Cytoplasmic male sterility in beta is associated with structural rearrangements of the mitochondrial DNA and is not due to interspecific organelle transfer.

Chloroplast (ct) and mitochondrial (mt) DNAs from four cytoplasmic male sterile (cms) and 22 normal fertile sugar beet lines and accessions of wild beets from the genus Beta have been compared with restriction analyses and Southern hybridizations. We have used restriction analyses of ctDNA as a phylogenetic marker to confirm the taxonomic relationships between the different cytoplasms. According to the ctDNA data, all four cms cytoplasms belong to the same taxonomic section, Beta. Restriction patterns of ct and mtDNA from fertile accessions produced analogous trees of similarity and showed a close correlation between the organellar DNA diversity and the accepted taxonomic classification of the species studied. However, the mt-DNA restriction profiles of the four cms types differed dramatically from each other and from those of all fertile accessions from the genus. No indication of cytoplasmic introgression was found in any of the four investigated cms types. Southern hybridization to mtDNA revealed variant genomic arrangements in the different fertile and cms cytoplasms, indicating that rearrangement of the mitochondrial genome is a common denominator to the different cms systems in Beta. It may, indeed, be a common property to spontaneously occurring cms in all or most species.