A model for incorporating novel alleles from the primary gene pool into elite crop breeding programs while reselecting major genes for domestication or adaptation

Cost, time, linkage drag, and genetic drift work against the incorporation of potentially valuable alleles from exotic or non-adapted germplasm into elite crop plants, particularly for quantitative traits. We present a model, motivated by narrow-leafed lupin (Lupinus angustifolius), for efficient incorporation of new alleles from exotic or non-adapted donors into elite gene pools during two phases of breeding. In Phase 1, probability functions from the binomial distribution provide at least 95% confidence that a potentially valuable donor allele (A') will survive two cycles of backcrossing to elite lines and is fixed in BC2-derived lines. During backcrossing, up to 6 major domestication or adaptation genes from the elite parents are reselected and made homozygous in BC2S0 : 1 family rows. Each plant in the BC2S0 : 1 contains on average 12.5% donor alleles, with >95% probability that a particular donor allele is homozygous in at least one fully domesticated plant in the BC2S0 : 1 population. Plants in these rows or subsequent field trials are selected for valuable quantitative traits, and crossed into elite germplasm to commence Phase 2. Phase 1 is rapid and relatively low cost, and provides a continuous flow of novel genetic diversity into the elite breeding pool.