The Russian wheat aphid (RWA), Diuraphis noxia (Mordvilko), has caused significant losses to wheat and barley in Canada, Mexico, and the USA during 1986–1990. Sources of resistance to the RWA have been found in wheat and related species. This study was conducted to determine the inheritance of resistance to the RWA in an amphiploid derived from crosses between Triticum tauschii and T. turgidum and to identify new sources of RWA resistance in T. tauschii. Many Triticum tauschii lines and amphiploids derived from crosses between T. tauschii and T. turgidum, T. tauschii and T. timopheevii, and T. ventricosum and T. turgidum have been screened for resistance to the Russian wheat aphid in greenhouse tests. The results of this study confirmed that resistance of these amphiploids is derived from T. tauschii, T. timopheevii, and T. ventricosum. New sources of RWA resistance were identified in T. tauschii species, the donor of the D genome in common wheat. A resistant amphiploid (synthetic hexaploid wheat) derived from a cross between T. tauschii and T. turgidum, was crossed with two susceptible common wheats (T. aestivum L.) 'Yorkstar' and 'Norstar' to study the inheritance of RWA resistance derived from T. tauschii. F1 and F2 reactions indicated that resistance to the RWA in this amphiploid is simple and recessive. The gene symbol Dn3 is proposed for resistance in T. tauschii SQ24. Key words: Russian wheat aphid, Diuraphis noxia, Triticum tauschii, amphiploid, resistance gene, inheritance
Variation between Ethiopian and North American barley varieties ( Hordeum vulgare) in response to Russian wheat aphid ( Diuraphis noxia) populations