High-density Mapping of a Russian Wheat Aphid Resistance Gene: Chromosome Survey Sequences in Use

The Russian wheat aphid (RWA), Diuraphis noxia, is a serious world invasive pest of small grain cereals. Several D. noxia strains (biotypes) varying in virulence have spread in all wheat and barley growing areas with the exception of Australia. Numerous genes contributing to RWA resistance were found in various wheat lines. A dominant gene Dn2401 identified in CI 2401 resistant to both D. noxia U.S. biotypes 1 and 2 was mapped on the short arm of the wheat chromosome 7D (7DS). Development of tightly linked markers and isolation of the resistance gene will facilitate marker-assisted breeding and/or direct gene transfer by molecular methods. To facilitate positional cloning of this gene in a complex polyploid wheat genome, we employ chromosome-based resources such as 7DS-specific BAC library, 7DS physical map and survey sequences of wheat group 7 chromosomes. Furthermore, a synteny-based tool GenomeZipper enabling virtual ordering of cereal genes along chromosomes as well as a newly constructed high-density Ae. tauschii linkage map assist us in highly focused saturation of the map within a 2.2 cM interval delimited by available microsatellite markers. Despite very low level of polymorphism in available mapping population, our approach enabled targeted development of ten new gene-associated SNP markers.

This work has been supported by Czech Science Foundation (grant award P501/12/2554), Internal Grant Agency PrF-2012-001 and Australian Research Council (grant award LP0882095).