Wheat is the dominant crop in temperate countries being used for human food and livestock feed. Its success depends partly on its adaptability and high yield potential but also on the gluten protein fraction which confers the viscoelastic properties that allow dough to be processed into bread, pasta, noodles, and other food products. Wheat also contributes essential amino acids, minerals, and vitamins, and beneficial phytochemicals and dietary fibre components to the human diet, and these are particularly enriched in whole-grain products. However, wheat products are also known or suggested to be responsible for a number of adverse reactions in humans, including intolerances (notably coeliac disease) and allergies (respiratory and food). Current and future concerns include sustaining wheat production and quality with reduced inputs of agrochemicals and developing lines with enhanced quality for specific end-uses, notably for biofuels and human nutrition.
Targeted selection and inbreeding have resulted in a lack of genetic diversity in elite hexaploid bread wheat accessions. Reduced diversity can be a limiting factor in the breeding of high yielding varieties and crucially can mean reduced resilience in the face of changing climate and resource pressures. Recent technological advances have enabled the development of molecular markers for use in the assessment and utilization of genetic diversity in hexaploid wheat. Starting with a large collection of 819 571 previously characterized wheat markers, here we describe the identification of 35 143 single nucleotide polymorphism‐based markers, which are highly suited to the genotyping of elite hexaploid wheat accessions. To assess their suitability, the markers have been validated using a commercial high‐density Affymetrix Axiom ® genotyping array (the Wheat Breeders’ Array), in a high‐throughput 384 microplate configuration, to characterize a diverse global collection of wheat accessions including landraces and elite lines derived from commercial breeding communities. We demonstrate that the Wheat Breeders’ Array is also suitable for generating high‐density genetic maps of previously uncharacterized populations and for characterizing novel genetic diversity produced by mutagenesis. To facilitate the use of the array by the wheat community, the markers, the associated sequence and the genotype information have been made available through the interactive web site ‘CerealsDB’.
Experiments on the Rothamsted and Woburn Experimental Farms studied the effects on take‐all of different break crops and of set‐aside/conservation covers that interrupted sequences of winter wheat. There was no evidence for different effects on take‐all of the break crops per se but the presence of volunteers, in crops of oilseed rape, increased the amounts of take‐all in the following wheat. Severity of take‐all was closely related to the numbers of volunteers in the preceding break crops and covers, and was affected by the date of their destruction. Early destruction of set‐aside/conservation covers was usually effective in preventing damaging take‐all in the following wheat except, sometimes, when populations of volunteers were very large. The experiments were not designed to test the effects of sowing dates but different amounts of take‐all in the first wheats after breaks or covers apparently affected the severity of take‐all in the following (second) wheats only where the latter were relatively late sown. In earlier‐sown second wheats, take‐all was consistently severe and unrelated to the severity of the disease in the preceding (first) wheats. Results from two very simple experiments suggested that substituting set‐aside/conservation covers for winter wheat, for 1 year only, did not seriously interfere with the development of take‐all disease or with the development or maintenance of take‐all decline (TAD). With further research, it might be possible for growers wishing to exploit TAD to incorporate set‐aside/conservation covers into their cropping strategies, and especially to avoid the worst effects of the disease on grain yield during the early stages of epidemics.
Small RNA s ( sRNA s), an important type of pathogenicity factor, contribute to impairing host immune responses. However, little is known about sRNA s in Puccinia striiformis f. sp. tritici ( Pst ), one of the most destructive pathogens of wheat ( Triticum aestivum L.). Here, we report a novel microRNA‐like RNA (milRNA) from Pst termed mi croRNA ‐like RNA 1 ( Pst ‐milR1), which suppresses wheat defenses during wheat– Pst interactions. We identified Pst ‐milR1 as a novel mil RNA in Pst . Biological prediction and co‐transformation showed that Pst ‐milR1 takes part in cross‐kingdom RNA interference ( RNA i) events by binding the wheat pathogenesis‐related 2 ( PR 2 ) gene. Silencing of the Pst ‐milR1 precursor resulted in increased wheat resistance to the virulent Pst isolate CYR 31. PR 2 knock‐down plants increased the susceptibility of wheat to the avirulent Pst isolate CYR 23. This suggests that Pst ‐milR1 represses the plant immune response by suppressing the expression of PR 2 . Taking our findings together, we postulate that Pst ‐milR1 is an important pathogenicity factor in Pst , which acts as an effector to suppress host immunity. Our results provide significant new insights into the pathogenicity of the stripe rust pathogen.