Construction of a genetic linkage map in the wild plant Mimulus using RAPD and isozyme markers.

As a first step to mapping quantitative trait loci for mating system differences, a genetic linkage map was generated from an interspecific backcross between Mimulus guttatus and Mimulus platycalyx. The linkage map consists of 99 RAPD and two isozyme markers. Eighty-one of these markers were mapped to 15 linkage groups, spanning 1437 contiguous centiMorgans, and covering 58% of the estimated genome. The genome length of Mimulus is estimated at 2474 +/- 35 cM; bootstrapping indicates that only ca. 40 markers are needed to give an accurate estimate of genome length. Further statistical analyses indicate that many RAPD markers cannot be ordered with certainty and that uncertain linkage groups tend to map nonlinearly even under commonly used mapping functions. Strategies for speeding up the mapping process for a wild species and possible applications of a partial linkage map in evolutionary studies are discussed. Key words : linkage map, mating system, Mimulus, RAPD.