Genetic Analysis and Molecular Mapping of Leaf Rust Resistance Genes in the Wheat Line 5R618

The wheat ( Triticum aestivum L.) line 5R618, bred at the China Agricultural University, is resistant in the seedling stage to the majority of the current Chinese pathotypes of wheat leaf rust ( Puccinia triticina ). To identify and map the leaf rust resistance gene in the 5R618 line, F 2 plants and F 2:3 families from a cross between 5R618 and Zhengzhou5389 (susceptible) were inoculated in the greenhouse with the Chinese P. triticina pathotype THJP. Results from the F 2 and F 2:3 populations indicate that a single dominant gene, temporarily designated Lr5R , conferred resistance. Using the molecular marker method, Lr5R was located on the 3DL chromosome. It was closely linked to the markers Xbarc71 and OPJ-09 with genetic distances of 0.9 cM and 1.0 cM, respectively. At present only one designated gene ( Lr24 ) is located on the 3DL chromosome. The genetic distance between Lr5R and Lr24 confirms that Lr5R is a new leaf rust resistance gene.