The present invention relates to a method for mapping traits in organisms, in particular in plants. The method according to the present invention comprises a) providing a population of SDR-O organisms, in particular plants, that each arise from one member of a population of unreduced cells resulting from second division restitution, in particular a population of unreduced spores; b) producing SDR-I progeny populations of each of these SDR-O organisms; c) phenotyping the SDR-I progeny populations to identify segregating traits within each SDR-I progeny population; d) if segregating progeny is present in a SDR-I progeny population genotyping the corresponding SDR-O organism and comparing the genotype thereof with the genotype of the other SDR-O organisms to identify heterozygous chromosomal regions associated with the occurrence of the segregating trait identified in the said SDR-I progeny population.
