Use of UV-C light to reduce Botrytis storage rot of table grapes

Single table grape berries (Vitis vinifera L. cv. Italia) were irradiated with ultraviolet-C (UV-C) doses ranging from 0.125 to 4 kJ m(-2) and inoculated with Botrytis cinerea. The pathogen was inoculated on artificial wounds at different times (0, 24, 48, 72, 96 and 144 h) after irradiation and the berries were stored either at 21 or 3 degrees C. To check the influence of UV-C irradiation on the wound-healing processes, trials using berries wounded just before the UV-C irradiation and inoculated at different times were also performed. Significantly lower numbers of infected berries and lesion diameter were found in berries treated with UV-C doses ranging from 0.125 to 0.5 kJ m(-2). There was also a significantly lower level of disease in berries inoculated after 24-48 h than in those inoculated just after (10-15 min) the UV-C treatment. Thus, pretreatment with low UV-C doses followed by artificial inoculation with B. cinerea reduces postharvest grey mould of table grapes, suggesting induced resistance to the disease, both in berries wounded before and after irradiation. The microbial epiphytic population on UV-C-treated berries was also monitored. Results showed a significantly higher increase in the population of yeasts (including yeast-like fungi) and bacteria on berries irradiated with 0.25 and 0.5 kJ m(-2) than on unirradiated control berries. (C) 1998 Elsevier Science B.V. All rights reserved.