Leaf spot on switch grass (Panicum virgatum), symptoms of a new disease caused byBipolaris oryzae

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Abstract
Switch grass (Panicum virgatum) is a native, perennial warm-season grass used for hay, summer grazing, soil conservation, and wildlife habitat. It is also being developed as a biomass crop for renewable energy. A previously unreported leaf-spot disease on switch grass was observed in North Dakota plantings. From 1999 to 2002, a fungus was consistently isolated from leaf spots on switch grass. It was identified as Bipolaris oryzae (teleomorph: Cochliobolus miyabeanus). Conidial morphology agreed with that of B. oryzae, and comparison of DNA sequences from glyceraldehyde-3-phosphate dehydrogenase also indicated that the isolates were B. oryzae. Greenhouse pathogenicity tests confirmed the ability of B. oryzae to cause symptoms of leaf spot on switch grass. This is the first time that B. oryzae, a common pathogen on rice (Oryza sativa), is reported to cause a disease on switch grass. This pathogen has the potential to diminish yields of switch grass under intensive plantings for high biomass production, particularly if a susceptible cultivar is seeded over a wide area. Additionally, Bipolaris zeae (teleomorph: Cochliobolus zeae) was isolated from switch grass, a new host for this fungus, and is herein reported for the first time from the United States.