Transmission of Switchgrass mosaic virus by Graminella aureovittata

Switchgrass mosaic virus (SwMV) was identified in switchgrass (Panicum virgatum) and was proposed as a new marafivirus based on its genome sequence and comparison with its closest relative, Maize rayado fino virus (MRFV), a type member of the genus Marafivirus. MRFV only infects maize (Zea mays) and its wild relatives, and is naturally transmitted by a corn leafhopper, Dalbulus maidis. Proving that SwMV is transmitted by a different species of leafhopper than D. maidis would provide additional evidence that SwMV is a new species of the genus Marafivirus. In 2010, three leafhopper species were identified in switchgrass fields near Champaign, Illinois - Graminella aureovittata, Graminella mohri and Flexamia atlantica. Switchgrass mosaic virus was detected by two independent RT-PCR assays in 100% of G. mohri and F. atlantica, and 95% of G. aureovittata. Twenty specimens of each species were evaluated. Of the three leafhoppers, only G. aureovittata transmitted the virus to 'Cave in Rock' switchgrass plants in a growth chamber. Transmission efficiency was 80% and only one of the eight SwMV-infected plants displayed mosaic/yellow streak symptoms. Switchgrass mosaic virus was detected in 78% and 83% of the switchgrass plants in the two fields from which the leafhoppers were collected. The detection of a leafhopper vector of SwMV will facilitate the transmission of the virus and the study of its impact on switchgrass biomass yield.