Effect of varying concentrations of melatonin on anthocyanin and sugar metabolism in grapes (Vitis labruscana L.)

Abstract

Importance of the work: The effects of melatonin on fruit maturation are still unclear and these effects may vary according to treatment concentrations.
Objectives: To investigate the effects of melatonin treatment on anthocyanin, sugar, abscisic acid (ABA) and indole 3-acetic acid (IAA) concentrations and their related genes.
Materials & Methods: In the first and second groups, clusters of ‘Kyoho’ grape vines were randomly immersed in 100 μM and 1,000 μM melatonin, respectively, with the surfactant Approach BI at 30 d after full bloom. In the third group, clusters of the untreated control were treated with Approach BI only.
Results: Treatment with 100 μM melatonin promoted anthocyanin accumulation and expression of the VlMYBA1-2 and VvUF3GT genes. In addition, it increased the concentrations of sugars, such as fructose, glucose and sucrose, and upregulated the expression of sugar biosynthesis-related genes (VvSUT11, VvSUS4, VvAI and VvHT1). Melatonin treatment increased ABA concentrations with the upregulation of VvNCED1 at 24 d after treatment. IAA concentrations and the expression of VvGH3-1 decreased in the 100 μM melatonin-treated berries. In contrast, the 1,000 μM melatonin treatment did not influence the anthocyanin or sugar concentrations.
Main finding: Melwatonin may affect anthocyanin and sugar metabolism through ABA and IAA biosynthesis. Treatment with 100 μM melatonin was most effective at increasing the anthocyanin and sugar concentrations in grapes.