Supplemental UV Radiation Controls Rose Powdery Mildew Disease under the Greenhouse Conditions

Abstract

Roses are the most economically important ornamental crops produced throughout the world. Powdery mildew caused by Podosphaera pannosa is a major disease of greenhouse roses, and chemical fungicides are absolutely necessary for disease control. Ultraviolet (UV) in solar radiation has been thought to contribute to plant resistance against pathogens and herbivores. Here, we show that supplementary radiation with low levels of UV suppresses the development of powdery mildew disease in greenhouse roses. Supplemental UV radiation with a UV-B fluorescent lamp during the night was more effective than in the daytime. Gene expression analysis revealed that genes involved in secondary metabolic pathways were induced in rose plants by low levels of UV radiation. Direct exposure to UV radiation inhibited rose powdery mildew conidial germination in a dose-dependent manner. These results suggest that UV radiation can suppress powdery mildew development through inhibition of fungal growth and activation of host defenses. Disease control using supplemental UV radiation will contribute to reducing the environmental burdens from fungicide use.