Soft Red Winter Wheat Cultivars Research Articles

Testing the efficacy of a newly released fungicide, Sphaerex, for control of Fusarium Head Blight in wheat

Fusarium head blight (FHB) is a destructive disease of wheat and other small-grain cereals. FHB causes reduction in crop yield due to pre-mature bleaching of spikes. Additionally, it deteriorates the crop quality due to the production of mycotoxins. An integrated management strategy is needed to effectively manage this disease. One of the most important strategies in the FHB management toolbox is chemical control. Fungicides start losing their efficacy over time due to the development of fungicide resistance in the pathogens. This necessitates the development and testing of new fungicides with multiple active ingredients or modes of action. In this 3-year study, we evaluated the effectiveness of a new fungicide with multiple active ingredients, Sphaerex (a proprietary mix of metconazole and prothioconazole) in an FHB-susceptible soft red winter wheat cultivar, Shirley in the eastern United States. Sphaerex provided significantly better control over untreated plots for FHB Incidence, FHB Severity, and DON content across all three years. The level of control of FHB and DON by Sphaerex was found to be similar to that provided by other standard FHB fungicides. The yield of the fungicide-treated plots was statistically similar to that of the untreated plots.

Reducing the generation time in winter wheat cultivars using speed breeding

AbstractReducing generation time is critical to achieving the goals of genetic gain in important crops like wheat (Triticum aestivum). Speed breeding (SB) has been shown to considerably reduce generation times in crop plants. Unlike spring wheat cultivars, winter wheat varieties require typically 6–9 weeks of cold treatment, called vernalization, for flowering which extends the generation time for the development of improved winter wheat cultivars. Here, we optimized the SB method using a set of 48 diverse soft red winter wheat (SRWW) cultivars by testing vernalization duration, light and temperature requirements, and the viability of seeds harvested after different durations post‐anthesis under extended daylight conditions. We have found that using a 22‐h setting (22 h day/2 h night, 25°C/22°C) in high‐density 50‐cell trays results in rapid generation advancement. We used genotypic data for a panel of soft red winter wheat varieties from the regional programs to determine the impact of photoperiod and vernalization alleles on the efficiency of the SB approach. Using a set of 48 SRWW cultivars and germplasm from Maryland and four other public breeding programs, we establish that this protocol can allow for the advancement of four generations per year in controlled conditions for winter wheat varieties, experimental lines, or emerging cultivars. Our work shows the potential to reduce generation time by ∼30 days per generation faster than what had been reported in the SB strategies for winter wheat, thus allowing for a quicker turnaround time from original cross to genetically stable experimental genotypes that can be tested in field settings.

Registration of ‘Pembroke 2021’ soft red winter wheat

AbstractKentucky's wheat (Triticum aestivum L.) crop is planted into a rotation in which corn (Zea mays L.) is followed by wheat, which is followed by double‐crop soybean [Glycine max (L.) Merr.]. The causal agent of Fusarium head blight (FHB), Fusarium graminearum Schwabe, overwinters in corn stubble; thus, the Kentucky wheat crop is always at risk for FHB. The preeminent goal of the University of Kentucky wheat breeding program is releasing FHB‐resistant winter wheat cultivars. ‘Pembroke 2021’ (Reg. no. CV‐1198, PI 701381) is an early‐maturing, semi‐dwarf, soft red winter wheat cultivar developed and released in 2020 by the Kentucky Agricultural Experiment Station for FHB resistance, high yield and test weight potential, and lodging resistance. Pembroke 2021, tested as KY 07C‐1145‐94‐12‐5, was developed from the cross ‘IL99‐15867’/B990081//KY97C‐0554‐04‐05. The pedigree of the KY parent is VA94‐54‐549/Roane//Kristy. Pembroke 2021 was named for the Pembroke silt loam soil series prevalent in the main wheat‐producing area of Kentucky. Pembroke 2021 was selected from F4:5 head rows using a modified bulk breeding method; selected rows carried the resistance allele at the following FHB resistance quantitative trait loci: 1B Jamestown, 1A Neuse, 4A Neuse, and 3B Massey. Pembroke 2021 was tested in Kentucky in multi‐location replicated yield trials, the Uniform Eastern Soft Red Winter Wheat Nursery, the Mason‐Dixon nursery, the Uniform Northern Winter Wheat Scab Nursery, and the Kentucky Wheat Variety Trial.

