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Managing winter annual grass weeds has long been a challenge in the dryland regions of the Pacific Northwest (PNW) where soft white winter wheat is grown. The recent development of quizalofop-resistant (CoAXium) wheat varieties allows growers to use quizalofop (QP), a herbicide that inhibits acetyl-CoA carboxylase (ACCase) for postemergence grass control. Field experiments were conducted over two winter wheat growing seasons in 2021–2022 and 2022–2023 near Adams, OR, to evaluate QP efficacy on feral rye and for crop safety. Downy brome and jointed goatgrass control with QP were assessed in 2021–2022 and 2022–2023, respectively. QP treatments provided effective control of feral rye (≥95%), downy brome (≥87%), and jointed goatgrass (99%) regardless of rate, adjuvant, and spray volume tested. Spring-applied QP caused no injury to winter wheat. Results indicate that the QP-resistant wheat technology can help PNW wheat growers selectively control winter annual grasses. Nomenclature: Quizalofop; downy brome, Bromus tectorum L.; feral rye, Secale cereale L.; jointed goatgrass, Aegilops cylindrica Host.; wheat, Triticum aestivum L.

Aegilops spp. is the closest genus to wheat ( Triticum spp.), which makes Aegilops great candidates to exhibit precursors of wheat features. Aegilops cylindrica Host displays excellent salt tolerance. In the current study, biochemical and phytochemical compounds in the leaves of two wheat cultivars, one hyper-salt tolerant Ae. cylindrica genotype and their amphidiploids (derived from “Chinese Spring” × Ae. cilindrica and “Roshan” × Ae. cylindrica ), grown under control and saline field conditions, were assessed. These compounds included total protein content, proline content, electrolyte leakage, total flavonoid content, total phenolic content, DPPH radical scavenging activity, and reducing power. In addition, phenolic components were also identified using HPLC analysis. Chlorogenic acid, ellagic acid, ferulic acid, syringic acid, vanillic acid, p-coumaric acid, caffeic acid, and gallic acid were the most abundant phenolic acids. Luteolin, apigenin, and rutin were the most abundant flavonoids in the leaves. Salt stress significantly increased all biochemical variables, with the exceptions of reducing power and p-coumaric acid. Interestingly, amphidiploid genotypes exhibited intermediate levels of most of the detected phenolic compounds between the two parental species. As demonstrated by bivariate correlations luteolin, chlorogenic acid, caffeic acid and apigenin could predict inhibition percentage by DPPH assay, suggesting a possible role in the cellular defense against oxidative stress in wheat. The amphidiploids and their wild parent performed significantly better than wheat cultivars on phenolic constituents, flavonoids, and maintaining redox homeostasis under salt stress conditions.

Key messageAlthoughAe. tauschiihas been extensively utilised for wheat breeding, the D-genome-containing allopolyploids have largely remained unexploited. In this review, we discuss approaches that can be used to exploit the D genomes of the differentAegilopsspecies for the improvement of bread wheat.The D genome of allohexaploid bread wheat (Triticum aestivum, 2n = AABBDD) is the least diverse of the three wheat genomes and is unarguably less diverse than that of diploid progenitor Aegilops tauschii (2n = DD). Useful genetic variation and phenotypic traits also exist within each of the wheat group species containing a copy of the D genome: allopolyploid Aegilops species Ae. cylindrica (2n = DcDcCcCc), Ae. crassa 4x (2n = D1D1XcrXcr), Ae. crassa 6x (2n = D1D1XcrXcrDcrDcr), Ae. ventricosa (2n = DvDvNvNv), Ae. vavilovii (2n = D1D1XcrXcrSvSv) and Ae. juvenalis (2n = D1D1XcrXcrUjUj). Although Ae. tauschii has been extensively utilised for wheat breeding, the D-genome-containing allopolyploids have largely remained unexploited. Some of these D genomes appear to be modified relative to the bread wheat and Ae. tauschii D genomes, and others present in the allopolyploids may also contain useful variation as a result of adaptation to an allopolyploid, multi-genome environment. We summarise the genetic relationships, karyotypic variation and phenotypic traits known to be present in each of the D genome species that could be of relevance for bread wheat improvement and discuss approaches that can be used to exploit the D genomes of the different Aegilops species for the improvement of bread wheat. Better understanding of factors controlling chromosome inheritance and recombination in wheat group interspecific hybrids, as well as effective utilisation of new and developing genetics and genomics technologies, have great potential to improve the agronomic potential of the bread wheat D genome.

