B73 has been backcrossed as male into the cytoplasm of several accessions of most of the described races of teosinte, as well as of Z. diploperennis. Most of the backcross lines are phenotypically indistinguishable from B73 after 4 to 5 backcrosses have been made. But B73 in the cytoplasm of 2 accessions of Jutiapa teosinte, in an old accession of "florida" teosinte (probably Zea luxurians), and in a new accession of Z. luxurians is small and slow growing and shows poor ear and kernel development. Hybrids of these strains (used as seed parent) with other maize genotypes are also weak, late in maturity and have poor ear and kernel development. Interestingly, B73 in Z. diploperennis cytoplasm is not reduced in vigor; B73 backcross lines in diploperennis cytoplasm appear to be identical in vigor and maturity to B73 in its own cytoplasm.
Donald N. Duvick
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