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Rhynchosporium commune is a destructive pathogen of barley, causing leaf scald. Previous microsatellite studies used Syria as a representative of cultivated barley's centre of origin, the Fertile Crescent. These suggested that R. commune and Hordeum vulgare (cultivated barley) did not co‐evolve in the host's centre of origin. The present study compares R. commune populations from Syria with those from Iran, which represents a secondary centre of origin for barley at the eastern edge of the Iranian Plateau. Results from this study also suggest that R. commune and barley did not co‐evolve in the centre of origin of cultivated barley. This was evidenced by the low pathogen genetic diversity in Iran, which was even lower than in Syria, indicating that the pathogen may have been introduced recently into Iran, perhaps through infected barley seed. Hierarchical analyses of molecular variance revealed that most genetic diversity in Iran and Syria is distributed within populations, with only 14% among populations. Analyses of multilocus association, genotype diversity and mating type frequency suggest that Iranian populations reproduce predominantly asexually. The presence of both mating types on barley and uncultivated grasses suggest a potential for sexual reproduction. Rhynchosporium commune was also found on Hordeum murinum subsp. glaucum, H. vulgare subsp. spontaneum, Lolium multiflorum and, for the first time, on Avena sativa. The variety of wild grasses that can be infected with R. commune in Iran raises concerns of these grasses acting as evolutionary breeding grounds and sources of inoculum. [ABSTRACT FROM AUTHOR]

Pathogen-associated molecular patterns ( PAMPs) are detected by plant pattern recognition receptors ( PRRs), which gives rise to PAMP-triggered immunity ( PTI). We characterized a novel fungal PAMP, Cell Death Inducing 1 (Rc CDI1), identified in the Rhynchosporium commune transcriptome sampled at an early stage of barley ( Hordeum vulgare) infection., The ability of Rc CDI1 and its homologues from different fungal species to induce cell death in Nicotiana benthamiana was tested following agroinfiltration or infiltration of recombinant proteins produced by Pichia pastoris. Virus-induced gene silencing ( VIGS) and transient expression of Phytophthora infestans effectors Pi AVR3a and Pex RD2 were used to assess the involvement of known components of PTI in N. benthamiana responses to Rc CDI1., Rc CDI1 was highly upregulated early during barley colonization with R. commune. Rc CDI1 and its homologues from different fungal species, including Zymoseptoria tritici, Magnaporthe oryzae and Neurospora crassa, exhibited PAMP activity, inducing cell death in Solanaceae but not in other families of dicots or monocots. Rc CDI1-triggered cell death was shown to require N. benthamiana Brassinosteroid insensitive 1-Associated Kinase 1 (NbBAK1), N. benthamiana suppressor of BIR1-1 (NbSOBIR1) and N. benthamiana SGT1 (NbSGT1), but was not suppressed by Pi AVR3a or Pex RD2., We report the identification of a novel Ascomycete PAMP, Rc CDI1, recognized by Solanaceae but not by monocots, which activates cell death through a pathway that is distinct from that triggered by the oomycete PAMP INF1. [ABSTRACT FROM AUTHOR]

