Double-stranded RNA viruses in a mycocinogenic strain of Cystofilobasidium infirmominiatum.

The viral particles (about 30 nm in diameter) that contain dsRNAs (2.0 and 6.3 kbp) encapsidated by a coat of protein were detected in a mycocin-secreting strain of Cystofilobasidium infirmominiatum isolated from plants in an oak forest (Moscow region). The mycocin with a molecular mass above 15 kDa is fungicidal (maximum activity at pH 4.5) and active mainly against some species of the Cystofilobasidiales and Filobasidiales ('Cryptococcus aerius' clade). Curing by incubation at elevated temperature resulted in the concomitant loss of dsRNAs and mycocinogenic activity, and cured derivatives became sensitive to the mycocin produced by the parent strain.