Mitochondrial DNA analyses of fertile and sterile maize plants derived from tissue culture with the Texas male sterile cytoplasm

Maize plants carrying Texas (T) cytoplasm are male-sterile and sensitive to Drechslera maydis race T toxin, whereas plants carrying Normal (N) cytoplasm are male-fertile and resistant to the toxin. Some plants regenerated from T cytoplasm tissue cultures exhibit a N cytoplasm-like phenotype with respect to malefertility and toxin-resistance. Analysis of the high molecular weight mitochondrial DNA (mtDNA) of such regenerants has shown that the plants do not contain N cytoplasm mtDNA. However, their mtDNAs do show sequence differences from each other and from the mtDNA of plants possessing T cytoplasm. No single alteration detected correlates with the change to malefertility or toxin resistance. Sequence alterations were also evident in high molecular weight mtDNA isolated from a plant regenerated from N cytoplasm callus. No changes in low molecular weight mtDNA molecules were observed in regenerants from N or T cytoplasm callus.