UV-C induced disease resistance and delayed ripening in tomato fruit with prior exposure to selected storage stresses.

摘要

The induction of disease resistance and delayed ripening by hormetic doses of UV-C in postharvest crops has been well established. However, it is not known whether UV-C induced effects are similar when produce are transiently exposed to other abiotic storage stresses prior to UV-C treatment. It was hypothesized that UV-C induced effects in crops could be modified if crops had previously been exposed to storage and handling stresses such as heat, cold, wounding and atmosphere (low or high O 2 or high CO 2), before administering UV-C treatment. Mature green tomato fruit were exposed to various storage stresses: heat (35掳C for 60 h); cold (1掳C for 7 days); hypo-O2 atmosphere (100% N 2 for 24 h); hyper-O 2 atmosphere (100% O 2 for 24 h); high CO 2 atmosphere (100% CO 2 for 8 h); and wounding. After 24 h, fruit were treated with hormetic UV-C dose of 3.7 kJ m -2 and stored at 13掳C and relative humidity of about 95% for 25 days. Fruit ripening was monitored by color measurement, and disease resistance was evaluated by inoculation of the fruit with Botrytis cinerea 12 days after UV-C treatment. The delay in color development of tomato by UV-C treatment was not generally affected even when the fruit had been previously exposed to various stresses. The enhanced delay in ripening of the fruit by cold stress and the diminished delay by heat stress are attributable to storage temperature history; whereas the diminished delay in its ripening due to wounding can be attributed to increased respiration rate of the wounded fruit. UV-C induced resistance in tomato was not affected by previous exposure to either hyper-O 2 or high CO 2 atmosphere. However, it was attenuated when the fruit had been previously exposed to wounding and cold stresses and to a smaller extent to hypo-O 2 atmosphere. Results suggest UV-C is a dominant stress over a variety of storage stresses and that UV-C generated signal path is transduced in tomato fruit, either fully or for a good measure even after exposure to other stresses, leading to the induction of the observed UV-C effects. CT XXVIII International Horticultural Congress on Science and Horticulture for People (IHC2010): International Symposium on Postharvest Technology in the Global Market, Lisbon, Portugal.