Abstract
The production of high-quality sparkling wines relies on the achievement of an optimal balance between sugar and acidity in the fruit at harvest. This contrasts with the warming trends favoring a too fast sugar rise at the expense of adequate acidity. The removal, around veraison, of photosynthetically active leaves from the distal part of the canopy has been proposed as a simple technique to delay sugar accumulation. In this research, we investigate over three seasons (2015–2017) in the white cv. Ortrugo, the effects of a mechanical mid-shoot leaf removal performed before veraison (PRE-LR) or at a total soluble solids (TSS) concentration of ~12 Brix (POST-LR) in comparison with non-defoliated vines (C). PRE-LR shifted the sugar increase in all the three seasons, but the effects were consistent until harvest only in 2015 and 2016 (−1.1 Brix and −1.4 Brix, respectively, if compared to C). Instead, acidity was unaffected. POST-LR resulted less effective in changing the composition of grapes over ripening. Both leaf removal treatments reduced the berry size (−5%) and yield (−19% PRE-LR and −14% POST-LR, in comparison with C). Finally, the treatments changed the berry morphology and the proportion between its components, with some peculiarities due to the seasons, but generally, increasing the relative skin mass. Overall, the effectiveness of the technique was below expectations, primarily, because the general ripening delay expected from removing a significant portion of mature and functioning leaves was offset by a quite unavoidable drop in malic acid due to excess of heat summation as compared to the genotype ripening requirements.
- Received June 2018.
- Revision received August 2018.
- Accepted October 2018.
- Published online October 2018
- ©2018 by the American Society for Enology and Viticulture
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