Tannin content and antioxidant capacity of five Greek red grape varieties

Tannins are located in skins and seeds and are responsible for important sensory and quality attributes of red grapes and wines, such as astringency, bitterness and colour stability. However, little is known regarding Greek Vitis vinifera varieties. The aim of this study is to evaluate the grape phenolic content and to present data that may contribute to the development of suitable winemaking techniques for these varieties. In this study berry attributes, skin and seed content of tannins and antioxidant capacity from five Greek Vitis vinifera varieties, namely 'Mavrotragano', 'Mandilaria', 'Kotsifali', 'Agiorgitiko' and 'Xinomavro' were analyzed. Significant differences were observed in berry weight and the distribution of berry component mass in mature berries, among the different varieties. 'Mandilaria' and 'Kotsifali' had the heavier berries while the higher contribution of skins and seeds in berry was observed in 'Agiorgitiko' and 'Mavrotragano' grapes respectively. According to the results, the higher content of seed tannins in berries was determined in 'Mandilaria' and the lower in 'Kotsifali'. Finally, varieties with high concentrations of tannins, 'Mandilaria' and 'Mavrotragano', also demonstrated significant high values of antioxidant capacity

A combined approach involving ampelographic description, berry oenological traits and molecular analysis to study native grapevine varieties of Greece

A combined approach involving phenotypical characterization (ampelographic description and oenological traits) and molecular analysis was applied on 91 accessions of native Greek grape varieties plus 3 references, all conserved in the Ampelographic Collection of the Aristotle University of Thessaloniki. The accessions were described in accordance to 48 OIV descriptors. Their berry oenological traits were determined at maturity to detect a high juice sugar concentration in most of the assessed varieties, whereas the titratable acidity was found to be extremely low, particularly in the white accessions. Moreover, skin anthocyanin and phenolic content fluctuated from 0.09 to 39.4 mg∙g-1 f.w. and from 2.05 to 30.65 mg∙g-1 f.w. respectively, whereas seed phenolic content was in the range of 2.83 and 32.72 mg∙g-1 f.w. Finally, the discriminative SSR analysis confirmed the differences and similarities among the analyzed varieties as can be evinced from the phylogenetic analysis where close genetic relationship has been detected between 'Fokiano' and 'Armeletousa', 'Moschato Spinas' and 'Moschato Samou', 'Vilana' and 'Asprouda Patron', and 'Mouchtouri' and 'Mavro Spetson'. In all these occasions, the parts of each pair possess similar morphological characteristics

Vineyard practices reduce the incidence of Aspergillus spp. and alter the composition of carposphere microbiome in grapes (Vitis vinifera L.)

Going through the new transitioning era of the “European Green Deal,” the search for alternative, non-chemical, disease control methods is essential. Aspergillus bunch rot is considered one of the most important diseases of grapevines resulting in severe yield losses and, major qualitative deterioration of grape products due to the production of mycotoxins. We investigated, in a two-year field study, the impact of agronomic practices like defoliation to enhance grape microclimate (DF), pruning method to reduce grape bunch density (LBD), and irrigation cut-off (NIR), at three developmental stages of grapevine (Pea size berry, Veraison, and Harvest), on (i) grape composition (titratable acidity, pH, and total soluble solids), (ii) on the frequency of occurrence of Aspergillus on grape berries, and (iii) on the overall composition of grape carposphere microbiome. The density of Aspergillus on grape berries was significantly reduced by the applied management practices (DF, LBD, and NIR). Amplicon sequencing analysis showed that both the phenological stage and the agronomic practices employed (particularly NIR and DF) imposed significant changes in the α-diversity and β-diversity of the grape carposphere bacterial and fungal communities. The NIR, LBD, and DF treatments which supported lower Aspergillus populations, network analysis revealed negative co-occurrence patterns between Aspergillus and several bacterial genera (Streptococcus, Rhodococcus, and Melitangium) reported to have antifungal properties suggesting potential natural attenuation mechanisms for the control of Aspergillus. Overall, our study (i) showed that the application of halting of irrigation and thinning of leaves and grape bunches, reduce the occurrence of Aspergillus and hence the incidence of Aspergillus Bunch rot disease and (ii) identified preliminary evidence for interactions of Aspergillus with members of the epiphytic grape bacterial communities that might be involved in the suppression of Aspergilli, an observation which will be further pursued in following studies in the quest for the discovery of novel biological control agents

Integrated analysis of climate, soil, topography and vegetative growth in Iberian viticultural regions

The Iberian viticultural regions are convened according to the Denomination of Origin (DO) and present different climates, soils, topography and management practices. All these elements influence the vegetative growth of different varieties throughout the peninsula, and are tied to grape quality and wine type. In the current study, an integrated analysis of climate, soil, topography and vegetative growth was performed for the Iberian DO regions, using state-of-the-art datasets. For climatic assessment, a categorized index, accounting for phenological/thermal development, water availability and grape ripening conditions was computed. Soil textural classes were established to distinguish soil types. Elevation and aspect (orientation) were also taken into account, as the leading topographic elements. A spectral vegetation index was used to assess grapevine vegetative growth and an integrated analysis of all variables was performed. The results showed that the integrated climate-soil-topography influence on vine performance is evident. Most Iberian vineyards are grown in temperate dry climates with loamy soils, presenting low vegetative growth. Vineyards in temperate humid conditions tend to show higher vegetative growth. Conversely, in cooler/warmer climates, lower vigour vineyards prevail and other factors, such as soil type and precipitation acquire more important roles in driving vigour. Vines in prevailing loamy soils are grown over a wide climatic diversity, suggesting that precipitation is the primary factor influencing vigour. The present assessment of terroir characteristics allows direct comparison among wine regions and may have great value to viticulturists, particularly under a changing climate

