Wei Zheng

Use of Minimal Pruning to Delay Fruit Maturity and Improve Berry Composition under Climate Change

Minimal pruning (MP) is a technique used to reduce labor costs and produce high-quality winegrapes. To evaluate the effects of MP on grapes cultivated in warm-climate regions, a long-term study on Tempranillo (Vitis vinifera L.) was conducted in Badarán, La Rioja, Spain. For each vintage between 1999 and 2013, yield and total soluble solids (TSS) were evaluated in grapes from MP vines and from conventionally hand-pruned (CHP) vines. In 2014 and 2015, grapes were analyzed at 22 Brix to assess the effects of MP on fruit maturation and quality. The long-term study showed that MP increased yield by 56% and reduced TSS by 9% compared to CHP. Results from 2014 and 2015 demonstrated that MP delayed fruit maturity (22 Brix) by ~17 days. At the same TSS level (22 Brix), MP vines had 24% lower berry weight, 57% lower cluster weight, and 51% greater yield. Must from MP fruit had greater total anthocyanin concentrations compared to must from CHP fruit (+17% in 2014 and +21% in 2015); however, potential improvements in wine color were more likely due to smaller berry size than to greater anthocyanin synthesis per unit area of berry skin. These results indicate that MP can delay berry ripening and may help to improve wine color.

Does full exposure of clusters have any negative effects on Tempranillo (Vitis vinifera L.) Grape Quality in La Rioja, Spain? The use of severe Cluster-zone Leaf Removal after Berry Set

A three-year experiment comprising severe leaf removal (LR) was carried out on Tempranillo grapes in Logrono, North-central Spain. For the LR treatment, six basal leaves, along with the basal lateral shoots, were removed two weeks after fruit set. Berry total soluble solids (TSS) were examined when the colour began to appear. Grapes from both the LR and control (C) vines were analysed at the same TSS level (≈ 22°Brix). LR advanced the onset of anthocyanin synthesis slightly but significantly. Yield components were not affected by LR and no symptoms of sunburn were observed. Both treatments showed similar juice pH and titratable acidity, although tartaric acid increased with LR while malic acid decreased with it. In spite of failing to increase the final anthocyanin concentration of the grape juice, LR enhanced the colour and body of the wine. These results indicate that a relatively early LR could be a viable way to improve the quality of grapes and wine under the climatic conditions of the Rioja wine region.