Emails: sengupt1@myumanitoba.ca, Curt.McCartney@umanitoba.ca

Leaf rust, caused by the fungus Puccinia triticina, is a prevalent disease of wheat affecting both yield and quality. Leaf rust resistance is an important trait, that is evaluated in the registration of wheat varieties in western Canada, and is an effective strategy for sustainable disease management. The genetic basis of this resistance remains unknown in Canada Western Red Winter (CWRW) wheat.

The objectives of this research were to; identify the quantitative trait loci (QTL) controlling leaf rust resistance using genome-wide association study (GWAS), and develop genomic selection (GS) models for improving leaf rust resistance in winter wheat. The wheat GWAS panel consisted of approximately 300 western Canadian winter wheat breeding lines and cultivars, and 100 winter wheat breeding lines and cultivars from the USA, eastern Canada, and Europe.

The GWAS panel was evaluated for leaf rust resistance in seedling tests, with multiple P. triticina races. This panel was also tested for resistance in inoculated field trials located in Winnipeg and Morden, Manitoba, following randomized alpha lattice designs, with two replicates per field trial, in the 2022-23 and 2023-24 growing seasons. Genotyping was done using the Illumina Infinium Wheat Barley 40K SNP array and the 25K wheat Infinium array.

The DNA marker and leaf rust datasets were used for GWAS. Significant QTLs associated with leaf rust resistance have been detected from the GWAS analyses, which indicated the presence of Lr genes in the GWAS panel, though the identity of these genes has yet to be determined. The leaf rust and SNP marker data were also used to develop genomic selection (GS) models for estimating leaf rust resistance in CWRW breeding germplasm.

The accuracy of these genomic selection (GS) models for predicting the leaf rust resistance of wheat germplasm was assessed via cross-validation. Improved knowledge of the resistance genes in Canadian winter wheat and DNA markers for selecting these genes will improve the efficiency of wheat breeding programs.