Gibberellic Acid-induced Seedlessness in Field-grown Vines of `Swenson Red' Grape

Abstract

We evaluated the extent to which `Swenson Red' seeded grape (Vitis × spp.) responded to single and repeated GA 3 applications to induce seedless fruit development. Field studies were conducted to test the time of pre-anthesis GA 3 application (18, or 24 May or 3 June), the usefulness of postanthesis application, the optimum GA 3 concentration (0, 0.075, 0.15, or 0.3 m m ), and the method of application. The treatment dates that gave a high percentage of seedless berries with an acceptable berry count per cluster were 24 May with postanthesis application and 3 June pre-anthesis only. The optimum GA 3 concentration was 0.15 m m applied both before and after anthesis. The most seedless berries developed when pre- and postanthesis applications were used, indicating many seedless fruit developed from flowers that would have abscised. There was no difference in percent heedlessness, number of berries per cluster, or number of seeds per berry between clusters dipped or sprayed with 0.3 m m GA 3 . Chemical uame used: gibberellic acid (GA 3 ).