Assessment of photosynthetic traits and temperature tolerance was performed on field-grown modern genotype (MG), and the local landrace (LR) of wheat (Triticum aestivum L.) as well as the wild relative species (Aegilops cylindrica Host.). The comparison was based on measurements of the gas exchange (A/ci, light and temperature response curves), slow and fast chlorophyll fluorescence kinetics, and some growth and leaf parameters. In MG, we observed the highest CO2 assimilation rate ACO2, electron transport rate (Jmax) and maximum carboxylation rate VCmax. The Aegilops leaves had substantially lower values of all photosynthetic parameters; this fact correlated with its lower biomass production. The mesophyll conductance was almost the same in Aegilops and MG, despite the significant differences in leaf phenotype. In contrary, in LR with a higher dry mass per leaf area, the half mesophyll conductance (gm) values indicated more limited CO2 diffusion. In Aegilops, we found much lower carboxylation capacity; this can be attributed mainly to thin leaves and lower Rubisco activity. The difference in CO2 assimilation rate between MG and others was diminished because of its higher mitochondrial respiration activity indicating more intense metabolism. Assessment of temperature response showed lower temperature optimum and a narrow ecological valence (i.e., the range determining the tolerance limits of a species to an environmental factor) in Aegilops. In addition, analysis of photosynthetic thermostability identified the LR as the most sensitive. Our results support the idea that the selection for high yields was accompanied by the increase of photosynthetic productivity through unintentional improvement of leaf anatomical and biochemical traits including tolerance to non-optimal temperature conditions.

Wheat gluten protein contains toxic peptides that trigger celiac disease in genetically susceptible individuals. These toxic peptides are primarily found in gliadin fractions, which are largely derived from the D subgenome of allohexaploid wheat. Aegilops species are valuable germplasm resources for wheat breeding. In this study, we analyzed the content and composition of alpha-gliadin CD epitopes in ten genotypes from five distinct species of the Aegilops genus: Aegilops tauschii , Aegilops crassa , Aegilops juvenalis , Aegilops cylindrica , and Aegilops ventricosa . This analysis was conducted using RNA sequencing of the main amplicon of alpha-gliadins that includes the most toxic CD peptides. Our results showed significant differences in the types and distribution patterns of identified CD epitopes across various species and accessions. All the canonical and the most toxic CD epitopes were detected in the studied Aegilops genotypes. However, the intact form of the 33-mer region was absent in all genotypes. Ae. ventricosa ‘AE 1511’ and Ae. juvenalis ‘AE 537’ exhibited the highest expression frequency for the p31-43 and DQ2.5-glia-α3 epitopes, categorizing them as the most toxic species. In contrast, Ae. crassa ‘TA1873’, Ae. cylindrica ‘AE 1658’, and Ae. crassa ‘AE 815’ showed the highest expression frequencies for DQ2.5-glia-α1a and DQ2.5-glia-α2, identifying them as the least toxic species. Our findings suggest that incorporating the D genome from Ae. crassa and Ae. cylindrica ‘AE 1658’ into wheat breeding programs might be a promising strategy for reducing gluten toxicity associated with celiac disease. Key message The D genome of Aegilops crassa and Aegilops cylindrica ‘AE 1658’ contains a relatively lower amount of toxic celiac disease epitopes than that of other Aegilops species.

