Effect of nighttime UV-C irradiation of strawberry plants on phenolic content of fruit: Targeted and non-targeted metabolomic analysis

BACKGROUND: The new approach of using UV-C irradiation followed by a specific dark period to control plant diseases has the potential to become a mainstream treatment in the production of strawberries and other fruits and vegetables. Thus, it is imperative to study the effects of this treatment on fruit quality. METHODS: In this study, short-day 'Chandler' strawberry plants grown in growth chamber from bloom to harvest were irradiated twice a week with nighttime UV-C light (253 nm peak value 12.36 J m-2 and the total dose of 50 J m(-2) in the range of 240-260 nm). The effects on the content of key phenolic compounds in mature fruit were studied with targeted analysis and a non-targeted metabolomic approach based on ultra-high performance liquid chromatography high resolution mass spectrometry (UHPLC-HRMS). Analysis of variance-principal component analysis (ANOVA-PCA) was used to associate variance with different experimental factors. RESULTS: Results indicate that the content of anthocyanins, glucosides and glucuronides of quercetin and kaempferol, catechin, pelargonidin rutinoside, and ellagic acid was not affected by UV-C treatment. ANOVA-PCA analysis of the metabolomicdataset showed no significant differences in composition and content of strawberry metabolites between UV-C and control groups; however, differences were observed between harvest times. CONCLUSIONS: Our findings strongly indicate that UV-C treatment of 50 J/m(2) twice per week did not affect nutritional values of strawberry fruit. The metabolomic approach combined with ANOVA-PCA used to evaluate strawberry fruit quality after UV-C irradiation proved to be a very powerful tool in providing an overall insight into fruit quality and accurately determines the influence of each experimental factor.