AFIELD experiment was carried out through two successive ……seasons of 2012 and 2013 on 8- years- old Crimson Seedless vine grown at 2.5 x 1.5 m apart in clay soil under drip irrigation system in a private vineyard located in Sharkia Governorate, Egypt. Grapevines were sprayed with GA3 at 0.0, 0.5, 1.0, 2.0 and 4.0 mg/l at full bloom (80 % calyptra fall) to evaluate the effect of GA3 as a thinning agent instead of hand thinning.
The obtained results markedly reveal that number of berries /bunch, bunch weight, yield/ vine, bunch compactness and berry compression force were significantly reduced with increasing GA
3 concentration. As an average of both seasons, number of berries/ bunch was decreased by 43.92, 62.44, 69.98 and 80.22 % as a result of spraying vines with GA3 at 0.5, 1.0, 2.0 and 4.0 mg/l, respectively in comparison with the control treatment. The corresponding reduction percentage in yield/ vine was 33.77, 54.25, 61.75 and 70.9 %, respectively. In contrast, weight of 100 berries, berry removal force were obviously increased with increasing GA3 concentrations in both seasons, due,
mainly, to increasing thinning level. Total soluble solid percentage (TSS%) and TSS/acid ratio were significantly increased as a result of GA
3 spraying treatments without significant differences between the tested concentrations in most cases, whereas total acidity percentages were reduced as compared with unsprayed vines in both seasons.
The obtained result of this study reveal that spraying GA
3 at 0.5 mg/l at full bloom was the optimum treatment for Crimson Seedless berry thinning, since this treatment obviously improved bunch and berry physical and chemical characteristics, as well as packable yield of tested table grape cv. without higher reduction in number of berries/ bunch, as well as yield and bunch weights as compared with the other tested GA3 concentrations and control.