Using Roche/454 technology, we sequenced the chloroplast genomes of 12 Triticeae species, including bread wheat, barley and rye, as well as the diploid progenitors and relatives of bread wheat Triticum urartu, Aegilops speltoides and Ae. tauschii. Two wild tetraploid taxa, Ae. cylindrica and Ae. geniculata, were also included. Additionally, we incorporated wild Einkorn wheat Triticum boeoticum and its domesticated form T. monococcum and two Hordeum spontaneum (wild barley) genotypes. Chloroplast genomes were used for overall sequence comparison, phylogenetic analysis and dating of divergence times. We estimate that barley diverged from rye and wheat approximately 8-9 million years ago (MYA). The genome donors of hexaploid wheat diverged between 2.1-2.9 MYA, while rye diverged from Triticum aestivum approximately 3-4 MYA, more recently than previously estimated. Interestingly, the A genome taxa T. boeoticum and T. urartu were estimated to have diverged approximately 570,000 years ago. As these two have a reproductive barrier, the divergence time estimate also provides an upper limit for the time required for the formation of a species boundary between the two. Furthermore, we conclusively show that the chloroplast genome of hexaploid wheat was contributed by the B genome donor and that this unknown species diverged from Ae. speltoides about 980,000 years ago. Additionally, sequence alignments identified a translocation of a chloroplast segment to the nuclear genome which is specific to the rye/wheat lineage. We propose the presented phylogeny and divergence time estimates as a reference framework for future studies on Triticeae.

Winter annual grass species such as jointed goatgrass (Aegilops cylindrica Host), downy brome (Bromus tectorum L.), and feral rye (Secale cereale L.) negatively affect winter wheat (Triticum aestivum L.) yields. To generate a novel in‐crop selective herbicide trait for winter annual grass control, mutagenesis was used to generate multiple winter wheat lines resistant to the acetyl co‐A carboxylase (ACCase) inhibitor quizalofop p‐ethyl (QPE). Field trials were performed to assess crop safety for wheat lines with one or two homoeologous mutations and to assess winter annual grass control with QPE treatments. Crop safety parameters including visual injury rating, plant height, grain yield, and kernel weight were evaluated following QPE treatment at multiple growth stages. The susceptible winter wheat cultivar Hatcher displayed 100% crop injury when treated at tillering in early spring or at jointing in late spring. Single‐gene lines generally had crop injury and yield loss, especially at the jointing application timing. The two‐mutation cultivars Incline AX and LCS Fusion AX had low to no injury or yield loss from QPE applications at all timings and no injury from high rate QPE applications (93 and 185 g ha−1) in either the fall or the spring. Control of downy brome and feral rye was highest (92–99%), while jointed goatgrass control ranged from a low of 73% at 93 g a.i. ha−1 to a high of 98% at 109 a.i. ha−1 QPE. Our data indicate that the targeted winter annual grass weeds are controlled by QPE at rates that have acceptable crop safety for two‐mutation QPE‐resistant wheat cultivars. Core Ideas Winter wheat cultivars with two acetyl co‐A carboxylase mutations had no yield loss from quizalofop treatment. Feral rye, downy brome, and jointed goatgrass were controlled by quizalofop. Quizalofop is a second postemergence selective mode of action for winter annual grasses.

