Gurcharn Singh Brar

Fusarium graminearum is a fungal pathogen that causes scab or head blight in small grain cereals and threatens global cereal production. Disease progression varies widely among individual plants of the same cultivar, reflecting both genetic and environmental heterogeneity. This complicates the identification of early host responses, because each individual plant in a population is at a slightly different phase of disease progression. Here we apply single plant-transcriptomics to a population of 121 malt-barley exposed to F. graminearum , enabling us to reconstruct a temporal sequence of regulatory processes during early infection. We identified several disease-resistance associated genetic variants that are already endemic in this high-yielding cultivar, suggesting potential as breeding targets. These variants were within proteins involved in ROS-burst production, a lectin-kinase PRR, and enzymes with DON-detoxification activity. Single plant-transcriptomics offers a novel strategy for characterising early plant-pathogen interactions, turning intra-population heterogeneity from an experimental barrier into an asset.

UA Brynn is an awned, hard red spring wheat ( Triticum aestivum L.) cultivar with high yield potential, reduced plant height with improved lodging tolerance, and strong disease resistance. In 3 years of evaluation in the High Yield Wheat Cooperative Test (2022–2024), UA Brynn attained 15.3% and 13.7% higher grain yield than the check cultivars AAC Brandon and AAC Penhold, respectively. It matured approximately 2 days later than both checks. UA Brynn is shorter than Carberry and AAC Brandon, but slightly taller (2.8 cm) than AAC Penhold, with lodging resistance similar to AAC Penhold. UA Brynn exhibited lighter test weight and lower grain protein concentration compared to AAC Brandon and AAC Penhold. However, it produced a heavier thousand kernel weight than AAC Brandon and Carberry, although lower than AAC Penhold. Notable quality parameters for UA Brynn include improved or excellent amylograph peak viscosity and enhanced clean flour yield in multiple years of testing. UA Brynn was rated resistant (R) to the prevalent races of leaf rust, stripe rust, and common bunt, moderately resistant (MR) to stem rust, and intermediate (I) to Fusarium head blight (FHB) over the 3 years of testing. End-use quality assessments indicate that UA Brynn meets or exceeds the standards for the Canada Prairie Spring Red (CPSR) wheat class.

Fusarium head blight (FHB), mainly caused by Fusarium graminearum and Fusarium culmorum , is a major wheat disease. Significant efforts have been made to improve resistance to FHB in bread wheat ( Triticum aestivum ), but more work is needed for durum wheat ( Triticum turgidum spp. durum ). Bread wheat has ample genetic variation for resistance breeding, which can be readily exploited, while durum wheat is characterized by higher disease susceptibility and fewer valuable resistance sources. The Wheat Initiative – Expert Working Group on Durum Wheat Genomics and Breeding has promoted a scientific discussion to define the key actions that should be prioritized for achieving resistance in durum wheat comparable to that found in bread wheat. Here, a detailed state of the art and novel tools to improve FHB resistance in durum are presented, together with a perspective on the next steps forward. A meta‐analysis grouping all quantitative trait loci (QTL) associated with FHB resistance in both bread and durum wheat has been conducted to identify hotspot regions that do not overlap with Rht alleles, which are known to negatively correlate with FHB resistance. A detailed list of QTL related to FHB resistance and deoxynivalenol contamination and durum lines carrying different sources of FHB resistance are provided as a strategic resource. QTL, closely linked markers and durum wheat lines carrying the useful alleles, can be selected to design an effective breeding program. Finally, we highlight the priority actions that should be implemented to achieve satisfactory resistance to FHB in durum wheat.

One of the challenges in using X-ray computed tomography (CT) for plant imaging is lack of contrast in anatomical structures and tissues due to similar density. Iodine is the most commonly used contrast agent and studies on additional contrast agents are scarce. In the present study, we describe the successful application of silver nitrate (AgNO₃) as a novel contrast agent in synchrotron-based CT of wheat. The lower K-edge of silver (25.514 keV) is more optimal for plant imaging than a high atomic number contrast agent, such as iodine (33.164 keV), for which the below- and above-edge images would have poorer absorption contrast (due to reduced ratio of absorption coefficients from plants). Particularly, this is applicable for studies at the Biomedical Imaging and Therapy beamline (BMIT-BM) at the Canadian Light Source due to the peak flux of the beamline being proximal to the K-edge of silver in comparison to iodine (leading to decreased image noise, increased contrast, and a better signal-to-noise ratio).

