This investigation was carried out during two successive seasons (2018 & 2019) in the vineyard of EL-Baramon experimental farm. Hort. Res. Inst. Mansoura, Dakahlia Governorate, Egypt. The experiment was conducted on Four/Five years-old Thompson seedless grapevines (H4strain). The vines were grown in a clay soil under surface irrigation system and cane pruning and trellised with Spanish baron system. The aim of this study was to reduce the compactness coefficient of clusters and improve the physical and chemical properties of cluster and berries in Thompson seedless grapes (H4strain). Gibberellic acid (GA3) and Brassinolide (BL) were foliar applied alone or in combinations at three stages, before bloom, during bloom stage and after complete set of berries.
The Results show that spraying the vines with Gibberellic acid (GA3) and Brassinolide (BL) alone or in combinations significant improved the cluster and berries traits, since they decreased the number of berries/cluster and increased the length and width of cluster consequently, decreasing the compactness coefficient of cluster. Also, clear improvements in cluster weight, yield and physical & chemical properties of berries were attained. The data also revealed that Gibberellic acid (GA3) was more effective on improving physical properties of clusters and berries while Brassinolide was preferable on improving chemical properties of berries.
The best achievements were dedicated to Gibberellic acid (3/4 recommended dose) + 0.5 ppm Brassinolide followed by Gibberellic acid (1/2 recommended dose) + 1.0 ppm Brassinolide.