Screening global wheat germplasm with a diverse collection of pathogen races expands the catalog of novel Yr loci and identifies new sources of broad-spectrum resistance against evolving Pst populations. Newly emerging highly virulent races of Puccinia striiformis f. sp. tritici (Pst) often defeat deployed resistance genes (Yr), highlighting the need for novel sources of durable resistance. A global diversity panel of 377 spring wheat (Triticum aestivum L.) lines was screened for all-stage resistance (ASR) against a panel of diverse 20 Pst isolates at the seedling stage and for adult-plant-stage resistance (APR) against natural mix of field races. Genome-wide association mapping identified 77 unique Yr loci. Of these, 34 overlapped with the previously mapped 1150 Yr loci, confirming the robustness of our GWAS results, while 43 were likely novel. Comparison of the nine adult-plant-stage Yr loci mapped in our study with known APR genes identified only one overlap, with Yr29. Except for Yr29, APR genes Yr18 and Yr36 were detected at low frequencies, indicating that resistance in our panel may arise from less characterized or novel sources. Two wheat lines, lacking widely effective Yr5 and Yr15 alleles, exhibited resistance to all 20 Pst races at the seedling stage and natural field races at the adult stage, suggesting that they may carry novel, broad-spectrum ASR alleles. Wheat improvement had no effect on the frequency of ASR alleles but resulted in a threefold increase in the frequency of APR alleles, suggesting that the latter were subjected to more consistent breeding selection over time. Our findings underscore the value of combined screening of diverse germplasm with diverse pathogen races to identify novel sources of broad-spectrum resistance for breeding stripe rust resistant cultivars.

Stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is a devastating wheat disease worldwide, and novel stripe rust resistance genes that can be readily used in wheat breeding are needed for sustainable wheat production. Winter wheat cultivar Samara exhibits high resistance to predominant Pst races in the United States. An F 2:3 population and an F 7 RIL population derived from the cross Samara × Jagalene were evaluated for responses to Pst race PSTv-37 at the seedling stage, leading to the conclusion that a single dominant gene conditions stripe rust resistance in Samara. A subset of F 2 plants was genotyped using genotyping-by-sequencing (GBS), and allele distribution analyses at each GBS-SNP locus revealed a genomic region harboring a stripe rust resistance gene, temporarily designated YrSA, in the terminal region of chromosome arm 2AL in Samara. Some GBS-SNPs in the target region were converted to KASP markers and linkage analysis delimited YrSA to an interval of 1.65 Mb between 784.71 Mb and 786.36 Mb in the Chinese Spring IWGSC RefSeq v2.1 reference sequence. The mapping results were further confirmed in the F 7 RIL population. YrSA is a new stripe rust resistance gene different from other genes previously reported on chromosome arm 2AL based on their locations, origins, and responses to Pst races. The physical order of YrSA with other permanently named Yr genes on 2AL is Yr1-Yr86-Yr32-YrSA. YrSA can be widely used to enhance wheat stripe rust resistance in the USA, and the newly developed KASP markers can be used in marker-assisted selection.

Abstract Stripe rust and leaf rust, caused by Puccinia striiformis f. sp. tritici and P. triticina , respectively, are the most destructive wheat diseases in the southern Great Plains. ‘Green Hammer’ is a hard red winter wheat (HRWW) cultivar released by Oklahoma State University in 2018 and has demonstrated a stable adult plant resistance to stripe rust and race-specific seedling resistance to leaf rust. To identify and map rust resistance loci, 109 doubled haploid (DH) lines derived from the cross between Green Hammer and another HRWW cultivar, ‘Lonerider’, were developed. Lonerider showed adult plant resistance to stripe rust but was susceptible to multiple P. triticina races. The DH lines were evaluated for stripe rust at the adult plant stage in greenhouse and field environments across Oklahoma, Kansas, and Washington, and for leaf rust at the seedling stage against seven U.S. P. triticina races and at the adult plant stage in Oklahoma and Texas. Genotyping-by-sequencing generated 6,078 polymorphic single-nucleotide polymorphisms used for genetic mapping. Quantitative trait loci (QTL) analysis identified 14 stripe rust and 8 leaf rust resistance QTL. For stripe rust, a major QTL in Green Hammer, QYr.osughln-2AS , was identified in the proximity of the 2N v S translocation. Three other major stripe rust resistance QTL were identified in Lonerider on chromosomes 2AL (two QTL) and 2BS (one QTL). For leaf rust, QLr.osughln-1DS and QLr.osughln-2DS.1 were the two major QTL identified in Green Hammer and most likely correspond to the all-stage resistance genes Lr21 and Lr39 , respectively. In this study, we identified previously characterized genes as well as unknown genes that can be utilized in wheat breeding programs to enhance resistance to leaf rust and stripe rust.

