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International audience; Grape canes are viticulture byproducts representing a sustainable source of valuable bioactive polyphenols. However, varietal origin and postharvest treatment greatly influence the effective concentration of biomolecules, thus limiting industrial development. With the aim to develop grape cane extracts with high polyphenol contents, the selection of a specific grape variety combined with optimized postharvest treatment is the major determinant. A previously described postharvest treatment comprising cutting grapevine stalks of 0.5 cm length and storage at 15–20 °C over 2 weeks was applied on a selection of 44 grape varieties representative of the genetic diversity of the whole European collection and performing the screening of polyphenol contents. Varietal rankings according to major polyphenols (catechin, epicatechin, E-resveratrol, E-piceatannol, E-ϵ-viniferin, E-miyabenol C, ampelopsin A, E-vitisin B, hopeaphenol, and isophopeaphenol) were performed with and without the postharvest treatment. We observed that postharvest treatment greatly influenced the total polyphenol composition but also the ranking of polyphenol-rich varieties. This polyphenol screening of grape canes from a large collection of European varieties revealed the importance of postharvest treatment together with the selection of varieties to develop natural extracts based on grapevine wood biomass enriched with molecules with health benefits.

International audience; Grape canes are byproducts of viticulture containing valuable bioactive stilbenoids including monomers and oligomers of E-resveratrol. Although effective contents in stilbenoids are known to be highly variable, the determining factors influencing this composition remain poorly understood. As stilbenoids are locally induced defense compounds in response to phytopathogens, this study assessed the impact of downy mildew infection during the growing season on the stilbenoid composition of winter-harvested grape canes. The spatial distribution between pith, conducting tissues, and cortex of E-piceatannol, E-resveratrol, E-ε-viniferin, ampelopsin A, E-miyabenol C, Z/E-vitisin B, hopeaphenol, and isohopeaphenol in grape canes from infected vineyards was strongly altered. In conducting tissues, representing the main site of stilbenoid accumulation, E-ε-viniferin content was higher and E-resveratrol content was lower. These findings suppose that the health status in vineyards could modify the composition of stilbenoids in winter-harvested grape canes and subsequently the potential biological properties of the valuable extracts.