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Bruce D.l. Fitt - One of the best experts on this subject based on the ideXlab platform.
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Genetic basis of control of Rhynchosporium secalis infection and symptom expression in barley
Euphytica, 2011Co-Authors: Mark E. Looseley, Adrian C. Newton, Bruce D.l. Fitt, Simon D. Atkins, Bart A. Fraaije, William T. B. Thomas, R. Keith, Malcolm Macaulay, J. Lynott, D. HarrapAbstract:The genetic basis of several different components of resistance to Rhynchosporium secalis in barley was investigated in a mapping population derived from a cross between winter and spring barley types. Both the severity of visual disease symptoms and amount of R. secalis DNA in leaf tissues were assessed in field trials in Scotland in the 2007/2008 and 2008/2009 growing seasons. Relative expression of symptoms was defined as the residual values from a linear regression of amount of R. secalis DNA against visual plot disease score at GS 50. Amount of R. secalis DNA and visual disease score were highly correlated traits and identified nearly identical QTL. The genetic control of relative expression of symptoms was less clear. However, a QTL on chromosome 7H was identified as having a significant effect on the expression of visual disease symptoms relative to overall amount of R. secalis colonisation.
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Isolation and characterisation of the mating-type (MAT) locus from Rhynchosporium secalis
Current Genetics, 2003Co-Authors: Simon J. Foster, Bruce D.l. FittAbstract:The mating-type ( MAT ) genes from Rhynchosporium secalis were isolated using PCR-based methods. Characterisation of the MAT idiomorphs suggests that R. secalis is closely related to the discomycetes Pyrenopeziza brassicae and Tapesia yallundae in terms of sequence and MAT locus gene composition. The MAT1-2 idiomorph contains a single gene encoding a protein with a high-mobility group (HMG) DNA-binding domain. The MAT1-1 idiomorph contains two genes, one encoding a protein with a HMG domain and the other encoding an alpha box domain. A second, previously undescribed, intron was identified within the P. brassicae MAT1-2-1 gene. Two introns were also present in the corresponding gene in R. secalis and this showed the similarity between these genes at the discomycete MAT1-2 locus. Using PCR, we identified isolates of both mating types from barley crops in different parts of the UK and showed that the composition of the MAT idiomorphs is conserved in these isolates. These findings support the hypothesis that R. secalis is a heterothallic discomycete which has an as yet unidentified teleomorph.
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Symptomless infection of Rhynchosporium secalis on leaves of winter barley.
Mycological Research, 1990Co-Authors: Helena Davis, Bruce D.l. FittAbstract:Areas of leaf blotch lesions were assessed visually on green leaves sampled from a barley crop in March and April. When these leaves were examined further, firstly on a light table and then microscopically after clearing and staining, infected areas without classical leaf blotch symptoms but with sporulating Rhynchosporium secalis were observed. Sporulating infections were also observed on symptomless areas of senescent flag leaves sampled in July.
Mohammed Jawhar - One of the best experts on this subject based on the ideXlab platform.
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Viability and pathogenicity of Rhynchosporium secalis after long-term storage
Acta Phytopathologica et Entomologica Hungarica, 2019Co-Authors: M. I. E. Arabi, H. Alek, E. Al-shehadah, Mohammed JawharAbstract:Long-term storage of Rhynchosporium secalis cultures is a challenge for any lab managing a working collection of isolates. In this work, the viability and pathogenicity of R. secalis stock cultures...