For winter wheat in the US Central Great Plains, phenotypic plasticity of yield is agronomically adaptive, that is, genotypes with higher plasticity have higher yield in high yielding environments with no tradeoff in stressful, low yielding environments. Using data from variety trials conducted between 2000 and 2022 and cultivars released between 1991 and 2022, we explored time trends in phenotypic plasticity and heritability of yield. Given that yield plasticity is agronomically adaptive in the Great Plains, we hypothesize that (i) newer cultivars will have higher yield plasticity; (ii) heritability of yield is declining in the time series; and (iii) genomic regions associated with yield depend on the environment and do not fully overlap with those associated with phenotypic plasticity of yield. Breeding for yield and agronomic adaptation increased phenotypic plasticity of yield at 0.5% year-1; broad sense heritability of yield decreased from 0.23 in 1993 to 0.15 in 2017. Genome-wide association analysis shows genomic regions associated with yield varied between high yielding and stressful environments and were partially independent of those associated with yield plasticity. Newer cultivars have a higher frequency of alleles associated with yield and its plasticity. We discuss implications for breeding and agronomy aimed at improving wheat phenotypes.

Fusarium head blight (FHB) is a serious disease of durum wheat ( Triticum turgidum subsp. durum ) worldwide. Most cultivated durum varieties are susceptible to FHB, and durum breeding programs have been challenged by limited sources of FHB resistance. Great efforts have been devoted to identifying and introgressing FHB resistance from tetraploid relatives of durum, such as cultivated emmer wheat ( T. turgidum subsp . dicoccum ), into adapted durum varieties. However, the quantitative trait loci (QTL) controlling the FHB resistance in cultivated emmer and its introgression lines have not been well characterized. In this study, we aimed to identify and map FHB resistance QTL in a population of 186 recombinant inbred lines (RILs) derived from a cross between durum cultivar ‘Joppa’ and the introgression line LPA-4, which carries FHB resistance from a cultivated emmer line (PI 254188). The population was genotyped using a genotyping-by-sequencing (GBS) approach for discovery of single nucleotide polymorphism (SNP) markers and phenotyped for FHB disease severity and Fusarium damaged kernel (FDK) in multiple greenhouse and field experiments. A genetic map with a total length of 1137.62 cM was generated with 757 unique SNP markers. QTL analysis identified six LPA-4-derived QTL for FHB resistance on chromosome arms 1BL, 3AS, 3AL, 5BS, 5BL, and 6BL and one Joppa-derived QTL on chromosome 7BL. Additionally, two LPA-4-derived QTL for resistance to FDK were detected on chromosomes 6AL and 6BS, respectively. This research provides new insights into FHB resistance in tetraploid emmer wheat and will facilitate the development of resistant durum cultivars in FHB resistance breeding programs.

