Red Winter Wheat Research Articles

Development and deployment of KASP markers for multiple alleles of Lr34 in wheat

Key messageHeterogeneous Lr34 genes for leaf rust in winter wheat cultivar ‘Duster’ and KASP markers for allelic variation in exon 11 and exon 22 of Lr34.Wheat, Triticum aestivum (2n = 6x = 42, AABBDD), is a hexaploid species, and each of three homoeologous genomes A, B, and D should have one copy for a gene in its ancestral form if the gene has no duplication. Previously reported leaf rust resistance gene Lr34 has one copy on the short arm of chromosome 7D in hexaploid wheat, and allelic variation in Lr34 is in intron 4, exon 11, exon 12, or exon 22. In this study, we discovered that Oklahoma hard red winter wheat cultivar ‘Duster’ (PI 644,016) has two copies of the Lr34 gene, the resistance allele Lr34a and the susceptibility allele Lr34b. Both Lr34a and Lr34b were mapped in the same linkage group on chromosome 7D in a doubled-haploid population generated from a cross between Duster and a winter wheat cultivar ‘Billings’ which carries the susceptibility allele Lr34c. A chromosomal fragment including Lr34 and at least two neighboring genes on its proximal side but excluding genes on its distal side was duplicated in Duster. The Duster Lr34ab allele was associated with tip necrosis and increased resistance against leaf rust at adult plants in the Duster × Billings DH population tested in the field, demonstrating the function of the Duster Lr34ab allele in wheat. We have developed KASP markers for allelic variation in exon 11 and exon 22 of Lr34 in wheat. These markers can be utilized to accelerate the selection of Lr34 in wheat.

Breeding Wheat for Resilience to Increasing Nighttime Temperatures

Increases in global mean temperature since 1960 are largely attributed to the rise in minimum nighttime temperatures thereby decreasing diurnal temperature variation. Increased night temperatures are known to affect crop development. A multi-year study investigating the effects of increased night temperatures on soft red winter wheat (Triticum aestivum L.) varieties was conducted during the 2015-2016 growing seasons at the University of Kentucky Spindletop Research Farm in Lexington, KY. Thirty-six cultivars and breeding lines were chosen based on their genotypes at photoperiod and vernalization loci. This material was planted in a randomized complete block experiment with two replications and two environments, control and passively warmed. To create a passively warmed environment, thermal covers were mounted to frames in plots and connected to a datalogger programmed to cover plants from dusk to dawn based on coordinate location. Night temperature increases ranged from 0.27–0.75 °C above ambient temperature. Grain yield, averaged across genotypes, was significantly reduced in the passively warmed environment by 224 kg ha−1 (p ≤ 0.05) or 6.44%; however, yield response to environment varied among genotypes with several genotypes displaying an increased yield in the warmed environment. Yield reductions may reflect reduced nitrogen utilization (9.4%; p ≤ 0.001) under increased night temperatures.

Registration of Hessian fly‐resistant germplasm KS18WGRC65 carrying H26 in hard red winter wheat ‘Overley’ background

AbstractHessian fly (HF; Mayetiola destructor Say) causes severe damage to wheat (Triticum aestivum L.) worldwide. Several resistance genes have been identified in wheat and wild relatives; however, HF populations are under strong selection pressure and evolve rapidly to overcome resistance. To ensure the availability of resistance sources, HF‐resistant germplasm KS18WGRC65 (TA5110, Reg. no. GP‐1042, PI 688251) was developed by Wheat Genetics Resource Center at Kansas State University as a breeding stock that carries resistance gene H26 from Aegilops tauschii Coss. KS18WGRC65 is a cytogenetically stable, homozygous, BC3F3:6 line derived from the cross between Ae. tauschii accession KU2147 and hard red winter wheat recurrent parent ‘Overley’. KS18WGRC65 exhibited no penalty for yield or other agronomic characters, making it a suitable source of HF resistance for wheat breeding.

