Modification of Methods for Identifying Populations to be Used for Improving Parents of Elite Single Crosses1

Abstract

One method of utilizing populations (either adapted or exotic) hybrid breeding programs, is to cross a population (Py) to one of the parents (e.g., I1) of an elite F1 (I1 × I2), self in the F2, and attempt to recover a line superior to I1. For a population to be useful in such a program, it must contain favorable alleles not present in the elite F1. A previous method for identifying such populations lacked generality. A modified method was developed that removes the assumption that frequency of favorable alleles in Py. is equal for all classes of loci except those for which the F1 lacks favorable alleles. The modified method provides estimates of gene frequencies (p̄j and p̄k) at loci for which the F1 is heterozygous. These estimates can be used to determine which of the parental inbreds should be improved by crossing to Py and whether to self directly in the F2 or to backcross prior to selfing. Effects of relaxing the assumption of complete dominance are shown. The modified method provided estimates nearer the true values than previously proposed methods when applied to a set of hypothetical data.