Genetics of Leaf Rust Resistance in the Hard Red Winter Wheat Cultivars Santa Fe and Duster

Leaf rust, caused by Puccinia triticina, is a common and important disease of hard red winter wheat (Triticum aeistivum L.) in the Great Plains of the United States. The hard red winter wheat cultivars 'Santa Fe' and 'Duster' have had effective leaf rust resistance since their release in 2003 and 2006, respectively. The objective of this research was to determine the identity of the leaf rust resistance genes in these cultivars. Both cultivars were vernalized and crossed with the susceptible spring wheat 'Thatcher', F-1 plants were backcrossed to Thatcher, and 90 backcross (BC) F-1 plants from each cross were grown out to develop BC1F2 families. Seedlings of the Thatcher*2/Santa Fe BC1F2 families segregated for two genes. The seedling resistance was correlated with the presence of the 2AS/2NS translocation from Aegilops ventricosa Tausch, which indicated one of the genes was Lr37. In field plots, the families segregated for a single gene that was independent of the seedling resistance and the 2NS translocation. Seedlings of the Thatcher*2/Duster BC1F2 families segregated for two genes. In field plots, the families segregated for two genes that were independent of the seedling resistance genes. Santa Fe has Lr37 on the 2NS translocation, an additional adult plant resistance gene, and was postulated to have Lr3a. A previous postulation of Lr17a in Santa Fe was determined to be incorrect. Duster was postulated to have Lr3a and Lr11 for seedling resistance and, based on a molecular marker, Lr34 plus another adult plant resistance gene for field resistance. Lines with the additional adult plant resistance gene in both crosses had leaf rust severity of 10 to 30% with a resistance response of small to large uredinia with chlorosis and necrosis. Santa Fe and Duster are valuable sources of leaf rust resistance for the southern Great Plains region.