글루텐 강도가 다른 미국산 연질밀가루의 건면 제조 적성 비교

Purpose: The present study compared the dry noodle-making performance of US soft wheat flours with different gluten strength. Methods: Three flours (weak, medium, and strong gluten strength - W, M, and S, respectively) milled from US Soft Red Winter (SRW) wheat cultivars and a commercial all-purpose flour (control) were analyzed for their physicochemical properties including pasting property, SDS sedimentation volume, solvent retention capacity (SRC), and dry noodle-making performance. Results: The three soft wheat flours were significantly different in SDS sedimentation volume, lactic acid SRC, and gluten performance index, whereas the all-purpose flour had similar SDS sedimentation value and lactic acid SRC to S flour, and gluten performance index similar to the M flour. The peak viscosity of pasting, final viscosity, and peak time of the all-purpose flour were within the range of soft flours. The resistance (R) and extensibility (E) of the fresh noodles were in the order of W<M<S flour. The R and E of the all-purpose flour were greater than all three soft wheat flours, but the R/E of the flour was similar to the S flour. The firmness and chewiness measured after boiling the dry noodles made with the S soft wheat flour were higher or similar, compared to those made with the all-purpose flour. Conclusions: Soft wheat flour with high gluten strength was suitable for making dry white-salted noodles. The SDS sedimentation volume, lactic acid SRC, and gluten performance index of the soft wheat flours could be useful indicators for selecting a soft wheat flour suitable for dry white-salted noodle production.

A new soft red winter wheat cultivar ‘GA 08535‐15LE29’ adapted to Georgia and the U.S. southeast region

AbstractSoft red winter wheat (SRWW) (Triticum aestivum L.) production in the southeastern United States is affected by biotic and abiotic stresses that can result in yield losses and reduced acreage. Developing new cultivars with high yield, good resistance to predominant pests, and acceptable quality to maximize value in regional markets is needed. The University of Georgia (UGA) SRWW breeding program, in collaboration with institutions in the region including the Southern UNiversities GRAINS (SUNGRAINS) programs, is responding to these challenges by developing and releasing superior cultivars adapted to the region. ‘GA 08535‐15LE29’ (Reg. no. CV‐1191, PI 693269) SRWW cultivar was developed and released by the UGA College of Agricultural and Environmental Sciences and licensed to Uni South Genetics seed company in 2018 as USG 3640. GA 08535‐15LE29 is well adapted to Georgia and the U.S. southeast region with high yield and good resistance to leaf (Puccinia triticina Erikss.) and stripe (P. striiformis Westend.) rusts, Fusarium head blight (caused by Fusarium graminearum Schwabe), powdery mildew (Erisyphe graminis), and Soil‐borne wheat mosaic virus (SBWMV) diseases. GA 08535‐15LE29 showed moderate field resistance to Hessian fly [Mayetiola destructor (Say)]. GA 08535‐15LE29 has Sbm1 and Yr17/Lr37/Sr38 for resistance to SBWMV and rust diseases and has good grain volume weight and acceptable milling and baking qualities.

A network modeling approach provides insights into the environment-specific yield architecture of wheat.

Wheat (Triticum aestivum) yield is impacted by a diversity of developmental processes which interact with the environment during plant growth. This complex genetic architecture complicates identifying quantitative trait loci that can be used to improve yield. Trait data collected on individual processes or components of yield have simpler genetic bases and can be used to model how quantitative trait loci generate yield variation. The objectives of this experiment were to identify quantitative trait loci affecting spike yield, evaluate how their effects on spike yield proceed from effects on component phenotypes, and to understand how the genetic basis of spike yield variation changes between environments. A 358 F5:6 recombinant inbred line population developed from the cross of LA-95135 and SS-MPV-57 was evaluated in 2 replications at 5 locations over the 2018 and 2019 seasons. The parents were 2 soft red winter wheat cultivars differing in flowering, plant height, and yield component characters. Data on yield components and plant growth were used to assemble a structural equation model to characterize the relationships between quantitative trait loci, yield components, and overall spike yield. The effects of major quantitative trait loci on spike yield varied by environment, and their effects on total spike yield were proportionally smaller than their effects on component traits. This typically resulted from contrasting effects on component traits, where an increase in traits associated with kernel number was generally associated with a decrease in traits related to kernel size. In all, the complete set of identified quantitative trait loci was sufficient to explain most of the spike yield variation observed within each environment. Still, the relative importance of individual quantitative trait loci varied dramatically. Path analysis based on coefficients estimated through structural equation model demonstrated that these variations in effects resulted from both different effects of quantitative trait loci on phenotypes and environment-by-environment differences in the effects of phenotypes on one another, providing a conceptual model for yield genotype-by-environment interactions in wheat.

