Characterization of a New Stripe Rust Resistance Gene on Chromosome Arm 2AL in Winter Wheat Cultivar Samara

Stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is a devastating wheat disease worldwide, and novel stripe rust resistance genes that can be readily used in wheat breeding are needed for sustainable wheat production. Winter wheat cultivar Samara exhibits high resistance to predominant Pst races in the United States. An F_2:3 population and an F₇ recombinant inbred line (RIL) population derived from the cross Samara × Jagalene were evaluated for responses to Pst race PSTv-37 at the seedling stage, leading to the conclusion that a single dominant gene conditions stripe rust resistance in Samara. A subset of F₂ plants was genotyped using genotyping-by-sequencing (GBS), and over 44,000 single-nucleotide polymorphisms (SNPs) were identified. Allele distribution analyses at each SNP locus revealed a genomic region harboring a stripe rust resistance gene, temporarily designated YrSA, in the terminal region of chromosome arm 2AL in Samara. Some GBS SNPs in the target region were converted to KASP markers, and linkage analysis delimited YrSA to an interval of 1.65 Mb between 784.71 and 786.36 Mb in the Chinese Spring IWGSC RefSeq v.2.1 reference sequence. The mapping results were further confirmed in the F₇ RIL population. YrSA is a new stripe rust resistance gene different from other genes previously reported on chromosome arm 2AL based on their locations, origins, and responses to Pst races. The physical order of YrSA with other permanently named Yr genes on 2AL is Yr1-Yr86-Yr32-YrSA. YrSA can be widely used to enhance wheat stripe rust resistance in the United States, and the newly developed KASP markers can be used in marker-assisted selection.