Résumé
Several studies suggest that UV-C radiation, known for its disinfecting effect, may also stimulate plant defenses. The objective of this study is to reduce the sensitivity of strawberry plants (Fragaria x ananassa) to Botrytis cinerea by application of non-deleterious doses of highly energetic UV-C light (254 nm) on leaves. Preliminary tests were carried out on strawberry plants: Cirafine, Charlotte and Candiss, to optimize the doses of UV-C to apply on plants and to test the sensitivity of these three cultivars to B. cinerea. The three cultivars showed different levels of susceptibility to B. cinerea: Cirafine was the most resistant followed by Charlotte and Candiss being the most sensitive. These observations were supported by histological examination and phenol levels in the leaves that indicated deeper penetration of B. cinerea into Candiss. Nine variations of treatments were applied to the plants, which were composed of varying UV-C doses and differing application frequencies. The treatment of UV-C applied at 0.85 and 1.70 kJ/m², four times every second day (p-value = 0.05), were shown to have a significant increase, around 25%, in the protection of Candiss against Bc1 strain of B. cinerea. Our observations show that exposing strawberry plants (Candiss) to low repeated doses of UV-C could improve their resistance against gray mold, while avoiding any apparent negative effects to the plants.