The fungal pathogen Puccinia graminis f. sp. tritici (Pgt) is the causative agent of stem rust on wheat (Triticum aestivum). Pgt has the potential to cause significant losses to wheat production in Canada, making it an economically important disease. No stem rust epidemics have occurred since the 1950s in western Canada due to the cultivation of resistant varieties.

The genetic basis for stem rust resistance in most Canadian wheat cultivars is not fully understood. The objective of this study is to identify resistance genes present in a winter wheat association mapping population, consisting of approximately 300 hard red winter wheats from western Canada, and 100 hard red winter wheats from other regions (United States, eastern Canada, and Europe).

The population was phenotyped for stem rust resistance in field trials and seedling assays and has been tested with single nucleotide (SNP) markers spanning the wheat genome.

The 25K Infinium SNP array and the Wheat Barley 40K Infinium SNP array were utilized in this study. Statistical analyses will identify quantitative trait loci (QTL). Field stem rust nurseries were grown at two locations, Winnipeg and Carman, Manitoba in 2023.

Field trials were randomized as alpha lattice designs with two replicates per trial. Plots were 1m long and inoculated with a mixture of Pgt races. Nurseries were mist irrigated to promote disease development. Data were collected on plant height, stand, heading date, and stem rust field severity and infection response.

Field trials will be repeated in 2024. Infection type data was recorded from indoor seedling inoculations with individual races. Preliminary results from genome-wide association study (GWAS) analysis suggest there are QTL of interest for resistance to stem rust located on chromosomes 1B, 2A, 2B, 2D, 3D, and 7B.