Mapping QTL for Resistance to New Virulent Races of Wheat Stripe Rust from Two Argentinean Wheat Cultivars

Abstract

During the last two decades, new virulent and aggressive races of Puccinia striiformis Westend. f. sp. tritici (Pst) have spread worldwide, causing devastating epidemics and prompting the search for new sources of resistance in wheat (Triticum aestivum L.). Between 2012 and 2017, we mapped four stripe rust resistance quantitative trait loci (QTL) effective against the Pst races present in California, USA, using recombinant inbred lines (RILs) developed from the cross between the Argentinean cultivars ‘Klein Proteo’ and ‘Klein Chajá’. The RIL population showed transgressive segregation in all six growing seasons relative to the parental lines, which showed moderate levels of Pst resistance. Analyses by year detected QTL conferring adult plant resistance on chromosomes 1BL, 2BS, 3D centromeric (from Klein Chajá), and 4DL (from Klein Proteo). QYr.ucw‐1BL, mapped in the Yr29 resistance gene region, was significant in all seasons (P < 0.01) and explained on average 31.0 to 32.8% of the observed variation. QYr.ucw‐2BS showed a stronger effect than QYr.ucw‐1BL in 2013 but was ineffective in 2014 and 2016. This QTL also conferred seedling resistance, suggesting that it is an all‐stage resistance gene. Centromeric QYr.ucw‐3D and QYr.ucw‐4DL showed smaller effects than the previous QTL and were significant only in some of the experiments. No significant interactions were detected among QTL, indicating the absence of digenic epistatic effects. The molecular markers identified in this study can be used to combine these genes and accelerate their deployment in wheat breeding programs.

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

“…However, more work is needed to conclude that Qyr.saas-1B is Yr29 . The Yr29 is an APR gene first reported in cultivar Pavon 76 [29], but has since been identified in many different genetic backgrounds, including Pastor [30], Francolin#1 [24], and Klein Chajá [27]. In the present study, CH55 showed high resistance to stripe rust in all four environments with low disease severities of 15–40, with Qyr.saas-1B explaining 6.24%–34.22% of the phenotypic variation.…”

“…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]. We concluded that Qyr.saas-1B was most likely Yr29 .…”

Genome-Wide Association Study Reveals the Genetic Architecture of Stripe Rust Resistance at the Adult Plant Stage in Chinese Endemic Wheat

“…QTL QYr.sicau-1AL.2 was located at about 535.92 Mb and was in close proximity to marker wsnp_Ex_rep_c81556_76277906 (IWA5754), which is associated with stripe-rust resistance in synthetic hexaploid wheat (Zegeye et al, 2014). QTL QYr.sicau-2BS was tagged by four markers in a 0.57-Mb region and overlapped with QTL QYr.ucw-2BS (Cobo et al, 2018). QTL QYr.sicau-7BL with the associated marker AX-109582878 was located at about 733.59 Mb and near QTLs QTL-7BL.1 (Muleta et al, 2017a) and QTL-7BL.3 (Muleta et al, 2017b).…”

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

“…This recognition triggers either hypersensitive reactions (Periyannan et al, 2013; Saintenac et al, 2013; Mago et al, 2015; Steuernagel et al, 2016; Marchal et al, 2018) or the coordinated upregulation of pathogenesis‐related genes that reduce pathogen growth (Zhang et al, 2017; Chen et al, 2018). Because deletions or amino acid changes in the effectors can help the pathogen to avoid detection by the nucleotide‐binding leucine‐rich repeat genes, race‐specific genes often remain effective only for a few years after their deployment in commercial cultivars (Chen et al, 2017b; Salcedo et al, 2017; Cobo et al, 2018).…”

“…Yr29 was first described in ‘Pavon 76’ (William et al, 2003) and has provided partial APR to leaf and stripe rust for more than 60 yr (Kolmer, 2015). Yr29 has been mapped in multiple studies with different genetic backgrounds in the distal region of the long arm of chromosome 1B (reviewed in Cobo et al, 2018). We recently mapped the adult‐plant stripe rust resistance locus QYr.ucw‐1BL on a 25.5‐cM region that overlaps with Yr29 (Cobo et al, 2018).…”