12W932-349 Soft red winter wheat

12W932-349 is a soft red winter wheat (Triticum aestivum L.) cultivar registered for Ontario, Canada. It has high grain yield with good pastry quality and is moderately resistant to Fusarium head blight. 12W932-349 is well adapted for the winter wheat growing areas of Ontario.

Wheat yellow mosaic virus resistant line, 'Kitami-94', developed by introgression of two resistance genes from the cultivar 'Madsen'.

'Kitahonami' is a soft red winter wheat (Triticum aestivum L.) cultivar that has high yield, good agronomic performance and good quality characteristics. It currently accounts for 73% of the wheat cultivation area of Hokkaido the northern island in Japan and 42% of Japan's overall wheat cultivation. However, this cultivar is susceptible to Wheat yellow mosaic virus (WYMV). WYMV has become widespread recently, with serious virus damage reported in Tokachi and Ohotsuku districts, which are the main wheat production areas in Hokkaido. Here, we report a new wheat breeding line 'Kitami-94', which was developed over four years by repeated backcrossing with 'Kitahonami' using DNA markers for WYMV resistance linked to the Qym1 and Qym2 from 'Madsen'. Basic maps of Qym1 and Qym2 were created and used to confirm that 'Kitami-94' reliably carried the two resistance genes. 'Kitami-94' demonstrated WYMV resistance, and had agronomic traits and quality equivalent to 'Kitahonami' except for higher polyphenol oxidase activity and lower thousand grain weight. 'Kitami-94' may be useful for elucidating the mechanism of WYMV resistance in the background of 'Kitahonami', and for developing new cultivars.

Impact of Nitrogen Rate in Conventional and Organic Production Systems on Yield and Bread Baking Quality of Soft Red Winter Wheat

Soft red winter wheat (SRW) is characterized by high yield and relatively low protein content. In Kentucky, there is growing demand from local artisan bread bakers for regionally produced flour, requiring production of grain with increased protein content and/or strength. The objective of this two-year field experiment was to evaluate the effect of nitrogen (N) management on five cultivars of winter wheat on yield and bread baking quality traits of modern and landrace SRW cultivars (Triticum aestivum L.). All five cultivars were evaluated using two N application rates in conventional and organic production systems. All traits measured were significantly affected by the agricultural production system and N rate, although plant height and other quality traits varied by study year. Significantly higher yields were achieved in the conventional system at a relatively low N rate (67.2 kg ha−1) in both study years (2017–2019) (p &lt; 0.01). Results were variable by cultivar and a locally bred, high-yielding cultivar (Pembroke 2014) had the highest lactic acid solvent retention capacity score and thousand kernel weight of the cultivars evaluated. In addition, a landrace cultivar (Purple Straw) had the highest grain N and plant height. A French soft wheat, Soissons, had the highest sedimentation value and Pembroke 2016 achieved the highest yield. The findings from this study suggest the possibility of attaining a desirable grain with quality traits of SRW wheat that meets the needs of local bread wheat production in Kentucky through improving the optimization of cultivar selection, N management and specific considerations for conventional and organic systems.

‘GA JT141‐14E45’: A new soft red winter wheat cultivar adapted to Georgia and the U.S. Southeast region

