Inter-subspecific maps of non-brittle rachis genes btr1/btr2 using occidental, oriental and wild barley lines

Brittle rachis of wild barley is controlled by two dominant complementary genes, Btr1 and Btr2, and mutation in either locus (btr1 or btr2) results in the non-brittle rachis of cultivated barley. In this study, a simple monogenic inheritance of non-brittle rachis was demonstrated, and moreover differentiation of multiple dominant alleles for either Btr1 or Btr2 among cultivated and wild barley lines was suggested. Two amplified-fragment-length polymorphism (AFLP) linkage maps of the genes were constructed using wild x btr1-type cultivar and wild x btr2-type cultivar F-2 populations. The order of AFLPs and the btr1/btr2 locus was constant between the wild x cultivar maps and a cultivar x cultivar map previously constructed. No suppression of recombination due to the inter-subspecific crosses was noticed in the interval studied. The btr1 locus and all AFLP loci were separated in the wild x btr1-type cultivar F-2 map, but the btr2 locus and eight AFLP loci did not recombine in the wild x btr2-type cultivar F-2 map, thus slightly different levels of affinity between parental cultivars with the wild line was suggested at the btr1/btr2 locus.