A Microsatellite marker for tagging Dn2, a wheat gene conferring resistance to the Russian wheat aphid

The Russian wheat aphid (RWA), Diuraphis noxia Mordvilko, is an economically important pest of wheat (Triticum aestivum L.). An effective means to control the RWA is through the use of resistant cultivars. While a phenotype-based selection has been useful for selection of resistant plants, it has inherent limitations. Screening can only be done during cool months of the year, and symptom expression is influenced by the environment. Pyramiding of two or more RWA resistance genes is also difficult because of the presence of only one aphid biotype in the USA at present. This study was conducted to develop a DNA marker that is tightly linked to Dn2, and to test the effectiveness of the marker as a tag for Dn2 among a limited number of cultivars tested. We report mapping of five microsatellite markers linked to Dn2. The closest marker was Xgwm437 at 2.8 cM, and it distinguished lines containing Dn2 from eight susceptible cultivars and seven resistant cultivars carrying other RWA resistance genes. Xgwm437 should be effective for marker-assisted selection of Dn2-containing plants and for combining Dn2 with other resistance genes in a gene pyramiding program.