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Survival and germinability of Rhynchosporium secalis conidia exposed to solar radiation
Hellenic Plant Protection Journal, 2018Co-Authors: E. Al-shehadah, A. Al-daoude, Mohammed JawharAbstract:Abstract Rhynchosporium secalis, the causal agent of barley scald disease, is a fungus commonly found in the environment. Disease spread within a field and between fields occurs through the aerial dispersal of the fungal spores. However, not much is known about the survival potential of fungal conidia exposed to solar radiation. In the present study, detached conidia of R. secalis were exposed simultaneously in the field to direct sunlight or placed in an adjacent ventilated enclosure in the dark for periods ranging from 0.5 to 8h. In addition, conidia were either exposed or not exposed to UV-C light (254 nm) for periods ranging between 0.5 and 60 min in the laboratory. After exposure, conidia were placed on water agar Petri dishes and allowed to germinate for 24h. Germinability of conidia was reduced by up to 94% after 8h of exposure to solar irradiance (670-860 Wm-2) in the field in comparison to the non-exposed control. Germinability of conidia in the laboratory was reduced up to ~100% by doses of UV-C light of 3.2±0.7 Wm-2. The results of this study will contribute to a better understanding of the relationship between climatic conditions and barley scald epidemics
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Transcriptome profile of early responsive genes in susceptible barley during Rhynchosporium secalis infection
Cereal Research Communications, 2016Co-Authors: A. Al-daoude, E. Al-shehadah, Mohammed Jawhar, A. Shoaib, M. Rajeh, M. I. E. ArabiAbstract:Scald caused by Rhynchosporium secalis, is an economically important disease found worldwide. In order to profile genes and pathways responding to R. seclais infection, leaf transcriptomes before and after fungus inoculation in susceptible barley were compared using cDNA-AFLP technique. Transcriptional changes of 144 expressed sequence tags (ESTs) were observed, of which 18 have no previously described function. Functional annotation of the transcripts revealed a wide range of pathways including cell wall fortification, cytoskeleton construction and metabolic processes at different time points. Furthermore, the results of RT-PCR analysis on candidate genes, ABC transporters and lycine-specific demethylase were consistent with the cDNA-AFLP data in their expression patterns. Taken together, our data suggest that susceptible barley reprograms metabolic and biological processes to initiate a suitable response R. secalis infection.
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Barley transcript regulation as Rhynchosporium secalis changes its trophic lifestyle.
Journal of Plant Pathology, 2015Co-Authors: A. Al-daoude, E. Al-shehadah, Mohammed Jawhar, A. Shoaib, A. A. Altahan, M. I. E. ArabiAbstract:Rhynchosporium secalis, the causal agent of barley scald disease, begins the infection process as a biotroph and switches to necrotrophism after colonization. It is well known that plants require distinct arsenals of genes to successfully respond to either biotrophic or necrotrophic pathogenic stages. To characterize the defense responses initiated by resistant and susceptible barley genotypes when R. secalis changes the trophic lifestyle, a temporal survey of transcript abundance at early points of infection was conducted. A total of 285 gene transcripts, 37 of which exhibited significant (P < 0.0001) differential accumulation in the resistant and susceptible cultivars, compared to non-inoculated controls, with 11 transcripts (4 defense-related) in common. Transcripts were divided into one of six general categories (defense, metabolism, regulatory, transport, miscellaneous, and unknown function), in which defense and metabolism had the greatest number of common transcripts in the resistant cultivar. Quantities of differentially accumulated gene transcripts in both cultivars were identified at 24 h post infection, the approximate time when R. secalis changes trophic lifestyle. Differentially and significantly accumulating transcripts either unique or common between susceptible and resistant barley genotypes suggest distinct defense responses based on the pathogen trophic lifestyle.
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RAPD and virulence analyses of Rhynchosporium secalis isolates from barley
2012Co-Authors: M. I. E. Arabi, Mohammed Jawhar, E. Al-shehadahAbstract:Scald caused by Rhynchosporium secalis has been the major yield-reducing factor for barley production during the last decade. Information on the variability of genetic and virulence in R. secalis is essential for the development of scald-resistant barley cultivars. Fifty–five monosporic isolates collected during 1996-2009 from major barley growing areas in Syria were analyzed to determine whether estimation of molecular variability would be of value for predicting a potential pathogenic change in R. secalis. The percentage of polymorphic loci and gene diversity of the population was estimated using 20 RAPD primers. High level of molecular variability existed within the population (H = 0.129). However, based on cluster analysis the 55 isolates were placed in six virulence and three RAPD groups. Poor relationship (0.042) between molecular and pathogenic variability was found. RAPD groups generally were not associated with geographic regions. The results indicate that DNA polymorphisms are independent of virulence, and that DNA fingerprinting has little value for monitoring the development of new virulent genotypes of this pathogen, nor does the presence of high levels of molecular variability necessarily suggest a high potential for evolution of new pathtypes.
