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Post‐veraison restriction of phloem import into Riesling (Vitis vinifera L.) berries induces transient and stable changes to fermentation‐derived and varietal wine volatiles

Böttcher, C., Boss, P.K., Harvey, K.E., Nicholson, E.L., Burbidge, C.A., Davies, C.
Australian journal of grape and wine research 2019 v.25 no.3 pp. 286-292
Vitis vinifera, amino acids, climate change, cultivars, cytokinins, elicitors, flavor, girdling, grapes, metabolites, monoterpenoids, odor compounds, oxidative stress, phloem, plant breeding, small fruits, sugars, vineyards, wines
BACKGROUND AND AIMS: The climate‐change driven uncoupling of grape (Vitis vinifera L.) berry ‘sugar‐ripeness’ and ‘flavour‐ripeness’ necessitates an improved understanding of the sugar/flavour nexus. METHODS AND RESULTS: Analysis of grape metabolites and wine volatiles derived from Riesling berries of peduncle‐girdled and Control bunches over the course of 30 days provided time‐dependent insights into changes to grape and wine composition associated with phloem import. Girdling resulted in stable berry mass and concentration of sugar and cytokinin and in reduced concentration of amino acids. Such changes to grape composition correlated with a lasting increase in wine monoterpenoids and a transient reduction in fermentation‐derived wine volatiles. CONCLUSIONS: Oxidative stress and restricted amino acid import, not sugar accumulation, were identified as possible elicitors for the increased accumulation of varietal wine aroma compounds in Riesling. SIGNIFICANCE OF THE STUDY: The concentration and composition of berry amino acids and cytokinin concentration in grapes during the later stages of rapid sugar accumulation may represent potential targets for vineyard management strategies and grapevine breeding to counter climate‐change driven modifications to the wine volatile profile of aromatic cultivars.