USE OF UV-C LIGHT TO REDUCE BOTRYTIS STORAGE ROT OF TABLE GRAPES

Single table grape berries (Vitis vinifera L. cv. Italia) were irradia ted with ultraviolet-C (UV-C) doses ranging from 0.125 to 4 kJ m(-2) a nd inoculated with Botrytis cinerea. The pathogen was inoculated on ar tificial 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 proces ses, trials using berries wounded just before the UV-C irradiation and inoculated at different times were also performed. Significantly lowe r numbers of infected berries and lesion diameter were found in berrie s treated with UV-C doses ranging from 0.125 to 0.5 kJ m(-2). There wa s also a significantly lower level of disease in berries inoculated af ter 24-48 h than in those inoculated just after (10-15 min) the UV-C t reatment. Thus, pretreatment with low UV-C doses followed by artificia l 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 populati on on UV-C-treated berries was also monitored. Results showed a signif icantly higher increase in the population of yeasts (including yeast-l ike 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.