To study virus-vector interactions between Soilborne wheat mosaic virus (SBWMV) or Wheat spindle streak mosaic virus (WSSMV) and Polymyxa graminis Ledingham, P. graminis was propagated in plants grown hydroponically. P. graminis accumulated to high levels in several barley cultivars tested. Multiple developmental stages of P. graminis could be identified in infected barley roots. Accumulation of SBWMV and WSSMV inside P. graminis sporosori in the roots of soil-grown winter wheat and hydroponically grown barley was compared to determine if data obtained from plants naturally infected plants and plants infected by manual inoculation were similar. WSSMV coat protein (CP), SBWMV RNAs, SBWMV movement protein but not SBWMV CP were detected in both soil-grown winter wheat and hydroponically grown barley roots. These data are the first direct evidence that SBWMV and WSSMV are internalized by P. graminis.