Genetically related isolates of the entomopathogenic fungus Metarhizium anisopliae harbour homologous dsRNA viruses

Several isolates of the entomopathogenic Metarhizium anisopliae that harboured dsRNA viruses of similar electrophoretic band sizes (1.8 and 2.0 kbp) were assessed for homologies of the dsRNA by Northern analysis. The isolates were also characterised genetically by RAPD and VCG. Similarly sized dsRNA, as visualised by electrophoresis, were not always homologous, suggesting that the comparison of dsRNA based solely on electrophoretic banding patterns is an unreliable method of dsRNA characterisation. Several isolates, but not all, harbouring multiple dsRNA patterns, including a 1.8 and 2.0 kbp doubler, also showed homologies to strains harbouring only the dsRNA banding doubler. This suggests that mixed infections of different dsRNA elements are found in M. anisopliae. Genetically similar fungi, based on RAPD banding patterns and vegetative compatibility, were more likely to harbour genetically related dsRNA. The findings suggested that dsRNA elements in M. anisopliae are horizontally transferred to genetically related isolates or are maintained through clonal lineages.