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Aegilops tauschii, the diploid wild progenitor of the D subgenome of bread wheat, is a reservoir of genetic diversity for improving bread wheat performance and environmental resilience. Here we sequenced 242 Ae. tauschii accessions and compared them to the wheat D subgenome to characterize genomic diversity. We found that a rare lineage of Ae. tauschii geographically restricted to present-day Georgia contributed to the wheat D subgenome in the independent hybridizations that gave rise to modern bread wheat. Through k-mer-based association mapping, we identified discrete genomic regions with candidate genes for disease and pest resistance and demonstrated their functional transfer into wheat by transgenesis and wide crossing, including the generation of a library of hexaploids incorporating diverse Ae. tauschii genomes. Exploiting the genomic diversity of the Ae. tauschii ancestral diploid genome permits rapid trait discovery and functional genetic validation in a hexaploid background amenable to breeding.

The article emphasizes the need for expanding the differential sets used in race typing experiments for plant pathologists to provide valuable information to plant breeders. Specifically focusing on stripe rust, a fungal disease that affects wheat crops, the article explains how the pathogen evolves and gains virulence over time, necessitating the continuous introgression of resistance from different sources. The article also highlights the importance of including relevant differential genotypes in race typing experiments to support the development of resistant cultivars. Additionally, the document provides a list of wheat cultivars and their corresponding resistance genes to stripe rust, along with discussing the significance of standardizing race typing conditions for more accurate and comparable results in studying the population dynamics of the stripe rust pathogen in North America. [Extracted from the article]

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, Ψ ; solute potential, Ψ s; stomatal conductance, g s; relative water content, RWC) showed that all three cultivars reached zero P (= Ψ – Ψ s) at a leaf Ψ of −1.1 MPa. Prior to that, P maintenance in 'Superb' and 'AAC Viewfield' was associated with a significant reduction in leaf Ψ 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 g s 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. 'Canada Western Red Spring' wheat cultivars are typically grown in rainfed areas with milder climates, but drought is increasing with climate change. Wheat can maintain yield under dry conditions through the physiological mechanism of osmotic adjustment. We show that two of three studied cultivars of 'Canada Western Red Spring' are capable of osmotic adjustment, permitting a degree of drought tolerance. [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]

Summary: Wheat stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is an important disease in Canada. The worldwide genetic structure of Pst populations have been characterized, excluding Canada. Here, we elucidated the genetic structure of the western Canadian Pst population using molecular markers, revealing the presence of four divergent lineages with predominantly clonal structure. In the worldwide context, two previously reported lineages were identified: PstS0 (22%), representing an old Northwestern‐European and PstS1 (35%), an invasive warm‐temperature adapted. Additionally, two new, unreported lineages, PstPr (9%) and PstS1‐related (35%), were detected, which produced more telia than other lineages and had double the number of unique recombination events. The PstPr was a recent invasion, and likely evolved in a diverse, recombinant population as it was closely related to the PstS5, PstS7/Warrior, PstS8/Kranich, and PstS9 lineages originating from sexually recombining populations in the centre of diversity. The DNA methylation analysis revealed DNA‐methyltransferase1‐homologs, providing compelling evidence for epigenetic regulation and as a first report, an average of ∼5%, 5hmC in the Puccinia epigenome merits further investigation. The divergent lineages in the Canadian Pst population with the potential for genetic recombination, as well as epigenetic regulation needs consideration in the context of pathogen adaptation and management. [ABSTRACT FROM AUTHOR]