This work reports the complete genome sequence, production of a polyclonal antiserum, and host range of a Brazilian strain of johnsongrass mosaic virus (JGMV) found infecting Panicum maximum in the state of São Paulo, Brazil. The complete genome sequence of this potyvirus, comprising 9874 nucleotides, showed 82 % amino acid sequence identity in the polyprotein to that of an isolate of JGMV from Australia. The experimental host range of this virus included mainly fodder species. Cultivated species such as rice, oats, sugarcane, rye, corn and wheat were not infected, suggesting that current isolates of this potyvirus do not represent a threat to these crops in Brazil.