RAPID INBREEDING IN MAIZE

The number of inbreeding generations required to produce homozygotes may be reduced if the more homozygous individuals in each breeding generation are selected phenotypically in the segregating progenies for further inbreeding. To demonstrate this, inbred lines and their F1, S1, and S2 progenies were studied for number of days from planting to anthesis, plant height and total leaf number. The data indicated that a high degree of control of rate of inbreeding may be obtained by proper use of heterotic characteristics in selection. The technique is a simple one: the selection of those individuals in a segregating array that most closely approach the characteristics of the ultimate homozygotes obtainable from the population. If these traits are undefined, then simple negative selection for heterotic attributes should suffice. In an S1 progeny of maize, an individual with the same number of leaves and (1) as short as and (2) as slow to flower as the parental inbreds will be likely to be more homozygous than its taller and earlier flowering sibs of like leaf number. Since the inbreeder's aim is not homozygosis per se but the development of agronomically useful homozygotes, the population dealt with should be sufficiently large to permit intense selection for outstanding individuals among the more homozygous members of each generation of selection. © 1969 The New York Botanical Garden.