Linkage analysis of anther-derived monoploids showing distorted segregation of molecular markers

Monoploids can be obtained from several diploid plant species by anther cul ture. Mapping of molecular markers using monoploids is greatly facilitated by the simple 1:1 segregation ratio expected from all heterozygous loci in the genome. Distorted segregation of molecular markers, however, appears to be a common phenomenon in many crop species and hinders the use of monoplo ids for mapping purposes. This report examines the segregation pattern of t wo marker genes linked together with one locus or separately with two indep endent loci which are responsible for the observed distortion. Each of the loci exhibiting distorted segregation has one of the two alleles which inhi bits regeneration of the gametic cells in vitro and disrupts the expected s egregation ratio of the linked markers. All possible situations in which li nkage occurs between markers and distortion-causing genes are considered. T heoretical results outlining the segregation pattern among these linkage ty pes indicate that the distinguishable distorted ratios can be used for mapp ing purposes. A protocol is given for the mapping of distorted gene markers based on existing gene mapping software. An example is presented of the ma pping of distorted RAPD markers of monoploids obtained from a diploid potat o genotype.