T. K. Turkington - One of the best experts on this subject based on the ideXlab platform.
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Pathogenic variation of Rhynchosporium secalis in Alberta
Canadian Journal of Plant Pathology, 2002Co-Authors: T. K. Turkington, J.h. Helm, C. BosAbstract:Leaf samples with scald symptoms were taken from various barley cultivars in 1997 and 1998 at nine locations in Alberta for examination of pathogenic variability. Two hundred and fifty-six single-spore isolates of Rhynchosporium secalis were differentiated into 52 pathotypes using 12 differentials, which consisted of seven accessions with major resistance genes and five commercial cultivars. Fifty-two percent of isolates were virulent on cv. Harrington only (pathotype 1); five pathotypes, consisting of close to 25% of isolates, were virulent only on 4 of 5 commercial cultivars; and about 45 pathotypes, consisting of about 25% of isolates, were virulent on commercial cultivars and accessions. No differential was resistant to all pathotypes, and many pathotypes were represented by single isolates. There was a difference in pathotype diversity and complexity among locations in Alberta. Calmar, Lacombe, and Edmonton sites comprised the greatest number of pathotypes that were virulent on up to seven differenti...
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Symptomless infection of barley seed by Rhynchosporium secalis
Canadian Journal of Plant Pathology, 2001Co-Authors: H. K. Lee, Jalpa P. Tewari, T. K. TurkingtonAbstract:Rhynchosporium secalis, causal agent of scald of barley, generally overwinters in barley residues. However, the pathogen can also infect seeds, producing typical scald symptoms. In the present study, symptomless seed-infection by R. secalis was demonstrated, using both cultural and polymerase chain reaction (PCR)-based detection assays. Seeds of the cv. Harrington without visible scald lesions were plated on lima bean agar supplemented with Bengal rose and streptomycin. In six independent trials, about 14% of seeds gave rise to colonies of R. secalis. A species-specific primer set, based on sequence analysis of the internal transcribed spacer regions of R. secalis, was also used to detect symptomless seed-infection. The primer set did not amplify the R. secalis diagnostic band in seed DNA extracts of the resistant cv. Seebe, but the scald pathogen was detected in symptomless seed DNA extracts of the susceptible cv. Harrington. The results indicated that appreciable symptomless seed-infection by R. secalis...
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Histopathological Study of Barley Cultivars Resistant and Susceptible to Rhynchosporium secalis.
Phytopathology®, 2000Co-Authors: K. Xi Carisse, T. K. Turkington, P. A. Burnett, J. P. Tewari, M. H. Chen, J.h. HelmAbstract:ABSTRACT Differences in the penetration process by Rhynchosporium secalis were compared in resistant and susceptible barley cultivars at the seedling stage. Percent penetration and percent host cell wall alteration (HCWA) differed significantly among cultivars and isolates as revealed by light microscopy. Based on these two variables, the cultivars were statistically separated into two groups that corresponded to their disease reactions. The resistant cultivars, Johnston and CDC Guardian, showed 81.2 to 99.4% HCWA and 0.1 to 20.1% penetration at encounter sites, whereas the susceptible cultivars, Harrington, Argyle, and Manley, had 30.1 to 78.3% HCWA and 31.8 to 81.8% penetration. In the current study, cv. Leduc, which is susceptible at the seedling stage and resistant at the adult stage, showed the same percent HCWA and penetration as did susceptible cultivars. A significant negative correlation (P < 0.01) was found between percent penetration and percent HCWA for cultivars inoculated with two isolates o...
