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

Authors: Sun, Jianghao; Janisiewicz, Wojciech; Takeda, Fumiomi; Evans, Breyn; Jurick, Wayne; ZHANG, MENGLIANG - Middle Tennessee State University; YU, LIANGLI - University Of Maryland; Chen, Pei

Submitted to: Journal of Berry Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/17/2020
Publication Date: 9/8/2020
Citation: Sun, J., Janisiewicz, W.J., Takeda, F., Evans, B.E., Jurick Ii, W.M., Zhang, M., Yu, L., Chen, P. 2020. Effect of nighttime UV-C irradiation of strawberry plants on phenolic content of fruit: targeted and non-targeted metabolomic analysis. Journal of Berry Research. 10(3):365-380. https://doi.org/10.3233/JBR-190482.
DOI: https://doi.org/10.3233/JBR-190482

Interpretive Summary: The new approach of using ultraviolet irradiation of plants followed by a specific dark period to control plant diseases and arthropods has the potential to become a mainstream treatment in the production of strawberries and other fruit, and vegetable crops. Thus, it is now imperative that the effects of this treatment on fruit quality are thoroughly investigated. In this study, we irradiated strawberry plants with ultraviolet light for 60 seconds twice a week at midnight from the time of bloom until harvest. Strawberries from ultraviolet treated and untreated plants were harvested and analyzed for content of phenolic compounds including ellagic acid, known for its beneficial effect to human health. The results indicate that the kind and level of different phenolics such as anthocyanins, glucosides and glucuronides of quercetin and kaempferol, catechin, pelargonidin rutinoside, and ellagic acid were not affected by the ultraviolet treatment. Small variations observed in phenolic content were related to harvest time, suggesting that environmental factors may be involved. Our results further indicate that the ultraviolet irradiation technology that we developed is safe and does not negatively affect important nutraceuticals in strawberry fruit.

Technical Abstract: 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 fruit, and vegetable crops. Thus, it is now imperative that the effects of this treatment on fruit quality are thoroughly investigated. In this study, we focused on the effect of bi-weekly nighttime irradiation, from bloom until harvest, of short-day ‘Chandler’ strawberry plants grown in a growth chamber with UV-C (253 nm peak value 12.36 J/m2 and the total dose of 50 J/m2 in the range of 240 – 260 nm) on the content of key phenolics in mature fruit. Targeted analysis and a non-targeted metabolomic approach based on ultra-high performance liquid chromatography (UHPLC) tandem with high resolution mass spectrometry was used to determine any changes in phenolic compounds of strawberries subjected to UV-C treatment. ANOVA combined with principle component analysis (ANOVA-PCA) was used to target variance with different experimental factors. The results indicate that the kind and level of anthocyanins, glucosides and glucuronides of quercetin and kaempferol, catechin, pelargonidin rutinoside, and ellagic acid were not effected by the UV-C treatment. ANOVA-PCA analysis of the metabolomic dataset indicates significant differences in the metabolites of strawberry from both UV-C and control groups resulting from the harvest time but not due to the UV-C irradiation effect itself in terms of the composition and level of the key phenolic compounds. Our findings strongly indicate that the UV-C treatment does not diminish important nutritional values of strawberry fruit.