Identification of Two New Loci for Adult Plant Resistance to Leaf Rust and Stripe Rust in the Chinese Wheat Variety 'Neimai 836'.

The characterization of leaf rust (caused by Puccinia triticina) and stripe rust (caused by Puccinia striiformis f. sp. tritici) resistance genes is the basis for breeding resistant wheat varieties and managing epidemics of these diseases in wheat. A cross between the susceptible wheat variety 'Apav#1' and resistant variety 'Neimai 836' was used to develop a mapping population containing 148 F5 recombinant inbred lines (RILs). Leaf rust phenotyping was done in field trials at Ciudad Obregon, Mexico in 2017 and 2018, and stripe rust data were generated at Toluca, Mexico in 2017 and in Mianyang, Ezhou, and Gansu, China in 2019. Inclusive complete interval mapping (ICIM) was used to create a genetic map and identify significant resistance quantitative trait loci (QTL) with 2,350 polymorphic markers from a 15K wheat single-nucleotide polymorphism (SNP) array and simple-sequence repeats (SSRs). The pleiotropic multi-pathogen resistance gene Lr46/Yr29 and four QTL were identified, including two new loci, QLr.hzau-3BL and QYr.hzau-5AL, which explained 3-16% of the phenotypic variation in resistance to leaf rust and 7-14% of that to stripe rust. The flanking SNP markers for the two loci were converted to Kompetitive Allele-Specific PCR (KASP) markers and used to genotype a collection of 153 wheat lines, indicating the Chinese origin of the loci. Our results suggest that Neimai 836, which has been used as a parent for many wheat varieties in China, could be a useful source of high level resistance to both leaf rust and stripe rust.