Abstract
The influence of light and thermal microclimate on berry quality of a Vermentino vineyard, managed with deficit irrigation strategies in north-western Sardinia, was analyzed. Two water deficit, pre- (ED) and post-veraison (LD), an irrigation (IC) and a non-irrigation (NC) control treatments were compared during berry development. Grapevine performances were evaluated by analyzing leaf gas exchange, source-sink balance, light and thermal microclimate effects on berry composition. Early and/or late deficit irrigation following a mild to moderate water stress threshold enabled high leaf physiological performances. Though with high stomatal conductance sensitivity to water deficit and anisohydric behavior, this variety exhibited high assimilation rate and quick recovery capacity after enduring moderate and severe water stress. All treatments achieved satisfactory sugar and acidic levels. Berry phenols were higher in LD due to lower canopy coverage and better light conditions compared to IC. Up to mid-ripening, cluster exposure to elevated temperatures negatively influenced phenolic accumulation, mostly in NC and to a lower extent in ED. In the last ripening weeks, total phenols was majorly influenced by light interception.
Highlights
Water deficit affects berry composition in red and white grapes [1,2,3]
Following a randomized design of 3 blocks with 3 vine rows each, 4 treatments were set: Early deficit (ED), for which vines were irrigated from fruit-set to veraison when Ψs decreased below -0.8 MPa; Late deficit (LD), supplying water from veraison until harvest, according to the same threshold; irrigated control (IC) in which Ψs was kept around -0.8 MPa during fruit development and ripening; and non-irrigated control (NC)
We showed that Vermentino is able to maintain high photosynthetic performance and water use efficiency under moderate water stress
Summary
Water deficit affects berry composition in red and white grapes [1,2,3]. Water stress-induced changes in cluster microclimate may lead to different berry phenolic content and partitioning [5,6,7]. Relationships between plant water status and accumulation of different phenolic groups in growing berries are not fully understood [8, 9]. We applied deficit irrigation strategies in a white grape variety and imposed mild to moderate water stress using a stem water potential (Ψs) threshold [10] above which vines were not re-watered. Variety performance under water stress was evaluated by analysing leaf gas exchange, sourcesink balance, light and thermal microclimate effects on berry
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