Background and objectives Hard red spring wheat (Triticum aestivum L.) (HRSW) is used for bread baking while durum wheat (Triticum turgidum L. ssp. durum) is used for pasta production. This study investigated the impact of alleles from durum wheat for yield component traits on HRSW end-use quality traits. Near-isogenic lines for four quantitative trait loci, QGw.mst-3B, QGw.mst-7A, QTn.mst-5B, and QYld.mst-2B, were evaluated in rainfed and irrigated environments. Findings Durum alleles were found to significantly impact end-use quality at all four loci. The durum allele QGw.mst-3B for increased kernel weight (KWT) positively impacted end-use quality traits with increases in kernel protein and loaf volume. The durum allele at QTn.mst-5B delayed heading date, impacting productive tiller number and KWT and additional end-use quality traits. The durum allele at QYld.mst-2B for GY showed both positive and negative effects on end-use quality. The durum allele for reduced spikelet number per spike at QGw.mst-7A had little to no impact on end-use quality. Conclusions Results from the present study indicate that the alleles from durum wheat are potential sources of cultivar improvement; however, interactions between yield component and end-use quality traits may influence utilization. Significance and novelty This study demonstrates the potential utility of introgressed durum yield component alleles for genetic improvement in HRSW.

'Dagmar' hard red spring wheat (Triticurn aestirum L.) (Reg. no. CV-1158, PI 690450) was released by the Montana Agricultural Experiment Station because of its excellent yield potential in dryland areas of Montana, solid stems, and superior enduse quality. Dagmar was a selection from the cross MT1133/MT1148 and was tested as experimental line MT1621. Dagmar has similar grain yield potential to 'Vida', the most widely grown cultivar in Montana. Stems of Dagmar are more solid than those of Vida, suggesting increased resistance to the wheat stem sawfly (Cephus cinctus Norton). Dagmar has higher grain protein and stronger gluten than Vida. Thus, Dagmar should be useful in Montana and adjoining states facing drought and wheat stem sawfly pressure.

Hexaploid bread wheat (Triticum aestivum L.) and tetraploid durum wheat (Triticum durum Desf.) have been cultivated in similar geographic areas for similar to 10,000 yr. The crossing barrier caused by ploidy difference suggests that different favorable alleles for yield-related traits may have accumulated in the two crops. Previous work allowed identification of favorable alleles at six quantitative trait loci (QTL) from durum wheat in a recombinant inbred line (RIL) population from a cross of 'Mountrail' durum and 'Choteau' spring wheat. The purpose of this study was to determine the impact of six durum alleles at yield component QTL in several spring wheat backgrounds. Three spring wheat cultivars were crossed with six hexaploid lines derived from the original Choteau/Mountrail cross to generate RILs. Heterozygous RILs, containing both the durum and the bread wheat alleles, were identified for each of the QTL. The heterozygous RILs were used to develop near-isogenic lines (NILs) for the six introgressed QTL. The NILs were grown in five environments under irrigated and rainfed conditions in Montana in 2017 and 2018. A durum allele QTL on chromosome 3B resulted in increased kernel weight in all five environments. The introgressed durum QTL alleles caused pleiotropic interactions among yield component traits. Environment and genetic background significantly affected the stability of introgressed QTL on yield components for four of the six QTL. Results suggest that alleles from durum may be useful for yield improvement of hexaploid spring wheat. However, interrelationships of yield components, pleiotropic interactions, and environment will affect the value of durum wheat alleles in hexaploid wheat backgrounds.

