Giesco
21st GiESCO International Meeting: ‘A Multidisciplinary Vision towards Sustainable Viticulture’ COMBINING LEAF-TO-FRUIT RATIO MANIPULATION WITH EXOGENOUS ABSCISIC ACID APPLICATION TO ADJUST THE CONCENTRATIONS OF SUGAR AND ANTHOCYANINS IN GRAPE BERRY 1 1 1 1 1 1
Lina WANG , Eloïse BROUARD , Ghislaine HILBERT , Christel RENAUD , Serge DELROT , Eric GOMÈS , Sabine GUILLAUMIE1, Zhanwu DAI1* 1 EGFV, Bordeaux Sciences Agro, INRA, Université de Bordeaux, ISVV, 33882 Villenave d’Ornon, France *Corresponding author: zhanwu.dai@inra.fr
Abstract: Context and purpose of the study – Global climate change is intensifying and the emergence of regional extreme weather events is increasing both in frequency and intensity. These environmental changes are modifying vine physiology and significantly impact grape berry composition. Warmer temperatures during the growing season increase must sugar content, while they reduce organic acids and anthocyanins levels, thus modifying wine quality and typicality. Viticultural practices such as leaf-to-fruit ratio manipulations and applications of plant hormones can be used to adapt to climate change and maintain the sustainability of wine production. To design efficient adaptation strategies, we need to gain better insights into the links between sugars and anthocyanins accumulation during berry development and ripening. Material and methods – Fruiting-cuttings made up of one vertical shoot with one grape cluster of cv. Cabernet Sauvignon were grown in 2017 and 2018 in a naturally lighted and semi-controlled greenhouse.Various leaf-to-fruit ratios (including 2, 4, 6, 8, 10, 12 leaves per cluster) were conducted, which were combined with spraying of 400mg/L abscisic acid (ABA) on berries at pre-veraison stage. Moreover, to directly test the effects of sugar and ABA on the anthocyanins biosynthesis and clarify the relationship between sugar, ABA and anthocyanins, in vitro berry culture experiments were also conducted. Berries were cultured in MS (Murashige & Skoog) solid medium for 2-3 weeks supplemented with different sugar levels (0%, 2%, 8%) combined with ABA, ABA biosynthesis inhibitor (NDGA), or Hexokinase inhibitors (NAG, GDH). All the berries were sampled and frozen immediately in liquid nitrogen, then used to analyze the sugar, ABA and anthocyanins contents. Results–Low leaf-to-fruit ratio reduced the concentrations of sugar, anthocyanins and ABA in grape berries. Moreover, anthocyanins concentrations in berries were more sensitive to changes in leaf-to-fruit ratio. Exogenous ABA spraying significantly increased the concentrations of anthocyanins for low leaf-to-fruit ratios, but only slightly increased their sugar concentration. These results suggest that the concentration of sugar in berry was less sensitive than anthocyanins to the level of ABA. Berry in vitro culture experiments showed that ABA and high concentrations of sugar induced anthocyanins biosynthesis during ripening. A synergetic effect existed on anthocyanins accumulation when ABA and high concentration of sugar were applied simultaneously to berries. Thus, interactions may exist between ABA and sugar to regulate anthocyanins biosynthesis.Our results showed thatcombining leaf-to-fruit ratio manipulation with exogenous ABA applications can offer a fine-tuned way to reduce sugar concentration, while maintaining anthocyanin concentrations in grape berry, paving the way for possible adaptation strategies for viticulture to global climate change.
Keywords: Environmental adaptation, Vitis vinifera, leaf-to-fruit ratio, ABA, sugar, anthocyanins.
Abstract: Context and purpose of the study – Global climate change is intensifying and the emergence of regional extreme weather events is increasing both in frequency and intensity. These environmental changes are modifying vine physiology and significantly impact grape berry composition. Warmer temperatures during the growing season increase must sugar content, while they reduce organic acids and anthocyanins levels, thus modifying wine quality and typicality. Viticultural practices such as leaf-to-fruit ratio manipulations and applications of plant hormones can be used to adapt to climate change and maintain the sustainability of wine production. To design efficient adaptation strategies, we need to gain better insights into the links between sugars and anthocyanins accumulation during berry development and ripening. Material and methods – Fruiting-cuttings made up of one vertical shoot with one grape cluster of cv. Cabernet Sauvignon were grown in 2017 and 2018 in a naturally lighted and semi-controlled greenhouse.Various leaf-to-fruit ratios (including 2, 4, 6, 8, 10, 12 leaves per cluster) were conducted, which were combined with spraying of 400mg/L abscisic acid (ABA) on berries at pre-veraison stage. Moreover, to directly test the effects of sugar and ABA on the anthocyanins biosynthesis and clarify the relationship between sugar, ABA and anthocyanins, in vitro berry culture experiments were also conducted. Berries were cultured in MS (Murashige & Skoog) solid medium for 2-3 weeks supplemented with different sugar levels (0%, 2%, 8%) combined with ABA, ABA biosynthesis inhibitor (NDGA), or Hexokinase inhibitors (NAG, GDH). All the berries were sampled and frozen immediately in liquid nitrogen, then used to analyze the sugar, ABA and anthocyanins contents. Results–Low leaf-to-fruit ratio reduced the concentrations of sugar, anthocyanins and ABA in grape berries. Moreover, anthocyanins concentrations in berries were more sensitive to changes in leaf-to-fruit ratio. Exogenous ABA spraying significantly increased the concentrations of anthocyanins for low leaf-to-fruit ratios, but only slightly increased their sugar concentration. These results suggest that the concentration of sugar in berry was less sensitive than anthocyanins to the level of ABA. Berry in vitro culture experiments showed that ABA and high concentrations of sugar induced anthocyanins biosynthesis during ripening. A synergetic effect existed on anthocyanins accumulation when ABA and high concentration of sugar were applied simultaneously to berries. Thus, interactions may exist between ABA and sugar to regulate anthocyanins biosynthesis.Our results showed thatcombining leaf-to-fruit ratio manipulation with exogenous ABA applications can offer a fine-tuned way to reduce sugar concentration, while maintaining anthocyanin concentrations in grape berry, paving the way for possible adaptation strategies for viticulture to global climate change.
Keywords: Environmental adaptation, Vitis vinifera, leaf-to-fruit ratio, ABA, sugar, anthocyanins.