Schematic outline of map-building strategies used in this study. Pilot maps were built for each of the ten populations separately to flip the phase of loci assigned to the wrong phase, to identify multi-locus markers, and to remove loci and lines with excessive numbers of singletons (apparent double crossovers). The quality-filtered datasets were then used to build seven 'component' maps for individual populations with sufficient numbers of lines and loci. The integrated dataset of all ten populations was used to build a consensus map. The quality of the locus order of the consensus map was evaluated by comparison against the order of loci in the component maps and a 'synthetic map' derived from the component maps.