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Advances in genomics have expedited the improvement of several agriculturally important crops but similar efforts in wheat (Triticum spp.) have been more challenging. This is largely owing to the size and complexity of the wheat genome1, and the lack of genome-assembly data for multiple wheat lines2,3. Here we generated ten chromosome pseudomolecule and five scaffold assemblies of hexaploid wheat to explore the genomic diversity among wheat lines from global breeding programs. Comparative analysis revealed extensive structural rearrangements, introgressions from wild relatives and differences in gene content resulting from complex breeding histories aimed at improving adaptation to diverse environments, grain yield and quality, and resistance to stresses4,5. We provide examples outlining the utility of these genomes, including a detailed multi-genome-derived nucleotide-binding leucine-rich repeat protein repertoire involved in disease resistance and the characterization of Sm16, a gene associated with insect resistance. These genome assemblies will provide a basis for functional gene discovery and breeding to deliver the next generation of modern wheat cultivars.

While imidazolinone herbicides are an attractive alternative for weed control, spring wheat (Triticum aestivum L.) is susceptible to most of these herbicides. Three mutant alleles conferring resistance to the imidazolinone herbicides were previously identified in spring wheat following seed mutagenesis, but little is known about the physiological and molecular basis of resistance conferred by these alleles. On the basis of acetohydroxyacid synthase (AHAS; E.C. 4.1.3.18) assays, imazethapyr resistance in genotypes TealIMI 10A (AhasL-D1), TealIMI 11A (AhasL-B1), TealIMI 15A, and BW755 (AhasL-D1) was due to a herbicide resistant form of AHAS. TealIMI 15A, which is homozygous for two resistance alleles, was the most resistant at the enzyme level, suggesting resistance in wheat is additive. Nucleotide sequence analysis of clones derived from susceptible cultivar CDC Teal and resistant lines indicated the presence of three genes coding for the catalytic subunit of AHAS. Using a collection of T. aestivum cv. Chinese Spring aneuploid and deletion lines, ahasL-D1, ahasL-B1, and ahasL-A1 mapped to the long arm of chromosomes 6D, 6B, and 6A, respectively. Comparison of partial AhasL-D1, and AhasL-B1 deduced amino acid allele sequences with wild-type sequences indicated resistance was due to a Ser-Asn substitution near the carboxyl terminal of resulting AHAS catalytic subunits. This substitution was not present on the single isolated clone of AhasL-A1 from TealIMI 15A. This is the first report of the molecular characterization of the AHAS gene family from wheat., ACETOHYDROXYACID SYNTHASE, also known as acetolactate synthase (ALS), is a key enzyme in the biosynthesis of the branched chain amino acids valine, leucine, and isoleucine in eukaryotes and prokaryotes (Singh, [...]

Wheat (Triticum aestivum L.) cultivar mixtures may stabilize yield across environments, control air-borne diseases, and manage pest populations in both conventional and organically managed systems. The objective of this study was to evaluate agronomic and end-use quality characteristics of wheat cultivar mixtures. Five Canada Western Red Spring wheat cultivars ('Go Early', 'Carberry', 'Glenn', 'CDC Titanium', and 'Lillian') differing in agronomic and quality traits were selected to compose 20 possible two-way and three-way combinations. Field experiments were conducted in four conventional and two organic environments in Alberta and Saskatchewan, Canada in 2016 and 2017. Wheat cultivar mixtures out-yielded their mid-component averages in both conventional and organic environments. Averaged across locations, two mixtures, Glenn-Lillian and Go Early-Glenn-Lillian, significantly out-yielded their mid-components. The overall yield increase ranged from 3.3 to 14.1%, with a mean of 0.18 Mg ha-1 over different environments. Grain yield was negatively correlated with protein content (r = -.53) and falling number was negatively correlated with sedimentation volume (r = -.66) in conventional systems. Protein content was positively correlated with falling number in both conventional (r = .60) and organic (r = .40) systems. Days to maturity was positively correlated with yield (r = .40) and sedimentation volume (r = .40), but negatively correlated with falling number (r = -.80) in organic system. Sole cultivars were more stable under conventional, and mixtures were more stable under organic management. Our results suggest that wheat cultivar mixtures may provide yield advantage under abiotic stresses in conventional, whereas superior yield and grain quality in organic management. [ABSTRACT FROM AUTHOR]

Fusarium head blight, caused primarily by Fusarium graminearum (Fg), is one of the most devastating diseases of wheat. Host resistance in wheat is classified into five types (Type‐I to Type‐V), and a majority of moderately resistant genotypes carry Type‐II resistance (resistance to pathogen spread in the rachis) alleles, mainly from the Chinese cultivar Sumai 3. Histopathological studies in the past failed to identify the key tissue in the spike conferring resistance to pathogen spread, and most of the studies used destructive techniques, potentially damaging the tissue(s) under study. In the present study, nondestructive synchrotron‐based phase contrast X‐ray imaging and computed tomography techniques were used to confirm the part of the wheat spike conferring Type‐II resistance to Fg spread, thus showcasing the application of synchrotron‐based techniques to image host–pathogen interactions. Seven wheat genotypes of moderate resistance to Fusarium head blight were studied for changes in the void space volume fraction and grayscale/voxel intensity following Fg inoculation. Cell‐wall biopolymeric compounds were quantified using Fourier‐transform midinfrared spectroscopy for all genotype‐treatment combinations. The study revealed that the rachilla and rachis nodes together are structurally important in conferring Type‐II resistance. The structural reinforcement was not necessarily observed from lignin deposition but rather from an unknown mechanism. Our manuscript reports the successful application of synchrotron‐based X‐ray imaging methods to study the wheat–Fusarium interaction, thus providing an understanding of the structural role of the spike in Type‐II resistance, which is defined as resistance to pathogen spread. The major merit associated with our manuscript is in terms of technical advancement because the methods and approaches/algorithms described can be applied to the study of plant biology, such as host–pathogen interactions or developmental changes in plant tissues. Our study is one of very few to study host–pathogen interactions and the first to be applied to the wheat–Fusarium interaction. It demonstrated the use of X‐ray imaging techniques for direct observation of the host–pathogen interaction without destructive sampling. [ABSTRACT FROM AUTHOR]

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The article discusses research that aims to measure the photosynthetic traits and biomass composition of various western Canadian spring wheat cultivars in order to determine which would be optimum for the production of ethanol. The use of chlorophyll fluorescence and leaf spectral reflectance and carbon dioxide (CO2) gas exchange is mentioned. According to the study, the McKenzie cultivar has higher cellulose content, which suggested that the plant may be more desirable for the production of ethanol.