MITOCHONDRIAL DNA VARIATION AND SYSTEMATICS OF LATIN AMERICAN MAIZE RACES

Mitochondrial DNAs (mtDNAs) from 93 indigenous Latin American Maize races were examined by electrophoresis for the presence of plasmid-like molecules, and were digested with BamHI and EcoRI restriction endonucleases and electrophoresed to produce characteristic fragment patterns for each race. Two previously unknown plasmid-like DNAs, designated R-1 and R-2, were discovered in 17 races and were partially characterized. R-1 has a length of about 7460 nucleotides while R-2 contains 5450 nucleotides. R-2 appears to be identical to the S-2 molecule of the cytoplasmic male sterile (cms) cms-S cytoplasm. Races were placed in one of 18 different groups on the basis of BamHI and EcoRI patterns and the presence or absence of plasmid-like elements. Seven races were classified as cytoplasmic male-steriles, and one or more races were placed in each major cms category, C, S and T. One race, Conico Norteno, possesses a cytoplasm which cannot be distinguished from the cms-S cytoplasm. The remaining races were placed in groups of cytoplasmic similarity which appear to follow geographic and racial affinities to a large extent, though some disparity was observed. Possible causes for this disagreement were outlined. The evolutionary and taxonomic implications of these findings are reviewed.