Selection Theory for Marker-Assisted Backcrossing

Abstract

Marker-assisted backcrossing is routinely applied in breeding programs for gene introgression. While selection theory is the most important tool for the design of breeding programs for improvement of quantitative characters, no general selection theory is available for marker-assisted backcrossing. In this treatise, we develop a theory for marker-assisted selection for the proportion of the genome originating from the recurrent parent in a backcross program, carried out after preselection for the target gene(s). Our objectives were to (i) predict response to selection and (ii) give criteria for selecting the most promising backcross individuals for further backcrossing or selfing. Prediction of response to selection is based on the marker linkage map and the marker genotype of the parent(s) of the backcross population. In comparison to standard normal distribution selection theory, the main advantage of our approach is that it considers the reduction of the variance in the donor genome proportion due to selection. The developed selection criteria take into account the marker genotype of the candidates and consider whether these will be used for selfing or backcrossing. Prediction of response to selection is illustrated for model genomes of maize and sugar beet. Selection of promising individuals is illustrated with experimental data from sugar beet. The presented approach can assist geneticists and breeders in the efficient design of gene introgression programs.

Variance of the Parental Genome Contribution to Inbred Lines Derived From Biparental Crosses

“…Application in selection theory: Selection for parental marker alleles in backcross populations was investigated and a comprehensive selection theory was developed by Frisch and Melchinger (2005). That approach takes into account (a) the exact distribution of the parental genome contribution and (b) that selection for the parental alleles at marker loci is actually an indirect selection for the parental alleles at all loci of the entire genome.…”

Genetic Dissection of Barley Morphology and Development

“…The theory of backcrossing and various types of genetic analyses involving backcrossing experiments in a wide range of species have been documented extensively in the literature (Hospital, 2005). The development of NILs can be accelerated considerably by molecular marker-assisted selection (Frisch and Melchinger, 2005), and today marker-assisted backcross breeding is commonly used in crop improvement.…”

Marker-Based Prediction of the Parental Genome Contribution to Inbred Lines Derived From Biparental Crosses

“…The prediction of the parental genome contribution to inbred lines complements the prediction of the donor genome proportion in backcross individuals described by Frisch and Melchinger (2005). The combination of both approaches allows monitoring of the parental genome proportion from the first backcross generation until the converted inbred line is finally developed.…”