Identification of Novel Stripe Rust Resistance in the US Pacific Northwest Winter Wheat

Stripe rust, caused by Puccinia striiformis f. sp. tritici is a devastating disease of wheat production world- wide including the US Pacific Northwest (PNW). Historically, major epidemics have happened in this region, and resulted in introducing both adult plant resistance and all-stage resistance into PNW wheat breeding programs. The objective of this study was 1) to identify loci associated with stripe rust resistance by genome wide association mapping (GWAS) using a wheat panel consisting of 468 soft white winter wheat adapted to the PNW, and 2) to compare consistent marker-trait associations with the linkage map re-constructed from a recombinant inbred line (RIL) population derived from a cross between ‘Coda’ and ‘Brundage’. Field evaluation for stripe rust resistance was carried out at Pullman, Central Ferry and Mount Vernon, WA in 2013, 2014 and 2015. Race specific resistance was evaluated for Pst-100, Pstv-11 and Pstv-51 under greenhouse conditions. The association panel was genotyped with Illumina 90,000 SNP array, and a total of 25,489 SNP were used for analysis. Mixed-linear model incorporating population structure and kinship was used for GWAS. Preliminary result showed that loci significantly associated with stripe rust resistance at the seedling stage were located on chromosomes 1A, 1B, 1D, 2B, 3D, 4A, 5A, 5B, 6B and 7B. The 1B loci were repeatedly identified in GWAS for field disease response as well as the linkage map in the Coda and Brundage RIL. These loci appeared to be novel and prevalent in PNW soft white winter wheat germplasm.