Winter cover crop production and water use in Southern Great Plains cotton

AbstractCover crops can provide several ecosystem services in agricultural cropping systems. Benefits may be enhanced with increasing cover crop biomass production. In water‐limited environments, feasibility of cover crop germination and production is not always certain. This study was conducted to determine differences in biomass production, water use, and water use efficiency (WUE) between monoculture cover crops and a mixture at Chillicothe, TX, in the Southern Great Plains under rainfed conditions in a continuous cotton (Gossypium hirsutum L.) cropping system over a 6‐yr period. Evaluated cover crops included Austrian winter pea (Pisum sativum L.), crimson clover (Trifolium incarnatum L.), hairy vetch (Vicia villosa L.), hard red winter wheat (Triticum aestivum L.), and a grass/broadleaf mixture. Although cover crops were planted after optimum planting dates and under varying climatic conditions, biomass production was 2863, 2480, and 2301 kg ha−1 for the mixture, pea, and vetch, respectively. Peas and the mixture were the most consistent, producing significantly greater biomass than wheat and clover but not more than vetch. The mixture resulted in greater WUE than wheat. Clover resulted in reduced biomass production and WUE than vetch, pea, and the mixture over the study period. A cover crop mixture did not produce significantly greater biomass or significantly increase water use efficiency compared with vetch and pea. Under dryland conditions, peas, vetch, and a mixture were shown to be viable cover crop options in Southern Great Plains cotton systems, performing as well as a wheat cover crop.

Biochemical characteristics of soft wheat grain associated with endosperm separation from bran and flour yield

AbstractBackground and objectivesEndosperm separation from bran during wheat grain milling has a substantial influence on flour yield, whereas little is known about the endosperm characteristics affecting its detachment from bran. The associations of the outer endosperm characteristics with its separation from bran during milling, and subsequently with flour yield, were determined.FindingsThe yields of flour and remnant endosperm of bran (REB) for ten soft red winter wheat varieties ranged from 66.7% to 75.9% and 1.7% to 3.7%, respectively. The ash, water‐soluble AX, and β‐glucan contents of the REB exhibited significant relationships with flour yield at p < .05. Wheat varieties of >75% flour yield exhibited higher ash and lower water‐soluble AX contents of the REB than the varieties of <68% flour yield. The ash and water‐soluble AX contents of flour also exhibited significant relationships with flour yield at p < .01.ConclusionsThe water‐soluble AX content of endosperm is implicated in the separation of endosperm from bran during milling of wheat grain.Significance and noveltyWheat grain outer endosperm that is low in water‐soluble AX could positively contribute to flour yield because of its role in the efficient detachment of endosperm from bran during milling.

Identification of quantitative trait loci associated with nitrogen use efficiency in winter wheat.

Maintaining winter wheat (Triticum aestivum L.) productivity with more efficient nitrogen (N) management will enable growers to increase profitability and reduce the negative environmental impacts associated with nitrogen loss. Wheat breeders would therefore benefit greatly from the identification and application of genetic markers associated with nitrogen use efficiency (NUE). To investigate the genetics underlying N response, two bi-parental mapping populations were developed and grown in four site-seasons under low and high N rates. The populations were derived from a cross between previously identified high NUE parents (VA05W-151 and VA09W-52) and a shared common low NUE parent, ‘Yorktown.’ The Yorktown × VA05W-151 population was comprised of 136 recombinant inbred lines while the Yorktown × VA09W-52 population was comprised of 138 doubled haploids. Phenotypic data was collected on parental lines and their progeny for 11 N-related traits and genotypes were sequenced using a genotyping-by-sequencing platform to detect more than 3,100 high quality single nucleotide polymorphisms in each population. A total of 130 quantitative trait loci (QTL) were detected on 20 chromosomes, six of which were associated with NUE and N-related traits in multiple testing environments. Two of the six QTL for NUE were associated with known photoperiod (Ppd-D1 on chromosome 2D) and disease resistance (FHB-4A) genes, two were reported in previous investigations, and one QTL, QNue.151-1D, was novel. The NUE QTL on 1D, 6A, 7A, and 7D had LOD scores ranging from 2.63 to 8.33 and explained up to 18.1% of the phenotypic variation. The QTL identified in this study have potential for marker-assisted breeding for NUE traits in soft red winter wheat.

Tri5 gene expression analysis during postharvest storage of wheat grain from field plots treated with a triazole and a strobilurin fungicide

