DOUBLE-STRANDED-RNA MYCOVIRUSES IN SPECIES OF ASPERGILLUS SECTIONS CIRCUMDATI AND FUMIGATI

Isolates (178) belonging to Aspergillus sections Fumigati, Candidi, Cl avati, and Circumdati were tested for the presence of double-stranded RNA (dsRNA) genomes. Altogether, 5.6% of the Aspergillus strains exami ned were infected with dsRNAs. dsRNA segments indicative of mycovirus infection were observed for the first time in Neosartorya hiratsukae, Neosartorya quadricincta, Petromyces alliaceus, and Aspergillus clavat us strains. Correlation was not observed between ochratoxin production and dsRNA content of the strains. This is the first report on the det ection of naturally occurring dsRNAs in Aspergillus species that are a ble to reproduce sexually. The detection of dsRNA in sexual aspergilli gave us a chance to examine the transmission of these segments throug h ascospores. A Neosartorya hiratsukae strain transmitted the dsRNAs e fficiently through sexual spores, while the stromata embedding the asc i in Petromyces alliaceus did not transmit one of the dsRNA segments. The 0.6-kb dsRNA segment that was present in the single-stromatal cult ures was found to be located in the mitochondrial fraction of this str ain. This observation indicates that some mechanisms exist in aspergil li to exclude cytoplasmically located dsRNA molecules from stromatal s tructures.