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Bruce A. Mcdonald - One of the best experts on this subject based on the ideXlab platform.

  • global diversity and distribution of three necrotrophic effectors in Phaeosphaeria nodorum and related species
    New Phytologist, 2013
    Co-Authors: Megan C. Mcdonald, Richard P. Oliver, Timothy L. Friesen, Patrick C. Brunner, Bruce A. Mcdonald
    Abstract:

    Population genetic and phylogenetic studies have shown that Phaeosphaeria nodorum is a member of a species complex that probably shares its center of origin with wheat (Triticum aestivum and Triticum durum). We examined the evolutionary histories of three known necrotrophic effectors (NEs) produced by P. nodorum and compared them with neutral loci. We screened over 1000 individuals for the presence/absence of each effector and assigned each individual to a multi-effector genotype. Diversity at each NE locus was assessed by sequencing c. 200 individuals for each locus. We found significant differences in effector frequency among populations. We propose that these differences reflect the presence/absence of the corresponding susceptibility gene in wheat cultivars. The population harboring the highest sequence diversity was different for each effector locus and never coincided with populations harboring the highest diversity at neutral loci. Coalescent and phylogenetic analyses showed a discontinuous presence of all three NEs among nine closely related Phaeosphaeria species. Only two of the nine species were found to harbor NEs. We present evidence that the three described NEs of P. nodorum were transmitted to its sister species, Phaeosphaeria avenaria tritici 1, via interspecific hybridization. © 2013 New Phytologist Trust.

  • Global diversity and distribution of three necrotrophic effectors in Phaeosphaeria nodorum and related species.
    The New phytologist, 2013
    Co-Authors: Megan C. Mcdonald, Richard P. Oliver, Timothy L. Friesen, Patrick C. Brunner, Bruce A. Mcdonald
    Abstract:

    Population genetic and phylogenetic studies have shown that Phaeosphaeria nodorum is a member of a species complex that probably shares its center of origin with wheat (Triticum aestivum and Triticum durum). We examined the evolutionary histories of three known necrotrophic effectors (NEs) produced by P. nodorum and compared them with neutral loci. We screened over 1000 individuals for the presence/absence of each effector and assigned each individual to a multi-effector genotype. Diversity at each NE locus was assessed by sequencing c. 200 individuals for each locus. We found significant differences in effector frequency among populations. We propose that these differences reflect the presence/absence of the corresponding susceptibility gene in wheat cultivars. The population harboring the highest sequence diversity was different for each effector locus and never coincided with populations harboring the highest diversity at neutral loci. Coalescent and phylogenetic analyses showed a discontinuous presence of all three NEs among nine closely related Phaeosphaeria species. Only two of the nine species were found to harbor NEs. We present evidence that the three described NEs of P. nodorum were transmitted to its sister species, Phaeosphaeria avenaria tritici 1, via interspecific hybridization.

  • Phylogenetic and population genetic analyses of Phaeosphaeria nodorum and its close relatives indicate cryptic species and an origin in the Fertile Crescent.
    Fungal genetics and biology : FG & B, 2012
    Co-Authors: Megan C. Mcdonald, Timothy L. Friesen, Patrick C. Brunner, Mohammad Razavi, Bruce A. Mcdonald
    Abstract:

    The origin of the fungal wheat pathogen Phaeosphaeria nodorum remains unclear despite earlier intensive global population genetic and phylogeographical studies. We sequenced 1683 bp distributed across three loci in 355 globally distributed Phaeosphaeria isolates, including 74 collected in Iran near the center of origin of wheat. We identified nine phylogenetically distinct clades, including two previously unknown species tentatively named P1 and P2 collected in Iran. Coalescent analysis indicates that P1 and P2 are sister species of P. nodorum and the other Phaeosphaeria species identified in our analysis. Two species, P. nodorum and P. avenaria f. sp. tritici 1 (Pat1), comprised ~85% of the sampled isolates, making them the dominant wheat-infecting pathogens within the species complex. We designed a PCR-RFLP assay to distinguish P. nodorum from Pat1. Approximately 4% of P. nodorum and Pat1 isolates showed evidence of hybridization. Measures of private allelic richness at SSR and sequence loci suggest that the center of origin of P. nodorum coincides with its host in the Fertile Crescent. We hypothesize that the origin of this species complex is also in the Fertile Crescent, with four species out of nine found exclusively in the Iranian collections.