Fusarium head blight (FHB) and the associated mycotoxin deoxynivalenol (DON) negatively impact the wheat industry worldwide. In North America, FHB is mainly caused by Fusarium graminearum sensu stricto. The purpose of this study was to evaluate, under storage conditions, the expression of the DON biosynthetic gene trichodiene synthase (Tri5) of F. graminearum in grain of hard red winter wheat cultivars ‘Overley’ (FHB-susceptible) and ‘Overland’ (moderately resistant to FHB) from field plots treated or untreated with the triazole fungicide Prosaro and the strobilurin fungicide Headline. Infected grain was stored and periodically sampled to determine gene expression by qRT-PCR analysis. The F. graminearum housekeeping gene GAPDH was consistently detected, indicative of metabolically active fungi, and Tri5 detection was significantly higher in ‘Overley’ compared with ‘Overland’. Tri5 gene expression and DON concentrations showed little to no correlation; consequently, Tri5 expression levels did not accurately predict DON concentrations. The strobilurin did not significantly reduce Tri5 gene expression compared with untreated wheat. In the triazole treatment, a significant reduction in the relative expression of Tri5 was detected after 120 days, as well as a downregulation of Tri5 from 60 to 120 days of storage in ‘Overley’. In grain from strobilurin-treated plots of both cultivars, the expression of Tri5 increased from 0 to 30 days after tempering. Genetic expression of Tri5 that is necessary for the production of DON can increase during storage of high-moisture grain. Fusarium fungi can persist in wheat kernels for several months postharvest and may actively produce toxin during this period.

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.

Transferability of Marker Trait Associations in Wheat Is Disturbed Mainly by Genotype × Year Interaction

Grain yield is the primary target for increasing soft red winter wheat production in the United States. Genome wide association studies were performed for yield-related traits using field-based evaluation of 270 elite breeding lines. Yield ranged from 3.9 to 7.5 tons·ha−1. The effect of genotype by year interaction was significant for most traits. Heritability estimates ranged from 0.21 for biomass to 0.84 for plant height. Biomass, kernel weight, and grain weight per spike were positively correlated with grain yield while days to heading and maturity were negatively correlated with grain yield. We used FarmCPU method and 45K markers to identify marker-trait associations. Fifty-nine MTAs were identified based on two-year phenotypic estimates. An association for grain yield on chromosome 7D showed a −logP value of 16.35 and explained 18% of the phenotypic variation. Associations were identified at −logP values of 6.30 and 4.08 on chromosomes 5A for thousand kernel weight and grain per spike that explained 10% and 6% of phenotypic variations, respectively. Grain yield and days to heading data from previous trials in other states were used to validate and evaluate the transferability of associations. We observed that for grain yield, only 7 out of 28 associations and for days to heading, only 8 out of 47 associations were validated across seemingly homogenous environments, indicating the majority of associations are not stable QTL across environments. This study suggests that achieving genetic gains appears to require utilizing genotype by environment interaction and local field based germplasm testing.

Occurrence of Viruses and Clavibacter michiganensis in Winter Wheat in Illinois, 2009 to 2011 and 2019 to 2020

Field surveys in 2009, 2010, 2011, 2019, and 2020 determined the incidence and diversity of viruses present in fields of soft red winter wheat (Triticum aestivum) in Illinois. In addition, the putative presence of the bacterial mosaic pathogen, Clavibacter michiganensis subsp. tessellarius (Cmt), was evaluated. A total of 341 fields were sampled across years, and plants were tested for barley yellow dwarf virus (BYDV-PAV; BYDV-MAV), barley stripe mosaic virus (BSMV), brome mosaic virus (BMV), cereal yellow dwarf virus (CYDV-RPV), High Plains virus (HPV), Potyvirus group (POTY), soil-borne wheat mosaic virus (SBWMV), tobacco mosaic virus (TMV), wheat spindle streak mosaic virus (WSSMV), wheat streak mosaic virus (WSMV), and Cmt using ELISA. Average field incidence across years varied by virus with BYDV-PAV (22%), WSSMV (16%), CYDV-RPV (7%), WSMV (3%), and HPV (0.5%) detected in samples. The bacterial mosaic pathogen (Cmt), or potentially a related species of Clavibacter, was detected the most frequently in each year, with an average incidence of 77%. The consistent detection of Cmt warrants further study to determine the nature of the organisms associated with positive Cmt tests and their role in Illinois wheat production systems.

