The Canada Western Red Spring wheat (Triticum aestivum L.) cultivars AAC Concord, AAC Prevail, CDC Hughes, Lillian, Glenlea, and elite line BW961 express a spectrum of resistance to leaf rust caused by Puccinia triticina Eriks. This study aimed to identify and map the leaf rust resistance of the cultivars using three doubled haploid populations, AAC Prevail/BW961 (PB), CDC Hughes/AAC Concord (HC), and Lillian/Glenlea (LG). The populations were evaluated for seedling resistance in the greenhouse and adult plant disease response in the field at Morden, MB for 3 years and genotyped with the 90K wheat Infinium iSelect SNP array. Genetic maps were constructed to perform QTL analysis on the seedling and field leaf rust data. A total of three field leaf rust resistance QTL segregated in the PB population, five in the HC, and six in the LG population. In the PB population, BW961 contributed two QTL on chromosomes 2DS and 7DS, and AAC Prevail contributed a QTL on 4AL consistent across trials. Of the five QTL in HC, AAC Concord contributed two QTL on 4AL and 7AL consistent across trials and a QTL on 3DL.1 that provided seedling resistance only. CDC Hughes contributed two QTL on 1DS and 3DL.2. Lillian contributed four QTL significant in at least two of the three trials on 2BS, 4AL, 5AL, and 7AL, and Glenlea two QTL on 4BL and 7BL. The 1DS QTL from CDC Hughes, the 2DS from BW961, the 4AL from the AAC Prevail, AAC Concord, and Lillian, and the 7AL from AAC Concord and Lillian conferred seedling leaf rust resistance. The QTL on 4AL corresponded with Lr30 and was the same across cultivars AAC Prevail, AAC Concord, and Lillian, whereas the 7AL corresponding with LrCen was coincident between AAC Concord and Lillian. The 7DS and 2DS QTL in BW961 corresponded with Lr34 and Lr2a, respectively, and the 1DS QTL in CDC Hughes with Lr21. The QTL identified on 5AL could represent a novel gene. The results of this study will widen our knowledge of leaf rust resistance genes in Canadian wheat and their utilization in resistance breeding.
Abstract Background Fusarium head blight (FHB) infection results in Fusarium damaged kernels (FDK) and deoxynivalenol (DON) contamination that are downgrading factors at the Canadian elevators. Durum wheat ( Triticum turgidum L. var. durum Desf.) is particularly susceptible to FHB and most of the adapted Canadian durum wheat cultivars are susceptible to moderately susceptible to this disease. However, the durum line DT696 is less susceptible to FHB than commercially grown cultivars. Little is known about genetic variation for durum wheat ability to resist FDK infection and DON accumulation. This study was undertaken to map genetic loci conferring resistance to DON and FDK resistance using a SNP high-density genetic map of a DT707/DT696 DH population and to identify SNP markers useful in marker-assisted breeding. One hundred twenty lines were grown in corn spawn inoculated nurseries near Morden, MB in 2015, 2016 and 2017 and the harvested seeds were evaluated for DON. The genetic map of the population was used in quantitative trait locus analysis performed with MapQTL.6® software. Results Four DON accumulation resistance QTL detected in two of the three years were identified on chromosomes 1 A, 5 A (2 loci) and 7 A and two FDK resistance QTL were identified on chromosomes 5 and 7 A in single environments. Although not declared significant due to marginal LOD values, the QTL for FDK on the 5 and 7 A were showing in other years suggesting their effects were real. DT696 contributed the favourable alleles for low DON and FDK on all the chromosomes. Although no resistance loci contributed by DT707, transgressive segregant lines were identified resulting in greater resistance than DT696. Breeder-friendly KASP markers were developed for two of the DON and FDK QTL detected on chromosomes 5 and 7 A. Markers flanking each QTL were physically mapped against the durum wheat reference sequence and candidate genes which might be involved in FDK and DON resistance were identified within the QTL intervals. Conclusions The DH lines harboring the desired resistance QTL will serve as useful resources in breeding for FDK and DON resistance in durum wheat. Furthermore, breeder-friendly KASP markers developed during this study will be useful for the selection of durum wheat varieties with low FDK and DON levels in durum wheat breeding programs.
