The effects of low-dose ultraviolet light-C treatment on polygalacturonase activity, delay ripening and Rhizopus soft rot development of tomatoes

Low-dose application of hormetic (adj. of hormetin, the agent of hormesis e.g. UV-C) ultraviolet light-C (UV-C) to 'Better Boy' and 'Floradade' tomatoes at maturity resulted in fruits that were significantly, firmer than non-irradiated control fruits at the same stage of maturity. As, firmness increased following UV-C treatment, polygalacturonase (PG) activity decreased. The enzyme activity was lower for UV-C treated fruits than the control. The PG activity in crude extract from decayed tomato tissue infected with Rhizopons stolonifer was lower than non-decayed fruits. UV-C treated tomatoes showed a 40% reduction in PG activity in decayed tissue compared to the control at 72 h after treatment. The lesion diameter, and percent infection of non-treated and UV-C treated tomatoes at 72 h after treatment, was 13.4 mm (100% infection), and 5.3 mm (47% infection), respectively. (C) 2003 Elsevier Ltd. All rights reserved.