Chromosomal location of genes for resistance to powdery mildew in Agropyron cristatum and mapping of conserved orthologous set molecular markers

Agropyron cristatum exhibits resistance to Blumeria graminis f. sp. tritici. Disomic and ditelosomic chromosome addition lines of A. cristatum in 'Chinese Spring' wheat were utilized to determine which A. cristatum chromosomes carry resistance gene(s). Resistance is conferred by gene(s) on chromosome arms 2PL and 6PL. The availability of molecular markers capable of detecting these chromosome arms in a wheat background would be very useful for marker-assisted introgression of 2PL and 6PL chromatin into common wheat. With this aim, 170 wheat conserved orthologous set (COS) markers (92 and 78 from wheat homoeologous groups 2 and 6 respectively) were assessed for their utility in A. cristatum. A total of 116 (68.2%) COS markers successfully amplified product in A. cristatum and 46 (40.0%) of these markers were polymorphic between A. cristatum and common wheat. From marker loci mapping on wheat homoeologous group 2 chromosomes, 23 markers (34.9%) were polymorphic between A. cristatum and common wheat and from them 13 markers were assigned to chromosome arm 2PL and six markers were mapped to chromosome 4P of A. cristatum showing that this chromosome is related to wheat homoeologous group 2. From marker loci mapping on wheat homoeologous group 6 chromosomes, 23 (46.0%) markers were polymorphic between A. cristatum and common wheat and from them 17 markers were located on chromosome 6P, six of them were mapped to chromosome arm 6PS and five to chromosome arm 6PL, respectively. The specific COS markers allocated on the long arms of chromosomes 2P and 6P may have a role in markerassisted screening in wheat breeding for powdery mildew disease resistance.