Figure 1.—

Experimental design. Plants grown from teosinte seeds were pollinated with maize pollen. The resulting seeds were grown, and the hybrid plants were also pollinated with maize pollen. Continued backcrossing always used the plant tracing back to teosinte as female, ensuring that the progeny had teosinte cytoplasm. Thus, for each cytoline, all plants in the lineage trace back ultimately to a single teosinte seed. Twelve seeds from each plant in the penultimate generation were used to produce families of 10 progeny for observation (only plant-six pedigree is shown), except that for those cytotypes showing substantially elevated defective kernel proportions (cytotypes 8–13; see results), 10 sixth-backcross families were grown. The first five plants in each seventh-generation family were manually backcrossed to obtain ear and kernel data.