BACKGROUND Rhynchosporium commune is a major fungal pathogen of barley crops, and the application of fungicides, such as quinone outside inhibitors ( QoIs), plays an important role in crop disease control. The genetic mechanisms linked to QoI resistance have been identified in the cytochrome b gene, with QoI resistance conferred by the G143A substitution. The objective of this study was to develop a high-throughput molecular assay to detect and identify mutations associated with QoI resistance within the Irish R. commune population. RESULTS Leaf lesions of R. commune sampled from 74 sites during 2009-2014 and isolates from 2006 and 2007 were screened for non-synonymous mutations of the cytochrome b gene using 454 targeted sequencing. The presence of the G143A substitution was confirmed in R. commune samples at one site in 2013 and at four sites in 2014; however, the frequency of the substitution in these samples was low (2-18%). The 454 sequencing results were confirmed by PCR-RFLP and Sanger sequencing. CONCLUSION The molecular assay that has been applied to this monitoring programme has shown that the application of 454 next-generation sequencing offers the potential for high throughput and accurate characterisation of non-synonymous mutations associated with fungicide resistance in a crop pathogen. © 2016 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Evolution of fungicide resistance is a major threat to food production in agricultural ecosystems. Fungal pathogens rapidly evolved resistance to all classes of fungicides applied to the field. Resistance to the commonly used azole fungicides is thought to be driven mainly by mutations in a gene ( CYP51) encoding a protein of the ergosterol biosynthesis pathway. However, some fungi gained azole resistance independently of CYP51 mutations and the mechanisms leading to CYP51-independent resistance are poorly understood. We used whole-genome sequencing and genome-wide association studies ( GWAS) to perform an unbiased screen of azole resistance loci in Rhynchosporium commune, the causal agent of the barley scald disease. We assayed cyproconazole resistance in 120 isolates collected from nine populations worldwide. We found that mutations in highly conserved genes encoding the vacuolar cation channel YVC1, a transcription activator, and a saccharopine dehydrogenase made significant contributions to fungicide resistance. These three genes were not previously known to confer resistance in plant pathogens. However, YVC1 is involved in a conserved stress response pathway known to respond to azoles in human pathogenic fungi. We also performed GWAS to identify genetic polymorphism linked to fungal growth rates. We found that loci conferring increased fungicide resistance were negatively impacting growth rates, suggesting that fungicide resistance evolution imposed costs. Analyses of population structure showed that resistance mutations were likely introduced into local populations through gene flow. Multilocus resistance evolution to fungicides shows how pathogen populations can evolve a complex genetic architecture for an important phenotypic trait within a short time span. [ABSTRACT FROM AUTHOR]

Leaf blotch is a globally important disease of barley crops and other grasses that is caused by at least five host-specialized species in the fungal genus Rhynchosporium. The pathogen R. commune (specialized to barley, brome-grass and Italian ryegrass) has long been considered to reproduce only by asexual means, but there has been accumulating evidence for recombination and gene flow from population genetic studies and the detection of complementary MAT1 -1 and MAT 1-2 isolates in a c. 1:1 ratio in the field. Here, it is demonstrated that 28 isolates of the closely related species R. agropyri (on couch-grass) and R. secalis (on rye and triticale), collected from Europe, were also either of MAT 1-1 or MAT 1-2 genotype and that the distribution of mating types did not deviate significantly from a 1:1 ratio. Evidence is then provided for MAT 1-1-1 and MAT 1-2-1 gene expression during mycelial growth for all three species. By contrast, 27 isolates of the more distantly related R. orthosporum (on cocksfoot) and R. lolii (on Italian and perennial ryegrasses) from Europe were exclusively of the MAT 1-1 genotype, and expression of the MAT 1-1-1 gene could not be detected during mycelial growth. These data suggest that cryptic sexual cycles are more likely to exist for R. commune, R. agropyri and R. secalis than for either R. orthosporum or R. lolii. A phylogenetic analysis of partial MAT 1-1 idiomorph sequences resolved these five species into two distinct groups ( R. commune, R. agropyri and R. secalis versus R. orthosporum and R. lolii) but provided only limited resolution within each group. [ABSTRACT FROM AUTHOR]