Hard red spring wheat (Triticum aestivum L.) grown in rainfed environments in the northern Great Plains of North America frequently encounter drought and heat stress during grain-fill, thus reducing yield. Delayed leaf senescence after heading, known as the stay-green trait, has been found to help spring wheat tolerate drought and heat stress during grain-fill. To better understand how the stay-green trait relates to expression of other agronomic traits, data was analyzed from a recombinant inbred line (RIL) population derived from a 'Vida'/MTHW0202 cross grown in rainfed and irrigated environments. The genetic architecture controlling traits measured in this study were also examined. Results found the stay-green trait was significantly correlated to overall yield (P < .001, r = .37) in rain-fed environments, but was not significantly correlated to yield (P = .26, r = .09) in irrigated environments. Three quantitative trait loci (QTL) located on chromosomes 2D, 4A, and 4D were associated with the stay-green trait. The 4A stay-green QTL, previously designated QGfd.mst-4A, was collocated with QTL for seed number per head, thousand kernel weight, and heading date. The 4D stay-green QTL overlaps the Rht-D1 plant height gene, and the allele prolonging the stay-green period co-segregates with the wild-type (tall) Rht-D1a allele. Results from this study provide a better understanding of the relationship between stay-green and agronomic traits in rainfed vs. irrigated environments. Additionally, understanding the genetic architecture controlling stay-green and agronomic traits will aid in selecting future drought-tolerant spring wheat varieties.

Investigation of resource availability on allele effects for four yield component quantitative trait loci provides guidance for the improvement of grain yield in high and low yielding environments. A greater understanding of grain yield (GY) and yield component traits in spring wheat may increase selection efficiency for improved GY in high and low yielding environments. The objective of this study was to determine allelic response of four yield component quantitative trait loci (QTL) to variable resource levels which were manipulated by varying intraspecific plant competition and seeding density. The four QTL investigated in this study had been previously identified as impacting specific yield components. They included QTn.mst-6B for productive tiller number (PTN), WAPO-A1 for spikelet number per spike (SNS), and QGw.mst-3B and TaGW2-A1 for kernel weight (KWT). Near-isogenic lines for each of the four QTL were grown in multiple locations with three competition (border, no-border and space-planted) and two seeding densities (normal 216 seeds m−2 and low 76 seeds m−2). Allele response at QTn.mst-6B was driven by changes in resource availability, whereas allele response at WAPO-A1 and TaGW2-A1 was relatively unaffected by resource availability. The QTn.mst-6B.1 allele at QTn.mst-6B conferred PTN plasticity resulting in significant GY increases in high resource environments. The gw2-A1 allele at TaGW2-A1 significantly increased KWT, SNS and GPC offering a source of GY improvement without negatively impacting end-use quality. QGw.mst-3B allelic variation did not significantly impact KWT but did significantly impact SPS. Treatment effects in both experiments often resulted in significant positive impacts on GY and yield component traits when resource availability was increased. Results provide guidance for leveraging yield component QTL to improve GY performance in high- and low-yield environments.

Abstract The wheat midge, Sitodiplosis mosellana Géhin (Diptera: Cecidomyiidae), is a serious pest of spring wheat in North America. Currently, most commercial cultivars in the state of Montana, United States of America are susceptible. A study was conducted to assess the variability of adapted spring wheat cultivars to wheat midge infestations. A secondary objective was to determine the relationship between wheat midge infestation levels and spring wheat agronomic traits, including yield, test weight, grain protein, plant height, and heading date. This relationship was determined by evaluating 16 hard red spring wheat cultivars over a six-year period at the Northwestern Agricultural Research Center, near Kalispell, Montana. Levels of infestation had a negative impact on grain yield and test weight. Overall, the average infestation level was 40 larvae/spike with the lowest being observed with “Reeder” and the highest for “Thatcher”. Concurrently, “Reeder” had the highest yield, whereas “Thatcher” had the lowest yield and the highest grain protein, demonstrating that wheat midge infestations were positively associated with grain protein. Heading date had a positive association with midge density with higher infestations associated with later maturing cultivars. The economic injury level was estimated at 12 and 20 midge larvae/spike for a market price of USD $0.27 and USD $0.16/kg, respectively.

