A skeletal linkage map of Hordeum bulbosum L. and comparative mapping withbarley (H-vulgare L.)

A restriction fragment length polymorphism (RFLP) based linkage map of a cr oss between two diploid Hordeum bulbosum (2n = 2x = 14) clones, PB1 and PB1 1, was constructed from 46 recombinant progeny clones. Since both parents a re heterozygous, separate and combined parental maps were constructed. All of the RFLP markers screened had previously been mapped in barley (H. vulga re L.) so that comparative maps could be produced. The PB1 linkage map cons ists of 20 RFLP marker loci assigned to four linkage groups covering 94.3 c M. The PB11 linkage map consists of 27 RFLP marker loci assigned to six lin kage groups covering 149.1 cM. Thirteen markers polymorphic in both parents were used as 'anchors' to create a combined linkage map consisting of 38 l oci assigned to six linkage groups and covering a genetic distance of 198 c M. Marker order was highly conserved in a comparison with the linkage map o f H. vulgare (Laurie et al., 1995). However, in contrast, the genetic dista nces for the same markers were very different being 649 cM and 198 cM respe ctively, a genetic distance ratio of 1:3.3. Thus although the map was short , it can be presumed to cover half the genome of H. bulbosum. This study pr ovides further confirmation of the close relationship between the two speci es and gives a basis for the development of marker mediated introgression t hrough interspecific hybridisation between the two species.