Believe it or not, QTLs are accurate

It is generally believed that mapping quantitative trait loci (QTLs) does not accurately position genes underlying polygenic traits on the genome, which limits the application of QTL analysis in marker-assisted selection and gene discovery. However, now that a few plant QTLs have been cloned or accurately tagged, it appears that they might be accurate to within 2 cM or less. This means that there will be circumstances when map-based cloning using only original mapping data would be a realistic option that avoids time-consuming and expensive fine mapping. Acceptance of this view would enhance the value of past and future mapping experiments, particularly those revealing small and environmentally sensitive QTLs that are often considered intractable at the molecular level.