AbstractIn Georgia and the southeast region of the United States, acreage of soft red winter wheat (SRWW) (Triticum aestivum L.) has decreased in recent years. There is an urgent need to release new cultivars with high yield potential, resistance to yield‐limiting diseases and insects, and good baking quality to maximize value in regional markets. To address this, the SRWW breeding program at the University of Georgia (UGA), in collaboration with the SUNGRAINS breeding programs, developed ‘GA JT141‐14E45’ (Reg. no. CV‐1183, PI 689519), a SRWW cultivar released by the UGA College of Agricultural and Environmental Sciences and licensed to AGSouth (AGS) Genetics as AGS 3030. GA JT141‐14E45 is widely adapted to the U.S. Southeast, having high yield, good resistance to diseases such as leaf rust, stripe rust, powdery mildew, and Soil‐borne wheat mosaic virus (SBWMV) and to current biotypes of Hessian fly (Mayetiola destructor Say). It has good resistance to Fusarium head blight (FHB) or scab. GA JT141‐14E45 has good grain volume weight and acceptable milling and baking quality. GA JT141‐14E45 was derived from the cross of ‘AGS 2026’/‘Jamestown’. Jamestown was used in the cross mainly for its resistance to FHB (FHB QTL 1A‐Neuse and 1B‐Jamestown). AGS 2026 is a UGA cultivar released in 2007 with very good disease resistance to rusts (Yr17/Lr37/Sr38), Hessian fly resistance (H13), and excellent yield.

A new soft red winter wheat cultivar, ‘GA 07353‐14E19’, adapted to Georgia and the U.S. Southeast environments

AbstractSoft red winter wheat (SRWW) (Triticum aestivum L.), historically a major crop in Georgia and the U.S. Southeast (SE) region, has been challenged by numerous biotic and abiotic constraints resulting in decreased hectarage in recent years. Hence, an urgent need exists to release new cultivars with high yield potential, good resistance to predominant diseases and insects, and acceptable quality attributes to capture and maximize value in regional markets. The SRWW breeding program at the University of Georgia (UGA), in collaboration with the Southeastern University GRAINS (SUNGRAINS) breeding programs, is responding to these challenges by developing and releasing superior SRWW cultivars adapted to Georgia and the SE wheat region. ‘GA 07353‐14E19’ (Reg. no. CV‐1179, PI 689520), a SRWW cultivar developed by the UGA small grains breeding program, was released by the UGA College of Agricultural and Environmental Sciences and licensed to Stratton Seed Company in 2017 as GO WHEAT 2032. GA 07353‐14E19 is adapted to the SE region with high yield, good resistance to prevalent diseases, including leaf and stripe rusts, Fusarium head blight, powdery mildew, and Soil‐borne wheat mosaic virus. GA 07353‐14E19 also showed good resistance to current biotypes of Hessian fly. GA 07353‐14E19 possesses the H13, Sbm1, and Yr17–Lr37–Sr38 genes that protect it against the above pests. It has very good grain volume weight and good milling and baking quality as a SRWW.

A novel adult plant leaf rust resistance gene Lr2K38 mapped on wheat chromosome 1AL.

Soft red winter wheat (SRWW) cultivar AGS 2038 has a high level of seedling and adult plant leaf rust (LR) resistance. To map and characterize LR resistance in AGS 2038, a recombinant inbred line (RIL) population consisting of 225 lines was developed from a cross between AGS 2038 and moderately resistant line UGA 111729. The parents and RIL population were phenotyped for LR response in three field environments at Plains and Griffin, GA, in the 2017-2018 and 2018-2019 growing seasons, one greenhouse environment at the adult-plant stage, and at seedling stage. The RIL population was genotyped with the Illumina iSelect 90K SNP marker array, and a total of 7667 polymorphic markers representing 1513 unique loci were used to construct a linkage map. Quantitative trait loci (QTL) analysis detected six QTL, QLr.ags-1AL, QLr.ags-2AS, QLr.ags-2BS1, QLr.ags-2BS2, QLr.ags-2BS3, and QLr.ags-2DS, for seedling and adult plant LR resistance. Of these, the major adult plant leaf rust resistance QTL, QLr.ags-1AL, was detected on all field and greenhouse adult plant tests and explained up to 34.45% of the phenotypic variation. QLr.ags-1AL, tightly flanked by IWB20487 and IWA4022 markers, was contributed by AGS 2038. Molecular marker analysis using a diagnostic marker linked to Lr59 showed that QLr.ags-1AL was different from Lr59, the only known LR resistance gene on 1AL. Therefore, the QTL was temporarily designated as Lr2K38. Lr2K38-linked marker IWB20487 was highly polymorphic among 30 SRWW lines and should be useful for selecting the Lr2K38 in wheat breeding programs.