Detailed knowledge of the evolutionary genetics of virulence is needed to understand and predict host-pathogen dynamics. This study used a virulence assay based on digital image analysis and treated virulence as a quantitative rather than a binary trait. Such quantitative data may better reflect the genetic underpinning of virulence in many pathogen systems and provide better resolution in statistical investigations. A greenhouse experiment based on a common garden design was conducted to measure virulence (% of leaf area covered by lesions) of 126 genetically distinct isolates of the barley scald pathogen, Rhynchosporium commune, originating from nine field populations around the world. Virulence in this pathosystem was found to be a quantitative trait with a continuous distribution in all populations. By comparing population genetic differentiation for virulence and neutral microsatellite markers (i.e. a QST/ GST comparison), evidence that virulence is under stabilizing selection across populations was found. Heritability values were high and ranged from 0·52 to 0·96 with a mean heritability of 0·84. Virulence was positively correlated with spore production as predicted by the trade-off theory of virulence evolution. Furthermore, an association analysis between virulence and sequence haplotypes of three known necrosis-inducing effector genes ( NIP1, NIP2 and NIP3) revealed a significant effect of NIP2 haplotypes and NIP1 deletions. Overall, the results support a quantitative model for virulence in the R. commune-barley pathosystem and very high evolutionary potential for this trait. [ABSTRACT FROM AUTHOR]

To predict the response of plant pathogens to climate warming, data are needed on current thermal adaptation, the pathogen's evolutionary potential, and the link between them. We conducted a common garden experiment using isolates of the fungal pathogen Rhynchosporium commune from nine barley populations representing climatically diverse locations. Clonal replicates of 126 genetically distinct isolates were assessed for their growth rate at 12°C, 18°C, and 22°C. Populations originatingfrom climates with higher monthly temperature variation had higher growth rate at all three temperatures compared with populations from climates with less temperature fluctuation. Population differentiation in growth rate (QST) was significantly higher at 22°C than population differentiation for neutral microsatellite loci (GST), consistent with local adaptation for growth at higher temperatures. At 18°C, we found evidence for stabilizing selection for growth rateas QST was significantly lower than GST. Heritability of growth rate under the three temperatures was substantial in all populations (0.58-0.76). Genetic variation was lower in populations with higher growth rate at the three temperatures and evolvability increased under heat stress in seven of nine populations. Our findings imply that the distribution of this pathogen is unlikely to be genetically limited under climate warming, due to its high genetic variation and plasticity for thermal tolerance. [ABSTRACT FROM AUTHOR]

Rhynchosporium commune is a haploid fungus causing scald or leaf blotch on barley, other Hordeum spp. and Bromus diandrus. Taxonomy Rhynchosporium commune is an anamorphic Ascomycete closely related to the teleomorph Helotiales genera Oculimacula and Pyrenopeziza. Disease symptoms Rhynchosporium commune causes scald-like lesions on leaves, leaf sheaths and ears. Early symptoms are generally pale grey oval lesions. With time, the lesions acquire a dark brown margin with the centre of the lesion remaining pale green or pale brown. Lesions often merge to form large areas around which leaf yellowing is common. Infection frequently occurs in the leaf axil, which can lead to chlorosis and eventual death of the leaf. Life cycle Rhynchosporium commune is seed borne, but the importance of this phase of the disease is not fully understood. Debris from previous crops and volunteers, infected from the stubble from previous crops, are considered to be the most important sources of the disease. Autumn-sown crops can become infected very soon after sowing. Secondary spread of disease occurs mainly through splash dispersal of conidia from infected leaves. Rainfall at the stem extension growth stage is the major environmental factor in epidemic development. Detection and quantification Rhynchosporium commune produces unique beak-shaped, one-septate spores both on leaves and in culture. The development of a specific polymerase chain reaction ( PCR) and, more recently, quantitative PCR (q PCR) has allowed the identification of asymptomatic infection in seeds and during the growing season. Disease control The main measure for the control of R. commune is the use of fungicides with different modes of action, in combination with the use of resistant cultivars. However, this is constantly under review because of the ability of the pathogen to adapt to host plant resistance and to develop fungicide resistance. [ABSTRACT FROM AUTHOR]

