Direct hybridization facilitates the simultaneous identification and introgression of QTL for adult plant resistance to the Ug99 stem rust lineage from tetraploid Khorasan wheat to common wheat

Abstract The Puccinia graminis f. sp. tritici ( Pgt ) Ug99 race group presents a major challenge to global wheat production. Satisfying current and future demands hinges on the discovery of new sources of resistance. It is imperative that the durability and diversity of Ug99 resistance is improved by identifying and deploying novel resistance genes. Progenitor species and wild relatives of common wheat ( Triticum aestivum ) have proven to be rich sources of genetic diversity. The Khorasan wheat ( Triticum turgidum ssp. turanicum ) accession CItr 11390 displays adult plant resistance (APR) to Ug99 races. 121 BC 1 F 5 -derived recombinant inbred lines were developed from a cross between CItr 11390 and MN07098-6 to map and introgress resistance loci from CItr 11390. The population was evaluated in Kenya and Ethiopia in 2019 and 2020. Two APR QTL from CItr 11390 were detected in multiple environments. QSr.umn-2A is believed to be the APR gene Sr63 on chromosome 2AL. QSr.umn-6BL was identified on 6BL upstream from Sr11 . The distance from Sr11 and lack of APR QTL reported on 6BL suggest QSr.umn-6BL is a novel locus. Additional QTL were mapped to chromosomes 1AS, 3AL, 3BL, 5AL, and 6BS in single environments. The population segregates for TKTTF seedling resistance conferred by Sr7a and a novel locus, QSr.umn-5A.1 . The population consists of the first hexaploid wheat lines to pyramid Sr7a , Sr57 / Lr34 / Yr18 , Sr63 , and QSr.umn-6BL . This study is the first report of Pgt resistance QTL from Khorasan wheat, and it demonstrates the feasibility of simultaneously identifying and transferring resistance QTL from tetraploid to hexaploid wheat.