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Exploiting our knowledge of how fungal plant pathogens use visible and UV light

Arne Stensvand: Norwegian Institute of Bioeconomy Research (NIBIO)

<div>Fungal plant pathogens evolved amidst natural cycles of light and darkness. The imposition of light-filtering or blocking material such as plastics or glass, or provision of supplemental electrical lighting is a recent event in their evolutionary history. Light filtering or light supplementation can fundamentally alter pathogen development and resultant disease severity as fungi sense, interpret and respond to light. Direct damage to pathogens by natural incoming UV can be blocked by plastics and glass. Conversely, it can be strategically employed through supplementation to suppress disease. Several examples will be provided of the use of UVB and UVC in glasshouse, plastic tunnel, and open field plantings of diverse crops for suppression of powdery mildews. Experiments using UV-transparent fluorocarbon plastics indicate a pronounced and previously underestimated effect of UV exclusion on severity of powdery mildews when sunlight is filtered by glass, polyethylene, or polycarbonate films; none of which transmit UV. Visible light, particularly supplemental red and blue light, can also be used to disrupt and misdirect fungal development through disruption of circadian systems (<em>e.g.,</em> continuous light and suppression of rose powdery mildew) and photoreceptor control of morphogenesis (<em>e.g</em>., red light suppression of powdery and downy mildews). We can use light to suppress disease, and refine production systems to avoid unintentionally exacerbating disease severity.</div>

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