["Killer" plasmid in natural strains of Saccharomyces].

Double stranded RNA's of thirteen wine strains of Saccharomyces belonging to different species and exhibiting killing activity were studied. Two strains of Oxford genetic stocks were used for control. All these strains have four different spectra of killer activity and contain two double stranded RNAs, L and M. All strains regardless of the type of killer activity have the same electrophoretic mobility of L. The mobility of M varies in different strains but is not connected with the spectrum of killing activity. All strains can be cured by cycloheximide. Cured variants have no M. Certain cured strains contain small portions of double stranded RNAs with electrophoretical mobility faster than of M.