Both airborne spores of Rhynchosporium secalis and seed infection have been implied as major sources of primary inoculum for barley leaf blotch (scald) epidemics in fields without previous history of barley cropping. However, little is known about their relative importance in the onset of disease. Results from both quantitative real-time PCR and visual assessments indicated that seed infection was the main source of inoculum in the field trial conducted in this study. Glasshouse studies established that the pathogen can be transmitted from infected seeds into roots, shoots and leaves without causing symptoms. Plants in the field trial remained symptomless for approximately four months before symptoms were observed in the crop. Covering the crop during part of the growing season was shown to prevent pathogen growth, despite the use of infected seed, indicating that changes in the physiological condition of the plant and/or environmental conditions may trigger disease development. However, once the disease appeared in the field it quickly became uniform throughout the cropping area. Only small amounts of R. secalis DNA were measured in 24 h spore-trap tape samples using PCR. Inoculum levels equivalent to spore concentrations between 30 and 60 spores per m3 of air were only detected on three occasions during the growing season. The temporal pattern and level of detection of R. secalis DNA in spore tape samples indicated that airborne inoculum was limited and most likely represented rain-splashed conidia rather than putative ascospores. [ABSTRACT FROM AUTHOR]

Rhynchosporium secalis is one of the most destructive pathogens of barley worldwide, causing yield decreases of up to 40% and reduced grain quality. Rhynchosporium is a polycyclic disease. Primary inoculum includes conidia produced on crop debris, infected seeds and possibly ascospores, although these have not yet been identified. Secondary disease spread is primarily by splash dispersal of conidia produced on infected leaves, which may be symptomless early in the growing season. Host resistance to R. secalis is mediated by both ‘major’ or host-specific genes (complete resistance) and ‘minor’ genes of smaller, generally additive effects (partial resistance). Crop growth stage and plant or canopy architecture can modify the expression of resistance. Resistance genes are distributed unevenly across the barley genome, with most being clustered on the short arms of chromosomes 1H, 3H, 6H and 7H, or in the centromeric region or on the long arm of chromosome 3H. Strategies used to manage rhynchosporium epidemics include cultivar resistance and fungicides, and also cultural practices such as crop rotation, cultivar mixtures and manipulation of sowing date, sowing rate or fertiliser rate. However, the high genetic variability of R. secalis can result in rapid adaptation of pathogen populations to render some of these control strategies ineffective when they are used alone. Sustainable control of rhynchosporium needs to integrate major-gene-mediated resistance, partial resistance and other strategies such as customized fungicide programmes, species or cultivar rotation, resistance gene deployment, clean seed and cultivar mixtures. [ABSTRACT FROM AUTHOR]

Atypical, green leaf blotch lesions were observed on senescent leaves in winter barley crops and sometimes developed on barley leaves inoculated with conidia of Rhynchosporium secalis in a glasshouse. Similar atypical lesions were induced on barley leaves inoculated with conidia of R. secalis and then grown in controlled environments at 10 °C and 80% rh. Microscopic examination of green lesions from these three sources showed that hyphae of R. secalis had colonized the subsidiary cells of stomata so that guard cells were swollen, resulting in enlarged stomatal pores. Additionally, spore initials bad erupted through the leaf cuticle of some leaves. Most spore initials did not develop into mature conidia when leaves were incubated for 24 h at 20 °C in a closed chamber at 100% rh, but aerial hyphae grew out from the leaf surface. Thus, atypical green lesions produced a much smaller number of spores than typical leaf blotch lesions. [ABSTRACT FROM AUTHOR]

The aim of this investigation was the incorporation of resistance to BaYMV and Rhynchosporium secalis into German winter barley varieties together with the maintenance of their high agronomic characters. The agronomic value of DH-lines after two backcrosses and three haploid steps were compared with the original parents. Lines with similar or superior results could be selected for all the agronomic features evaluated. This method of recurrent selection with repeated haploid steps can therefore lead to the development of lines useful for practical purposes. [ABSTRACT FROM AUTHOR]

