GENETIC RESPONSE FROM MARKER ASSISTED SELECTION IN AN OUTBRED POPULATION FOR DIFFERING MARKER BRACKET SIZES AND WITH 2 IDENTIFIED QUANTITATIVE TRAIT LOCI

Effect of flanking quantitative trait loci (QTL)-marker bracket size o n genetic response to marker assisted selection in an outbred populati on was studied by simulation of a nucleus breeding scheme. In addition , genetic response with marker assisted selection (MSS) from two quant itative trait loci on the same and different chromosome(s) was investi gated. QTL that explained either 5% or 10% of phenotypic variance were simulated. A polygenic component was simulated in addition to the qua ntitative trait loci. In total, 35% of the phenotypic variance was due to genetic factors. The trait was measured on females only. Having sm aller marker brackets flanking the QTL increased the genetic response from MAS selection. This was due to the greater ability to trace the Q TL transmission from one generation to the next with the smaller flank ing QTL-marker bracket, which increased the accuracy of estimation of the QTL allelic effects. Greater negative covariance between effects a t both QTL was observed when two QTL were located on the same chromoso me compared to different chromosomes. Genetic response with MAS was gr eater when the QTL were on the same chromosome in the early generation s and greater when they were on different chromosomes in the later gen erations of MAS.