Pangenomes are collections of annotated genome sequences of multiple individuals of a species. The structural variants uncovered by these datasets are a major asset to genetic analysis in crop plants. Here, we report a pangenome of barley comprising long-read sequence assemblies of 76 wild and domesticated genomes and short-read sequence data of 1,315 genotypes. An expanded catalogue of sequence variation in the crop includes structurally complex loci that have become hot spots of gene copy number variation in evolutionarily recent times. To demonstrate the utility of the pangenome, we focus on four loci involved in disease resistance, plant architecture, nutrient release, and trichome development. Novel allelic variation at a powdery mildew resistance locus and population-specific copy number gains in a regulator of vegetative branching were found. Expansion of a family of starch-cleaving enzymes in elite malting barleys was linked to shifts in enzymatic activity in micro-malting trials. Deletion of an enhancer motif is likely to change the developmental trajectory of the hairy appendages on barley grains. Our findings indicate that rapid evolution at structurally complex loci may have helped crop plants adapt to new selective regimes in agricultural ecosystems.

Bread wheat ( Triticum aestivum ) is a globally dominant crop and major source of calories and proteins for the human diet. Compared to its wild ancestors, modern bread wheat shows lower genetic diversity caused by polyploidisation, domestication, and breeding bottlenecks ^1,2 . Wild wheat relatives represent genetic reservoirs, harbouring diversity and beneficial alleles that have not been incorporated into bread wheat. Here, we establish and analyse pangenome resources for Tausch’s goatgrass, Aegilops tauschii , the donor of the bread wheat D genome. This new pangenome facilitated the cloning of a disease resistance gene and haplotype analysis across a complex disease resistance locus, allowing us to discern alleles from paralogous gene copies. We also reveal the complex genetic composition and history of the bread wheat D genome, involving previously unreported contributions from genetically and geographically discrete Ae. tauschii subpopulations. Together, our results reveal the complex history of the bread wheat D genome and demonstrate the potential of wild relatives in crop improvement.

Bacterial leaf streak, bacterial blight and black chaff caused by Xanthomonas translucens pathovars are major diseases affecting small grains. Xanthomonas translucens pv. translucens and X. translu...

Background: The population structure of crop pathogens such as Puccinia striiformis f. sp. tritici (Pst), the cause of wheat stripe rust, is of interest to researchers looking to understand these pathogens on a molecular level as well as those with an applied focus such as disease epidemiology. Cereal rusts can reproduce sexually or asexually, and the emergence of novel lineages has the potential to cause serious epidemics such as the one caused by the ‘Warrior’ lineage in Europe. In a global context, Pst lineages in Canada were not well-characterized and the origin of foreign incursions was not known. Additionally, while some Pst mating type genes have been identified in published genomes, there has been no rigorous assessment of mating type diversity and distribution across the species. Results: We used a whole-genome/transcriptome sequencing approach for the Canadian Pst population to identify lineages in their global context and evidence tracing foreign incursions. More importantly: for the first time ever, we identified nine alleles of the homeodomain mating type locus in the worldwide Pst population and show that previously identified lineages exhibit a single pair of these alleles. Consistently with the literature, we find only two pheromone receptor mating type alleles. We show that the recent population shift from the ‘PstS1’ lineage to the ‘PstS1-related’ lineage is also associated with the introduction of a novel mating type allele (Pst-b3-HD) to the Canadian population. We also show evidence for high levels of mating type diversity in samples associated with the Himalayan center of diversity for Pst, including a single Canadian race previously identified as ‘PstPr’ (probable recombinant) which we identify as a foreign incursion, most closely related to isolates sampled from China circa 2015. Conclusions: These data describe a recent shift in the population of Canadian Pst field isolates and characterize homeodomain-locus mating type alleles in the global Pst population which can now be utilized in testing several research questions and hypotheses around sexuality and hybridization in rust fungi.

For wheat (Triticum aestivum), sustained crop yield at limited soil water availability has been linked to osmotic adjustment (OA) – a physiological mechanism that aids maintenance of leaf hydration status, turgor (P) and growth. ‘Canada Western Red Spring’ (CWRS) wheat cultivars are typically grown in rainfed areas with milder climates, but ongoing climate change is increasesing the frequency and intensity of drought events. The overarching goal of this study was to elucidate if commercially used CWRS cultivars (‘Superb’, ‘Stettler’, ‘AAC Viewfield’) have the ability for leaf OA. Measurements of leaf water relation parameters (water potential, ?; solute potential, ?s; stomatal conductance, gs; relative water content, RWC) showed that all three cultivars reached zero P (= ? – ?s) at a leaf ? of -1.1 MPa. Prior to that, P maintenance in ‘Superb’ and ‘AAC Viewfield’ was associated with a significant reduction in leaf ?s and OA contributed 0.53 MPa (‘Superb’) and 0.73 MPa (‘AAC Viewfield’). Our data analyses provided no support for the existence of OA in ‘Stettler’. Under water deficit, leaf gs was significantly higher in ‘AAC Viewfield’ compared to ‘Stettler’; it was intermediate in ‘Superb’. Together, drought tolerance in CWRS wheat cultivars is most likely linked to the degree of OA.