Molecular characterization of cytoplasmic male sterility in Lolium perenne

Six CMS lines of Lolium perenne and the corresponding maintainer (N) lines were distinguished by RFLP analysis of mtDNA as well as of total DNA. Southern hybridisations of the (S)-cytoplasms displayed only two different types of hybridisation patterns. One type comprised the five NPZ lines with a novel CMS system (MSL, Male Sterility Lolium) and the other type was associated with the sixt line, l(S), having an unstable CMS expression. The corresponding normal (N)-cytoplasms revealed three different types of hybridisation patterns using the gene probe cox/II. Two different types were observed within the group of the MSL lines and an additional pattern in the remaining line l(N). The expression of the (S)cytoplasms was investigated microscopically by scoring the pollen fertility. Whereas line l(S) showed portions of fertile pollen of up to 100 percent, the MSL lines containing the novel (S)cytoplasm expressed complete pollen sterility.