Distribution and quantitative variation of mitochondrial plasmid-like DNAs in cultivated rice (Oryza sativa L.)

Distribution of four kinds of mitochondrial plasmid-like DNAs, Bl, B2, B3 and B4 was investigated by Southern analysis using 85 accessions of cultivated rice (Oryza sativa L.). The frequencies of these molecules found in cultivars differed from each other. The mitochondrial genome were categorized into nine types according to their presence or absence. They were found mostly in ecospecies Indica, a few in Javanica, and not found in Japonica. The result indicated the polymorphic and monomorphic patterns of the mitochondrial genomic organization within Indica and Japonica cultivars, respectively. Quantitative variation was found among four kinds of mitochondiral plasmid-like DNAs, suggesting that these molecules were unequally distributed or replicated during the process of mitochondrial division.