Seven winter barley cultivars expressing different field resistance against leaf blotch (Rhynchosporium secalis) and 60 doubled haploid (DLI) lines descending from an F1 hybrid resistant × susceptible were used to develop a test for the quantitative determination of disease severity. Differences in the level of resistance could be measured very precisely after artificial infection of seedlings at the 4-leaf-stage and a subsequent incubation at 7 C. The protein of six isolates was used for antiserum production which was subsequently supplied for serological testing (Enzyme-Linked-lmmunosorbent-Assay) of infected leaves. The results of visible scoring of the seedlings was significantly correlated with measuring with the ELISA reader. The results of the seedling test also corresponded to field scores after natural infection. [ABSTRACT FROM AUTHOR]

In 1992, samples of Rhynchosporium secalis from 19 winter barley crops in England and Wales were examined for carbendazim resistance. Of the 120 isolates obtained, 142% were resistant to carbendazim. A larger survey was carried out in England and Wales in 1993 when samples from 74 crops were examined. On this occasion 1&6% of the 639 isolates obtained were resistant to carbendazim, and resistant isolates were detected in 46% of crops. [ABSTRACT FROM AUTHOR]

Thirty single-spore isolates of Rhynchosporium secalis were assayed in vitro to assess relative sensitivities to the fungicide triadimenol. Minimum inhibitory concentrations ranged from 0.2 to 3.2 μg/ml. Isolates collected in 1981 from winter barley crops treated with triadimenol + fuberidazole, triadimefon, or prochloraz were as sensitive as those from untreated crops, and four isolates collected prior to the widespread use of these fungicides were not especially sensitive. All isolates tested in the greenhouse on winter and spring barley were controlled by Baytan (tria-dimenol and fuberidazole). [ABSTRACT FROM AUTHOR]

This article cites a study that determined the species of Rhynchosporium (R.) occurring on Lolium (L.) multiflorum, their relative frequency, and the host range of common isolates. The variation between and within cultivars was assessed with a view to increasing the level of resistance in L. multiflorum by breeding. R. orthosporum was isolated from L. multiflorum from breeders' plots at Aberystwyth, Wales twice as often as R. secalis. Of 20 genotypes of L. multiflorum, 17 ranked similarly for level of resistance to both pathogen species.

The reactions of 37 cultivars and two candidate lines of barley to five isolates of Rhynchosporium secalis and their mixtures were determined in assays under greenhouse conditions. Fungal isolates were collected from Ankara province and surrounding areas in Turkey. There were clear differences in the reactions of the cultivars to the fungal isolates and isolates differed in pathogenicity for each cultivar. Of all genotypes tested, seven cultivars (cvs Erginel 90, Şahin 91, Kıral 97, Akhisar 98, Çetin 2000, Çumra 2001, Avcı 2002) and one candidate line (candidate 4) were found to be resistant to all isolates and their mixtures. A5 was found to be the most virulent fungal isolate. [ABSTRACT FROM AUTHOR]

This article introduces uncommon plant diseases and pests in Great Britain. A powdery mildew disease occurring on Veronica longifolia var. subsessilis in Buckinghamshire, England in 1934, was briefly mentioned. Immature perithecia were found and the fungus was identified as apparently Sphaerotheca fuliginea Salm. In addition, lesions suspected to be due to Rhynchosporium orthosporum were seen on plants of Lolium perenne from the headland of a field under wheat.

A method is described by which large volumes of conidial suspension of Rhynchosporium secalis can be obtained easily. [ABSTRACT FROM AUTHOR]

This article discusses the occurrence of Rhynchosporium orthosporum on Italian Ryegrass. In the second week of March 1960, stunted plants of S22 and HI strains of Italian ryegrass, Lolium miiltiflorum, were seen in a nine-acre field at Wadhurst in East Sussex, England. The foliage was chlorotic, with the older leaves brown and shrivelled. Affected plants were in several patches about one or two yards in diameter. Examination of individual leaves showed light green or greyish areas with irregular dark-brown margins and bearing cylindrical conidia which were mostly one-septate.