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ARS Home » Pacific West Area » Corvallis, Oregon » Forage Seed and Cereal Research Unit » Research » Publications at this Location » Publication #350500
Title: First report of Cocksfoot mottle virus infecting Dactylis glomerata in forage production fields in California

Author
item Martin, Ruth
item Martin, Robert
item PUTNAM, MELODIE - Oregon State University

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/25/2018
Publication Date: 8/10/2018
Citation: Martin, R.C., Martin, R.R., Putnam, M.L. 2018. First report of Cocksfoot mottle virus infecting Dactylis glomerata in forage production fields in California. Plant Disease. https://doi.org/10.1094/PDIS-02-18-0277-PDN.
DOI: https://doi.org/10.1094/PDIS-02-18-0277-PDN

Interpretive Summary: Orchardgrass (Dactylis glomerata L.) is a cool season perennial grass commonly used in pastures and also grown for hay and silage. A sobemovirus, Cocksfoot mottle virus (CfMV), was recently reported in seed production fields in Oregon, USA, where 79% of the orchardgrass fields surveyed in 2016 were infected with CfMV. Cocksfoot mottle virus causes yellow streaking in mild cases, but these symptoms can progress into whitening of the leaves, followed by necrosis and plant death in severe cases. The virus is spread by beetles and by mechanical transmission. The presence of this virus is associated with stand decline in Europe, Japan, New Zealand, and Canada. During the summer of 2017, several forage growers in California were experiencing extensive die off in their fields. Samples were tested for CfMV using DAS-ELISA, and all symptomatic samples were positive for CfMV, but they were also positive for several other pathogens. The presence of CfMV was confirmed through PCR and sequencing. The presence of the virus, combined with extreme temperatures and drought conditions, may have weakened the plants and made them more susceptible to other pathogens, leading to plant death in the forage fields. This is the first report of CfMV in forage fields in California.

Technical Abstract: Orchardgrass (Dactylis glomerata L.) is a cool season perennial grass commonly used in pastures and also grown for hay and silage. A virus infecting orchardgrass, Cocksfoot mottle virus (CfMV),was first described in 1963 in England. The symptoms of CfMV are visible in spring with yellow streaking in mild cases, but these symptoms can progress into whitening of the leaves, followed by necrosis and plant death in severe cases. During the summer of 2017, several forage growers in northern California that were experiencing extensive die off in their fields requested testing for CfMV and other pathogens. All symptomatic samples were positive for CfMV, but they were also positive for several other pathogens. The identity of the virus was confirmed by RT-PCR using CfMV-specific primers, followed by sequencing of the amplicons. The sequences of the isolates were most closely related to CfMV isolates from the Willamette Valley of Oregon or from Ohio. This is the first report of CfMV in orchardgrass forage production fields in California. While infection with CfMV can be lethal, it is also possible that the presence of CfMV in combination with more extreme weather patterns experienced in the last few years may have weakened the plants and increased susceptibility to other pathogens, leading to the devastation observed in orchardgrass fields in northern California. Growers are encouraged to look for symptoms of CfMV in early spring and to prevent mechanical transmission of CfMV virus by harvesting clean fields first, and by cleaning machinery thoroughly between fields. Additionally, growers are encouraged to grow CfMV-resistant cultivars, if possible.