The effect of postharvest application of UV-C radiation on the phenolic compounds of conventional and organic grapes (Vitis labrusca cv. ‘Concord’)

• Post-harvest UV-C treatment induces bioactive compounds in “Concord” grapes.
• The positive effect of UV-C depends on the grape production system.
• Bioactive compounds are co-related with phenylpropanoid biosynthesis.

It is known that ultraviolet light has a major role in the ontogeny of the plants, and may also induce the production of secondary metabolites. The aim of this study was to evaluate the cultivar ‘Concord’, produced in conventional and organic production systems, treated with UV-C radiation after harvest. Grapes were evaluated for chemical composition, the antioxidant activity and the relative accumulation of gene transcripts related to secondary metabolism of the grapevine. UV-C radiation stimulated gene expression of the phenolic compounds biosynthetic and also caused accumulation of these metabolites, and these changes were dependent on the production system. The results showed that the conventional grapes had a higher accumulation of transcripts of the genes PAL, CHS and STS which ANS compared to organically produced grape. After harvest, UV-C stimulates the accumulation of transcripts of these genes. Organic grapes had a higher antioxidant activity. UV-C radiation resulted in an increase of antioxidant activity in grapevines from different production systems.