The wheat stem sawfly (WSS) (Cephus cinctus Norton) is a major yield-reducing pest of wheat (Triticum aestivum L.). Varieties with pith-filled, or solid, stems provide a measure of resistance by inhibiting larval survival inside the stem. Durum wheat (Triticum turgidum L.) has resistance to the wheat stem sawfly even in the absence of known genes for stem solidness. To determine the genetic basis of resistance in durum wheat, a susceptible durum wheat, PI 41353, was identified from among 1,211 landrace accessions from around the world screened in WSS-infested sites. A recombinant inbred line (RIL) population of 105 individuals was developed from a cross of PI 41353 with a typically resistant variety, Pierce. The RIL were screened in a total of three WSS-infested locations in Montana over a two year period. A genetic map was constructed with 2,867 SNP-based markers. A quantitative trait locus (QTL) analysis identified six QTL associated with resistance. An allele from resistant cultivar Pierce at a QTL on chromosome 3A, Qss.msub-3AL, caused a 25% reduction in stem cutting. Assessment of near-isogenic lines that varied for alleles at Qss.msub-3AL showed that the Pierce allele was also associated with higher stem solidness as measured early in stem development, which is a critical stage for WSS oviposition and larval development. Stem solidness of Pierce and other resistant durum wheat lines largely disappeared later in plant development. Results suggest a genetic mechanism for WSS resistance observed in durum wheat, and provide an additional source of WSS resistance for hexaploid bread wheat.

ABSTRACTSolid stems provide resistance to the wheat stem sawfly (WSS, Cephus cinctus Nort.) in wheat (Triticum aestivum L.). A major quantitative trait locus, designated Qss.msub‐3BL, controls most of the variation for stem solidness. Two alleles that differ for temporal expression of stem solidness have been identified. An allele derived from the cultivar ‘Rescue’, designated Qss.msub‐3BL.b, results in solid stems throughout stem development. An allele derived from the cultivar ‘Conan’, designated Qss.msub‐3BL.c, causes high stem solidness early in plant development, but solidness declines as the plant matures. The objective of this study was to develop near‐isogenic lines (NILs) derived from marker‐assisted backcrossing to compare the impact of Qss.msub‐3BL alleles in different genetic backgrounds on stem solidness, WSS resistance, and agronomic traits. The Conan‐derived allele Qss.msub‐3BL.c resulted in lower WSS infestation than the Rescue‐derived allele Qss.msub‐3BL.b in two genetic backgrounds. Both alleles showed a high level of early stem solidness, though this declined as the stem matured for NIL with the Conan‐derived allele. The Conan‐derived allele Qss.msub‐3BL.c resulted in lower WSS infestation and stem cutting than the allele for hollow stems in two genetic backgrounds. Based on yield trials grown over 2 yr, there were no significant differences in grain yield between the NIL pairs. Our results indicate the Conan‐derived allele at Qss.msub‐3BL results in lower infestation of WSS and does not significantly affect agronomic performance, thus providing a novel source of resistance for the development of WSS‐resistant cultivars.

Wheat landrace accessions were chosen from areas of the world with historical European wheat stem sawfly (Cephus pygmaeus L.) selection pressure to develop six recombinant inbred line (RIL) populations. Molecular maps were constructed, and resistance due to antibiosis and antixenosis was assessed at sites in Montana naturally infested by Cephus cinctus Norton, the wheat stem sawfly (WSS). Novel QTLs were identified along with QTL previously identified in elite germplasm. A newly identified QTL on chromosome 1B provided a new source for pith-filled solid stems. An allele for resistance on chromosome 4A unrelated to solid stems was identified in four of the six RIL populations. A landrace from Turkey, PI 166471, contained alleles at three QTLs causing high levels of larval mortality. None of the QTLs were related to stem solidness, but their combined effect provided resistance similar to that observed in a solid-stemmed check cultivar. These results show the utility of genetic populations derived from geographically targeted landrace accessions to identify new alleles for insect resistance. New PCR-based molecular markers were developed for introgression of novel alleles for WSS resistance into elite lines. Comparison of results with previous analysis of elite cultivars addresses changes in allele frequencies during the wheat breeding process.

