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Background and Aims:In some years, the table grape cultivar Crimson Seedless does not reach the commercially acceptable level of red colour in Mediterranean climates, with negative consequences for the grower. Application of abscisic acid (S-ABA) and sucrose could be a tool for overcoming this problem. Methods and Results: A commercial formulation of S-ABA (400 mg/L) and sucrose (10%) was applied to Crimson Seedless at the beginning of veraison and 5 days later in order to verify the effect on harvestable bunches, skin colour, chemical characteristics, anthocyanin content, antioxidant activity and S-ABA concentration either in the skin or the pulp of the berry. The application of S-ABA and sucrose improved the colour of the berries and increased the amount of harvestable bunches at the first pick (80-95%) compared with that of the control treatment (43%). Ripening attributes (total soluble solids, pH, titratable acidity) were not affected by the application of either S-ABA or sucrose. The S-ABA concentration in skin and pulp increased significantly after the treatments and at first harvest. Abscisic acid increased the concentration of anthocyanins and showed a positive effect on the antioxidant activity. Conclusion: Abscisic acid and sucrose improved the colour of the berry skin, with improved results obtained when S-ABA was applied alone and at the beginning of veraison. Sucrose, although to a less extent, was also effective in improving skin colour and increasing the number of harvestable bunches at the first pick. Significance of the Study: This study provides new information about the positive effect of either S-ABA or sucrose on colour, anthocyanin concentration and antioxidant activity of the berry. Moreover, bunches could be harvested in fewer picks with important economic consequences for the grower and with an S-ABA concentration in the berry within the physiological values.

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Some plant growth regulators, including ethephon, can stimulate abscission of mature grape berries. The stimulation of grape berry abscission reduces fruit detachment force (FDF) and promotes the development of a dry stem scar, both of which could facilitate the production of high quality stemless fresh-cut table grapes. The objective of this research was to determine how two potential abscission treatments, 1445 and 2890 mg/L ethephon, affected FDF, pre-harvest abscission, fruit quality, and ethephon residue of Thompson Seedless and Crimson Seedless grapes. Both ethephon treatments strongly induced abscission of Thompson Seedless berries causing >90% pre-harvest abscission. Lower ethephon rates, a shorter post-harvest interval, or berry retention systems such as nets, would be needed to prevent excessive pre-harvest losses. The treatments also slightly affected Thompson Seedless berry skin color, with treated fruit being darker, less uniform in color, and with a more yellow hue than non-treated fruit. Ethephon residues on Thompson Seedless grapes treated with the lower concentration of ethephon were below legal limits at harvest. Ethephon treatments also promoted abscission of Crimson Seedless berries, but pre-harvest abscission was much lower (≅49%) in Crimson Seedless compared to Thompson Seedless. Treated fruits were slightly darker than non-treated fruits, but ethephon did not affect SSC, acidity, or firmness of Crimson Seedless, and ethephon residues were below legal limits.