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Histopathology and isolation of Rhynchosporium secalis from infected barley seed
Seed Science and Technology, 1999Co-Authors: H. K. Lee, J. P. Tewari, T. K. TurkingtonAbstract:Rhynchosporium secalis-infected barley seeds collected during 1996 and 1997 were examined. The scald symptoms were distributed over the lemmas, paleas, awns, glumes and rachises, but were more common on glumes and awns. Fungal growth consisting of hyphae and spores was mostly present on the inner surfaces of lemmas, paleas and glumes in masses surrounded by what appeared to be mucilaginous material. Hyphae and spores along with mucilaginous material were also observed on the outer surfaces of the awns and rachises. Lemmas and paleas with lesions were incubated for various periods in sterile distilled water amended with streptomycin and the scald pathogen was successfully isolated using a streaking method. By this method, number of seeds, lemmas and paleas from which gave rise to scald fungus colonies, did not vary much for different incubation periods. However, as the incubation time was increased, contaminants often overwhelmed the scald colonies. Therefore, either no incubation or an incubation period of 12 hr was suitable for isolating the scald fungus using the streaking method. This appears to be the first report on successful isolation of the scald fungus from infected barley seed.
Bruce A. Mcdonald - One of the best experts on this subject based on the ideXlab platform.
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Phylogeographical analyses reveal global migration patterns Blackwell Publishing Ltd of the barley scald pathogen Rhynchosporium secalis
2013Co-Authors: Pascal L. Zaffarano, Bruce A. Mcdonald, Celeste C. LindeAbstract:A phylogeographical analysis of the scald pathogen Rhynchosporium secalis was conducted using nuclear DNA sequences from two neutral restriction fragment length polymorphism loci and the mating-type idiomorphs. Approximately 500 isolates sampled from more than 60 field populations from five continents were analysed to infer migration patterns and the demographic history of the fungus. Migration rates among continents were generally low, consistent with earlier reports of significant population subdivision among continents. Northern Europe was mainly a source population for global migration. We hypothesize that the pathogen only recently moved out of its centre of origin, resulting in founder populations that are reproductively isolated due to the contemporary absence of long-distance gene flow
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Phylogeographical analyses reveal global migration patterns of the barley scald pathogen Rhynchosporium secalis.
Molecular Ecology, 2009Co-Authors: Pascal L. Zaffarano, Bruce A. Mcdonald, Celeste C. LindeAbstract:A phylogeographical analysis of the scald pathogen Rhynchosporium secalis was conducted using nuclear DNA sequences from two neutral restriction fragment length polymorphism loci and the mating-type idiomorphs. Approximately 500 isolates sampled from more than 60 field populations from five continents were analysed to infer migration patterns and the demographic history of the fungus. Migration rates among continents were generally low, consistent with earlier reports of significant population subdivision among continents. Northern Europe was mainly a source population for global migration. We hypothesize that the pathogen only recently moved out of its centre of origin, resulting in founder populations that are reproductively isolated due to the contemporary absence of long-distance gene flow.
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The origin and colonization history of the barley scald pathogen Rhynchosporium secalis
Journal of Evolutionary Biology, 2007Co-Authors: Patrick C. Brunner, Stefanie Schürch, Bruce A. McdonaldAbstract:The origins of pathogens and their past and present migration patterns are often unknown. We used phylogenetic haplotype clustering in conjunction with model-based coalescent approaches to reconstruct the genetic history of the barley leaf pathogen Rhynchosporium secalis using the avirulence gene NIP1 and its flanking regions. Our results falsify the hypothesis that R. secalis emerged in association with its host during the domestication of barley 10 000 to 15 000 years ago in the Fertile Crescent and was introduced into Europe through the migration of Neolithic farmers. Estimates of time since most recent common ancestor (2500–5000 BP) placed the emergence of R. secalis clearly after the domestication of barley. We propose that modern populations of R. secalis originated in northern Europe following a host switch, most probably from a wild grass onto cultivated barley shortly after barley was introduced into northern Europe. R. secalis subsequently spread southwards into already established European barley-growing areas.