Stripe rust, caused by Puccinia striiformis f. sp. tritici, is among the most destructive wheat (Triticum aestivum L.) diseases. Identifying resistance genes is crucial for the development of resistant cultivars. Baker's Ann, a hard winter wheat cultivar developed by Oklahoma State University, has shown stable adult plant resistance to stripe rust. To dissect the genetic basis underlying stripe rust resistance in Baker's Ann, 125 doubled haploid lines, derived from the cross OK12D22004-016 × Baker's Ann, were evaluated at the adult plant stage in the greenhouse and in field environments in Oklahoma, Kansas, and Washington. This population was genotyped using genotyping‑by‑sequencing, which produced 7268 single‑nucleotide polymorphisms for genetic mapping. Quantitative trait loci (QTLs) analysis identified six loci, four from Baker's Ann on chromosomes 2DL, 4BS, 4BL, and 7BL, and two from OK12D22004-016 on chromosomes 2AS and 2AL. Although OK12D22004-016 is susceptible in the US Great Plains, it was found to carry QYr.osu-2AS, which was linked to Yr17 on the 2NvS translocation and explained up to 30% of the phenotypic variation but was effective in a single location in Washington. Two major QTLs were identified in Baker's Ann: QYr.osu-2DL on chromosome 2DL that explained up to 57% of the phenotypic variation, and QYr.osu-4BL on chromosome 4BL that explained up to 15% of the phenotypic variation. Resistance in Baker's Ann resulted from additive effects of the four QTLs. Kompetitive allele-specific PCR markers were developed for QYr.osu-2DL to facilitate marker-assisted selection for stripe rust resistance.

The necrotrophic fungus Parastagonospora nodorum is the causal agent of septoria nodorum blotch (SNB) of wheat. To determine the prevalence of SNB sensitivity genes in a contemporary U.S. hard winter wheat (HWW) , we evaluated a panel of 619 breeding lines and cultivars against five P. nodorum isolates and five necrotrophic effectors (NEs), SnToxA, SnTox1, SnTox3, SnTox267 and SnTox5, and genotyped the panel using genotyping-by-sequencing (GBS) markers and diagnostic Kompetetive-allele specific PCR (KASP) markers for the sensitivity genes Tsn1-B1 , Snn1-B1 , and Snn3-B1/B2 . GBS analysis identified 34,357 GBS-single nucleotide polymorphism (SNP) markers . Evaluations against P. nodorum isolates showed that 40-67% of the genotypes were susceptible in the panel. Toxin infiltration assays showed that 54%, 2%, 37%, 13%, and 15% of the genotypes were sensitive to SnToxA, SnTox1, SnTox3, SnTox267, and SnTox5, respectively. Diagnostic KASP markers for Tsn1-B1 , Snn1-B1 , and Snn3-B1/B2 showed prediction accuracies of 98%, 75%, and 92% for the corresponding effectors SnToxA, SnTox1, and SnTox3, respectively. Genome-wide association studies (GWAS) not only confirmed the presence of the previously characterized sensitivity genes Tsn1-B1 , Snn1-B1 , Snn2 , Snn3-B1/B2 , and Snn5-B1 , but also identified new loci to be associated with responses to P. nodorum isolates and NEs. Of which, Qsnb.osu-2AS on chromosome 2AS was associated with responses to all five isolates. We developed KASP markers KASP_S4B_643615365 , KASP_ S2D_16184991 , and KASP_S2A_9833162 linked to Snn5-B1 , Snn2 , and Qsnb.osu-2AS , respectively. These findings should guide breeding for SNB resistance in hard winter wheat.

A genome-wide association study using 90 K wheat SNP arrays identified nine QTLs with 38 SNP markers significantly associated with Fusarium head blight resistance in US wheat. Six putative novel QTLs were identified from the US wheat with three for type II resistance, two for low DON and FDK and one for all three traits. Wheat Fusarium head blight (FHB) is a devastating disease of wheat worldwide. Growing FHB-resistant wheat is the most effective and eco-friendly approach to reduce the losses. To identify native FHB resistance quantitative trait loci (QTLs), a population of 201 US winter wheat breeding lines and cultivars were genotyped using 90 K wheat single nucleotide polymorphism (SNP) arrays and phenotyped for the percentage of symptomatic spikelets (PSS) in a spike in three greenhouse experiments, and for PSS, Fusarium damaged kernels (FDK) and deoxynivalenol (DON) content in two field experiments. Genome-wide association studies (GWAS) identified 38 SNPs that were significant for at least two of the three traits or a single trait in at least two experiments on chromosomes 1A, 1D, 2B, 3A, 3B, 4A, 5B and 5D. Among them, QPss.hwwg-1AS, QPss.hwwg-1DS and QPss.hwwg-3AL are likely novel QTLs for reduced PSS from US winter wheat, and QFDon.hwwg-4AL, QFDon.hwwg-5BL and QFDon.hwwg-5DL are novel QTLs for low FDK and DON. Among them, only QFDon.hwwg-5BL had significant effects on all the three FHB traits. Most of these QTLs showed additive effects. Among the tested accessions, hard winter wheat ‘T153,’ ‘T154’ and ‘OK05128’ harboring all resistance marker alleles for low PSS, FDK and DON, therefore, they are good resistant parents for improving FHB resistance.

