UV-C light and pulsed light as alternatives to chemical and biological elicitors for stimulating plant natural defenses against fungal diseases

UV-C light, notably under the forms of either short duration illuminations supplied by mercury vapour lamps or LEDs, or flashes of pulsed light supplied by xenon lamps, can be at the origin of inhibitory and damaging effects in plants. But when UV-C light is applied at hormetic doses, it can exert beneficial effects on plants and on harvested organs. This review, largely based on observations made on fruits and vegetables after harvest, presents direct and indirect (based on observations on the secondary metabolism) evidence that UV-C light can stimulate plant natural defenses against fungal diseases. The mechanisms of UV-C light perception and the signaling, regulatory and metabolic pathways involved are not well documented in the literature. It may however be safely hypothesized that oxidative stress plays an important role in UV-C light perception and signaling, possibly besides other mechanisms. Based of the high potential of UV-C light as an elicitor of plant defenses, especially in horticulture, the review advocates strongly in favor of increasing of our understanding of the physiological basis of UV-C effects on plants.