The Triticeae‐CAP spring wheat nested association mapping population (Reg. No. MP‐10, NSL 527060 MAP) consisting of recombinant inbred line (RIL) populations derived from 32 spring wheat (Triticum aestivum L.) accessions each crossed to a common spring wheat parent, ‘Berkut’, has been released. The spring wheat accessions consisted of 29 landraces and three cultivars. Each population consists of approximately 75 lines for a total of 2325 RILs (Reg. Nos. GSTR No. 14701–GSTR 17133). The RILs have all been genotyped with the Illumina wheat iSelect 90K single nucleotide polymorphism array using the Infinium assay method and through genotype‐by‐sequencing. This nested association mapping population provides a genotyped germplasm resource for the wheat community. A potential strategy for use of the material is to screen the parents for a trait of interest, followed by analysis of RIL of populations that are likely to be segregating for a target trait or sequence.

Maturity traits such as days to heading and days to physiological maturity have a large impact on agronomic characteristics of wheat (Triticum aestivum L.) cultivars grown in specific environments. Extended green leaf and green glume duration after heading in hard red spring wheat have been shown to result in longer grain‐fill duration, increased kernel weight, and higher grain yield in dry environments. The genetic relationship between maturity traits, seed quality, and functional bread‐making characteristics was investigated for three sets of recombinant inbred lines derived from crosses between hard red spring wheat parents. Early heading date was correlated with increased seed quality as indicated by test weight and kernel weight in all three genetic populations. Days to heading was not consistently correlated with functional quality related to bread‐baking. Longer green glume and green leaf duration after heading were typically positively related to seed quality traits including test weight and kernel weight in the three populations. However, increased green leaf and green glume duration after heading were often negatively correlated with functional quality parameters related to bread baking. Our results suggest that selection for long green leaf or green glume duration after heading to stabilize grain yield in a warmer climate may also result in a decrease in bread‐making potential.

Background and objectives Whole wheat flour has weaker mixing properties and produces bread with smaller loaf volume than bread made from white flour. The objective of this research was to test the effect of an allele for increased dough strength on the quality of bread made from whole wheat flour. Findings An allele for increased strength at the Gli‐B1 locus was introduced by backcrossing into four hard white spring wheat backgrounds. Whole wheat flour was used for a mill and bake analysis with near‐isogenic lines containing alternative alleles at Gli‐B1 grown in dryland and irrigated environments. The allele for strong gluten did not impact flour protein. However, the strong gluten allele resulted in increased dough strength and greater loaf volume in near‐isogenic lines from different genetic backgrounds and under multiple environments. Conclusions The allele for strong gluten at Gli‐B1 may be useful to improve the end‐use quality of hard white wheat for the purpose of making whole wheat leavened bread. Significance and Novelty Introgression of specific genes for gluten proteins may positively impact baking quality of whole wheat.

Inbred cultivars and advanced breeding lines have been subjected to numerous recombination cycles, have strong allelic selection for desired traits, and share important attributes for adaptation and agronomic performance. Genetic variation in elite gene pools captured using molecular markers is immediately useful for cultivar development. The primary goal of this study was to implement a genome‐wide association study for 17 agronomic traits using elite inbred lines. A panel consisting of 237 elite hard red spring wheat (Triticum aestivum L.) lines from different wheat breeding institutions in North America were evaluated in 11 locations over 2 yr. A total of 19,192 polymorphic single‐nucleotide polymorphism (SNP) markers from the Illumina 90K SNP array and markers linked to major genes controlling plant height, photoperiod sensitivity, and vernalization were used to assay the population. Linkage disequilibrium was observed to decay within a map distance of ∼3 cM in the A and B genomes and 7 cM in the D genome. A total of 226 marker‐trait associations were identified. Potentially novel associations were detected for grain yield on chromosome 2B and kernels per spike on 1B and 7D, whereas others colocalized with well‐known adaptation loci for photoperiod response, vernalization, and plant height. The frequency of positive alleles for specific marker‐trait associations differed among the programs, suggesting targets for introgression by the respective breeding programs.