Wheat stripe rust, caused by the biotrophic fungal pathogen Puccinia striiformis f. sp. tritici (Pst), is among the top crop diseases incurring huge economic losses worldwide. Identification of new stripe rust-resistant sources that can be easily used in wheat cultivar development is essential for food security. PI 622129, an Iranian wheat landrace, exhibits high resistance to the predominant U.S. Pst races. A recombinant inbred line (RIL) population from the cross PI 622129 × Stardust was genotyped using single-nucleotide polymorphisms generated by genotyping-by-sequencing. The RIL population was evaluated for responses to the Pst race PSTv-37 at the seedling stage in three environments, and quantitative trait loci (QTLs) analysis revealed four QTLs for stripe rust resistance on chromosome arms 2DS, 5BS, 2AL, and 7BL. Of these, QYr.stars-2DS and QYr.stars-5BS are major QTLs that explained 21 to 38% and 11.6 to 27.2% of the total phenotypic variance, respectively, in three experiments. QYr.stars-2DS is a new stripe rust resistance locus that was identified in the interval of 2.58 to 5.54 Mb on chromosome arm 2DS based on the Chinese Spring IWGSC RefSeq v.2.1 reference genome. Another QTL, QYr.stars-5BS, is close to Yr47 and was delimited to the interval 8.1 to 9.0 Mb in the reference genome. QYr.stars-2AL and QYr.stars-7BL were mapped to the terminal and QTL-rich regions on chromosome arms 2AL (750.8 to 752.5 Mb) and 7BL (718.1 to 721.2 Mb), respectively. KASP markers were developed to facilitate rapid introgression of these QTLs into locally adapted lines via marker-assisted selection.

Summary statement Knockouts of cytokinin oxidase‐dehydrogenase (TaCKX2.2) homeologs increased grain number per spike, grain size, grain weight per spike, and final yield without negative impacts on other major agronomic traits, revealing a novel approach to improve grain yield by manipulating the TaCKX2.2 gene family in wheat.

Hessian fly (HF), Mayetiola destructor (Say), is a serious pest of wheat (Triticum aestivum L.) worldwide. Using resistance genes from alien sources is a promising strategy for developing HF-resistant cultivars. The HF resistance gene H25 in the wheat line KS92WGRC20 was originally transferred from chromosome 6R of rye (Secale cereale L.) into the proximal region of the long arm on wheat chromosome 4A. However, the introgressed 6R segment has not been characterized and diagnostic markers for H25 have been lacking, limiting its use in breeding programs. This study developed a population of 188 recombinant inbred lines (RILs) from Jagger × KS92WGRC20 and analyzed the population using single-nucleotide polymorphism (SNP) markers generated by genotyping-by-sequencing (GBS). Phenotypic segregation analysis and gene mapping confirmed H25 as the sole HF resistance gene in KS92WGRC20. Two kompetitive allele-specific PCR (KASP) markers, K6R_316905104 and K6R_316905114, were converted from GBS-SNPs and validated in two wheat diversity panels, one with 203 winter wheat accessions from the major US wheat growing areas and the other containing 38 wheat lines that carry various known HF resistance genes. In addition, a gel-based dominant PCR marker was also developed. Moreover, a genomic region spanning 310–480 Mb was proposed as a putative introgressed segment of chromosome 6R based on analysis of GBS data from the RIL population using the rye Lo7 as reference genome. Together, these results provide practical molecular tools and new insights into the 6R introgression carrying H25, facilitating its efficient deployment in wheat breeding programs.

