Origins and Distribution of Panicum Mosaic Virus and Sugarcane Mosaic Virus on Stenotaphrum secundatum in Australia.

Stenotaphrum secundatum is a premium turf grass in warm temperate and subtropical regions of the world and is the most important turf species in Australia based on the value of its production. A new disease called buffalo grass yellows (BGY) has become a problem on turf farms in Australia. We surveyed turf farms in New South Wales (NSW), Queensland (Qld) and Western Australia to determine whether panicum mosaic virus (PMV) and sugarcane mosaic virus (SCMV) were associated with BGY. PMV was only found on three farms, two located in the Hawkesbury Valley near Sydney, and a third at Echuca, about 800 km to the southwest of the former location. SCMV was more prevalent, present in all major cultivars and states surveyed. We analyzed phylogenetic relationships for SCMV and found that isolates infecting S. secundatum in Australia belonged to three clades. The first included Australian isolates typical of the population of viruses circulating in Digitaria didactyla . The second included a single NSW isolate from S. secundatum 'SS100' that grouped with otherwise American isolates of SCMV recorded in S. secundatum and Saccharum officinale from Florida, and Zea mays from Ohio. Finally, an isolate of SCMV from S. secundatum originating from a turf farm in southeast Qld grouped with viruses mostly infecting maize; this record is potentially the first maize-adapted strain of SCMV in Australia. Our study sheds light on the aetiology of the BGY disease syndrome and invasion history of PMV and SCMV in Australia.