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Isolation and characterization of microsatellite loci from the barley scald pathogen, Rhynchosporium secalis
Molecular Ecology Notes, 2005Co-Authors: Celeste C. Linde, Marcello Zala, Bruce A. McdonaldAbstract:Fifteen primer pairs were designed for 14 polymorphic microsatellite loci, which were isolated and characterized from genomic libraries of Rhynchosporium secalis . Conditions for multiplexing and simultaneous genotyping of up to eight loci in a single run are described. The number of alleles per polymorphic locus ranged from two to 13 in populations from Switzerland and Australia. Genotypic diversity ranged from 61.5 to 66.7. Gene diversity ranged from 0.08 to 0.89 for individual polymorphic loci, with averages of 0.54 and 0.62 for the populations from Switzerland and Australia, respectively. Variable levels of polymorphism make these ideal markers for population genetic analyses.
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Further evidence for sexual reproduction in Rhynchosporium secalis based on distribution and frequency of mating-type alleles.
Fungal Genetics and Biology, 2003Co-Authors: Celeste C. Linde, Marcello Zala, Sara Ceccarelli, Bruce A. McdonaldAbstract:Abstract Rhynchosporium secalis , the causal agent of scald on barley, is thought to be exclusively asexual because no teleomorph has been found. Partial sequences of the HMG-box and α-domain of Rhynchosporium secalis isolates were identified and used to develop a PCR assay for the mating-type locus. PCR amplification of only one of these two domains was possible in each strain, suggesting that R. secalis has a MAT organization that is similar to other known heterothallic fungi. A multiplex PCR with primers amplifying either a MAT1-1- or MAT1-2- specific amplicon was used to determine the distribution of mating types in several R. secalis populations. In total, 1101 isolates from Australia, Switzerland, Ethiopia, Scandinavia, California, and South Africa were included in the analysis. Mating types occurred in equal frequencies for most of these populations, suggesting frequency-dependent selection consistent with sexual reproduction. In addition, both mating types were frequently found occupying the same lesion or leaf, providing opportunities for isolates of opposite mating type to interact and reproduce sexually. We propose that R. secalis should be considered a sexual pathogen, although the sexual cycle may occur infrequently in some populations.
M. I. E. Arabi - One of the best experts on this subject based on the ideXlab platform.
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Viability and pathogenicity of Rhynchosporium secalis after long-term storage
Acta Phytopathologica et Entomologica Hungarica, 2019Co-Authors: M. I. E. Arabi, H. Alek, E. Al-shehadah, Mohammed JawharAbstract:Long-term storage of Rhynchosporium secalis cultures is a challenge for any lab managing a working collection of isolates. In this work, the viability and pathogenicity of R. secalis stock cultures...
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Transcriptome profile of early responsive genes in susceptible barley during Rhynchosporium secalis infection
Cereal Research Communications, 2016Co-Authors: A. Al-daoude, E. Al-shehadah, Mohammed Jawhar, A. Shoaib, M. Rajeh, M. I. E. ArabiAbstract:Scald caused by Rhynchosporium secalis, is an economically important disease found worldwide. In order to profile genes and pathways responding to R. seclais infection, leaf transcriptomes before and after fungus inoculation in susceptible barley were compared using cDNA-AFLP technique. Transcriptional changes of 144 expressed sequence tags (ESTs) were observed, of which 18 have no previously described function. Functional annotation of the transcripts revealed a wide range of pathways including cell wall fortification, cytoskeleton construction and metabolic processes at different time points. Furthermore, the results of RT-PCR analysis on candidate genes, ABC transporters and lycine-specific demethylase were consistent with the cDNA-AFLP data in their expression patterns. Taken together, our data suggest that susceptible barley reprograms metabolic and biological processes to initiate a suitable response R. secalis infection.