Indaziflam (Rejuvra®), a preemergence herbicide first registered in vine and tree nut crops, was recently approved for applications to rangeland for winter annual grass control. Indaziflam controls cheatgrass (Bromus tectorum L.) for at least 3 yr, and control can extend into a fourth and fifth year; however, it is very difficult to find indaziflam residues in the soil 2 yr after application. Indaziflam could be absorbed by seeds still retained on the plant and on the soil surface in sufficient concentrations to stop establishment. To test this hypothesis, B. tectorum seeds and jointed goatgrass (Aegilops cylindrica Host) spikelets were treated with indaziflam and imazapic at rates from 5.4 to 175 g ai ha−1 using a greenhouse track sprayer delivering 187 L ha−1. Treated seeds were planted into field soil, and plants were allowed to grow for 21 d under greenhouse conditions. Growth was compared with growth of non-treated controls. In addition, a second set of treated seeds were exposed to rainfall 1 and 24 h after treatment and rainfall amounts ranging from 3 to 24 mm to determine whether rainfall impacted herbicide performance. Bromus tectorum was so sensitive to indaziflam that establishment was eliminated at all rates. Imazapic inhibited B. tectorum establishment with an ED90 of 67 g ai ha−1. Indaziflam effectively inhibits A. cylindrica establishment with an ED90 of 7.4 g ai ha−1 compared with imazapic with an ED50 of 175 g ai ha−1. Indaziflam’s impact on A. cylindrica establishment was not significantly impacted by rainfall, indicating that the herbicide was absorbed to the seed coat. These findings support the hypothesis that indaziflam’s long-term control could result from its ability to inhibit establishment of seeds retained in the canopy and those on the soil surface at the time of application.

Knowledge of the natural patterns of genetic variation and their evolutionary basis is required for sustainable management and conservation of wheat germplasm. In the current study, the genetic diversity and population structure of 100 individuals from four Triticum and Aegilops species (including T. aestivum, Ae. tauschii, Ae. cylindrica, and Ae. crassa) were investigated using two gene-based markers (start codon targeted (SCoT) polymorphism and CAAT-box derived polymorphism (CBDP)) and simple-sequence repeats (SSRs). The SCoT, CBDP, and SSR markers yielded 76, 116, and 48 polymorphism fragments, respectively. The CBDP marker had greater efficiency than the SCoT and SSR markers due to its higher polymorphism content information (PIC), resolving power (Rp), and marker index (MI). Based on an analysis of molecular variance (AMOVA) performed using all marker systems and combined data, there was a higher distribution of genetic variation within species than among them. Ae. cylindrica and Ae. tauschii had the highest values for all genetic variation parameters. A cluster analysis using each marker system and combined data showed that the SSR marker had greater efficiency in grouping of tested accessions, such that the results of principal coordinate analysis (PCoA) and population structure confirmed the obtained clustering patterns. Hence, combining the SCoT and CBDP markers with polymorphic SSR markers may be useful in genetic fingerprinting and fine mapping and for association analysis in wheat and its germplasm for various agronomic traits or tolerance mechanisms to environmental stresses.

BackgroundEvaluation of genetic diversity and relationships among crop wild relatives is an important task in crop improvement. The main objective of the current study was to estimate molecular variability within the set of 91 samples from Triticum aestivum, Aegilops cylindrica, and Aegilops crassa species using 30 CAAT box–derived polymorphism (CBDP) and start codon targeted (SCoT) markers.ResultsFifteen SCoT and Fifteen CBDP primers produced 262 and 298 fragments which all of them were polymorphic, respectively. The number of polymorphic bands (NPB), polymorphic information content (PIC), resolving power (Rp), and marker index (MI) for SCoT primers ranged from 14 to 23, 0.31 to 0.39, 2.55 to 7.49, and 7.56 to 14.46 with an average of 17.47, 0.34, 10.44, and 5.69, respectively, whereas these values for CBDP primers were 15 to 26, 0.28 to 0.36, 3.82 to 6.94, and 4.74 to 7.96 with a mean of 19.87, 0.31, 5.35, and 6.24, respectively. Based on both marker systems, analysis of molecular variance (AMOVA) indicated that the portion of genetic diversity within species was more than among them. In both analyses, the highest values of the number of observed (Na) and effective alleles (Ne), Nei’s gene diversity (He), and Shannon’s information index (I) were estimated for Ae. cylindrica species.ConclusionThe results of cluster analysis and population structure showed that SCoT and CBDP markers grouped all samples based on their genomic constitutions. In conclusion, the used markers are very effective techniques for the evaluation of the genetic diversity in wild relatives of wheat.