Berry Thinning and Cluster Thinning Influence Vegetative Growth, Yield, Fruit Composition, and Net Photosynthesis of ‘Seyval blanc’ Grapes

Abstract

Crop reduction on single-shoot ‘Seyval blanc’ grapevines by either berry or cluster thinning resulted in a decrease in total fruit weight and an accompanying increase in berry weight, °Brix, and vegetative growth. Titratable acidity and pH of the juice were not consistently affected by either berry or cluster thinning. Net leaf photosynthesis at 43 days past full bloom increased with higher cluster number per plant. Berry weight was greatest when the crop of berries were borne in three clusters per shoot rather than in a single cluster. Berry thinning appears to be an acceptable substitute to cluster thinning for crop reduction of ‘Seyval blanc’ grapes.