Wheat breeders worldwide are seeking new sources of resistance to Puccinia graminis f. sp. tritici race TTKSK. To prioritize field-resistant landraces for follow-up genetic studies to test for the presence of new resistance genes, seedling response to P. graminis f. sp. tritici race TTKSK, molecular markers linked to specific Sr genes, segregation ratios among progeny from crosses, and bulked segregant analyses (BSA) were used. In total, 33 spring wheat landraces with seedling resistance to P. graminis f. sp. tritici race TTKSK were crossed to a susceptible genotype, LMPG-6. The segregation ratios of stem rust reactions in F2 seedlings fit a single dominant gene model in 31 populations and progeny from two crosses gave ambiguous results. Using the 90K wheat single-nucleotide polymorphism genotyping platform, BSA showed that the seedling resistance in 29 accessions is probably controlled by loci on chromosome 2BL. For the three remaining accessions, BSA revealed that the seedling resistance is most likely controlled by previously unreported genes. For confirmation, two populations were advanced to the F2:3 and screened against P. graminis f. sp. tritici race TTKSK. Segregation of the F2:3 families fit a 1:2:1 ratio for a single dominant gene. Using the F2:3 families, BSA located the TTKSK locus on chromosome 6DS to the same location as Sr42.
Bibliographical noteFunding Information:
We thank S. Stoxen and S. Gale for their technical assistance. This research was supported by the USDA-ARS National Plant Disease Recovery System, the USDA-ARS CRIS project 2050-21000-029-00D, and the Durable Rust Resistance in Wheat (DRRW) project managed by Cornell University and funded by the Bill and Melinda Gates Foundation and the United Kingdom Department for International development. This work was supported, in part, by National Research Initiative Competitive Grant 2011-68002-30029 (Triticeae-CAP) from the USDA National Institute of Food and Agriculture.
© 2016, American Phytopathological Society. All rights reserved.