Exogenous ACC, ABA, and/or Ethylene Enhance Berry Color Without Reducing Postharvest Performance in ‘Benitaka’ and ‘Rubi’ Table Grapes

The objective of this work was to assess the association of ACC (1-aminocyclopropane-1-carboxylic acid), S-ABA (abscisic acid), and ethephon on color development and anthocyanin accumulation in berries, as well as on other quality attributes of ‘Benitaka’ and ‘Rubi’ table grapes grown in a subtropical region, in addition to postharvest conservation of clusters and vine regrowth. As a statistical model, a randomized block design consisting of nine treatments and four replications was used. The treatments included different associations of ACC, S-ABA, and ethephon, by using the commercial formulations Accede®, ProTone®, and Ethrel® containing 400 g kg−1 of ACC, 100 g L−1 of S-ABA, and 720 g L−1 of ethephon, respectively. The total anthocyanins, berry color index (CIRG), physicochemical characteristics, and cluster color coverage were assessed weekly, while berry firmness was assessed at harvest. After being harvested, the clusters were placed under cold storage at 1.0 ± 1.0 °C, and after 45 days, their postharvest attributes were assessed, as well as the vine regrowth in the following season. The exogenous and combined application of compounds at véraison was demonstrated to be a strategy to trigger the development of color in ‘Benitaka’ and ‘Rubi’ table grapes. For the ‘Benitaka’ table grape, the clusters treated with the different combinations of ACC and S-ABA, ethephon and S-ABA, or ethephon alone resulted in the highest concentration of total anthocyanins and the highest CIRG means (4.90; 4.86; 4.82; 4.81, 4.73, and 4.70 mg g−1 for anthocyanins, and 6.12, 6.08, 5.97, 5.92, 5.85, and 5.74 for CIRG, respectively). For the ‘Rubi’ table grape, the combinations of ACC and S-ABA at 7 days after véraison (DAV), or ethephon and S-ABA at 7 and 14 days, resulted in higher means of anthocyanins and CIRG (3.86, 3.51, and 3.40 mg g−1 for anthocyanins and 5.05, 4.68, 4.82, and 4.79 for CIRG, respectively). Furthermore, the firmness of the berries of both cultivars remained unchanged, and after 45 days of cold storage, no reduction in the quality of the evaluated postharvest attributes was found. It was concluded that a single application of ACC 0.20 g L−1 + S-ABA 0.250 g L−1 at 7 DAV was sufficient to promote the accumulation of anthocyanins and resulted in an intense and uniform color in the berries for both varieties assessed, with no adverse impacts on the postharvest conservation of the clusters or on the regrowth of the vines. The significance of this research was to demonstrate that table grapes with insufficient skin color can be improved through a combination of S-ABA and ACC at lower concentrations of active ingredients.