COLOURING IMPROVEMENT OF CRIMSON SEEDLESS GRAPES BY USING PHENYLALANINE, COUMARIC ACID AND ABSCISIC ACID

Abstract
This investigation was conducted for two successive seasons (2017 & 2018) in a private vineyard located at El-Nubaria region, El-Behira governorate, Egypt to study the effect application of phenylalanine, coumaric acid and abscisic acid on bunch quality attributes of Crimson Seedless grape cultivar. The chosen vines were six-year-old, grown in a sandy soil, spaced at 1.5 X 3 meters apart and irrigated by the drip irrigation system. The vines were cane-pruned during the third week of January with bud load of 100 buds/vine so as to leave (10 canes X 10 buds/cane) with trellised by Gable supporting system. Seven treatments were carried out by spraying the clusters as follows: tap water (Control), phenylalanine at 250ppm, phenylalanine at 500ppm, coumaric acid at 500ppm, coumaric acid at 1000ppm, abscisic acid at 300ppm and abscisic acid at 400ppm. Clusters were sprayed twice: the first spray at veraison stage (20% berry colour), while the second spray was done two weeks later.
The results showed that spraying with phenylalanine, coumaric acid and abscisic acid at the higher concentration significantly had the best values in improving fruit quality attributes compared to those at the lower concentration of these ones in both seasons. Spraying with phenylalanine followed by coumaric acid followed by abscisic acid attained the best results in terms of improving fruit quality attributes by increasing average berry weight, size and dimensions as well as enhancing berry maturity by increasing total soluble solids, total soluble solids/acid ratio, total sugars and anthocyanin in berry skin and decreasing total acidity in berry juice of Crimson Seedless grapes.
From obtained results, it can be said that spraying with phenylalanine at 500ppm was the most effective in improving fruit quality attributes for Crimson Seedless grapes.