  • Effect of hosts on competition among clones and evidence of differential selection between pathogenic and saprophytic phases in experimental populations of the wheat pathogen Phaeosphaeria nodorum
    BMC evolutionary biology, 2011
    Co-Authors: Rubik J. Sommerhalder, Bruce A. Mcdonald, Fabio Mascher, Jiasui Zhan
    Abstract:

    Background Monoculture, multi-cropping and wider use of highly resistant cultivars have been proposed as mechanisms to explain the elevated rate of evolution of plant pathogens in agricultural ecosystems. We used a mark-release-recapture experiment with the wheat pathogen Phaeosphaeria nodorum to evaluate the impact of two of these mechanisms on the evolution of a pathogen population. Nine P. nodorum isolates marked with ten microsatellite markers and one minisatellite were released onto five replicated host populations to initiate epidemics of Stagonospora nodorum leaf blotch. The experiment was carried out over two consecutive host growing seasons and two pathogen collections were made during each season.

  • Sexual recombinants make a significant contribution to epidemics caused by the wheat pathogen Phaeosphaeria nodorum.
    Phytopathology, 2010
    Co-Authors: Rubik J. Sommerhalder, Bruce A. Mcdonald, Fabio Mascher, Jiasui Zhan
    Abstract:

    We conducted a 2-year mark-release-recapture field experiment to quantify the relative contributions of immigration and sexual and asexual reproduction to epidemics of Stagonospora nodorum blotch caused by Phaeosphaeria nodorum. The epidemic was initiated using nine genetically distinct P. nodorum isolates. Infected plants were sampled four times across two growing seasons. In total, 1,286 isolates were recovered and assayed with 10 microsatellite markers and 1 minisatellite marker. The proportion of isolates having multilocus haplotypes (MLHTs) identical to the inoculated isolates decreased steadily from 86% in the first collection to 25% in the fourth collection. The novel isolates that had different MLHTs compared with the marked inoculants originated through immigration and sexual recombination. By the end of the experiment, nearly three-quarters of the novel isolates originated from sexual recombination. Our results indicate that recombinant offspring and airborne immigrant ascospores can make significant contributions to epidemics of Stagonospora nodorum blotch during a growing season.

Peter P Ueng - One of the best experts on this subject based on the ideXlab platform.

  • Genetic diversity of the white collar-2 (wc-2) gene in cereal Phaeosphaeria pathogens.
    Plant Pathology Bulletin, 2009
    Co-Authors: Ericka Yan-hsin Chiu, Pi-fang Linda Chang, Ling-yan Gao, Chun-chi Chou, Peter P Ueng
    Abstract:

    The white collar-2 (wc-2) gene encodes a light responsive white collar-2 (wc-2) protein that forms a heterodimeric complex with white collar-1 protein, activates numerous light-dependent reactions including asexual sporulation and pathogenic aggressiveness, and maintains circadian clocks in ascomycete fungi. The structure of the wc-2 gene and phylogenetic relationships based on the deduced polypeptide sequences in cereal Phaeosphacria pathogens were investigated. The wc-2 gene in 2 Phaeosphaeria nodorum (barley- (PN-b) and wheat- (PN-w) biotypes), 4 Phaeosphaeria avenaria (1 P. a. f. sp. avenaria, Paa and 3 P. a. f. sp. triticea, Pat1, Pat2 and Pat3), 1 Phaeosphaeria sp. from Polish rye (P-rye) and 1 Phaeosphaeria sp. from dallis grass (P-dg) contained two introns, transcribed to produce 1, 410 bp mRNA and encoded a 469 amino acid polypeptide. Based on the deduced polypeptide sequences, Phaeosphaeria species were phylogetically closely related as a group, with the exception of Pat2 isolates from wild foxtail barley (Hordeum jubatum L.).

  • RNA polymerase II gene (RPB2) encoding the second largest protein subunit in Phaeosphaeria nodorum and P. avenaria.
    Mycological research, 2006
    Co-Authors: Arkadiusz Malkus, Kuangren Chung, Barry M. Cunfer, Pi-fang Linda Chang, Sabina M Zuzga, Jonathan Shao, Edward Arseniuk, Peter P Ueng
    Abstract:

    A 5586 bp sequence (accession no. DQ278491), which includes the RNA polymerase II gene (RPB2) encoding the second largest protein subunit (RPB2), was obtained from the wheat biotype Phaeosphaeria nodorum (PN-w) by PCR amplification. The 3841 bp full length RPB2 gene contains two exons and a 52 bp intron, and encodes a complete 1262 amino acid protein. Similar to the C-terminals of the beta subunits of prokaryotes and yeast RNA polymerases, the deduced RPB2 protein contained many structural features needed for gene transcription. Based on the phylogenetic analysis with the deduced RPB2 polypeptide sequences, the PN-w was closely related to the maize pathogen Cochliobolus heterostrophus. Size differences were found in the full length RPB2 gene of cereal Phaeosphaeria species, mainly due to differences in intron size. No nucleotide substitutions were found in homothallic P. avenaria f.sp. triticea (Pat1) and barley biotype P. nodorum (PN-b) isolates used in this study. The nucleotide and deduced amino acid sequences of the RPB2 gene in Pat1 were closely related to that in PN-w.

  • the tri functional histidine biosynthesis gene his in wheat stagonospora nodorum blotch pathogen Phaeosphaeria nodorum
    Plant Pathology Bulletin, 2006
    Co-Authors: Arkadiusz Malkus, Kuangren Chung, Chungjan Chang, Peter P Ueng
    Abstract:

    The histidine biosynthesis gene (his) sequence was obtained from wheat-biotype Phaeosphaeria nodorum genomic DNA using a ”step down” PCR amplification technique. The 2700-bp his gene fragment contained two exons and a 51-bp intron. The two exons of this gene encoded a complete 881-amino acid protein. Like the histidine synthesis proteins in other filamentous ascomycetes, the deduced protein contained the conserved domains for three biosynthetic activities: phosphoribosyl-AMP cyclohydrolase (PRA-CH; EC 3.5.4.19), phosphoribosyl-ATP pyrophosphohydrolase (PRA-PH; EC 3.6.1.31), and histidinol dehydrogenase (HDH; EC 1.1.1.23). The substrate and zinc ion binding location in this tri-functional histidine biosynthesis protein is discussed.

  • RNA polymerase II gene (RPB2) encoding the second largest protein subunit in Phaeosphaeria nodorum and P. avenaria
    Mycological Research, 2006
    Co-Authors: Arkadiusz Malkus, Kuangren Chung, Barry M. Cunfer, Pi-fang Linda Chang, Sabina M Zuzga, Jonathan Shao, Edward Arseniuk, Peter P Ueng
    Abstract:

    A 5586 bp sequence (accession no. DQ278491), which includes the RNA polymerase II gene (RPB2) encoding the second largest protein subunit (RPB2), was obtained from the wheat biotype Phaeosphaeria nodorum (PN-w) by PCR amplification. The 3841 bp full length RPB2 gene contains two exons and a 52 bp intron, and encodes a complete 1262 amino acid protein. Similar to the C-terminals of the beta subunits of prokaryotes and yeast RNA polymerases, the deduced RPB2 protein contained many structural features needed for gene transcription. Based on the phylogenetic analysis with the deduced RPB2 polypeptide sequences, the PN-w was closely related to the maize pathogen Cochliobolus heterostrophus. Size differences were found in the full length RPB2 gene of cereal Phaeosphaeria species, mainly due to differences in intron size. No nucleotide substitutions were found in homothallic P. avenaria f.sp. triticea (Pat1) and barley biotype P. nodorum (PN-b) isolates used in this study. The nucleotide and deduced amino acid sequences of the RPB2 gene in Pat1 were closely related to that in PN-w. (c) 2006 The British Mycological Society. Published by Elsevier Ltd. All rights reserved

  • Sequence diversity of β-tubulin (tubA) gene in Phaeosphaeria nodorum and P. avenaria
    FEMS microbiology letters, 2005
    Co-Authors: Arkadiusz Malkus, Chungjan Chang, Pi-fang Linda Chang, Edward Arseniuk, Ewelina Reszka, Peter P Ueng
    Abstract:

    Full-length coding sequences of the beta-tubulin gene (tubA) were PCR-amplified and sequenced from 42 Phaeosphaeria isolates, including 16 P. nodorum and 23 P. avenaria species from cereals, two Polish isolates from rye (Secale cereale L.), and one isolate from dallis grass (Paspalum dilatatum Poir). A tubA gene of size 1556bp was identified in wheat- and barley-biotype P. nodorum (PN-w and PN-b), P. avenaria f. sp. avenaria (Paa), homothallic P. avenaria f. sp. triticea (P.a.t.) (Pat1) and the P.a.t. isolate (Pat3) from the State of Washington. The tubA gene length polymorphisms were detected in two P.a.t. isolates (Pat2) from foxtail barley (Hordeum jubatum L.), one from dallis grass and two Polish isolates from rye. These size differences were due to the variation of intron lengths among these three Phaeosphaeria species. All Phaeosphaeria isolates have identical 1344bp exons that can be translated into a 447 amino acid beta-tubulin. Like glyceraldehyde-3-phosphate dehydrogenase, the beta-tubulin amino acid sequence was identical in all Phaeosphaeria species used in this study, with the exception of the two Pat2 isolates. Six amino acid differences were evident in the beta-tubulin of these Pat2 isolates.