'GoWheat 9216H' (Reg. no. CV-1224, PI 708101) is a hard red winter wheat (Triticum aestivum L.) that was bred and released by the Texas A&M AgriLife Research Wheat Improvement Program in 2021. GoWheat 9216H is an F4-derived line advanced from the cross 'X09A440S' ( = TX07A001482/TAM 401)/'Duster' that was made in Bushland, TX, in 2010. GoWheat 9216H is a medium-maturing, semi-dwarf, awned and white glumed wheat that has demonstrated high grain yield potential across many Texas environments in both irrigated and dryland conditions. GoWheat 9216H is resistant to stem rust (Sr; Puccinia graminis Pers.:Pers f. sp. tritici Erikss. & E. Henn.), leaf rust (Lr; P. triticina Erikss.), and stripe rust (Yr; P. striiformis Westend. f. sp. tritici Erikss.), with marker data suggesting it carries Lr34, Lr37, Lr68, Yr17, Yr18, YrM1225, and Sr38. It is moderately resistant to Hessian fly [Mayetiola destructor (Say)]. This cultivar shows good baking and milling quality traits equivalent to high-quality checks and further features large seeds and high grain volume weight. Its height is similar to that of recently released Texas A&M cultivars, but it has a later maturity date. GoWheat 9216H is poised to perform well under both irrigated and dryland conditions in the Texas Rolling Plains, South and Central Texas, and the Blacklands, as well as in other regions across the state with similar adaptation zones.

Abstract Key message Characterized and unknown septoria nodorum blotch susceptibility/resistance genes were identified in contemporary U.S. hard winter wheat. The necrotrophic fungus Parastagonospora nodorum is the causal agent of septoria nodorum blotch (SNB) of wheat. To determine the prevalence of SNB sensitivity genes in a contemporary U.S. hard winter wheat (HWW), we evaluated a panel of 619 breeding lines and cultivars against five P. nodorum isolates and five necrotrophic effectors (NEs), SnToxA, SnTox1, SnTox3, SnTox267 and SnTox5, and genotyped the panel using genotyping-by-sequencing (GBS) markers and diagnostic Kompetetive-allele specific PCR (KASP) markers for the sensitivity genes Tsn1-B1 , Snn1-B1 , and Snn3-B1/B2 . GBS analysis identified 34,357 GBS-single nucleotide polymorphism (SNP) markers. Evaluations against P. nodorum isolates showed that 40-67% of the genotypes were susceptible in the panel. Toxin infiltration assays showed that 54%, 2%, 37%, 13%, and 15% of the genotypes were sensitive to SnToxA, SnTox1, SnTox3, SnTox267, and SnTox5, respectively. Diagnostic KASP markers for Tsn1-B1 , Snn1-B1 , and Snn3-B1/B2 showed prediction accuracies of 98%, 75%, and 92% for the corresponding effectors SnToxA, SnTox1, and SnTox3, respectively. Genome-wide association studies (GWAS) not only confirmed the presence of the previously characterized sensitivity genes Tsn1-B1 , Snn1-B1 , Snn2 , Snn3-B1/B2 , and Snn5-B1 , but also identified new loci to be associated with responses to P. nodorum isolates and NEs. Of which, Qsnb.osu-2AS on chromosome 2AS was associated with responses to all five isolates. We developed KASP markers KASP_S4B_643615365 , KASP_ S2D_16184991 , and KASP_S2A_9833162 linked to Snn5-B1 , Snn2 , and Qsnb.osu-2AS , respectively. These findings should guide breeding for SNB resistance in hard winter wheat.

