Mitochondrial DNA duplication/deletion events and polymorphism of the C group of male sterile maize cytoplasms.

Five accessions of members of the C group of male sterile maize cytoplasms (BB, C, ES, PR, and RB) in two nuclear backgrounds (A619 and A632) were examined to elucidate the nature of mitochondrial genome diversity within a related group of cytoplasms. Cosmid and plasmid clones carrying single copy and recombinationally active sequences from N and S cytoplasms of maize were used as probes. Although restriction patterns are quite similar, each of the five could be discriminated by evidence of sequence duplication and recombination, deletion of recombinationally active sequences of N, normal cytoplasm, population of mini-circular DNAs, and by restriction patterns. Each member of the group carried a 1,913 bp minicircular mtDNA, while all entries but RB carried a 1,445 bp minicircular mtDNA. Members of the C group clearly are not molecularly identical; evolution of the group included principal genome reorganization involving sequence duplication/deletion events, apparently independent of the cms trait.