UV irradiation induces resistance against fruit rot disease and improves the quality of harvested mangosteen

Abstract

Fruit rot disease and short shelf life are the limiting factors of mangosteen fruit. This study focused on investigating the effect of ultraviolet (UV) irradiation in controlling fruit rot disease and on quality improvement in harvested mangosteen. Mangosteen fruit artificially inoculated with L. theobromae were treated with UV-B or UV-C irradiation at dosages of 0 (control), 6, 13, 26, and 40 kJ m−2 and stored at 25 °C for 7 d. The results indicate that UV-C treatment exhibited higher fungicidal potential in preventing fruit rot disease than UV-B treatment. UV-C treatment at a dose of 13 kJ m-2 was the most effective in reducing disease incidence and lesion diameter, followed by UV-C at a dose of 26 kJ m−2, whereas the effects of UV-C at a higher dosage (40 kJ m−2) and a lower dosage (6 kJ m−2) showed no significant difference from the untreated fruit. Therefore, UV-C irradiation at doses of 13 kJ m−2 was selected to investigate the induction of disease resistance and improvement of mangosteen quality. Naturally infected mangosteen fruit were exposed to UV-C irradiation at a dose of 13 kJ m−2 and untreated fruit served as the control. All fruit samples were kept at 13 °C for 21 d. The results showed that UV-C treatment reduced fruit rot disease and induced the activity of key plant defense-related enzymes, including phenylalanine ammonia lyase (PAL), peroxidase (POD), chitinase and β-1,3-glucanase, besides increasing the content of total phenolics and hydrogen peroxide (H2O2). In addition, the fruit treated with UV-C could delay weight loss, respiration rate, color changes of peel and calyx and maintain total chlorophyll in the calyx of mangosteen. The results suggest that UV-C application is an alternative approach to suppress fruit rot disease and improve the postharvest quality of mangosteen.