Wheat (Triticum aestivum) is an important staple crop that sustains over one-third of the global population. Powdery mildew, an economically important disease caused by Blumeria graminis f. sp. tritici (Bgt), significantly affects wheat production in many wheat-growing regions. Therefore, identification of novel powdery mildew resistance genes that can be easily used in wheat cultivar development is essential for meeting the needs of the increasing global human population. PI 606247 (formerly 'Samara') is a winter wheat cultivar developed in the Czech Republic in 1995 that exhibits resistance to representative U.S. Bgt isolates. An F7 recombinant inbred line (RIL) population derived from PI 606247 × Jagalene was evaluated for responses to Bgt isolate OKS(14)-B-3-1. Genetic analysis indicated that a single gene, designated PmSA, conditions powdery mildew resistance in PI 606247. Selective genotyping of a subset of RILs identified a set of SNPs co-segregating with powdery mildew resistance in the terminal region of chromosome arm 2BL. Linkage analysis using kompetitive allele specific PCR (KASP) markers located PmSA to a 14.43 Mb interval between 686.69 Mb and 701.12 Mb in the Chinese Spring IWGSC RefSeq v2.1 reference sequence. PmSA is a new powdery mildew resistance gene differing from the others in the terminal region of 2BL in genomic location, origin, and responses to a set of Bgt differential isolates. PmSA is valuable for enhancing powdery mildew resistance, and the KASP markers closely linked to PmSA can facilitate its rapid deployment in wheat cultivars via marker-assisted selection.

Loss-of-function mutations induced by CRISPR-Cas9 in the TaGS3 gene homoeologs show non-additive dosage-dependent effects on grain size and weight and have potential utility for increasing grain yield in wheat. The grain size in cereals is one of the component traits contributing to yield. Previous studies showed that loss-of-function (LOF) mutations in GS3, encoding Gγ subunit of the multimeric G protein complex, increase grain size and weight in rice. While an association between allelic variation in the GS3 homologs of wheat and grain weight/size has been detected previously, the effects of LOF alleles at TaGS3 on these traits remain unknown. We used genome editing to create TaGS3 mutant lines with varying LOF homeo-allele dosages. Contrary to the results obtained in rice, editing all three TaGS3 homoeologous copies resulted in a significant decrease in grain length (4.4

Newly emerging highly virulent races of Puccinia striiformis f. sp. tritici (Pst) often defeat deployed resistance genes ( Yr ), highlighting the need for novel sources of durable resistance. A global diversity panel of 377 spring wheat ( Triticum aestivum L.) lines was screened for all-stage resistance (ASR) against 20 diverse Pst isolates at the seedling stage and adult plant resistance (APR) against natural mix of field races. Genome-wide association mapping identified 77 unique Yr loci. Of these, 33 overlapped with the previously reported ~1,100 loci, while 44 were likely novel. Nine mapped Yr loci were effective at the adult plant stage and showed no overlap with the known APR genes. Two wheat lines, though lacked the widely effective Yr5 and Yr15 genes, exhibited resistance to all 20 Pst races at the seedling stage and natural field races at the adult stage, suggesting that they may carry novel, broad-spectrum resistance alleles. APR genes Yr18 , Yr29 , and Yr36 were detected at low frequencies, indicating that much of the observed resistance may arise from less characterized or novel sources. Wheat improvement had no effect on the frequency of ASR alleles but resulted in a three-fold increase in the frequency of APR alleles, suggesting that the latter were subjected to more consistent breeding selection over time. Our findings underscore the value of combined screening of diverse germplasm with the diverse panels of pathogen races to identify novel sources of broad-spectrum resistance for breeding stripe rust resistant cultivars. ### Competing Interest Statement The authors have declared no competing interest. Gates Foundation, https://ror.org/0456r8d26, INV-004430 USDA National Institute of Food and Agriculture, 2022–68013-36439 (WheatCAP)

Farmer seed purchase patterns historically drive end-use quality into a subordinate position to yield enhancement and protection in hard red winter (HRW) wheat (Triticum aestivum L.) breeding programs. Evolving consumer food purchase decisions could conceivably swing this priority pendulum back near the center. 'Paradox' (Reg. no. CV-1223; PI 705146), 'Breadbox' (Reg. no. CV-1221; PI 705144), and 'Firebox' (Reg. no. CV-1222; PI 705145) HRW wheat cultivars were developed with magnified dough strength as the first breeding priority and released in 2023. Our objectives herein were to document their novel rheology relative to contemporary HRW wheat, determine correlated changes in agronomic performance, and assess Paradox's potential as a strengthening component in bread flour blends. Marker-assisted backcrossing with Glu-B1al as the molecular target was conducted through the BC2F2 generation, from which experimental lines OK15MASBx7 ARS 8-29 (Paradox), OK15MASBx7 ARS 8-20 (Breadbox), and OK15DMASBx7 ARS 6-8 (Firebox) were derived via conventional inbreeding or doubled haploidization. Relative to the HRW controls, Paradox and Breadbox produced a sevenfold greater peak time and fourfold greater stability time, whereas changes in Firebox were more moderate but still superior to the HRW controls. None of the cultivars was diminished for agronomic or milling characteristics, and their novel dough strength was unrelated to grain protein concentration. All three cultivars have entered non-commoditized supply chains as ingredient flour intended for products requiring more gluten strength, including many formulations for pan bread.

