Introgressing Multiple Quantitative Trait Loci through Backcross Breeding Programs

The ability to introduce favorable alleles for multiple genes from a donor breed into a commercial breed through a backcross program of limited size was evaluated. The effects of fraction selected, marker interval, and number of quantitative trait loci were considered. Informative flanking markers were used to select progeny with the largest expected number of recipient QTL alleles for 5 generations. With <5% selected, sufficient progeny were available that were heterozygous for all markers at three QTL and QTL frequencies remained close to 50%. For larger fractions selected, larger marker intervals, and more QTL, reductions from 50% frequencies were greater and increased over generations. However, even with 20% selected, three QTL and marker intervals of 5 or 20 cM, mean QTL frequencies in generation 5 were 35 and 30%, which was sufficient to allow subsequent selection to fix the QTL. This indicates that it is possible to introduce multiple favorable QTL alleles into a commercial breed. The optimal breeding and selection strategy and the economic feasibility of such an approach requires further analysis, which is underway.