Effects of light emitting diode irradiation at night on abscisic acid metabolism and anthocyanin synthesis in grapes in different growing seasons

The effects of red- and blue-light irradiation at night on abscisic acid (ABA) synthesis and anthocyanin and sugar concentrations were examined in grape vines, which were grown in two different seasons. In grapes cultivated with early heating, the ABA concentrations were highest in blue-light-emitting diode (LED)-treated skin; however, those in grapes cultivated in the ordinary growing season were highest in red-LED-treated skin. The expressions of 9-cis-epoxycarotenoid dioxygenase (VvNCED1) and ABA 8′-hydroxylase (VvCYP707A1) were high in each treatment at veraison regardless of the growing season. In both seasons, anthocyanin concentrations were highest under the blue-LED treatment, followed by the red-LED treatment. The expressions of VlMYBA1-2, VlMYBA2, and VvUFGT coincided with anthocyanin concentrations. Sugar concentrations were increased by the blue-or red-LED treatment dependent on the growing season. The results suggest that blue- or red-LED irradiation at night may influence the ABA and anthocyanin metabolism including VvNCED1, VlMYBA1-2, and VlMYBA2 and sugar synthesis in grape berries, although the degree of the effects differs with the growing season.