Development of a PCR Assay and Marker-Assisted Transfer of Leaf Rust Resistance Gene Lr58 Into Hard Red Winter Wheats.

New and additional resistance genes are needed in wheat to develop wheat varieties that are resistant against highly variable and dynamic leaf rust pathogen.The small wheat-Aegilops triuncialis introgression T2BS·2BL-2^tL(0.95) carrying leaf rust resistance gene Lr58 is a source of resistance against many isolates of the rust pathogen in US and India. Rust resistance gene Lr58 was transferred to the hard red winter wheat (HRWW) cultivars Jagger and Overley by standard backcrossing and marker-assisted selection (MAS). A codominant PCR-based sequence tagged site (STS) marker was developed based on the sequence information of the RFLP marker (XksuH16) diagnostically detecting the alien segment in T2BS·2BL-2^tL(0.95). STS marker was used to select backcross F₁ plants with rust resistance and the codminant marker polymorphism detected by primer pair NCW-Lr58-MAS-1 efficiently indentifyed the homozygous BC₃F₂ plants with rust resistance gene Lr58. Diagnostic polymorphism detected by STS marker NCW-Lr58-MAS-1 was consistent between the resistant source and a set of wheat cultivars selected by the US Wheat Coordinated Agricultural Project except for a cultivar from Indiana. Detection of diagnostic codominant polymorphism in both the agarose based and capillary based flatforms suggests the utility and compatibility of the STS marker in the MAS programs in US involving robust genotyping flatforms. Screening the backcross derivatives carrying Lr58 with rust races at seedling stage suggested the transferred rust resitance in adapted winter wheats is stable and is not affected by the background effects. The HRWW germplasm with Lr58 will provide breeders with adapted lines having an additional source of resistance that can be used to achieve durability of rust resistance.