. Conclusion: Xinomavro seemed to favor the synthesis of more stable forms of anthocyanins under limited water supply (acylated over non-acylated and tri-oxygenated & methoxylated on the B-ring over di-oxygenated & hydroxylated) while Agiorgitiko had an opposite behavior, which might imply a need for a different irrigation strategy. Significance and impact of the study: To the best of our knowledge, this is the first comparative report of anthocyanin composition and profile in berry skin, under contrasting water status, for the two most important red winegrapes of Greece.

Vitis vinifera L. cv. ‘Agiorgitiko’ is one of the most important red grape varieties of Greece, cultivated almost exclusively in the region of Nemea in north-eastern Peloponnese. This work aimed to study the influence of some commonly applied viticultural practices on the polyphenolic composition of ‘Agiorgitiko’. Leaf removal at veraison, irrigation, and a combination of both, were applied and the phenolic content of the grapes and of the produced wines was compared. The results showed that leaf removal decreased berry size, enhanced total anthocyanin, total phenol and malvidin 3-O-monoglucoside accumulation in skins and increased the amount of extractable anthocyanins in the juice. The combination of irrigation and leaf removal caused a significant increase in total phenols in the skin and in the amount of extractable anthocyanins in juice. As far as the produced wines were concerned, color intensity, tannin content and total polyphenols were increased due to leaf removal. Both irrigation and leaf removal resulted in wines with the highest concentration of malvidin 3-O-monoglucoside, although neither practice resulted in any significant difference in anthocyanin concentration of the wines. Vines where only irrigation was applied produced berries with reduced extractable anthocyanins, increased seed total phenols and lower wine total tannins. The study showed that increasing cluster sun exposure of ‘Agiorgitiko’ vines may be, overall, beneficial to the quality of the produced wine.

The aim of this study was to estimate the genetic diversity of Greek and Bulgarian grapevine varieties with the use of microsatellite markers. The studied samples were collected from various productive vineyards, consisting of eight Greek and nine Bulgarian native varieties. In order to create a genetic profile for each sample, a multiplex PCR reaction method was used amplifying simultaneously seven microsatellite loci. Statistical analysis of data showed that there was a high degree of genetic heterogeneity among most of the varieties studied, highlighting the discriminative power of the chosen set of markers. Moreover, the synonymy of (I) Greek Pamid and Bulgarian Pamid and (II) Greek Zoumiatiko and Bulgarian Dimyat was suggested, as each variety pair had identical allele profiles in all loci examined. Regarding the Greek Mavrud and Bulgarian Mavrud varieties, there was a close genetic relationship between them, however, they did not share common alleles in all microsatellite loci and, therefore, should not be characterized as synonyms. On the other hand, Greek and Bulgarian Keratsouda, which were supposed to be common varieties, were found to be genetically different, supporting that these two varieties should be considered as homonyms. Despite the genotypic assay performed herein, we believe that additional molecular work is needed for the efficient management of Greek and Bulgarian grapevine genepools, as well as to safely suggest any synonym or homonym annotation.

Aims: In order to investigate the effect of vine training system on grape phenolic composition, a divided canopy system (Lyre) and a vertical shoot positioned trellis with two different pruning systems (Royat and Guyot) were applied in a commercial vineyard of cv. Xinomavro (Vitis vinifera L.). The quality of the produced grapes was determined with respect to three analytical parameters: anthocyanin content, tannin composition and proanthocyanidin structure. Methods and results: Monomeric anthocyanins, flavan-3-ol monomers and oligomers, tannin mean degree of polymerization (mDP), galloylation percentage (%G), and extension and terminal subunit structure were determined in seeds and skins by HPLC and LC/MS. Total phenolics, anthocyanin content, tannin concentration and antioxidant activity were measured in whole berries. Grapes and wines of the Lyre system were characterized by increased concentration of total and individual anthocyanins and total phenols. Individual flavan-3-ol monomers and oligomers were highest in Royat grape skins and Guyot seeds. Concerning proanthocyanidin structure, Royat grapes had significantly higher mDP and lower %G in skin and seed polymeric tannin fractions, compared to the other two systems, possibly leading to a lower grape astringency potential. Conclusion: Training system may affect grape anthocyanin concentration, total flavan-3-ol content as well as skin and seed proanthocyanidin structure (mDP, %G, extension and terminal subunits). Significance and impact of the study: The results of the present study could be of high importance to both grape growers and winemakers. Xinomavro grapes are rather poor in anthocyanins while being characterized by dry and astringent tannins. By adopting Lyre as a training system, higher anthocyanin contents could be achieved in grapes, resulting in wines with more attractive colour when adopting a longer pre-fermentation skin contact process. On the contrary, grapes of the Royat system might be more appropriate to produce full-bodied wines with higher ageing potential, due to their more appropriate tannin structure, by using longer maceration periods.

