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

Marker-assisted selection can accelerate recovery of the recurrent parent g enome (RPG) in backcross breeding. In this study, we used computer simulati ons to compare selection strategies with regard to (i) the proportion of th e 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 publis hed maize (Zea mays L.) genetic map consisting of 80 markers. Selection for the target allele was based on phenotypic evaluation. In comparison to a c onstant population size across all generations, increasing population sizes from generation BC1 to BC3 reduced the number of required MDP by as much a s 50% without affecting the proportion of the RPG. A four-stage selection a pproach, emphasizing in the first generations selection for recombinants on the carrier chromosome of the target allele, reduced the required number o f MDP by as much as 75% in comparison to a selection index taking into acco unt all markers across the genome. Adopting the above principles for the de sign of marker-assisted backcross programs resulted in substantial savings in the number of MDP required.