A method for subgrouping the S-type of CMS forms in maize.

Simple correlations were calculated between nine different cms sources (cms-S, -R, -ML, -L, -CA, -EK, -C, -Rb, -T) on the basis of the weighted restoring reactions of 41 inbred lines. The Principal Component Analysis was applied to a 9 × 9 matrix which clearly grouped cytoplasms according to their similarities. The Principal Component I included S, R, ML, L, CA and EK cytoplasms; the Principal Component II contained C and Rb cytoplasms while T-cytoplasms was placed in Principal Component III. This corresponds to the main groupings indicated in the literature (Beckett 1971). However, after varimax rotation of the Principal Components, the S main group, including the 6 tested cytoplasms, fell into 3 subgroups: I.: S, R, ML; II.: L, CA; III.: EK.These data indicate that the Principal Component Analysis can be used to select a limited number of cms sources from the S group, representing the variability of the cytoplasmic gene pool of that group.