Comparison and integration of genetic maps generated from F2 and BC1-type mapping populations in perennial ryegrass

Linkage maps of perennial ryegrass were constructed from F₂ and BC₁‐type populations using, predominantly, restriction fragment length polymorphism data based on heterologous probes used in mapping other grass species. The maps identified seven linkage groups, which covered a total of 515 cM (F₂) and 565 cM (BC₁). They were aligned using 38 loci identified in both populations (common loci) and a possible marker order for all mapped loci in either population was identified in an integrated map. The estimated recombination frequencies and map distances between adjacent common loci were compared between the two data sets and regions of heterogeneity identified. Overall, the common markers identified a map distance of 446 cM in the F₂ population and 327 cM in the BC₁ population, reflecting a higher recombination frequency in the former, although the difference was not evenly spread over the seven linkage groups.