High Intensity Selection for Percent Oil in Corn1

Seven cycles of high‐intensity within half‐sib family selection for percent oil in the ‘Reid Yellow Dent’ corn (Zea mays L.) cultivar resulted in an increase in oil from 4.0 to 9.1%, while kernel weight and ear height were reduced slightly and grain moisture at harvest increased. No significant changes in yield, silking date, or plant height were found. Realized heritability for percent oil was 43%.Estimates of genetic variance for percent oil and 100‐kernel‐weight were obtained in 1977 and 1978, for Cycles 0 and 5. All estimates of additive genetic variance (ó2A) were greater than zero; however, change in ó2A occurred between cycles. Estimates of dominance genetic variance did not differ from zero.A comparison of the predicted gains from within half‐sib family selection, mass selection, and combined selection among and within half‐sib families revealed that maximum gain is expected when a higher selection intensity is used within half‐sib families than among half‐sib families.