Hard red spring and winter wheat (Triticum aestivum L.) differ due to the need for vernalization to induce flowering in winter wheat, adaptation to different environments, and the requirement for higher grain protein content for end‐use quality in spring wheat. Genetic studies on spring × winter wheat crosses to identify beneficial alleles are difficult due to segregation of vernalization (Vrn) genes. For this experiment, ‘Yellowstone’, a widely grown winter wheat cultivar, was converted to the spring habit through marker‐assisted backcrossing of Vrn‐A1 and is now referred to as ‘S‐Yellowstone’. S‐Yellowstone was crossed to the spring wheat cultivar ‘Choteau’ to produce a population of 95 spring habit recombinant inbred lines (RILs). The RILs and parents were evaluated in field trials for 2 yr where S‐Yellowstone had higher grain yield and lower grain protein than Choteau. A quantitative trait locus (QTL) on chromosome 4A had pleiotropic effects on several traits. The S‐Yellowstone allele at this locus resulted in more seeds per head, accounting for 59.5% of the variation across all environments. The QTL was designated QSnh.mst‐4A. However, the S‐Yellowstone QSnh.mst‐4A allele also resulted in lower grain protein across all environments. Results suggest that the favorable QSnh.mst‐4A allele for seed number per head identified in the winter wheat parent might be useful for increasing yield in spring wheat, but consequences of the negative pleiotropic effects on grain protein content might be significant.

SummaryRecombination affects the fate of alleles in populations by imposing constraints on the reshuffling of genetic information. Understanding the genetic basis of these constraints is critical for manipulating the recombination process to improve the resolution of genetic mapping, and reducing the negative effects of linkage drag and deleterious genetic load in breeding. Using sequence‐based genotyping of a wheat nested association mapping (NAM) population of 2,100 recombinant inbred lines created by crossing 29 diverse lines, we mapped QTL affecting the distribution and frequency of 102 000 crossovers (CO). Genome‐wide recombination rate variation was mostly defined by rare alleles with small effects together explaining up to 48.6% of variation. Most QTL were additive and showed predominantly trans‐acting effects. The QTL affecting the proximal COs also acted additively without increasing the frequency of distal COs. We showed that the regions with decreased recombination carry more single nucleotide polymorphisms (SNPs) with possible deleterious effects than the regions with a high recombination rate. Therefore, our study offers insights into the genetic basis of recombination rate variation in wheat and its effect on the distribution of deleterious SNPs across the genome. The identified trans‐acting additive QTL can be utilized to manipulate CO frequency and distribution in the large polyploid wheat genome opening the possibility to improve the efficiency of gene pyramiding and reducing the deleterious genetic load in the low‐recombining pericentromeric regions of chromosomes.

Most barley cultivars have some degree of resistance to the wheat stem sawfly (WSS), Cephus cinctus Norton (Hymenoptera: Cephidae). Damage caused by WSS is currently observed in fields of barley grown in the Northern Great Plains, but the impact of WSS damage among cultivars due to genetic differences within the barley germplasm is not known. Specifically, little is known about the mechanisms underlying WSS resistance in barley. We characterized WSS resistance in a subset of the spring barley CAP (Coordinated Agricultural Project) germplasm panel containing 193 current and historically important breeding lines from six North American breeding programs. Panel lines were grown in WSS infested fields for two consecutive years. Lines were characterized for stem solidness, stem cutting, WSS infestation (antixenosis), larval mortality (antibiosis), and parasitism (indirect plant defense). Variation in resistance to WSS in barley was compared to observations made for solid-stemmed resistant and hollow-stemmed susceptible wheat lines. Results indicate that both antibiosis and antixenosis are involved in the resistance of barley to the WSS, but antibiosis seems to be more prevalent. Almost all of the barley lines had greater larval mortality than the hollow-stemmed wheat lines, and only a few barley lines had mortality as low as that observed in the solid-stemmed wheat line. Since barley lines lack solid stems, it is apparent that barley has a different form of antibiosis. Our results provide information for use of barley in rotation to control the WSS and may provide a basis for identification of new approaches for improving WSS resistance in wheat.