Getting to the core of hard red winter wheat quality

AbstractAs the wheat industry works to create more high‐quality food products for consumers, it is necessary for plant breeders to develop new wheat varieties with improved milling and baking characteristics that maximize production efficiency while reducing dependency on vital wheat gluten or other flour additives. The purpose of this study was twofold: (i) to test a popular belief that plant breeding, over time, has gradually produced varieties lacking the necessary characteristics—namely, dough strength—to allow migration from flour additives, and (ii) to perform a specific assessment of gluten compression‐recovery (CORE) analysis as a potential tool for wheat breeding programs to supplement industry‐standard tests such as the farinograph. The farinograph and other recording dough mixers (RDMs) are used to make breeding decisions and are crucial to the success of a breeding program, a farmer's operation, and the milling and baking industries. Through this project, we determined that gluten elasticity, a key metric of CORE analysis, increased at the rate of 1.6% per breeding generation since the introduction of the heirloom variety, Turkey, and thus countering claims that higher yielding varieties lack the gluten strength once present in breeding generations long ago. A second significant finding of this project was that CORE analysis revealed differences in gluten quality among commercial wheat varieties that were more difficult to detect with more traditional, but cumbersome, flour quality tests available through the farinograph, opening up the prospect for wheat researchers to use gluten compression‐recovery analysis as a selection tool in variety development.

Genotypic variation and stability for nitrogen use efficiency in winter wheat

AbstractWheat (Triticum aestivum L.) products account for a large portion of the total dietary calories and protein consumed globally, thus requiring efficient N management systems for optimal grower profitability and to reduce negative environmental impacts of nontarget fertilization. This investigation sought to evaluate genotypic variation for N use efficiency (NUE), assess yield stability, and validate traits for improvement of crop performance across N rates. Three separate studies were conducted over four growing seasons in the eastern United States that varied in the number of N rates and site‐seasons. Study I was conducted using five N rates over three site‐seasons, Study II was conducted using three N rates over six site‐seasons, and Study III was conducted using two N rates over nine site‐seasons. Genotype × N rate interactions were more frequently observed for grain yield when three or more N rates were used in the experimental design. The three studies identified significant genotypic variation for NUE and identified wheat lines that consistently expressed high grain yields over N‐site‐seasons. Aboveground biomass at physiological maturity was strongly associated with grain yield in Study II when 67 kg N ha−1 (r = .66, P ≤ .05) was applied and in Study III when 67 kg N ha−1 (r = .71, P ≤ .05), and 134 kg N ha−1 (r = .89, P < .001) was applied. Findings from this investigation inform soft red winter wheat breeders on diverse sources of breeding materials and target traits to improve NUE.

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.

Comparing Genetic Variation within Red Winter Wheat Populations with and without Image-Based Optical Sorter Selection

Head scab is historically a devastating disease affecting not just all classes of wheat but also barley and other small grains around the world. Fusarium head blight (FHB), or head scab, is caused most often by Fusarium graminearum (Schwabe), (sexual stage – Gibberella zeae) although several Fusarium spp. can cause the disease. This study was conducted to determine the effect of mass selection for FHB resistance using an image-based optical sorter. lines were derived from the C0 and C2 of two populations to compare genetic variation within populations with and without sorter selection. Our overall hypothesis is that sorting grain results in improved Fusarium head blight resistance. Both of the used wheat derived line populations have genetic variation, and population 1 has more than population 17. They are significantly different from each other for fusarium damged kernel (FDK), deoxynivalenol (DON), and other FHB traits. Although both populations are suitable to be grown for bulks, population 1 seems better since it has more genetic variation as well as lower FDK and DON, and earlier heading date. Lines within each population were significantly different and some lines in each population had significantly lower FDK and DON after selection using an optical sorter. Some lines had significant reduction in both FDK and DON, and some others had either FDK or DON reduction. Lines of population 1 that had significant reduction, were more numerous than in population 17, and FDK and DON reduction were greater.

Comparing Genetic Variation within Red Winter Wheat Populations with and without Image-Based Optical Sorter Selection

Head scab is historically a devastating disease affecting not just all classes of wheat but also barley and other small grains around the world. Fusarium head blight (FHB), or head scab, is caused most often by Fusarium graminearum (Schwabe), (sexual stage – Gibberella zeae) although several Fusarium spp. can cause the disease. This study was conducted to determine the effect of mass selection for FHB resistance using an image-based optical sorter. lines were derived from the C0 and C2 of two populations to compare genetic variation within populations with and without sorter selection. Our overall hypothesis is that sorting grain results in improved Fusarium head blight resistance. Both of the used wheat derived line populations have genetic variation, and population 1 has more than population 17. They are significantly different from each other for fusarium damged kernel (FDK), deoxynivalenol (DON), and other FHB traits. Although both populations are suitable to be grown for bulks, population 1 seems better since it has more genetic variation as well as lower FDK and DON, and earlier heading date. Lines within each population were significantly different and some lines in each population had significantly lower FDK and DON after selection using an optical sorter. Some lines had significant reduction in both FDK and DON, and some others had either FDK or DON reduction. Lines of population 1 that had significant reduction, were more numerous than in population 17, and FDK and DON reduction were greater.