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Barley transcript regulation as Rhynchosporium secalis changes its trophic lifestyle.
Journal of Plant Pathology, 2015Co-Authors: A. Al-daoude, E. Al-shehadah, Mohammed Jawhar, A. Shoaib, A. A. Altahan, M. I. E. ArabiAbstract:Rhynchosporium secalis, the causal agent of barley scald disease, begins the infection process as a biotroph and switches to necrotrophism after colonization. It is well known that plants require distinct arsenals of genes to successfully respond to either biotrophic or necrotrophic pathogenic stages. To characterize the defense responses initiated by resistant and susceptible barley genotypes when R. secalis changes the trophic lifestyle, a temporal survey of transcript abundance at early points of infection was conducted. A total of 285 gene transcripts, 37 of which exhibited significant (P < 0.0001) differential accumulation in the resistant and susceptible cultivars, compared to non-inoculated controls, with 11 transcripts (4 defense-related) in common. Transcripts were divided into one of six general categories (defense, metabolism, regulatory, transport, miscellaneous, and unknown function), in which defense and metabolism had the greatest number of common transcripts in the resistant cultivar. Quantities of differentially accumulated gene transcripts in both cultivars were identified at 24 h post infection, the approximate time when R. secalis changes trophic lifestyle. Differentially and significantly accumulating transcripts either unique or common between susceptible and resistant barley genotypes suggest distinct defense responses based on the pathogen trophic lifestyle.
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RAPD and virulence analyses of Rhynchosporium secalis isolates from barley
2012Co-Authors: M. I. E. Arabi, Mohammed Jawhar, E. Al-shehadahAbstract:Scald caused by Rhynchosporium secalis has been the major yield-reducing factor for barley production during the last decade. Information on the variability of genetic and virulence in R. secalis is essential for the development of scald-resistant barley cultivars. Fifty–five monosporic isolates collected during 1996-2009 from major barley growing areas in Syria were analyzed to determine whether estimation of molecular variability would be of value for predicting a potential pathogenic change in R. secalis. The percentage of polymorphic loci and gene diversity of the population was estimated using 20 RAPD primers. High level of molecular variability existed within the population (H = 0.129). However, based on cluster analysis the 55 isolates were placed in six virulence and three RAPD groups. Poor relationship (0.042) between molecular and pathogenic variability was found. RAPD groups generally were not associated with geographic regions. The results indicate that DNA polymorphisms are independent of virulence, and that DNA fingerprinting has little value for monitoring the development of new virulent genotypes of this pathogen, nor does the presence of high levels of molecular variability necessarily suggest a high potential for evolution of new pathtypes.
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MOLECULAR AND PATHOGENIC VARIATION IDENTIFIED AMONG ISOLATES OF Rhynchosporium secalis FROM SYRIA
Journal of Plant Pathology, 2008Co-Authors: M. I. E. Arabi, Mohammed Jawhar, E. Al-shehadahAbstract:The fungus Rhynchosporium secalis is the causal agent of barley scald disease. Sixty-three isolates of diverse geographical origin within Syria were analyzed for pathogenicity and variability of genomic DNA through random amplified polymorphic DNA (RAPD) markers. The isolates were highly variable and 18 unique haplotypes were identified. A neighbour-joining diagram, based on Nei’s genetic distances, showed that isolates formed three phylogenetic groups, and did not fall into clusters linked with geographical origin or pathogenicity, which suggests a regional dispersal of the fungus. However, most isolates with different pathogenicity levels were in the same clusters. The information obtained from this study is crucial for studying genetic variation in R. secalis and is important for future selection of isolates to develop durable barley scald resistance.