ARS | Publication request: A New Leaf Spot Disease on Switchgrass (Panicum Virgatum)caused by Bipolaris Oryzae

Submitted to: Canadian Journal Of Plant Pathology
Publication Acceptance Date: April 16, 2004
Publication Date: September 22, 2004
Citation: Krupinsky, J.M., Berdahl, J.D., Schoch, C.L., Rossman, A.Y. 2004. A New Leaf Spot Disease On Switchgrass (Panicum Virgatum)caused By Bipolaris Oryzae. Canadian Journal Of Plant Pathology 26:371-378.

Interpretive Summary: Switchgrass is a warm-season grass used for hay, summer grazing, soil conservation, and wildlife habitat. Switchgrass is also being developed as a renewable fuel crop. The use of switchgrass as a biofuel crop could benefit our agricultural economy by providing a source of income for producers and lower our dependence on foreign oil supplies. A previously unreported leaf spot disease on switchgrass was observed in plantings at Mandan, North Dakota. From 1999-2002 a fungus was isolated consistently from foliar leaf spots on switchgrass. It was identified as Bipolaris oryzae. Genetic comparisons indicated a close relationship between isolates obtained from switchgrass and a test isolate of B. oryzae and the size and shape of spores agreed with that of B. oryzae. When the fungus is applied to switchgrass in research tests, B. oryzae causes foliar leaf spot disease symptoms on switchgrass. This is the first time B. oryzae, a common pathogen on rice, is reported as a disease on switchgrass. The disease has the potential to become a problem on switchgrass under plantings for high biomass production, particularly if a cultivar that can become infected with the fungus is seeded over a wide area. In addition, Bipolaris zeae is reported here for the first time on switchgrass and was not known previously from any host in the United States.

Technical Abstract: Switchgrass (Panicum virgatum) is a native, perennial warm-season grass used for hay, summer grazing, soil conservation, and wildlife habitat. Switchgrass is also being developed as a biomass crop for renewable energy. A previously unreported leaf spot disease on switchgrass was observed in plantings at Mandan, North Dakota. From 1999-2002 a fungus was isolated consistently from foliar leaf spots on switchgrass. It was identified as Bipolaris oryzae [teleomorph: Cochliobolus miyabeanus]. GPD DNA sequence comparisons indicated a close relationship between isolates obtained from switchgrass and a test isolate of B. oryzae and conidial morphology agreed with that of B. oryzae. Inoculation tests confirmed the ability of B. oryzae to cause foliar leaf spot disease symptoms on switchgrass. This is the first time B. oryzae, a common pathogen on rice (Oryza sativa), is reported as a disease on switchgrass. The disease has the potential to become a problem on switchgrass under intensive plantings for high biomass production, particularly if a susceptible cultivar is seeded over a wide area. In addition, Bipolaris zeae Sivan. [teleomorph: Cochliobolus zeae H.S. Chang] was isolated from Panicum virgatum, a new host for this fungus, and is herein reported for the first time from the United States.