A High‐Resolution Map of Wheat QYr.ucw‐1BL, an Adult Plant Stripe Rust Resistance Locus in the Same Chromosomal Region as Yr29

Abstract

Core Ideas The adult‐plant stripe rust resistance locus QYr.ucw‐1BL is effective against new virulent races of the stripe rust pathogen. QYr.ucw‐1BL was mapped to a 332‐kb region including 13 genes associated with disease resistance. QYr.ucw‐1BL and the durable stripe rust resistance gene Yr29 map to the same region and confer similar resistance reactions. Exome capture data were useful for accelerating marker development and establishing haplotypes associated with resistant and susceptible lines. High‐throughput molecular markers have been developed to accelerate the deployment of QYr.ucw‐1BL and the durable stripe rust resistance gene Yr29. The appearance of highly virulent and more aggressive races of Puccinia striiformis f. sp. tritici (Pst) during the last two decades has led to stripe rust epidemics worldwide and to the rapid erosion of effective resistance genes. In this study, we mapped an adult‐plant resistance locus from the Argentinean wheat (Triticum aestivum L.) cultivar Klein Chajá, which is effective against these new Pst races. By using wheat exome capture data and a large population of 2480 segregating plants (4960 gametes), we mapped QYr.ucw‐1BL within a 0.24‐cM region [332 kb in International Wheat Genome Sequencing Consortium (IWGSC) RefSeq version 1.0] on chromosome arm 1BL. This region overlaps with current maps of the adult‐plant Pst resistance gene Yr29, which has remained effective for more than 60 yr. An allelism test failed to find recombination between QYr.ucw‐1BL and Yr29 and yielded similar resistance phenotypes for the two loci. These results, together with similar haplotypes in the candidate region, suggested that QYr.ucw‐1BL and Yr29 might represent the same gene. However, we cannot rule out the possibility of tightly linked but different genes because most of the 13 genes in the candidate region are annotated with functions associated with disease resistance. To evaluate their potential as QYr.ucw‐1BL/Yr29 candidate genes, we characterized their polymorphisms between resistant and susceptible haplotypes. Finally, we used these polymorphisms to develop high‐throughput markers to accelerate the deployment of these Pst resistance loci in wheat breeding programs.

Identification of QTLs for Stripe Rust Resistance in a Recombinant Inbred Line Population

“…It was physically located between 664.08 Mbp and 673.64 Mbp in the distal region of chromosome 1BL (Table 9, Table S1, Figure 4a). This region is rich in stripe rust resistance genes and QTLs, such as Yr21 [20], Yr24 / Yr26 [21], and Yr29 [22,23]. The physical interval of Qyr.saas-1B overlapped with Yr29 , QYr.cim-1BL1 [24], QYr.cim-1BL2 [25], QYr.spa-1B [26], QYr.ucw-1BL [23,27], and QYr.sicau-1B.3 [28].…”

Analysis of miRNA expression associated with the Lr46 gene responsible for APR resistance in wheat (Triticum aestivum L.)

“…However, the authors do not rule out the hypothesis that these genes may be combined into one mechanism of immunity (Lagudah, 2011). Cobo et al (2018) showed that the 332-kb csLV46G22 marker flanking the QYr.ucw-1BL candidate region has been mapped and is closely related to Yr29 (Ren et al 2017;Dong et al 2017;Ponce-Molina et al, 2018 Table 1 The concentration of miR164 in the analyzed cultivars (tested before inoculation and after 6, 12, 24, and 48 h after inoculation in biological and technical replicates)-average of replicates Analyzed genotypes miR164 concentration (copies/μl)-average of replicates , and the miRNAs for tests were chosen based on sequence complementarity to the gene of interest. Out of two identified miRNAs, it was impossible to detect and analyze the expression profile of miR5085.…”

“…In the current study, the 242-bp product of amplification of Xwmc44 marker, which is linked to the leaf rust resistance gene Lr46, was identified in 4 out of 5 analyzed cultivars (Pavon'S', Myna'S', Frontana'S', and Sparrow'S') confirming the presence of the desired gene. Cobo et al (2018) mapped the Yr29 yellow rust resistance locus in the 332-kb region of the 1BL chromosome arm in adult plants. This region is rich in genes that are also associated with resistance to brown rust Lr46, stem rust Sr58, and powdery mildew Pm39.…”

“…Resistance genes present in this chromosome region have been effective for over 60 years and are widespread in CIMMYT wheat germplasm (Singh et al, 2011). Cobo et al (2018) reported that single genes found at this locus provide resistance to many different pathogens (Krattinger et al, 2009;Moore et al, 2015). However, the authors do not rule out the hypothesis that these genes may be combined into one mechanism of immunity (Lagudah, 2011).…”

QTL Mapping of Wheat Stripe Rust Resistance in Relation to Epidermal Flavonoids Measured Using a Leaf‐Clip, Optical Sensor

“…4, suggesting the locus might be linked to the same gene. Additional indirect evidence supports this hypothesis: the closest SNP marker (IWA1791) was located at ?2.1 cM from IWB34935, a SNP marker recently identified for Yr29 by Cobo et al (2018), and Drysdale is known to possess the Yr29 gene for stripe rust resistance (Wellings et al, 2012). The locus on chromosome 3B (IWA1702) explained 19.8% of the phenotypic variation observed in the nursery experiment of 2015 and was located in the proximity of the Sr2/Yr30 genes.…”