Effects of ozonated water irrigation on the quality of grafted watermelon seedlings

Ozonated water is an important postharvest sanitizer and an interesting alternative to keep nursery crops sanitized. Ozonated water (OW, 750 mV) and electrolyzed water (EW, 495 mV) were compared to a control (CTRL, water without sanitizer treatment), applied as overhead micro sprinkler irrigation, in grafted watermelon seedling plants grown under greenhouse conditions. As results we found a reduction in micronutrients (Fe, Mn, Cu, Zn and B) and macronutrients (Ca and Mg) in grafted watermelon leaves treated with OW, although the OW did not affect the photosynthesis rate or plant development. Additionally, EW reduced the vitamin C content at days 45 and 57 compared to the OW and CTRL samples. OW and EW showed higher total phenolic content (TPC) than the CTRL at days 45 and 49. However, no significant differences were observed in TPC and antioxidant capacity among treatments at day 57. On the other hand, catalase activity increased in OW samples after days 49 and was maintained at day 57, but no significant changes in lipid peroxidation was observed among treatments. As main conclusion, OW caused a moderate stress in grafted watermelon seedlings increasing the oxidative status to balance the redox system that could provide plants with higher bioactive compounds.