Mapping of QTL for adult plant stripe rust resistance genes in a Sichuan wheat landrace and the evaluation of their breeding effects

Stripe rust, caused by <italic>Puccinia striiformis</italic> f. sp. <italic>tritici</italic> (Pst), is a worldwide wheat disease that causes large losses in production. The lack of in-depth understanding of genetic and breeding utilization effects, coupled with the linkage of undesirable traits, are the key factors that limit the wide application of most of the discovered wheat stripe rust resistance genes in breeding and production. Our previous studies have shown that the wheat landraces, Hongmangmaizi (HM), exhibited stable adult plant stripe rust resistance to prevalent physiological races and pathogenic groups of stripe rust in China. In order to reveal the genetic basis of HM adult plant resistance to stripe rust, F₁, F₂, and F_2:3 segregating populations derived from the cross between Avocet S and HM were inoculated with mixed <italic>Pst</italic> and evaluated for stripe rust reaction at adult stage in the field. Through bulked segregation analyses (BSA) using 55K single-nucleotide polymorphism array and exon sequencing technology, we identified two quantitative trait loci (QTL) on chromosomes 7AL and 7DS, designated as <italic>QYr.HM-7AL</italic> and <italic>QYr.HM-7DS</italic>, explaining 11.64%-15.25% and 24.33%-40.58% of the phenotypic variance, respectively. Through integrated linkage, genetic and physical map analyses indicated that the major QTL <italic>QYr.HM-7DS</italic> was corresponding to the <italic>Yr18</italic> gene, whereas <italic>QYr.HM-7AL</italic>, which was the second most stable QTL, should be a potential novel QTL for adult-stage stripe rust resistance. Furthermore, the kompetitive allele- specific PCR (KASP) markers, tightly linked with <italic>QYr.HM-7AL</italic>, were developed and validated. Based on construction of BC₁F₂ genetic improvement population derived from a cross between Mianmai 1618 × HM, the main QTL genetic effect of stripe rust resistance and its synergistic effect on yield related traits were analyzed. The results showed that the two QTL (<italic>Yr18</italic> and<italic> QYr.HM-7AL</italic>) could significantly reduce the damage of stripe rust and had a positive effect on spike length and tillering number under the genetic background of Mianmai 1618. The above results indicated that the QTLs of adult-stage stripe rust resistance from HM could be used in wheat yield breeding programs.