Abstract
Supercoiled mitochondrial DNA (mtDNA) has been isolated in preparative amounts from five different plant species and compared on agarose gels. The gels reveal considerable mtDNA size heterogeneity within each species as well as substantial differences in the range and frequency of the mtDNA size classes among the different plants. The two lowest size classes of three of the plants have been extracted and their molecular weights determined. Comparison of two N. tabacum W38 culture lines has revealed significant differences in their mtDNA size classes. However, despite the totally different supercoil patterns, these two lines have almost identical restriction digests. The availability of preparative amounts of separated mtDNA size classes will make it possible to carry out a detailed analysis of plant mitochondrial genomes.