Postharvest physio-pathological disorders in table grapes as affected by UV-C light.

To gain knowledge on the influence of postharvest treatments with ultraviolet-C light upon the keeping quality of table grapes, a trail was performed employing commercially mature 'Corina', 'Dawn Seedless', 'Centennial Seedless' and 'Gran Perlon' grape cultivars (cvs). After grading, bunches were subjected to 0.0, 0.5, 1.5 or 3 kJm(-2) and then stored at 5 degrees C and 90% relative humidity (RH) for 6 weeks followed by a 2 day shelf-life at 25 degrees C and 70% RH. A weekly inspection was performed and a visual evaluation of the appearance, treatment damage, stems browning and berry shrivelling was performed. Weight loss, decay and shatter were quantified at the end of storage and shelf-life. Regardless the cv and UV-C dose, fruit appearance was acceptable until the end of storage and shelf-life. Among the cvs, the highest score was held by 'G. Perlon'. After the fourth week of storage, the berries of 'Centennial S.' turned light brown and darkened over time when treated with 3.0 kJm(-2). Stem browning was not induced by the light treatment, but resulted cv depended and was pronounced for 'Centennial S.' and 'Dawn S.'. Berry shrivelling was insignificant, while shatter was very high in 'Corina' and did not depend upon UV-C treatment. Regarding weight loss, differences could not be attributed to the light treatment and after storage it ranged from 3 up to 5%. Decay was significantly reduced by light treatment and the efficacy increased by raising the dose. Botrytis cinerea was the main cause of decay with 'Corina' being the most jeopardized, followed by 'Dawn S.' and 'Centennial S.', whereas 'G. Perlon' resulted the less affected. In conclusion, hormetic effects of postharvest light treatment on table grapes were observed in almost all cvs with 'G. Perlon' having the best performance.