Host range, symptoms and effects on pasture production of a Victorian isolate of ryegrass mosaic potyvirus

Abstract

A local isolate of ryegrass mosaic potyvirus (RMV) was identified from a pasture in Leongatha, south-east Victoria. The virus was mechanically inoculated to ryegrass and oats but could not be detected by ISEM in inoculated and symptomless wheat, cocksfoot or barley. Symptoms associated with infection varied between a white mosaic and a brown necrosis. The presence or absence of RMV did not significantly affect the total herbage yields of field plots. However, infection with RMV resulted in reductions in dry weight of 5-50% in the ryegrass component of total herbage yields; the reduction in ryegrass was compensated by increased weed growth. The extent of the reductions in ryegrass associated with RMV infection varied with both species and cultivar. Both the host range study and the herbage yields from the field trial showed that the Victorian isolate of RMV differed from isolates reported overseas.