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Title: Suppression of cucumber powdery mildew by UV-B is affected by background light quality

Author
item SUTHAPARAN, A - Norwegian University Of Life Sciences
item STENSVAND, A - Norwegian Institute For Food Research
item SOLHAUG, K - Norwegian University Of Life Sciences
item TORRE, S - Norwegian University Of Life Sciences
item TELFER, K - Norwegian University Of Life Sciences
item RUDD, A - Norwegian University Of Life Sciences
item Cadle-Davidson, Lance
item MORTENSEN, L - Norwegian University Of Life Sciences
item GADOURY, D - Cornell University
item SEEM, R - Cornell University
item GISLEROD, H - Norwegian University Of Life Sciences

Submitted to: American Phytopathological Society Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 3/15/2012
Publication Date: 5/1/2012
Citation: Suthaparan, A., Stensvand, A., Solhaug, K.A., Torre, S., Telfer, K.H., Rudd, A.K., Cadle Davidson, L.E., Mortensen, L.M., Gadoury, D., Seem, R., Gislerod, H.R. 2012. Suppression of cucumber powdery mildew by UV-B is affected by background light quality. American Phytopathological Society Abstracts. Phytopathology 102:S.

Interpretive Summary:

Technical Abstract: Brief (5-10 min) exposure to UV-B radiation (280-300 nm) suppressed powdery mildew (Podosphaera xanthii) on Cucumis sativus. The effect was enhanced by red light (600-660 nm), but offset by blue light (420-500 nm) and UV-A (300-420 nm). Compared to untreated controls, 2 h red light from specific light emitting diodes (LEDs) reduced disease severity by 25.4 percent, and by 98 percent when combined with brief exposure to UV-B. We hypothesized that UV-B damaged fungal DNA, that blue light and UV-A were involved in DNA repair, and that red light exacerbated damage to DNA. We confirmed the expression of genes similar to phytochrome, cryptochrome, white collar, and photolyase (light-dependent DNA repair) using next generation sequencing of Erysiphe necator. Sequence and expression analysis of these light-responsive genes from P. xanthii will be reported. Our findings may explain how powdery mildews, which are principally external to the host and lack protective pigmentation, nonetheless thrive despite their lack of obvious protection from UV radiation. Our results suggest that efficacy of UV-B treatments against powdery mildews will be greatly enhanced by applying them during the night period, thereby circumventing the counteracting effects of blue light and UV-A, particularly when UV-B is used in combination with red light. Brief night exposure to UV-B, and/or inexpensive and specific LEDs may provide additional tools to suppress powdery mildews in diverse crops.