Double-stranded RNA mycoviruses in species of Aspergillus sections Circumdati and Fumigati.

Isolates (178) belonging to Aspergillus sections Fumigati, Candidi, Clavati, and Circumdati were tested for the presence of double-stranded RNA (dsRNA) genomes. Altogether, 5.6% of the Aspergillus strains examined 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 clavatus strains. Correlation was not observed between ochratoxin production and dsRNA content of the strains. This is the first report on the detection of naturally occurring dsRNAs in Aspergillus species that are able to reproduce sexually. The detection of dsRNA in sexual aspergilli gave us a chance to examine the transmission of these segments through ascospores. A Neosartorya hiratsukae strain transmitted the dsRNAs efficiently through sexual spores, while the stromata embedding the asci in Petromyces alliaceus did not transmit one of the dsRNA segments. The 0.6-kb dsRNA segment that was present in the single-stromatal cultures was found to be located in the mitochondrial fraction of this strain. This observation indicates that some mechanisms exist in aspergilli to exclude cytoplasmically located dsRNA molecules from stromatal structures.