Fusarium head blight (FHB) is a highly destructive fungal disease of wheat to which host resistance is quantitatively inherited and largely influenced by the environment. Resistance to FHB has been associated with taller height and later maturity; however, a further understanding of these relationships is needed. An association mapping panel (AMP) of 192 predominantly Canadian spring wheat was genotyped with the wheat 90K single-nucleotide polymorphism (SNP) array. The AMP was assessed for FHB incidence (INC), severity (SEV) and index (IND), days to anthesis (DTA), and plant height (PLHT) between 2015 and 2017 at three Canadian FHB-inoculated nurseries. Seven multi-environment trial (MET) datasets were deployed in a genome-wide association study (GWAS) using a single-locus mixed linear model (MLM) and a multi-locus random SNP-effect mixed linear model (mrMLM). MLM detected four quantitative trait nucleotides (QTNs) for INC on chromosomes 2D and 3D and for SEV and IND on chromosome 3B. Further, mrMLM identified 291 QTNs: 50 (INC), 72 (SEV), 90 (IND), 41 (DTA), and 38 (PLHT). At two or more environments, 17 QTNs for FHB, DTA, and PLHT were detected. Of these 17, 12 QTNs were pleiotropic for FHB traits, DTA, and PLHT on chromosomes 1A, 1D, 2D, 3B, 5A, 6B, 7A, and 7B; two QTNs for DTA were detected on chromosomes 1B and 7A; and three PLHT QTNs were located on chromosomes 4B and 6B. The 1B DTA QTN and the three pleiotropic QTNs on chromosomes 1A, 3B, and 6B are potentially identical to corresponding quantitative trait loci (QTLs) in durum wheat. Further, the 3B pleiotropic QTN for FHB INC, SEV, and IND co-locates with TraesCS3B02G024900 within the Fhb1 region on chromosome 3B and is ~3 Mb from a cloned Fhb1 candidate gene TaHRC. While the PLHT QTN on chromosome 6B is putatively novel, the 1B DTA QTN co-locates with a disease resistance protein located ~10 Mb from a Flowering Locus T1-like gene TaFT3-B1, and the 7A DTA QTN is ~5 Mb away from a maturity QTL QMat.dms-7A.3 of another study. GWAS and QTN candidate genes enabled the characterization of FHB resistance in relation to DTA and PLHT. This approach should eventually generate additional and reliable trait-specific markers for breeding selection, in addition to providing useful information for FHB trait discovery.
Fusarium head blight (FHB) has rapidly become a major challenge to successful wheat production and competitive end-use quality in western Canada. Continuous effort is required to develop germplasm with improved FHB resistance and understand how to incorporate the material into crossing schemes for marker-assisted selection and genomic selection. The aim of this study was to map quantitative trait loci (QTL) responsible for the expression of FHB resistance in two adapted cultivars and to evaluate their co-localization with plant height, days to maturity, days to heading, and awnedness. A large doubled haploid population of 775 lines developed from cultivars Carberry and AC Cadillac was assessed for FHB incidence and severity in nurseries near Portage la Prairie, Brandon, and Morden in different years, and for plant height, awnedness, days to heading, and days to maturity near Swift Current. An initial linkage map using a subset of 261 lines was constructed using 634 polymorphic DArT and SSR markers. QTL analysis revealed five resistance QTL on chromosomes 2A, 3B (two loci), 4B, and 5A. A second genetic map with increased marker density was constructed using the Infinium iSelect 90k SNP wheat array in addition to the previous DArT and SSR markers, which revealed two additional QTL on 6A and 6D. The complete population was genotyped, and a total of 6,806 Infinium iSelect 90k SNP polymorphic markers were used to identify 17 putative resistance QTL on 14 different chromosomes. As with the smaller population size and fewer markers, large-effect QTL were detected on 3B, 4B, and 5A that were consistently expressed across environments. FHB resistance QTL were co-localized with plant height QTL on chromosomes 4B, 6D, and 7D; days to heading on 2B, 3A, 4A, 4B, and 5A; and maturity on 3A, 4B, and 7D. A major QTL for awnedness was identified as being associated with FHB resistance on chromosome 5A. Nine small-effect QTL were not associated with any of the agronomic traits, whereas 13 QTL that were associated with agronomic traits did not co-localize with any of the FHB traits. There is an opportunity to select for improved FHB resistance within adapted cultivars by using markers associated with complementary QTL.
