Detection of DsRNA Viruses in Isolates of Australian Smut Fungi and Their Serological Relationship to Viruses Found in Ustilago maydis From the U.S.A.

DsRNA was detected in two killer strains of smut fungi collected in Australia. This was determined by digestion of dsRNA preparations with RNase in the presence of high and low salt concentrations and detection of the nucleic acid using agarose gel electrophoresis. Isometric particles approximately 40 nm in diameter were detected using electron microscopy in the same isolates. These particles were shown to be serologically related but not identical to the P1 Ustilago maydis. virus-like particle (VLP) as determined by immunodiffusion using an antiserum to the P1 VLP. This shows that VLPs similar to those in North America also occur in Australia. Neither isometric particles nor dsRNA were detected in three other killer strains of smut fungi or in 11 sensitive strains. This indicates that there is a lack of correlation between killer activity and the presence of a dsRNA VLP in some Australian isolates of smut fungi.