Leaf rust (Puccinia triticina) and stripe rust (Puccinia striiformis f. sp. tritici) are among the most prevalent foliar diseases in wheat, causing significant annual yield losses worldwide. To identify rust resistance genes in U.S. winter wheat, we conducted a genome-wide association study (GWAS) on resistance to leaf and stripe rusts in U.S. winter wheat cultivars and elite advanced breeding lines. Using simple sequence repeats (SSRs) and wheat 90K single nucleotide polymorphism (SNP) arrays, we identified two novel quantitative trait loci (QTLs), QLr.hwwg-2BL and QLr.hwwg-4AL, and four QTLs corresponding to known genes Lr74, Lr77, Lr18 and Lr68 for leaf rust resistance. We also identified five QTLs conferring stripe rust resistance, which included the three previously characterized loci Yr17/YrM1225 on the 2NS/2AS translocation, Yr30/Sr2 on 3BS, and QYr.hwwg-2BS, along with two putative novel loci, QYr.hwwg-2AS.2 and QYr.hwwg-4BL, with the latter located in a QTL-rich region. The QTLs identified in this study will be useful for improving durable resistance to leaf and stripe rusts in new wheat cultivars using marker-assisted gene-pyramiding strategy.

Fusarium head blight (FHB), caused by Fusarium graminearum Schwabe, is one of the most devastating diseases in wheat (Triticum aestivum L.). The synthetic hexaploid wheat line Largo was developed from a cross between the durum wheat [T. turgidum ssp. durum (Desf.) Husn.] variety Langdon and the Aegilops tauschii Cosson accession PI 268210, and it was previously found to have a moderate level of FHB resistance. This study was conducted to identify quantitative trait loci (QTL) associated with FHB resistance using a population of 188 recombinant inbred lines (RILs) from a cross between Largo and the susceptible wheat line ND495. The RILs were evaluated for Type II resistance in two greenhouse and two field environments. The disease severity and 90K single-nucleotide polymorphism marker data were used for QTL analysis, which revealed six QTL on chromosomes 1D, 2D, 5B, and 7D. Four QTL (QFhb.rwg-1D, QFhb.rwg-5B, QFhb.rwg-7D.1, and QFhb.rwg-7D.3) from Largo had minor effects, whereas two QTL (QFhb.rwg-2D and QFhb.rwg-7D.2) from ND495 showed large effects on FHB resistance. The result suggested that ND495 may possess suppressor or susceptibility gene(s) suppressing or masking FHB resistance controlled by the resistance QTL. Among these QTL, four coincided with previously reported QTL, including Fhb9, and two (QFhb.rwg-1D and QFhb.rwg-7D.1) are likely novel QTL. From the six QTL regions, 10 Kompetitive allele-specific PCR markers were developed and validated for marker-assisted selection. The QTL detected from the resistant and susceptible parents enhance our understanding of FHB resistance expression and provide new resources for improving FHB resistance in wheat.

The GWAS and testing with Yr gene linked markers identified 109 loci including 40 novel loci for all-stage and adult plant stage resistance to stripe rust in 459 US contemporary hard winter wheat genotypes. Stripe rust is a destructive wheat disease, caused by Puccinia striiformis f. sp. tritici (Pst). To identify sources of stripe rust resistance in US contemporary hard winter wheat, a panel of 459 Great Plains wheat genotypes was evaluated at the seedling stage against five US Pst races and at the adult plant stage in field environments in Oklahoma, Kansas, and Washington. The results showed that 7–14