Influence of Girdling and Gibberellic Acid on Yield Components, Fruit Composition, and Vestigial Seed Formation of `Sovereign Coronation' Table Grapes

Vestigial seeds of `Sovereign Coronation' table grapes frequently form partial seedcoats that are perceptible during consumption. This problem was addressed through cane/cordon girdling and gibberellic acid (GA 3 ) sprays. `Sovereign Coronation' vines were subjected to one of five treatments [untreated control; cane/cordon girdled; 15 ppm GA 3 at bloom (GA1); GA1 + 40 ppm GA 3 14 days later (GA2); GA2 + 40 ppm GA 3 14 days later]. GA 3 had no effect on yield or clusters per vine, but postbloom GA 3 treatments increased cluster and berry weights and reduced berries per cluster. Fruit maturity was not consistently affected by the treatments, although slight increases in ° Brix and pH and decreases in titratable acidity (TA) were associated with postbloom GA 3 treatments. Use of postbloom GA 3 applications reduced the number and weight of vestigial seeds with developed seedcoats, and reduced the number and weight of undeveloped seeds as well in 2 of 3 years. Girdling increased cluster and berry weights, decreased ° Brix and TA, and increased pH. Transpiration rate of leaves on girdled vines was also higher than control vines on one sampling date. Data suggest that use of bloom and postbloom GA 3 applications to `Sovereign Coronation' may reduce the formation of perceptible vestigial seeds and thus improve the marketability of this cultivar.