A Combination of Leaf Rust Resistance Genes, Including and , Is the Key to the Durable Resistance of the Canadian Wheat Cultivar, Carberry.

The hexaploid spring wheat cultivar, Carberry, was registered in Canada in 2009, and has since been grown over an extensive area on the Canadian Prairies. Carberry has maintained a very high level of leaf rust ( Eriks.) resistance since its release. To understand the genetic basis of Carberry's leaf rust resistance, Carberry was crossed with the susceptible cultivar, Thatcher, and a doubled haploid (DH) population of 297 lines was generated. The DH population was evaluated for leaf rust in seven field environments at the adult plant stage. Seedling and adult plant resistance (APR) to multiple virulence phenotypes of was evaluated on the parents and the progeny population in controlled greenhouse studies. The population was genotyped with the wheat 90 K iSelect single nucleotide polymorphism (SNP) array, and quantitative trait loci (QTL) analysis was performed. The analysis using field leaf rust response indicated that Carberry contributed nine QTL located on chromosomes 1B, 2B (2 loci), 2D, 4A, 4B, 5A, 5B, and 7D. The QTL located on 1B, 2B, 5B, and 7D chromosomes were observed in two or more environments, whereas the remainder were detected in single environments. The resistance on 1B, detected in five environments, was attributed to and on 7D, detected in seven environments to . The first 2B QTL corresponded with the adult plant gene, , while the second QTL corresponded with . The seedling analysis showed that Carberry carries , , and . Five epistatic effects were identified in the population, with synergistic interactions being observed for with , , and . The durable rust resistance of Carberry is attributed to and in combination with these other resistance genes, because the resistance has remained effective even though the population has evolved virulent to , and .