Wheat leaf rust, caused by Puccinia triticina Erikss., is one of the most common and damaging diseases of wheat in Canada and throughout the world. To understand the P. triticina population virulence analysis of the population in Canada has been conducted annually for over 80 years. The virulence profile of the P. triticina population and virulence to key resistance genes changes significantly over time, and differs between regions. Recently, genetic analysis via DNA sequencing of representative isolate from the P. triticina populations from 2018-2022 initially revealed three diverse groups in Canada. All isolates within group one had the same two mating type alleles, group two isolates all had a second combination of alleles, whereas group three isolates were partitioned into eight sub-groups encompassing different genetic clades. A fourth distinct group was later found from British Columbia. To combat leaf rust, the resistance genes Lr2a, Lr13, Lr14a, Lr16, Lr21 and Lr34 have been used extensively in Canadian spring wheat cultivars. Lr34, Lr46 and Lr67 are unique among resistance genes in that they are non-race specific, conditioning partial resistance to all isolates, while also providing resistance to other wheat diseases. Critically, Lr34 and Lr67 was demonstrated to confer resistance to Fusarium Head Blight. The complete picture underlying Lr34 functions is not fully understood, but only Lr34res lines accumulate the fungistatic compound 1-O-p-coumaroyl-3-O-feruloylglycerol. Lr34 also produces leaf tip necrosis, this is enhanced at low temperatures. Combinations of race-specific leaf rust resistance genes, with Lr34, Lr46 and/or Lr67, have the best potential to protect wheat from a dynamic Canadian leaf rust population.
Fusarium head blight (FHB) has a negative impact on cereal food safety, quality and yield. The majority of FHB resistance genes in wheat (Triticum spp.) have been identified based on reaction to Fusarium graminearum, which, in Canada, has two prevalent trichothecene chemotypes, 3-acetyl-deoxyinvalenol (ADON) and 15-ADON. Three hexaploid (Triticum aestivum L.) and four tetraploid (Triticum turgidum L. ssp. durum and Triticum turgidum L. spp. dicoccoides (Korn. ex Asch. & Graebn.) Thell.) wheat genotypes with different genes for resistance and with different reactions to F. graminearum were evaluated in replicated greenhouse trials to determine if the resistance genes currently deployed in Canadian wheat are effective against both the 3-ADON and 15-ADON chemotypes. The development of FHB was rated as disease severity. The genotypes showed differential responses, with a higher level of disease development in the hexaploid wheat genotypes inoculated with the 3-ADON than with the 15-ADON chemotype. The opposite was observed in the tetraploid wheat genotypes. Tetraploid genotype BGRC3487 and a hexaploid genotype ND2710 showed similar resistance to both 3-ADON and 15-ADON chemotypes. These would be effective sources to breed lines resistant to both 3-ADON and 15-ADON chemotypes and reduce FHB risk.
