Many important crops (wheat, potato, strawberry, rose, etc.) are polyploid. This complicates genetic analyses, as the same locus can be present on multiple homologous or homoeologous chromosomes. SSR markers are suitable for mapping in segregating populations of polyploids as they are multi-allelic, making it possible to detect different marker alleles of the same locus on multiple homologous r homoeologous chromosomes. If a SSR primer pair gives fewer alleles than the ploidy level, quantification of allele dosages increases information content. We show the power of this approach for the generation of a genetic map in a auto-tetraploid garden rose population. Alleles were scored quantitatively using the area under the peaks in ABI electropherograms, and allele dosages were inferred based on the ratios between the peak areas for two alleles in which these two alleles occurred together. We hereby start with some reference cases in which the ratio’s are determined between alleles that are in simplex condition. We thus resolved the full progeny genotypes, generated more data and mapped markers more accurately, including “null” alleles. The maps will be used for locating QTLs for winterhardiness in tetraploid roses.