SummaryExtensive herbicide usage has led to the evolution of resistant weed populations that cause substantial crop yield losses and increase production costs. The multiple herbicide‐resistant (MHR) Avena fatua populations utilised in this study are resistant to members of all selective herbicide families, across five modes of action, available for A. fatua control in US small grain production, and thus pose significant agronomic and economic threats. Resistance to acetolactate synthase and acetyl‐CoA carboxylase inhibitors is not conferred by known target site mutations, indicating that non‐target site resistance (NTSR) mechanisms are involved. Understanding the inheritance of NTS MHR is of upmost importance for continued agricultural productivity in the face of the rapid increase in resistant weed populations worldwide. As few studies have examined the inheritance of NTSR in autogamous weeds, we investigated the inheritance and genetic control of NTSR in the highly autogamous, allohexaploid species A. fatua. We found that NTSR in MHRA. fatua is controlled by three separate, closely‐linked nuclear genes for flucarbazone‐sodium, imazamethabenz‐methyl and pinoxaden. The single‐gene NTSR inheritance patterns reported here contrast with other examples in allogamous species and illustrate the diversity of evolutionary responses to strong selection.

Wheat stem rust, caused by Puccinia graminis f. sp. tritici Eriks. & E. Henn, can incur yield losses in susceptible cultivars of durum wheat, Triticum turgidum ssp. durum (Desf.) Husnot. Although several durum cultivars possess the stem rust resistance gene Sr13, additional genes in durum wheat effective against emerging virulent races have not been described. Durum line 8155-B1 confers resistance against the P. graminis f. sp. tritici race TTKST, the variant race of the Ug99 race group with additional virulence to wheat stem rust resistance gene Sr24. However, 8155-B1 does not confer resistance to the first-described race in the Ug99 race group: TTKSK. We mapped a single gene conferring resistance in 8155-B1 against race TTKST, Sr8155B1, to chromosome arm 6AS by utilizing Rusty/8155-B1 and Rusty*2/8155-B1 populations and the 90K Infinium iSelect Custom bead chip supplemented by KASP assays. One marker, KASP_6AS_IWB10558, cosegregated with Sr8155B1 in both populations and correctly predicted Sr8155B1 presence or absence in 11 durum cultivars tested. We confirmed the presence of Sr8155B1 in cultivar Mountrail by mapping in the population Choteau/Mountrail. The marker developed in this study could be used to predict the presence of resistance to race TTKST in uncharacterized durum breeding lines, and also to combine Sr8155B1 with resistance genes effective to Ug99 such as Sr13. The map location of Sr8155B1 cannot rule out the possibility that this gene is an allele at the Sr8 locus. However, race specificity indicates that Sr8155B1 is different from the known alleles Sr8a and Sr8b.

Plant landraces have long been recognized as potential gene pools for biotic and abiotic stress-related genes. This research used spring wheat landrace accessions to identify new sources of resistance to the wheat stem sawfly (WSS) (Cephus cinctus Norton), an important insect pest of wheat in the northern Great Plains of North America. Screening efforts targeted 1409 accessions from six geographical areas of the world where other species of grain sawflies are endemic or where a high frequency of accessions possesses the resistance characteristic of solid stems. Resistance was observed in approximately 14% of accessions. Half of the lines displayed both antixenosis and antibiosis types of resistance. Among the resistant accessions, 41% had solid or semi-solid stems. Molecular genetic screening for haplotypes at the solid stem QTL, Qss.msub.3BL, showed that 15% of lines shared the haplotype derived from 'S-615', the original donor of the solid stem trait to North American germplasm. Other haplotypes associated with solid stems were also observed. Haplotype diversity was greater in the center of origin of wheat. Evaluation of a representative set of resistant landrace accessions in replicated field trials at four locations over a three year period identified accessions with potential genes for reduced WSS infestation, increased WSS mortality, and increased indirect defense via parasitoids. Exploitation of distinct types of plant defense will expand the genetic diversity for WSS resistance currently present in elite breeding lines.

Genetic diversity in quantitative loci associated with plant traits used by insects as cues for host selection can influence oviposition behavior and maternal choice.