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Phenolic compounds represent a large family of plant secondary metabolites, essential for the quality of grape and wine and playing a major role in plant defense against biotic and abiotic stresses. Phenolic composition is genetically driven and greatly affected by environmental factors, including water stress. A major challenge for breeding of grapevine cultivars adapted to climate change and with high potential for wine-making is to dissect the complex plant metabolic response involved in adaptation mechanisms. A targeted metabolomics approach based on ultra high-performance liquid chromatography coupled to triple quadrupole mass spectrometry (UHPLC-QqQ-MS) analysis in the Multiple Reaction Monitoring (MRM) mode has been developed for high throughput profiling of the phenolic composition of grape skins. This method enables rapid, selective, and sensitive quantification of 96 phenolic compounds (anthocyanins, phenolic acids, stilbenoids, flavonols, dihydroflavonols, flavan-3-ol monomers, and oligomers…), and of the constitutive units of proanthocyanidins (i.e., condensed tannins), giving access to detailed polyphenol composition. It was applied on the skins of mature grape berries from a core-collection of 279 Vitis vinifera cultivars grown with or without watering to assess the genetic variation for polyphenol composition and its modulation by irrigation, in two successive vintages (2014)(2015). Distribution of berry weights and δ 13 C values showed that non irrigated vines were subjected to a marked water stress in 2014 and to a very limited one in 2015. Metabolomics analysis of the polyphenol composition and chemometrics analysis of this data demonstrated an influence of water stress on the biosynthesis of different polyphenol classes and cultivar differences in metabolic response to water deficit. Correlation networks gave insight on the relationships between Pinasseau et al.Grapevine Polyphenols Response to Drought the different polyphenol metabolites and related biosynthetic pathways. They also established patterns of polyphenol response to drought, with different molecular families affected either positively or negatively in the different cultivars, with potential impact on grape and wine quality.

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-Species effects and ecological conditions on ten heartwood ellagitannins (vescalin, castalin, roburins A-E, grandinin, vescalagin and castalagin) and ellagic acid were investigated in a 100 years old stand of 5 ha located in western France (La Petite Charnie State Forest, Sarthe). The sample included a total of 286 trees (118 sessile oaks, 158 pedunculate oaks and 10 individuals with an intermediate morphology) located in three ecological zones (plateau, slope, small valley). The main factor influencing oak extractives level was botanical species. The ecological zone effect appears negligible. Pedunculate oak is generally richer in ellagitannins (48.4 mg/g against 34.4 for sessile oak), although a clear boundary between the two species cannot be established. Ellagitannin content was found to be correlated with ring width for pedunculate oak and not for sessile oak. The vescalagin/castalagin ratios differed between the two species (0.69 for Quercus robur against 0.53 for Quercus petraea). The distribution of ellagitannin contents is not strongly structured spatially.ellagitannin / oak wood / Quercus robur L. / Quercus petraea Liebl. / variability / ecological conditions Résumé -Effet de l'espèce et des conditions écologiques sur le contenu du bois en ellagitanins dans un peuplement équien de chêne (Quercus robur L., Quercus petraea Liebl.). Les effets de l'espèce et des conditions écologiques sur le contenu du duramen externe de dix ellagitanins (vescaline, castaline, roburines A à E, grandinine, vescalagine, castalagine) et de l'acide ellagique ont été étudiés dans un peuplement équien (100 ans) de chêne d'une surface de 5 ha située dans l'ouest de la France (forêt domaniale de La Petite Charnie, Sarthe). L'échantillon total se composait de 286 arbres (118 chênes sessiles, 158 chênes pédonculés et 10 chênes intermédiaires) répartis en mélange dans trois zones écologiques du peuplement (plateau, pente et fond de vallon). Le facteur principal qui influence la teneur en ellagitanin est l'espèce botanique, alors que le facteur « zone » est négligeable dans les conditions expérimentales considérées. Le bois de chêne pédonculé est plus riche en ellagitanins que celui du chêne sessile (48,4 mg/g pour le chêne pédonculé ; 34,4 mg/g pour le chêne sessile), mais une distinction claire entre les deux espèces ne peut être établie. Une corrélation entre la teneur en ellagitanin et la largeur de cerne est observée pour le chêne pédonculé à la différence du cas du chêne sessile. Le rapport vescalagine/castalagine est plus élevé pour le chêne pédonculé que pour le chêne sessile (0,69 et 0,53). La structuration spatiale est faible. ellagitanin / bois de chêne / Quercus robur L. / Quercus petraea Liebl. / variabilité intrapeuplement / conditions écologiques