Determining The Effect of Mass Selection for FHB Resistance in Soft Red Winter Wheat Using an Image-Based Optical Sorter

Fusarium head blight (FHB) or head scab, caused by Fusarium graminearum Schwabe [telomorph: Gibberella zeae Schwein.(Petch)], is one of the most destructive diseases of wheat (Triticum aestivum L.) worldwide. Numerous strategies for scab resistance breeding are in use, including phenotypic selection for low severity and marker-assisted selection for resistance QTL. The most destructive consequences of scab are evidenced through a reduction in grain quality, and the presence of mycotoxins, the most common of which is deoxynivalenol (DON). Thus, there is great interest among breeders in selecting for resistance to both of these traits. To this end, a study was devised as follows. In 2010, 20 bulk F3 SRW wheat populations with scab resistant parents in their pedigrees were harvested by population from unreplicated plots near Lexington, KY. The plots were affected by a naturally occurring mild-moderate scab epidemic. The grain was sorted on a USDA/ARS and National Manufacturing Seed Sorter System with color camera according to a calibration that reflected visual differences between asymptomatic grain and grain showing FHB symptoms. This process was repeated in 2011 using grain from plots that had conidial suspension applied at anthesis. In 2012, an unreplicated plot study of the C0, C1 and C2 cycles of selection, inoculated with grain spawn and conidial suspension, was evaluated for Fusarium damaged kernels (FDK) and DON concentration. An additional cycle of selection was conducted by running the bulk grain through the sorter. In October 2012, 4 selection cycles of the 20 populations were planted in a RCB experiment at Lexington and Princeton, KY. Bulk populations were planted in both scab nursery and plots, and C3 accepted and rejected of all populations and derived lines of 2 populations were planted in the scab nursery in Lexington, KY. Some populations had FDK and DON reduction with selection, and some derived lines had either numerical or significant reduction with selection. Although the accepted fraction had non-significant reduction compared with the rejected fraction over the populations, FDK and DON means were obviously lower in accepted than in rejected fractions.

Gb8, a new gene conferring resistance to economically important greenbug biotypes in wheat.

A new greenbug resistance gene Gb8 conferring broad resistance to US greenbug biotypes was identified in hard red winter wheat line PI 595379-1 and was mapped to the terminal region of chromosome 7DL. Greenbug [Schizaphis graminum (Rondani)] is a worldwide insect pest that poses a serious threat to wheat production. New greenbug resistance genes that can be readily used in wheat breeding are urgently needed. The objective of this study was to characterize a greenbug resistance gene in PI 595379-1, a single plant selection from PI 595379. Genetic analysis of response to greenbug biotype E in an F2:3 population derived from a cross between PI 595379-1 and PI 243735 indicated that a single gene, designated Gb8, conditioned resistance. Linkage analysis placed Gb8 in a 2.7-Mb interval in the terminal bin of chromosome 7DL (7DL3-082-1.0), spanning 595.6 to 598.3Mb in the Chinese Spring IWGSC RefSeq version 1.0 reference sequence. Gb8 co-segregated with a newly developed SSR marker Xstars508, positioned at 596.4Mb in the reference sequence. Allelism tests showed that Gb8 was different from three permanently named genes on the same chromosome arm and the estimated genetic distance between Gb8 and Gb3 was 15.35 ± 1.35cM. Gb8 can be directly used in wheat breeding to enhance greenbug resistance.

Effectiveness of Genomic Selection by Response to Selection for Winter Wheat Variety Improvement.

Prediction performance for winter wheat grain yield and end-use quality traits. Prediction accuracies evaluated by cross-validations are significantly overestimated. Nonparametric algorithms outperform the parametric alternatives in cross-year predictions. Strategically designing training population improves response to selection. Response to selection varies across growing seasons and environments. Considering the practicality of applying genomic selection (GS) in the line development stage of a hard red winter (HRW) wheat (Triticum aestivum L.) variety development program (VDP), the effectiveness of GS was evaluated by prediction accuracy and by the response to selection across field seasons that demonstrated challenges for crop improvement under significant climate variability. Important breeding targets for wheat improvement in the southern Great Plains of the United States, including grain yield, kernel weight, wheat protein content, and sodium dodecyl sulfate (SDS) sedimentation volume as a rapid test for predicting bread-making quality, were used to estimate the effectiveness of GS across harvest years from 2014 (drought) to 2016 (normal). In general, nonparametric algorithms reproducing kernel Hilbert space (RKHS) and random forest (RF) produced higher accuracies in both same-year cross-validations (CVs) and cross-year predictions for the purpose of line selection. Further, the stability of GS performance was greatest for SDS sedimentation volume but least for wheat protein content. To ensure long-term genetic gain, our study on selection response suggested that across this sample of environmental variability, and though there are cases where phenotypic selection (PS) might be still preferred, training conducted under drought or in suboptimal conditions could provide an encouraging prediction outcome when selection decisions were made in normal conditions. However, it is not advisable to use training information collected from a normal season to predict trait performance under drought conditions. Finally, the superiority of response to selection was most evident if the training population (TP) can be optimized.

