Benzothiadiazole Affects Grape Polyphenol Metabolism and Wine Quality in Two Greek Cultivars: Effects during Ripening Period over Two Years.

Grape berries are one of the most important sources of phenolic compounds, either consumed fresh or as wine. A pioneer practice aiming to enrich grape phenolic content has been developed based on the application of biostimulants such as agrochemicals initially designed to induce resistance against plant pathogens. A field experiment was conducted in two growing seasons (2019-2020) to investigate the effect of benzothiadiazole on polyphenol biosynthesis during grape ripening in Mouhtaro (red-colored) and Savvatiano (white-colored) varieties. Grapevines were treated at the stage of veraison with 0.3 mM and 0.6 mM benzothiadiazole. The phenolic content of grapes, as well as the expression level of genes involved in the phenylpropanoid pathway were evaluated and showed an induction of genes specifically engaged in anthocyanins and stilbenoids biosynthesis. Experimental wines deriving from benzothiadiazole-treated grapes exhibited increased amounts of phenolic compounds in both varietal wines, as well as an enhancement in anthocyanin content of Mouhtaro wines. Taken together, benzothiadiazole can be utilized to induce the biosynthesis of secondary metabolites with oenological interest and to improve the quality characteristics of grapes produced under organic conditions.

Abscisic Acid and Chitosan Modulate Polyphenol Metabolism and Berry Qualities in the Domestic White-Colored Cultivar Savvatiano.

During the last decade, several studies demonstrated the effect of biostimulants on the transcriptional and metabolic profile of grape berries, suggesting their application as a useful viticultural practice to improve grape and wine quality. Herein, we investigated the impact of two biostimulants-abscisic acid (0.04% w/v and 0.08% w/v) and chitosan (0.3% w/v and 0.6% w/v)-on the polyphenol metabolism of the Greek grapevine cultivar, Savvatiano, in order to determine the impact of biostimulants' application in the concentration of phenolic compounds. The applications were performed at the veraison stage and the impact on yield, berry quality traits, metabolome and gene expression was examined at three phenological stages (veraison, middle veraison and harvest) during the 2019 and 2020 vintages. Results showed that anthocyanins increased during veraison after treatment with chitosan and abscisic acid. Additionally, stilbenoids were recorded in higher amount following the chitosan and abscisic acid treatments at harvest. Both of the abscisic acid and chitosan applications induced the expression of genes involved in stilbenoids and anthocyanin biosynthesis and resulted in increased accumulation, regardless of the vintage. Alterations in other phenylpropanoid gene expression profiles and phenolic compound concentrations were observed as well. Nevertheless, they were mostly restricted to the first vintage. Therefore, the application of abscisic acid and chitosan on the Greek cultivar Savvatiano showed promising results to induce stilbenoid metabolism and potentially increase grape defense and quality traits.

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.

Explore the Rare-Molecular Identification and Wine Evaluation of Two Autochthonous Greek Varieties: "Karnachalades" and "Bogialamades".

Wines produced from autochthonous Vitis vinifera varieties have an essential financial impact on the national economy of Greece. However, scientific data regarding characteristics and quality aspects of these wines is extremely limited. The aim of the current study is to define the molecular profile and to describe chemical and sensory characteristics of the wines produced by two autochthonous red grapevine varieties-"Karnachalades" and "Bogialamades"-grown in the wider area of Soufli (Thrace, Greece). We used seven microsatellites to define the molecular profile of the two varieties, and then we compared their profile to similar molecular data from other autochthonous as well as international varieties. Grape berries were harvested at optimum technological maturity from a commercial vineyard for two consecutive vintages (2017-2018) and vilification was performed using a common vinification protocol: the 2017 vintage provided wines, from both varieties, with greater rates of phenolics and anthocyanins than 2018, whereas regarding the sensory analysis, "Bogialamades" wine provided a richer profile than "Karnachalades". To our knowledge, this is the first study that couples both molecular profiling and exploration of the enological potential of the rare Greek varieties "Karnachalades" and "Bogialamades"; they represent two promising varieties for the production of red wines in the historic region of Thrace.