Characterization of DNA comet and cellulose radical signal in Valencia oranges treated with different forms of ionizing radiation

Postharvest phytosanitary treatment of fruits with ionizing radiation has immense potential to promote international fruit trade. The effects of different forms of ionizing radiation on Valencia oranges stored for various durations were examined using a DNA comet assay, and radiation-induced radicals were quantified by electron spin resonance (ESR) spectroscopy. In non-irradiated seeds, the DNA appeared mostly undamaged, while irradiated samples had significantly longer DNA comet tail lengths. In contrast, DNA obtained from the flesh of the fruit was indistinguishable between the irradiated and non-irradiated samples. An extension in DNA comet tail length was observed as a function of storage time and applied irradiation dose. The ESR spectra of irradiated oranges displayed a characteristic triplet at g = 2.006 with a distance between extreme peaks of 6 mT. Irradiated samples could be distinguished from non-irradiated samples even after prolonged storage for 6 weeks. Finally, the results of these two assays were not affected by using different sources of ionizing radiation. Detection methods such as ESR and the DNA comet assay can be used to control the trade of oranges exposed to gamma rays, electron beam, and X-rays for quarantine applications.