Quantitative Trait Loci Associated With Durable Resistance to Stripe Rust in Winter Wheat

Development of wheat cultivars with durable resistance to stripe rust is a priority due to continuous evolution of new pathogen races. A recombinant inbred line (RIL) population was developed from a cross between Madsen and Foote soft white winter wheat. Madsen has provided effective resistance to stripe rust in the Pacific Northwest region of the United States for over 30 years, whereas Foote was initially resistant to stripe rust but has since become susceptible. The goal of this study was to identify quantitative trait loci (QTLs) for stripe rust resistance in a 217 RIL population of Foote × Madsen. The population was evaluated for stripe rust across five environments from 2014 to 2020, genotyped, and compared with the reference genome of the International Wheat Genome Sequencing Consortium. QTL analysis was conducted using best linear unbiased predictors (BLUPs) across experiments with composite and multiple interval mapping in R/qtl. Results indicated two major QTLs, QYr . orst‐2AS , which is probably associated with the known stripe rust resistance gene Yr17 , and QYr . orst‐1AS . The combination of QYr . orst‐1A and QYr . orst‐2AS substantially reduced rust severity. Two additional minor QTLs, QYr . orst‐2AS/DS and QYr . orst‐4DL , were also found. Growth chamber studies at the seedling stage identified four additional QTLs not detected in the field (three from Madsen and two from Foote), but were not definitively associated with previously reported resistance QTLs. Results add to evidence that durability of the Yr17 chromosomal region in combination with other resistance QTLs is a robust result and a potentially valuable target for marker assisted selection.