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Abstract Introducing and characterizing variation through mutagenesis plus functional genomics can accelerate resistance breeding as well as our understanding of crop plant immunity. To reveal new germplasm resources for fungal disease resistance breeding in elite durum wheat, we challenged the diverse alleles in a sequenced and cataloged ethyl methanesulfonate mutagenized population of elite tetraploid wheatTriticum turgidumsubsp.durumcv ‘Kronos’ with stripe rust. We screened 2,000 mutant lines and identified sixteen enhanced disease resistance (EDR) lines with persistent resistance to stripe rust over four years of field testing. To find broad-spectrum resistance, we challenged these lines with other major biotrophic and necrotrophic pathogens, including those causing Septoria tritici blotch, tan spot, Fusarium head blight and leaf rust. Enhanced resistance to multiple fungi was found in 13 of 16 EDR lines. Five EDR lines showed spontaneous lesion formation in the absence of pathogens, providing new mutant resources to study plant stress response in the absence of the confounding effects of pathogen infection. We mapped exome capture sequencing data of the EDR lines to a recently released long-read Kronos genome to aid in the identification of causal mutations. We located an EDR resistance locus to an 175 Mb interval on chromosome 1B. Importantly, these phenotypically characterized EDR lines are newly described durum germplasm coupled with improved functional genomics resources that are readily available for both wheat fungal resistance breeding and basic plant immunity research. 

Abstract Fusarium head blight (FHB; caused byFusarium graminearum) is a destructive disease of wheat (Triticumspp.), barley (Hordeum vulgare), rye (Secale cerealeL.), and triticale (×TriticosecaleWittmack) not only reducing their yield but also contaminating the grain with mycotoxins such as deoxynivalenol (DON). Developing varieties with genetic resistance is integral to successfully manage FHB. Triticale acreage worldwide is steadily increasing. However, the genetic diversity of triticale for FHB resistance is not well characterized. In the present study, a sequential screening of a set of winter triticale accessions from a global collection was done for their type‐2 FHB resistance and DON accumulation. In the first‐year screening, 298 triticale accessions were tested for FHB in an artificially inoculated, misted‐field nursery with high inoculum density. Most of the triticale accessions were susceptible to FHB, and only 8% of the accessions showed resistance in the field nursery screening. Next, the 24 resistant accessions identified in the nursery screening were tested for 2 years in greenhouse and 17 accessions showed significantly lower FHB severity in Year 2 and/or Year 3. These 17 resistant accessions were further tested for their FHB severity and DON accumulation in Year 4 in greenhouse and for DON accumulation in Year 5 in the field FHB nursery. Eight accessions showed significantly lower FHB severity and nine accessions showed DON accumulation of less than 1 mg/kg in Year 4 greenhouse testing. Eleven accessions had significantly lower DON concentration than the susceptible check in the Year 5 field screening. The resistant accessions common across all years identified in the study can be used for enhancing FHB resistance and reducing DON accumulation in triticale breeding programs. 

Abstract Feeding the world's ever‐increasing population requires continuous development of high‐yielding and disease‐resistant cultivars of food crops such as wheat (Triticum aestivumL.). Speed breeding, which utilizes longer photoperiod times and higher temperatures, is a technique that accelerates plant development and is rapidly being adopted by wheat breeders across the globe to fast‐track cultivar development. Plant diseases are a major threat to crop production, and breeding for disease resistance is a major goal of crop breeders. Fusarium head blight (FHB), caused byFusarium graminearum, is a major disease of small grain cereals, affecting their yield and quality. The aim of present work was to assess if speed breeding conditions can be used to accelerate reliable assessment of FHB severity and mycotoxin deoxynivalenol (DON) accumulation in wheat varieties. We screened a set of six spring wheat genotypes with different levels of genetic resistance (two moderately susceptible, two highly susceptible, one moderately resistant, and one resistant) for their response to FHB at 14 days after inoculation (dai) and 21 dai and DON accumulation under normal versus speed breeding conditions. FHB severity and DON accumulation were found to be highly correlated at all time points under normal and speed breeding conditions. Robust differentiation between resistant and susceptible genotypes could be achieved at 14 dai rather than the normal period of 21 dai, saving at least a week in phenotyping. Combined with the accelerated growth, flowering, and maturity under these conditions, efficient FHB screening and DON evaluation under speed breeding conditions will fast‐track development of resistant wheat varieties. 