Aims: Vine water deficit is widely accepted as a powerful means to control grape and wine attributes. However, quality improvement is often achieved at the expense of a reduction in yield, especially when water deficit conditions are applied during the preveraison period. The aim of the present work was to test an irrigation regime based on manipulating water availability from veraison to harvest, as a means to control berry and wine composition with minimum effect on reproductive growth parameters. Methods and results: A field trial was conducted during two consecutive years (2007-2008) in Nemea, Southern Greece. Three irrigation treatments were applied on seven-year-old, vertical shoot positioned and spur pruned Agiorgitiko vines (Vitis vinifera L.), from veraison through harvest : irrigation at 70 % of crop evapotranspiration (ETc) (I70), irrigation at 30 % of ETc (I30) and non irrigated (NI). Irrigation amount produced significant differences in postveraison midday stem water potential pattern, especially during the drier year 2008. Yield was increased by irrigation in 2008, whereas berry growth was unaffected in both seasons. Berries of NI vines achieved higher total skin anthocyanin content in 2007, although individual anthocyanin levels were not affected by water regime. Irrigation effect on skin tannins was inconsistent but seed tannins were higher in I70 vines, with increased levels of catechin and epicatechin monomers. Among wine attributes, tannin concentration, but not anthocyanin, was mostly responsive to water deficit-induced changes in berry phenolic composition. The wines made from I70 grapes had a higher tannin content than those made from NI grapes. Conclusions: The results presented show that postveraison water regime had a significant effect on skin anthocyanins and, more markedly, on seed tannins, without altering berry growth parameters. Especially for seed tannins, this effect appears to predominate over variations in climatic conditions between years. Significance and impact of the study: This trial suggests that Agiorgitiko vines grown on the loamy soils of Nemea perform better under non irrigated conditions during the postveraison period since rainfed vines had improved phenolic composition (higher colour with lower contribution of seed tannins) without significant loss in productivity.

The effect of different P-sources on growth, leaf chemical composition, and fruit soluble solids and acid content was evaluated in mycorrhizal Victoria grapevine variety gralted onto the rootstocks 3309C or 11 OR. Mycorrhizal and non mycorrhizal plants were grown in 20 L pots containing 20 kg soil supplemented with different P-forms: (Calcium bis-dihydrogen-phosphate, tri-calcium phosphate, aluminium phosphate, iron (III) phosphate) with different solubility, equivalent to 90 kg P.ha-1. The percent of mycorrhizal root colonization was higher in insoluble P-form treatments compared to control or to soluble P-form treatment (CaDP), ranging from 66 to 84 % in treatments receiving insoluble P, from 36.67 to 38.33 % in control and from 25.33 to 27.33 % in soluble P-form treatments. The roots of 110R rootstock showed higher colonization rate compared to the 3309C. Mycorrhizal colonization increased both the pruning weight and number of nodes of the vines, up to 9 and 1.9 times respectively, according to the rootstock- P form combination. Mycorrhizal vines showed increased leaf concentrations in N, P, K, Ca. Fruit total soluble solids of mycorrhizal vines were about 30 % lower compared with those of the non mycorrhizal vines. Both factors, mycorrhizal colonization and P-forms had no significant effect in fruit titratable acidity.

Tannin accumulation and composition were determined in skins and seeds isolated from Vitis vinifera cv. Syrah grapes submitted to contrasting water regimes under semiarid climatic conditions. Three irrigation treatments were conducted, starting at berry set through harvest of two growing seasons, 2011 and 2012: irrigation at 100% of crop evapotranspiration ETc (FI), irrigation at 50% of ETc (DI) and non-irrigated (NI). Seed total tannins did not vary with maturity but those of skins underwent a progressive decline (especially in 2011), expressed both on a fresh weight and on a per berry basis. Skin total tannin concentration and content per berry were increased under NI and DI conditions, mainly in 2012. In contrast, seed total tannins (in 2012) and flavan-3-ol monomers and tannin oligomers (both years) were higher in the fully irrigated vines (FI). Skin polymer size increased during ripening, NI and DI skins showing higher mean degree of polymerization (mDP) compared to FI at harvest. NI was also associated with a lower percentage of galloylation (%G) in skin oligomeric fraction (in 2012) and a lower percentage of prodelphinidins in the skin polymeric fraction (both years) at harvest. The mDP and %G of seed extracts did not vary during ripening and were higher in NI but only in 2012. According to the results, management of vine water status was shown to influence tannin amount and composition of Syrah grapes grown under semiarid conditions.

The influence of grapevine water status on vine physiological mecanisms and vigour, as well as on berry ripening and wine characteristics, was studied during the summer of 1997 in the Nemea vine growing area (Peloponnesus, Greece). This involved three non irrigated vineyards planted with the local variety Saint-George (Agiorgitiko). These vineyards differed by their soil texture and by the presence of a water table within reach of the roots. The soil of the plot "A", located at 350 m in altitude, contained a high amount of gravel and stones between 0 and 50 cm in depth. The subsoil contained nearly 50 p. cent of clay. The plot "L" was located on a plain at 300 m in altitude. Its soil was very loamy. The plot "N" was located on a plain at 260 m in altitude. Its soil contained a high amount of clay and loam but its main caracteristic was the presence of a permanent water table within reach of the roots. Vine water status was evaluated throughout the season by measurements of leaf water potential Ψ. Additional measurements of soil water content were executed by means of a TDR moisture probe (Time Domaine Reflectometry). Water uptake of the vines showed great differences on the three plots. On the plot A, water uptake of the vines diminished brutally from June (pre-dawn Ψ= -0,2 MPa) through September (pre-dawn Ψ= -1,0 MPa); measurements of stomatal conductance in early September showed that stomata remained practically closed throughout the day. On the plot N, water was easily available to the vines throughout the summer. Pre-dawn leaf water potential remained between 0 and -0,2 MPa from June till September. Stomatal conductance, measured in early September, was high. On L, vine water status was intermediate: pre-dawn leaf water potential declined throughout the season, but not as dramatically as on A. Stomatal conductance, measured in early September, was intermediate between N and A. Water availability had a clear effect on vegetative growth. Growth slackening occured early in the season on A and late on N. On plot A, berries were smaller and showed high sugar and anthocyanin concentration and low malic acid content. Wine from A, obtained by mini-vinification (3,5 hl), was rich in alcohol, anthocyanins and tanins. On N, berries had a low sugar and anthocyanin content. Wine from grapes grown on N was poor in alcohol and polyphenolics. Berry and wine composition was intermediate on L.