Abstract
Post-harvest applications of UV-C radiation have proven very efficient in reducing the development of post-harvest diseases in many species including lettuce (Lactuca sativa L.). Several studies suggest that UV-C radiation is effective not only because of its disinfecting effect but also because it may stimulate plant defenses. Pre-harvest treatment with UV-C radiation may thus offer an interesting potential for lettuce protection, provided that application doses are effective while excluding any harmful effects on the plants. Here we provide evidence that 0.85kJm−2 and 1.70kJm−2 represent doses of UV-C radiation that are not deleterious for lettuce plants. We used several criteria to evaluated the effect of UV-C radiation on the plant, including histological observations; the concentration of malondialdehyde, an indicator of membrane integrity, as well as parameters derived from measurements of chlorophyll fluorescence, such as maximal efficiency of photosystem II (Fv/Fm) and the Performance Index of Strasser. We observed that a single dose of 0.85kJm−2 slightly increased plant resistance to grey mould (Botrytis cinerea L.) while a single dose of 1.70kJm−2 had the opposite effect. When a 0.85kJm−2 dose was applied 4 times, at two-day intervals, there was an increase in the total phenol content of leaves, and in PAL, CAT, and MDAHR activities. Leaves inoculated 2 days after the latter UV-C treatment showed significantly decreased sensitivity (−30%) when compared to the control.
Published Version
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