Based on their consistency over environments, two QTL identified in Lillian on chromosomes 5A and 7A could be useful targets for marker assisted breeding of common bunt resistance. Common bunt of wheat (Triticum aestivum L.) caused by Tilletia tritici and T. laevis is an economically important disease because of losses in grain yield and reduced grain quality. Resistance can be quantitative, under the control of multiple small effect genes. The Canada Western Red Spring wheat variety Lillian is moderately resistant to common bunt races found on the Canadian prairies. This study was conducted to identify and map quantitative trait loci (QTL) conferring resistance against common bunt in Lillian. A doubled haploid population comprising 280 lines was developed from F1 plants of the cross of Lillian by Vesper. The lines were inoculated at seeding with the two races L16 (T. laevis) and T19 (T. tritici), grown in field near Swift Current, SK, in 2014, 2015 and 2016 and assessed for disease incidence. The lines were genotyped with the 90 K iSelect SNP genotyping assay, and a high-density genetic map was constructed. Quantitative trait locus analysis was performed with MapQTL.6® software. Two relatively stable common bunt resistance QTL, detected in two of the 3 years, were identified on chromosomes 5A and 7A from Lillian. In addition, three less stable QTL, appearing in one out of 3 years, were identified: one was contributed by Lillian on chromosome 3D and two were contributed by Vesper on chromosomes 1D and 2A. Epistatic interaction was identified for the bunt incidence between 3D and 7A resulting in greater bunt resistance. Future bunt resistance breeding will benefit from combining these QTL through gene pyramiding.
Resistance breeding is an effective strategy against wheat stripe (yellow) rust caused by Puccinia striiformis f. sp. tritici (Pst). To identify and map quantitative trait loci (QTL) associated with stripe rust resistance, a durum wheat doubled haploid population (n = 87) derived from 'Strongfield/Blackbird' was evaluated for disease severity near Toluca, Mexico (2017–2019) and Lethbridge, Canada (2016–2019). The population was genotyped with the wheat 90 K Illumina iSelect single nucleotide polymorphism (SNP) array and simple sequence repeat (SSR) markers, and QTL analysis was performed with MapQTL 6. We identified stripe rust-resistance QTL contributed by 'Blackbird' on chromosomes 3A (2 loci, designated QYr.spa-3A.1, QYr.spa-3A.2) and 5B (QYr.spa-5B), and 'Strongfield' on 2B (QYr.spa-2B). All seem to represent QTL not reported previously. The QYr.spa-3A.2 was most consistently effective against Pst races across the Lethbridge and Toluca nurseries. With a LOD value of 4.9, QYr.spa-3A.2 explained a maximum phenotypic variation of 22.7% observed at the Toluca 2019 nursery. The QYr.spa-2B from 'Strongfield' and QYr.spa-3A.1 from 'Blackbird' expressed in multiple years at Toluca but were not detected at Lethbridge. QYr.spa-5B was identified in the Lethbridge 2016 environment. The identified QTL should be valuable in diversifying resistance genes used in breeding durum wheat cultivars with stripe rust resistance. 'Blackbird' was particularly useful for introducing the new QTL QYr.spa-3A.2 resistance that is effective in Canada and Mexico into traditional durum wheat germplasm. SNP markers associated with QTL will have application in marker-assisted breeding of resistance to Pst in durum wheat.
This study was conducted to identify and map stem rust resistance genes in Canada Western Red Spring (CWRS) wheat variety 'AAC Prevail' and elite line 'BW961ʹ. A population of 227 doubled haploid lines from 'AAC Prevail'/'BW961ʹ and parents were evaluated for their response to stem rust (Puccinia graminis) at Njoro, Kenya, from 2016–2019 and genotyped using a targeted genotyping by sequencing SeqSNP assay. 'AAC Prevail' and 'BW961ʹ were susceptible to race TTKSK in seedling tests in Canada. We identified stable QTL (significant in most environments tested) associated with field stem rust resistance on chromosome arms 2BS and 7AL, and minor QTL on 5AL, 6AS and 7BL. The QTL on 5AL, 7AL and 7BL were contributed by 'AAC Prevail', while those on 2BS and 6AS were contributed by 'BW961ʹ. The QTL on 7AL was detected across all environments and explained 9.5% to 39% of the variation in disease severity (DS) and infection response (IR). The QTL on 2BS was associated with DS in all environments and in three of four environments for IR, and explained 4.8% to 12% of the variation in DS and IR. In two environments, the combination of 2BS and 7AL significantly enhanced field stem rust resistance compared with either QTL singly. Using SNP markers closely linked to the novel QTL on 2BS and 7AL, Kompetitive Allele Specific PCR markers were developed and validated in the population. These results provide breeders with new information and markers to utilize these sources of stem rust resistance.