Identification and validation of Fusarium head blight resistance QTL in the U.S. soft red winter wheat cultivar ‘Jamestown’

AbstractUse of genetic resistance is one of the most important strategies to manage the devastating disease Fusarium head blight (FHB) in wheat. Numerous quantitative trait loci (QTL) having varying effects on reducing FHB and the mycotoxin deoxynivalenol (DON) accumulation have been reported from Asian, European, or distant sources such as wild relatives of wheat (Triticum aestivum L.). However, coming from nonadapted backgrounds, the incorporation of such QTL into regional breeding programs has often resulted in the simultaneous transfer of other undesirable traits. Therefore, it is important to identify, characterize, and deploy sources of genetic resistance that do not suffer from poor adaptability and/or linkage drag. In the present work, QTL associated with FHB resistance in a high‐yielding, moderately resistant soft red winter wheat cultivar ‘Jamestown’ were mapped and validated. The QTL mapping was done using a recombinant inbred line (RIL) population of Pioneer ‘25R47’ × Jamestown having 186 individuals. Phenotyping over 2 yr at three locations, and genotyping using the 90K single nucleotide polymorphism (SNP) platform identified two new QTL, named QFHB.vt‐1B.1 and QFHB.vt‐1B.2, on the chromosome 1B long arm. The QTL contributed to FHB incidence, FHB severity, Fusarium‐damaged kernels, and DON content. Independent mapping of these QTL using two additional RIL populations of FG95195 × Jamestown (170 RILs) and Jamestown × LA97113UC‐124 (77 RILs) validated their stability and effectiveness in different genetic backgrounds. Kompetitive allele specific polymerase chain reaction (KASP) assays were developed using linked SNPs for marker‐assisted selection of the QTL. These QTL are being used in breeding programs to develop FHB‐resistant, high‐yielding varieties.

Genome‐wide analysis and prediction of Fusarium head blight resistance in soft red winter wheat

AbstractFusarium head blight (FHB) is a disease in wheat (Triticum aestivum L.) caused by the fungal pathogen Fusarium graminearum Schwabe. Fusarium head blight poses potential economic losses and health risks due to the accumulation of the mycotoxin deoxynivalenol (DON) on infected seed heads. The objectives of this study were to identify novel FHB resistance loci using a genome‐wide association study (GWAS) approach and to evaluate two genomic selection (GS) approaches to improve prediction accuracies for FHB traits in a population of 354 soft red winter wheat (SRWW) genotypes. The GS approaches included GS+GWAS, where markers associated with a trait were used as fixed effects, and multivariate GS (MVGS), where correlated traits were used as covariates. The population was evaluated in FHB nurseries in Fayetteville and Newport, AR, and Winnsboro, LA, from 2014 to 2017. Genotypes were phenotyped for DON, Fusarium‐damaged kernels (FDK), incidence (INC), and severity (SEV). Forty‐two single nucleotide polymorphism (SNP) markers were significantly (false discovery rate, q [FDRq] ≤ .10) associated with resistance traits across 17 chromosomes. Ten significant SNPs were identified for DON, notably on chromosomes 2BL and 3BL. Eleven were identified for FDK, notably on chromosomes 4BL, 3AL, 1BL, 5BL, and 5DL. Nine were identified for INC, notably on chromosomes 2BS, 2BL, 7BL, 5DL, 6AS, and 5DS. Twelve were identified for SEV, notably on chromosomes 3BL, 4AL, and 4BL. The naïve GS models significantly outperformed the GS+GWAS model for all traits, whereas MVGS models significantly outperformed the naïve GS models for all traits. Results from this study will facilitate the development of SRWW cultivars with improved FHB resistance.

Fusarium Head Blight and Rust Diseases in Soft Red Winter Wheat in the Southeast United States: State of the Art, Challenges and Future Perspective for Breeding.

