Abstract

The effect of abscisic acid (ABA) on the color of 'Crimson Seedless' grapes was linked to expression of the key anthocyanin pathway gene UDP-glucose:flavonoid 3-O-glucosyltransferase (UFGT). In the skins of ABA treated fruits, the level of mRNA UFGT increased markedly within one week and then returned to levels that were similar to those of non-treated fruits after three weeks. The mRNA UFGT levels from untreated fruits were similar from veraison to nine weeks later. The color of ABA treated fruit also changed quickly. One week after application, the skins of trated fruits had lower lightness (L*) and hue (h°), and they remained darker and more red-colored throughout the experiment.