Marker assisted selection or marker aided selection (MAS) is an indirect selection process where a trait of interest is selected based on a marker(morphological, biochemical or DNA/RNA variation) linked to a trait of interest (e.g. productivity, disease resistance, a biotic stress tolerance, and quality), rather than on the trait itself. This process is used in plant and animal breeding. For example, using MAS to select individuals with disease resistance involves identifying a marker allele that is linked with disease resistance rather than the level of disease resistance. The assumption is that the marker associates at high frequency with the gene or quantitative trait locus (QTL) of interest, due to genetic linkage (close proximity, on the chromosome, of the marker locus and the disease resistance-determining locus).
Marker Assisted Selection