Hordeum bulbosum, a wild relative of barley (Hordeum vulgare) is known for its resistance to a large number of important barley pathogens. Over the last decades the introgression of chromosome segments of H. bulbosum into H. vulgare was enabled though interspecific crossing between both species. These so-called Hordeum bulbosum introgressions may often carry important disease resistance genes. The project “TRANSBULB” aims to develop molecular markers for six such H. vulgare/H. bulbosum introgressions, which are known to bear desired resistance genes.  This should be achieved by using the latest available comprehensive genomic information of H. vulgare.  Molecular markers will allow a precise genetic characterization of the H. bulbosum introgressions as well as the selection of progeny plants carrying narrowed introgression sizes, owning to recombination. The latter is necessary, as besides the desired disease resistance gene the introgressed H. bulbosum segments may also carry “wild” Hordeum genes, which are likely to be deleterious or disadvantageous for yield performance in adapted cultivated barley. The work plan is structured as followed: (I) Identification of the conserved (homeologous) part of the H. bulbosum introgression in H. vulgare; (II) Development of PCR based markers using the available barley genome information; (III) Identification of polymorphisms between H. vulgare and H. bulbosum; (IV) Determination of the exact dimensions of H. bulbosum introgressions; (V)  Development of whole-genome-shotgun sequencing data of H. bulbosum for a de novo assembly of gene carrying areas of the H. bulbosum genome, as a basis for the efficient, multi-parallel, genome-wide search for sequence polymorphisms; (VI) Mapping of the resistance genes in a minimum of two introgression lines; (VII) Selection of plants with reduced introgression sizes and their utilization to develop double haploid lines, which will be used for yield evaluation trials and as starting material for pre-breeding. As a result of the project we will provide a nearly unlimited amount of markers for four (maximum six) introgression lines. These can be applied to select plants with reduced introgression sizes, which will be a valuable source in barley breeding programs.  Diagnostic markers will serve barley breeders as improved selection tools. The gained information will support prospective cloning of the genes of interest.