A high-density molecular map for ryegrass (Lolium perenne) using AFLP markers

AFLP markers have been successfully employed for the development of a high- density linkage map of ryegrass (Lolium perenne L.) using a progeny set of 95 plants from a testcross involving a doubled-haploid tester. This genetic map covered 930 cM in seven linkage groups and was based on 463 amplified fragment length polymorphism (AFLP) markers using 17 primer pairs, three is ozymes and five EST markers. The average density of markers was approximate ly 1 per 2.0 cM. However, strong clustering of AFLP markers was observed at putative centromeric regions. Around these regions, 272 markers covered ab out 137 cM whereas the remaining 199 markers covered approximately 793 cM. Most genetic distances between consecutive pairs of markers were smaller th an 20 cM except for five gaps on groups A, C, D, F and G. A skeletal map wi th a uniform distribution of markers can be extracted from this high-densit y map, and can be applied to detect and map QTLs. We report here the applic ation of AFLP markers to genome mapping, in Lolium as a prelude to quantita tive trait locus (QTL) identification for diverse agronomic traits in ryegr ass and for marker-assisted plant breeding.