Virus aggregates and pinwheels in plants infected with mite-transmitted ryegrass mosaic virus

Mulligan (1960) reported that ryegrass mosaic virus (RMV) had long rod-shaped particles that were often broken in preparation. Brandes (1964) confirmed the particle shape and determined a modal length of 703 nm and Brandes & Bercks (1965) placed RMV in the potato virus S group together with another mite-transmitted virus, wheat streak mosaic (WSMV), because their particles were slightly shorter and stiffer than those classified with potato virus Y. Shepard & Carroll (1967) found pinwheel inclusions, thought typical of the PVY group (Edwardson, 1966), in wheat infected by WSMV. Gibbs (1969) suggested that WSMV and RMV should be placed in a subgroup of the PVY group.

We maintained RMV in the glasshouse by mechanical inoculation to Italian ryegrass (Lolium multiflorum) cv. S. 22 and oats (Avena sativa) cv. Blenda. It was distinguished from other grass viruses by particle size and morphology, host range and vector transmission, as described by Catherall (1970).