DETECTING MARKER-QTL LINKAGE AND ESTIMATING QTL GENE EFFECT AND MAP LOCATION USING A SATURATED GENETIC-MAP

A simulation study was carried out on a backcross population in order to determine the effect of marker spacing, gene effect and population size on the power of marker-quantitative trait loci (QTL) linkage expe riments and on the standard error of maximum likelihood estimates (MLE ) of QTL gene effect and map location. Power of detecting a QTL was vi rtually the same for a marker spacing of 10 cM as for an infinite numb er of markers and was only slightly decreased for marker spacing of 20 or even 50 cM. The advantage of using interval mapping as compared to single-marker analysis was slight. ''Resolving power'' of a marker-QT L linkage experiment was defined as the 95% confidence interval for th e QTL map location that would be obtained when scoring an infinite num ber of markers. It was found that reducing marker spacing below the re solving power did not add appreciably to narrowing the confidence inte rval. Thus, the 95% confidence interval with infinite markers sets the useful marker spacing for estimating QTL map location for a given pop ulation size and estimated gene effect.