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Journal of the American Pomological Society
(J Am Pom Soc)

American Pomological Society

Volume 58 Number 4 Article 30 Pages: 220-225
Year 2004 Month 10
Title: Influence of Application Time and Gibberellic Acid Concentration on 'Seyval Blanc' Grapes
Authors: D.C. Ferree, D.M. Scurlock and J.C. Schmid
Gibberellic acid (GA3) applied at bloom was more effective than an application four weeks after bloom in reducing cluster weight and yield and increasing juice soluble solids. Cluster weight, good berries per cluster, and berries with rot were increased by hand-thinning at bloom. Cluster weights compared to unthinned vines were decreased linearly as GA3 concentration increased. Berry weight increased and berries per cluster decreased linearly with increasing rates of GA3. The effects of GA3 on clusters per vine and juice titratable acidity were inconsistent over the three-year study. Juice soluble solids increased with increasing GA concentration with a similar effect on pH in two out of three years. Although an optimum concentration was not determined, GA3 at approximately 60 ppm resulted in a response similar to handthinning in reducing yield and improving juice quality.

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