Comparison of selection strategies for marker-assisted backcrossing of a gene

Marker-assisted selection can accelerate recovery of the recurrent parent genome (RPG) in backcross breeding. In this study, we used computer simulations to compare selection strategies with regard to (i) the proportion of the RPG recovered and (ii) the number of marker data points (MDP) required in a backcross program designed for introgression of one target allele from a donor line into a recipient line. Simulations were performed with a published maize (Zea mays L.) genetic map consisting of 80 markers. Selection for the target allele was based on phenotypic evaluation. In comparison to a constant population size across all generations, increasing population sizes from generation BC₁ to BC₃ reduced the number of required MDP by as much as 50% without affecting the proportion of the RPG. A four-stage selection approach, emphasizing in the first generations selection for recombinants on the carrier chromosome of the target allele, reduced the required number of MDP by as much as 75% in comparison to a selection index taking into account all markers across the genome. Adopting the above principles for the design of marker-assisted backcross programs resulted in substantial savings in the number of MDP required.