Effects of double-stranded RNA viruses on the reproduction of Phaffia rhodozyma.

DsRNA viruses were transferred from a virus-containing strain to a virus-free strain of Phaffia rhodozyma by protoplast fusion. The resulting new strain carried all three types of dsRNA of the virus-containing strain and had the electrophoretic karyotype of the virus-free strain. The effects of the dsRNA viruses on the host fitness were checked by following the asexual and the sexual reproductivity. The results demonstrated that viruses have no effect on the growth rate during the lag and log phases of the vegetative reproduction, but the maximum cell numbers in the stationary phase differ significantly. Inconclusive results were obtained as concerns the effects of viruses on the sexual reproduction.