ABSTRACT
Marker-assisted selection (MAS) is a form of indirect selection for a desired change in a trait based on a marker as distinct from direct phenotypic selection on the trait itself. Enzymes, proteins and blood group polymorphisms were investigated as suitable markers for quantitative traits in early research. In general, these studies were not very successful in detecting quantitative trait loci (QTL) because there were a limited number of markers, and tight linkages between marker and trait were rare (Bovenhuis et al., 1997). Nevertheless, blood group markers for the B21 and B12 haplotypes have been used as selection criteria to decrease susceptibility to Marek’s disease (McKay, 1998).
