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Suppression of wheat powdery mildew (Blumeria graminis f. sp. tritici) by nighttime exposure to UV-B radiation

Leah Granke: Dow AgroSciences

<div>Greenhouse testing is critical to the discovery of new fungicides. Test quality for slow-growing pathogens such as <em>Zymoseptoria tritici</em> can be impacted by powdery mildew if an aggressive fungicide treatment program is not followed. In this study, we found that ultraviolet (UV)-B radiation (305-315 nm, 4-6 W/m<sup>2</sup>) applied for 8 h (16 h light: 8 h UV-B) suppressed wheat powdery mildew by limiting conidial germination, colony development, and sporulation in growth chamber studies. Treatment during the entire 8 h dark cycle worked better than treatment for 6h. Treatment for 4 h was not significantly different from no treatment at all. UV-B was more effective as a 0 day protectant than as a 1 day curative treatment. UV-B applied overhead provided greater suppression of powdery mildew on the adaxial surface of the leaf than the abaxial surface. Wheat that was pre-treated with UV-B daily (16 h light: 8 h UV-B) for 1 month prior to inoculation was as susceptible to <em>Z. tritici </em>as wheat that received no UV-B pre-treatment. Nighttime exposure to UV-B appears to be a viable non-chemical strategy for suppression of wheat powdery mildew caused by <em>Blumeria graminis </em>f. sp.<em> tritici</em>.</div>