Influence of Pectic Oligosaccharides and 5-Aminolevulinic Acid Along with Abscisic Acid on Growth, Yield and Quality Attributes of Crimson Seedless Grape Cultivar

Crimson Seedless is a highly valued table grape cultivar, but under Egyptian climatic conditions, its berries often fail to reach full red coloration. The current investigation was carried out during the 2024 and 2025 seasons, in a commercial vineyard at Sadat City to improve the vegetative growth aspects, yield, and fruit quality attributes of Crimson Seedless. Eight treatments were performed as follows: abscisic acid at 200ppm, pectic oligosaccharides at 1500ppm, and 5-aminolevulinic acid at 200ppm were applied either individually or in combination among them; in addition control (untreated vines). Both pectic oligosaccharides and 5-aminolevulinic acid were foliar sprayed on three dates: the 1st date (after bud burst stage), the 2nd date (at fruit set stage), and the 3rd date (at véraison stage), while abscisic acid was sprayed twice on the clusters; the first spray was at the onset of the véraison stage, and the second spray was done two weeks later. All treatments significantly enhanced yield and fruit quality compared with the control. Among them, the triple combination of abscisic acid + pectic oligosaccharides + 5-aminolevulinic acid proved to be the most effective in enhancing yield, cluster weight and berry weight, higher TSS%, and lower acidity, as well as yielding the highest anthocyanin concentration, followed by the dual combination of pectic oligosaccharides + 5-aminolevulinic acid, while pectic oligosaccharides and 5-aminolevulinic acid alone produced intermediate values. Abscisic acid alone was lower, and the control recorded the minimum values.