Efficient marker-based recurrent selection for multiple quantitative traitloci

We studied the efficiency of recurrent selection based solely on marker gen otypes (marker-based selection), in order to increase favourable allele fre quency at 50 previously detected quantitative trait loci (QTLs). Two select ion procedures were investigated, using computer simulations: (1) Truncatio n Selection (MTS), in which individuals are ranked based on marker score, a nd best individuals are selected for recombination; and (2) QTL Complementa tion Selection (QCS), in which individuals are selected such that their QTL composition complements those individuals already selected. Provided QTL l ocations are accurate, marker-based selection with a population size of 200 was very effective in rapidly increasing frequencies of favourable QTL all eles. QCS methods were more effective than MTS for improving the mean frequ ency and fixation of favourable QTL alleles. Marker-based selection was not very sensitive to a reduction in population size, and appears valuable to optimize the use of molecular markers in recurrent selection programmes.