Inheritance and Genetic Mapping of Russian Wheat Aphid Resistance in Iranian Wheat Landrace Accession PI 626580

Russian wheat aphid (RWA), Diuraphis noxia (Kurdjumov), is a significant insect pest of wheat (Triticum aestivum L.) and has had a major economic impact worldwide, especially on winter wheat in the western United States. Development of resistant cultivars remains the most viable method for RWA control, although the continuing emergence of new RWA biotypes virulent to deployed resistance genes reinforces the need for the discovery of new sources of resistance. Iranian wheat landrace accession PI 626580 has shown high levels of resistance to RWA biotypes 1 (RWA1) and 2 (RWA2), but the inheritance and chromosomal location of this resistance is unknown. The objectives of this study were to determine the inheritance of RWA2 resistance, identify closely linked markers, and map the chromosomal location of RWA2 resistance found in PI 626580. Bulked segregant analysis was conducted with a mapping population of 154 F-2 individuals derived from a single plant selection made from PI 626580 and 'Yuma' (a susceptible wheat cultivar). Phenotypic segregation of RWA2 resistance suggested a single dominant gene, provisionally designated Dn626580. Linkage mapping analysis identified three simple sequence repeat (SSR) markers, Xbarc214, Xgwm473, and Xgwm437, proximally linked to Dn626580 near the centromere on the short arm of chromosome 7D at distances of 1.8, 5.0, and 8.2 cM, respectively. Dn626580, a new resistance gene found in PI 626580, could be used alone or by pyramiding with other resistance genes to develop cultivars with effective RWA resistance.