Post-harvest UV-B irradiation induces changes of phenol contents and corresponding biosynthetic gene expression in peaches and nectarines

•Peach and nectarine fruits were post-harvest irradiated with UV-B radiation.•UV-B treatment affected phenolic compounds in a genotype-dependent way.•UV-B irradiation mainly influenced the skin tissue.•UV-B treatment increased health-promoting phenolics in ‘Big Top’ and ‘Suncrest’. In the present study the possibility of enhancing phenolic compound contents in peaches and nectarines by post-harvest irradiation with UV-B was assessed. Fruits of ‘Suncrest’ and ‘Babygold 7’ peach and ‘Big Top’ nectarine cultivars were irradiated with UV-B for 12h, 24h and 36h. Control fruits underwent the same conditions but UV-B lamps were screened by benzophenone-treated polyethylene film. The effectiveness of the UV-B treatment in modulating the concentration of phenolic compounds and the expression of the phenylpropanoid biosynthetic genes, was genotype-dependent. ‘Big Top’ and ‘Suncrest’ fruits were affected by increasing health-promoting phenolics whereas in ‘Babygold 7’ phenolics decreased after UV-B irradiation. A corresponding trend was exhibited by most of tested phenylpropanoid biosynthesis genes. Based on these results UV-B irradiation can be considered a promising technique to increase the health-promoting potential of peach fruits and indirectly to ameliorate the aesthetic value due to the higher anthocyanin content.