Among the biotic constraints to wheat (Triticum aestivum L.) production, fusarium head blight (FHB), caused by Fusarium graminearum, leaf rust (LR), caused by Puccinia triticina, and stripe rust (SR) caused by Puccinia striiformis are problematic fungal diseases worldwide. Each can significantly reduce grain yield while FHB causes additional food and feed safety concerns due to mycotoxin contamination of grain. Genetic resistance is the most effective and sustainable approach for managing wheat diseases. In the past 20 years, over 500 quantitative trait loci (QTLs) conferring small to moderate effects for the different FHB resistance types have been reported in wheat. Similarly, 79 Lr-genes and more than 200 QTLs and 82 Yr-genes and 140 QTLs have been reported for seedling and adult plant LR and SR resistance, respectively. Most QTLs conferring rust resistance are race-specific generally conforming to a classical gene-for-gene interaction while resistance to FHB exhibits complex polygenic inheritance with several genetic loci contributing to one resistance type. Identification and deployment of additional genes/QTLs associated with FHB and rust resistance can expedite wheat breeding through marker-assisted and/or genomic selection to combine small-effect QTL in the gene pool. LR disease has been present in the southeast United States for decades while SR and FHB have become increasingly problematic in the past 20 years, with FHB arguably due to increased corn acreage in the region. Currently, QTLs on chromosome 1B from Jamestown, 1A, 1B, 2A, 2B, 2D, 4A, 5A, and 6A from W14, Ning7840, Ernie, Bess, Massey, NC-Neuse, and Truman, and 3B (Fhb1) from Sumai 3 for FHB resistance, Lr9, Lr10, Lr18, Lr24, Lr37, LrA2K, and Lr2K38 genes for LR resistance, and Yr17 and YrR61 for SR resistance have been extensively deployed in southeast wheat breeding programs. This review aims to disclose the current status of FHB, LR, and SR diseases, summarize the genetics of resistance and breeding efforts for the deployment of FHB and rust resistance QTL on soft red winter wheat cultivars, and present breeding strategies to achieve sustainable management of these diseases in the southeast US.

Effect of temperature on survival and yield components of field‐acclimated soft red winter wheat

AbstractFreeze tolerance is greatest in winter wheat (Triticum aestivum L.) during winter dormancy and decreases as the plant develops in the spring. Above‐average temperatures during the winter and spring have resulted in wheat resuming growth earlier in the season, exposing a less freeze‐tolerant plant to an increased risk of spring freeze events. The objective of this study was to determine the effect of temperature on seed yield components and biomass of field‐acclimated winter wheat at Feekes 6, 8, and 10.5.1 growth stages. Five soft red winter wheat cultivars were transplanted from the field into pots at each Feekes growth stage identified above. Plants were placed into freeze chambers with temperature treatments ranging from −16 to 4°C. Plants were exposed to the treatment temperature for 15 min and placed in a cooler maintained at 4°C. After 20 h, plants were moved to an open‐air greenhouse and grown to maturity. At maturity, yield component and biomass data were recorded. Temperature treatments of −10, −7, and −3°C reduced seed weight at Feekes 6, 8, and 10.5.1 growth stages, respectively, compared with plants held at 4°C. Plant biomass was reduced at Feekes 6 and 8 growth stages at −10 and −4°C, respectively. These guidelines will help producers better estimate the potential value of a freeze‐damaged wheat crop.

Integrated Management of Stripe Rust and Overwintering of Puccinia striiformis f. sp. tritici in Wisconsin

Puccinia striiformis f. sp. tritici (Pst) is the causal agent of stripe rust and is one of the most problematic pathogens of winter and spring wheat in the United States. Planting resistant cultivars and applying foliar fungicides are common management practices to control this pathogen. In this 2-year study, two fungicides applied at three growth stages were tested on three soft red winter wheat cultivars varying in levels of resistance to stripe rust. Both fungicides (prothioconazole + tebuconazole and pyraclostrobin) applied at Feekes 8 and 10 reduced disease index and increased yield compared with the nontreated control in susceptible (‘Pro Seed 420’) and moderately susceptible (‘Kaskaskia’) cultivars. The highly resistant cultivar (‘Pro Seed 380’) had the greatest yields, and fungicide treatments had no effect on disease levels or yield. In an accompanying study, Pst was found to survive over the 2016 to 2017 winter on the susceptible cultivar Pro Seed 420. This study confirmed that resistance and properly timed fungicide applications play a crucial role in managing stripe rust on winter wheat. This study also demonstrated that Pst can overwinter in Wisconsin, and the impact of this occurrence should be examined further.

