Genealogical Analyses of 3 Cultivated and 1 Wild Specimen of Vitis vinifera from Greece.

Grapevine (Vitis vinifera) has been an important crop with considerable cultural and economic significance for over 2,500 years, and Greece has been an important entry point into Europe for lineages that were domesticated in Western Asia and the Caucasus. However, whole-genome-based investigation of the demographic history of Greek cultivars relative to other European lineages has only started recently. To understand how Greek cultivars relate to Eurasian domesticated and wild populations, we sequenced 3 iconic domesticated strains ('Xinomavro,' 'Agiorgitiko,' 'Mavrotragano') along with 1 wild accession (the vinetree of Pausanias-a historically important wild specimen) and analyzed their genomic diversity together with a large sample of publicly available domesticated and wild strains. We also reconstructed genealogies by leveraging the powerful tsinfer methodology which has not previously been used in this system. We show that cultivated strains from Greece differ genetically from other strains in Europe. Interestingly, all the 3 cultivated Greek strains clustered with cultivated and wild accessions from Transcaucasia, South Asia, and the Levant and are amongst the very few cultivated European strains belonging to this cluster. Furthermore, our results indicate that 'Xinomavro' shares close genealogical proximity with European elite cultivars such as 'Chardonnay,' 'Riesling,' and 'Gamay' but not 'Pinot.' Therefore, the proximity of 'Xinomavro' to Gouais/Heunisch Weiss is confirmed and the utility of ancestral recombination graph reconstruction approaches to study genealogical relationships in crops is highlighted.

The Effect of Water Deficit on Two Greek Vitis vinifera L. Cultivars: Physiology, Grape Composition and Gene Expression during Berry Development.

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.

Differentiation of Wines Treated with Wood Chips Based on Their Phenolic Content, Volatile Composition, and Sensory Parameters.

The effects of both wood chips addition and contact time on phenolic content, volatile composition, color parameters, and organoleptic character of red wine made by a native Greek variety (Agiorgitiko) were evaluated. For this purpose, chips from American, French, Slavonia oak, and Acacia were added in the wine after fermentation. A mixture consisting of 50% French and 50% Americal oak chips was also evaluated. In an attempt to categorize wine samples, various chemical parameters of wines and sensory parameters were studied after 1, 2, and 3 mo of contact time with chips. The results showed that regardless of the type of wood chips added in the wines, it was possible to differentiate the samples according to the contact time based on their phenolic composition and color parameters. In addition, wood-extracted volatile compounds seem to be the critical parameter that could separate the samples according to the wood type. The wines that were in contact with Acacia and Slavonia chips could be separated from the rest mainly due to their distinct sensory characters.

Discrimination of varietal wines according to their volatiles.

A method is being proposed in order to discriminate bottled wines of different varieties when no other information is known. The advantages of the method consist in the fact that anyone who wants to certify the variety, which is written on the label or the area of origin, can use such a technique to achieve the conformity. Additionally, the method can be easily applied by laboratories equipped with a GC. The differentiation has been achieved by using only seven of the total extracted volatiles, mainly higher alcohols and higher alcohol esters, namely 3-methyl-1-butanol, 2,3-butanediol, ethyl lactate, 3-methyl-1-butyl acetate, 2-phenylethanol, phenyl ethyl acetate and p-hydroxy phenyl ethanol. These key compounds are not relevant to a single variety. The proposed method does not take into account variables such as the year of vintage and fermentation procedures (agitation, temperature).

Sensory assessment and chemical measurement of astringency of Greek wines: Correlations with analytical polyphenolic composition.

The purpose of this study was to measure the astringency of selected Greek red wines and to assess the relationship between sensory and chemical data. Nine red wines produced by three native Greek grape varieties (agiorgitiko, xinomavro and mavrodafni) were used and their astringency and bitterness was assessed by a trained panel. In addition, their astringency was estimated chemically employing the ovalbumin precipitation method. Their polyphenolic composition was also determined by High Performance Liquid Chromatography (HPLC). The sensory data showed that mandilaria was the most astringent variety whereas agiorgitiko was the least. Statistical analysis of the results indicated that the chemical data obtained for astringency significantly correlated with the sensory determinations. In addition, significant correlations were obtained between the sensory data and the wine polyphenolic composition.