Accuracy of genomic selection for grain yield and agronomic traits in soft red winter wheat

BackgroundGenomic selection has the potential to increase genetic gains by using molecular markers as predictors of breeding values of individuals. This study evaluated the accuracy of predictions for grain yield, heading date, plant height, and yield components in soft red winter wheat under different prediction scenarios. Response to selection for grain yield was also compared across different selection strategies- phenotypic, marker-based, genomic, combination of phenotypic and genomic, and random selections.ResultsGenomic selection was implemented through a ridge regression best linear unbiased prediction model in two scenarios- cross-validations and independent predictions. Accuracy for cross-validations was assessed using a diverse panel under different marker number, training population size, relatedness between training and validation populations, and inclusion of fixed effect in the model. The population in the first scenario was then trained and used to predict grain yield of biparental populations for independent validations. Using subsets of significant markers from association mapping increased accuracy by 64–70% for grain yield but resulted in lower accuracy for traits with high heritability such as plant height. Increasing size of training population resulted in an increase in accuracy, with maximum values reached when ~ 60% of the lines were used as a training panel. Predictions using related subpopulations also resulted in higher accuracies. Inclusion of major growth habit genes as fixed effect in the model caused increase in grain yield accuracy under a cross-validation procedure. Independent predictions resulted in accuracy ranging between − 0.14 and 0.43, dependent on the grouping of site-year data for the training and validation populations. Genomic selection was “superior” to marker-based selection in terms of response to selection for yield. Supplementing phenotypic with genomic selection resulted in approximately 10% gain in response compared to using phenotypic selection alone.ConclusionsOur results showed the effects of different factors on accuracy for yield and agronomic traits. Among the factors studied, training population size and relatedness between training and validation population had the greatest impact on accuracy. Ultimately, combining phenotypic with genomic selection would be relevant for accelerating genetic gains for yield in winter wheat.

RNAi‐Mediated Silencing of Endogenous Wheat Genes EIF(Iso)4E‐2 and EIF4G Induce Resistance to Multiple RNA Viruses in Transgenic Wheat

ABSTRACTWheat (Triticum aestivum L.) lacks sources of effective resistance to the potyviruses Wheat streak mosaic virus (WSMV) and Triticum mosaic virus (TriMV). Potyviruses use host eukaryotic initiation factors (eIFs) to facilitate initial translation of their genomes, and many plant virus resistance genes are due to mutations in eIFs. Therefore, we hypothesized that silencing TaeIF(iso)4E and TaeIF4G would provide effective and broad‐spectrum virus resistance. Three transgenic wheat lines with an RNA interference (RNAi) hairpin construct targeting TaeIF(iso)4E and four lines with a hairpin construct targeting TaeIF4G were recovered through wheat transformation. Early generation lines were found to be resistant to WSMV and TriMV, and co‐inoculation of both. The lines were selfed to the T5 generation to insure transgene stability, as well as crossed onto the hard red winter wheat cultivar ‘Karl 92’ to test the RNAi constructs in a more adapted genetic background. Phenotypically, transgenic lines were found to be resistant to WSMV, TriMV, and mixed infections of both, were resistant to Soil‐borne wheat mosaic virus, and demonstrated a significant reduction in Barley yellow dwarf virus infection. The RNAi effectiveness on viral RNA was evaluated using reverse transcription quantitative polymerase chain reaction (PCR). An 18‐fold reduction in WSMV and TriMV viral RNA was found in the T5 transgenic lines when compared with control plants. Viral RNA reduction was also found in the F1, and BC1F1 crosses to Karl 92. These results demonstrate that a single, endogenously derived transgene in wheat can provide resistance to multiple viruses and provides a proof of concept for future gene editing.