Associations between morphological and FHB traits in a soft red winter wheat population

Fusarium head blight (FHB) is a destructive disease in wheat (Triticum aestivum) and other small grains. Morphological traits can act as barrier between pathogen and plant and provide a passive form of resistance to disease. The objectives were: (1) to phenotype 250 soft red winter wheat (SRWW) breeding lines and cultivars for morphological traits in 2015–2016; (2) to estimate their correlations with disease resistance; and (3) to identify QTL for morphological traits associated with FHB resistance through genome-wide association study (GWAS). Morphological traits measured were anther extrusion, plant height, peduncle length, spike length (SL), spikelet number (SN), spike density (SD), spike inclination (SI). Agronomic traits included heading date and yield. Disease traits were: FHB-rating, incidence, severity, FHB-index, Fusarium damaged kernels and deoxynivalenol (DON) concentration. There were significant (p < 0.01) differences among genotypes for all morphological traits measured. Moderate heritabilities (0.41–0.66) for spike traits were estimated. Morphological and disease traits were generally negatively correlated; e.g. there was a significant (p < 0.01) negative correlation between spike inclination and DON. GWAS identified 29 significant (p < 0.001) SNPs associated with morphological traits, ranging from − 3.54 to 9.58% of the trait mean. Potential SNPs for yield were located on chromosomes 1B, 3B and 6A. Despite the small effects identified for the SNPs, several morphological traits should be considered for phenotypic and/or genomic selection in FHB resistance breeding programs.

Virulence of Puccinia triticina, the Wheat Leaf Rust Fungus, in the United States in 2017.

Samples of wheat leaves infected with the leaf rust fungus, Puccinia triticina, were obtained in 2017 from agricultural experiment station plots, demonstration plots, and farm fields in the Great Plains, the Ohio Valley, the southeastern states, California, and Washington in order to determine the prevalent virulence phenotypes present in the United States. A total of 65 virulence phenotypes were identified among the 469 single uredinial isolates that were tested on 20 near-isogenic lines of Thatcher wheat that differ for leaf rust resistance genes. Virulence phenotypes MBTNB at 11.3% of the overall population, and MCTNB at 7.0%, were the first and third most common phenotypes. Both phenotypes were found mostly in the southeastern states and Ohio Valley region. Phenotype TFTSB at 10.9% was the second most common phenotype and was found mostly in southern Texas. Virulence to leaf rust resistance gene Lr39, which is present in hard red winter wheat cultivars, was highest in the Great Plains region. Virulence to Lr11 and Lr18, which are present in soft red winter wheat cultivars, was highest in the southeastern states and Ohio Valley region. Virulence to Lr21, which is present in hard red spring wheat cultivars, was highest in the northern Great Plains region. The predominate P. triticina phenotypes from the soft red winter wheat regions of the southeastern states and Ohio Valley area differed from those in the hard red winter and hard red spring wheat areas of the Great Plains region. Collections from Washington had unique virulence phenotypes that had not been previously detected.

Genetic mapping of a major gene for leaf rust resistance in soft red winter wheat cultivar AGS 2000

Leaf rust (LR), caused by Puccinia triticina (Pt), is a major disease of wheat worldwide. Genetic resistance is the most effective, economic, and environmentally safe method to reduce losses caused by LR. Seventy-nine LR resistance genes have been identified so far; however, only a few of them are still effective due to the constant evolution of new Pt races. The objectives of this study were to characterize the genetic basis of LR resistance in the soft red winter wheat (SRWW) cultivar AGS 2000 at seedling stage, and identify markers for marker-assisted selection (MAS). A mapping population of 175 recombinant inbred lines (RILs) was developed from a cross between the susceptible cultivar Pioneer® variety 26R61 (26R61) and AGS 2000. Two out of four Pt races (MBTNB, MFGKG, TCRKG, and MCTNB) showed segregating reactions for the parental lines and RIL population at the seedling stage. Whole genome QTL analysis detected a single common QTL for resistance to both Pt races (MFGKG and MBTNB) on chromosome 2BS. The gene was flanked by wPt-666389 and wPt-2600 markers and explained up to 75.3% of phenotypic variation for Pt race MBTNB, and is therefore a Mendelian factor. LR resistance genes, Lr13, Lr16, Lr23, Lr48, and Lr73, were all detected on 2BS; however, based on their physical and genetic positions, the gene was distinct and therefore temporarily designated as LrA2K. The closely linked marker Xwmc770 to LrA2K has been validated on a set of wheat cultivars and can be used in MAS for LR resistance.