Evaluation of the use of LIDAR laser scanner to map pruning wood in vineyards and its potential for management zones delineation

Vine vigour assessment has been a major concern of precision viticulture studies in order to identify areas of uniform vine performance within vineyards. Moreover, the counting and weighing of winter dormant canes is considered as the most informative measurement to indicate vine balance and is commonly performed manually by grape growers for management purposes. The main concern of this measurement is that it is time consuming and laborious and it cannot accommodate detailed sampling density. In the present study, the potential of using laser scanner technology as an automated, easy and rapid way to perform mapping of the winter pruning wood across the vineyard was investigated. The study was conducted during 2010 and 2011, in a one hectare commercial vineyard in central Greece, planted with cv. Agiorgitiko, a traditional Greek variety for the production of red wine. Parameters of topography, soil depth, soil texture, canopy properties (NDVI), yield, and grape quality were mapped and analysed in conjunction to winter canes weighing at pruning time. The mapping of the dormant canes was carried out using a 2D laser scanner sensor prior to pruning and manually measuring the pruning weight on a 10 × 20 m grid. Laser scanner measurements showed significant relationship in both 2010 and 2011 with pruning weight (r = 0.809 and r = 0.829 respectively, p < 0.001), yield and early season NDVI, showing the potential of using laser scanner measurements to assess variability in vine vigour within vineyards. These results suggest that laser scanners offer great promise to characterize within field variability in vine performance. © 2017, Springer Science+Business Media New York

A study on the effects of climate change on viticulture on Santorini Island

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. © 2022, International Viticulture and Enology Society. All rights reserved

Management zones delineation using fuzzy clustering techniques in grapevines

Precision viticulture aims at managing vineyards at a sub-field scale according to the real needs of each part of the field. The current study focused on delineating management zones using fuzzy clustering techniques and developing a simplified approach for the comparison of zone maps. The study was carried out in a 1.0 ha commercial vineyard in Central Greece during 2009 and 2010. Variation of soil properties across the field was initially measured by means of electrical conductivity, soil depth and topography. To estimate grapevine canopy properties, NDVI was measured at different stages during the vine growth cycle. Yield and grape composition (must sugar content and total acidity) mapping was carried out at harvest. Soil properties, yield and grape composition parameters showed high spatial variability. All measured data were transformed on a 48-cell grid (10 x 20 m) and maps of two management zones were produced using the MZA software. Pixel-by-pixel comparison between maps of electrical conductivity, elevation, slope, soil depth and NDVI with yield and grape composition maps, set as reference parameters, allowed for the calculation of the degree of agreement, i.e. the percentage of pixels belonging to the same zone. The degree of agreement was used to select the best-suited parameters for final management zones delineation. For the year 2009 soil depth, early and mid season NDVI were used for yield-based management zones while for quality-based management zones ECa, early and mid season NDVI were utilized. For the year 2010 ECa, elevation and NDVI acquired during flowering and veraison were used for the delineation of yield-based management zones while for quality-based management zones ECa and NDVI acquired during flowering and harvest were utilized. Results presented here could be the basis for simple management zone delineation and subsequent improved vineyard management

Viticulture-climate relationships in Greece: The impacts of recent climate trends on harvest date variation

Climate characteristics and relationships with indigenous varieties in Greece are examined to better understand how these varieties perform in their native climate and assess the impact regional climate change has on the Greek wine industry. Thus, harvest dates (ΔH) for eight indigenous varieties and regions, along with climate data, were gathered and systematically explored using linear regression models and principal component analysis for three &apos;effective&apos; growing season time period definitions (calendar year, growing season and ripening period). The eight study regions had marked differences in their general climatic characteristics, mainly between mainland and island areas. ΔH response was not particularly sensitive to time period definition. In five out of eight regions, a systematic shift of ΔH was identified (earlier harvest), mainly driven by changes in maximum and minimum temperatures. Significant trends in climate parameters and viticulture-climate relationships were more evident for island regions when compared to mainland locations. Moreover, areas with late ripening varieties were shown to be less sensitive to climate changes. Only in one region harvest was delayed, possibly due to non-climate factors. The identification of up-to-date climate and grapevine phenology relationships could be an important step for broader and more confident future assessments of climate suitability for viticulture and climate change impacts in Greece, and provide insights into how lesser known varieties might perform in other regions. © 2013 Royal Meteorological Society

Management zones delineation using fuzzy clustering techniques in vines

This paper presents the results of applying precision agriculture in a 1 ha commercial vineyard in Greece in 2009 and 2010. A field elevation map was produced using RTK-GPS. Soil electrical conductivity was measured using EM-38 sensor. Crop Circle sensor was used to measure canopy properties during the growth period. Yield and grape quality (sugar content) mapping was carried out at harvest. Yield and ECa showed high spatial variability. Management zones for the measured parameters were defined using the MZA software. For all measured parameters, two and three zones were delineated. Comparison between the zone maps for the measured parameters showed that high percentage of pixels belonged to the same zones. This could be the basis for successful management zone delineation and subsequent improved vineyard management