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

DsRNA viruses were transferred from a virus-containing strain to a virus-fr ee strain of Phaffia rhodozyma by protoplast fusion. The resulting new stra in 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 e ffect on the growth rate during the lag and log phases of the vegetative re production, but the maximum cell numbers in the stationary phase differ sig nificantly. Inconclusive results were obtained as concerns the effects of v iruses on the sexual reproduction.