Abstract Einkorn wheat (Triticum monococcum) is an ancient grain crop and a close relative of the diploid progenitor (T. urartu) of polyploid wheat. It is the only diploid wheat species having both domesticated and wild forms and therefore provides an excellent system to identify domestication genes and genes for traits of interest to utilize in wheat improvement. Here, we leverage genomic advancements for einkorn wheat using an einkorn reference genome assembly combined with skim-sequencing of a large genetic population of 812 recombinant inbred lines (RILs) developed from a cross between a wild and a domesticatedT. monococcumaccession. We identify 15,919 crossover breakpoints delimited to a median and average interval of 114 Kbp and 219 Kbp, respectively. This high-resolution mapping resource enables us to perform fine-scale mapping of one qualitative (red coleoptile) and one quantitative (spikelet number per spike) trait, resulting in the identification of small physical intervals (400 Kb to 700 Kb) with a limited number of candidate genes. Furthermore, an important domestication locus for brittle rachis is also identified on chromosome 7A. This resource presents an exciting route to perform trait discovery in diploid wheat for agronomically important traits and their further deployment in einkorn as well as tetraploid pasta wheat and hexaploid bread wheat cultivars. 

Abstract Einkorn (Triticum monococcum) was the first domesticated wheat species, and was central to the birth of agriculture and the Neolithic Revolution in the Fertile Crescent around 10,000 years ago^1,2. Here we generate and analyse 5.2-Gb genome assemblies for wild and domesticated einkorn, including completely assembled centromeres. Einkorn centromeres are highly dynamic, showing evidence of ancient and recent centromere shifts caused by structural rearrangements. Whole-genome sequencing analysis of a diversity panel uncovered the population structure and evolutionary history of einkorn, revealing complex patterns of hybridizations and introgressions after the dispersal of domesticated einkorn from the Fertile Crescent. We also show that around 1% of the modern bread wheat (Triticum aestivum) A subgenome originates from einkorn. These resources and findings highlight the history of einkorn evolution and provide a basis to accelerate the genomics-assisted improvement of einkorn and bread wheat. 

Fusarium head blight (FHB), caused by the hemibiotrophic fungus Fusarium graminearum, is one of the major threats to global wheat productivity. A wheat pore-forming toxin-like (PFT) protein was previously reported to underlie Fhb1, the most widely used quantitative trait locus in FHB breeding programs worldwide. In the present work, wheat PFT was ectopically expressed in the model dicot plant Arabidopsis. Heterologous expression of wheat PFT in Arabidopsis provided a broad-spectrum quantitative resistance to fungal pathogens including F. graminearum, Colletotrichum higginsianum, Sclerotinia sclerotiorum, and Botrytis cinerea. However, there was no resistance to bacterial or oomycete pathogens Pseudomonas syringae and Phytophthora capsici, respectively in the transgenic Arabidopsis plants. To explore the reason for the resistance response to, exclusively, the fungal pathogens, purified PFT protein was hybridized to a glycan microarray having 300 different types of carbohydrate monomers and oligomers. It was found that PFT specifically hybridized with chitin monomer, N-acetyl glucosamine (GlcNAc), which is present in fungal cell walls but not in bacteria or oomycete species. This exclusive recognition of chitin may be responsible for the specificity of PFT-mediated resistance to fungal pathogens. Transfer of the atypical quantitative resistance of wheat PFT to a dicot system highlights its potential utility in designing broad-spectrum resistance in diverse host plants. [Formula: see text] Copyright © 2023 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license . 

Abstract Since emerging in Brazil in 1985, wheat blast has spread throughout South America and recently appeared in Bangladesh and Zambia. Here we show that two wheat resistance genes, Rwt3 and Rwt4 , acting as host-specificity barriers against non- Triticum blast pathotypes encode a nucleotide-binding leucine-rich repeat immune receptor and a tandem kinase, respectively. Molecular isolation of these genes will enable study of the molecular interaction between pathogen effector and host resistance genes.