Gary C Bergstrom - One of the best experts on this subject based on the ideXlab platform.

  • Relative Contribution of Seed-Transmitted Inoculum to Foliar Populations of Phaeosphaeria nodorum.
    Phytopathology, 2007
    Co-Authors: Rebecca S Bennett, Michael G Milgroom, Raazesh Sainudiin, Barry M. Cunfer, Gary C Bergstrom
    Abstract:

    ABSTRACT A marked-isolate, release-recapture experiment was conducted to assess the relative contributions of seed-transmitted (released isolates) versus all other inocula to foliar and grain populations of Phaeosphaeria nodorum in winter wheat rotated with nonsusceptible crops in New York and Georgia, United States. Seed infected with two distinct groups of marked isolates of P. nodorum containing rare alleles (identified by amplified fragment length polymorphisms [AFLPs]) and balanced for mating type were planted in experimental field plots in two locations in each state. Recapture was done by isolating P. nodorum from leaves showing necrotic lesions at spring tillering and flowering stages, and mature grains from spikes showing glume blotch. Isolates from these samples were genotyped by AFLPs and categorized as released or nonreleased to infer sources of inoculum. Both infected seed and other sources of the pathogen contributed significant primary inocula to populations recovered from leaves and harves...

  • population structure of seedborne Phaeosphaeria nodorum on new york wheat
    Phytopathology, 2005
    Co-Authors: Rebecca S Bennett, Michael G Milgroom, Gary C Bergstrom
    Abstract:

    ABSTRACT Population genetic and epidemiological studies have resulted in different hypotheses about the predominant source of primary inoculum in the Phaeosphaeria nodorum-wheat pathosystem (i.e., sexually derived, windborne ascospores versus asexual or seedborne inoculum). We examined the genetic structure of seedborne populations of P. nodorum as a further step toward evaluating the hypothesis that seedborne inoculum is an important contributor to foliar epidemics in New York's rotational wheat fields. In all, 330 seedborne isolates from seven field populations were genotyped at 155 amplified fragment length polymorphism loci. Seedborne populations possessed high levels of genotypic diversity, with virtually every isolate (326/330) having a unique haplotype. As in previous population genetic studies of P. nodorum, we found low levels of gametic disequilibrium, although we could reject the null hypothesis of random mating with the index of association test for two populations. Thus, genotypically diverse...

  • Population Structure of Seedborne Phaeosphaeria nodorum on New York Wheat.
    Phytopathology, 2005
    Co-Authors: Rebecca S Bennett, Michael G Milgroom, Gary C Bergstrom
    Abstract:

    ABSTRACT Population genetic and epidemiological studies have resulted in different hypotheses about the predominant source of primary inoculum in the Phaeosphaeria nodorum-wheat pathosystem (i.e., sexually derived, windborne ascospores versus asexual or seedborne inoculum). We examined the genetic structure of seedborne populations of P. nodorum as a further step toward evaluating the hypothesis that seedborne inoculum is an important contributor to foliar epidemics in New York's rotational wheat fields. In all, 330 seedborne isolates from seven field populations were genotyped at 155 amplified fragment length polymorphism loci. Seedborne populations possessed high levels of genotypic diversity, with virtually every isolate (326/330) having a unique haplotype. As in previous population genetic studies of P. nodorum, we found low levels of gametic disequilibrium, although we could reject the null hypothesis of random mating with the index of association test for two populations. Thus, genotypically diverse and seemingly panmictic populations of P. nodorum that have been observed in wheat foliage could be derived from seedborne primary inoculum. Although sexual reproduction and recombination may contribute to the diversity of foliar populations of P. nodorum, population genetic data do not rule out seed as a source of primary inoculum. Further experimentation will be needed to determine definitively the relative importance of windborne ascospores and seed-borne asexual inoculum in epidemics of Stagonospora nodorum blotch in New York.

  • Identity and conservation of mating type genes in geographically diverse isolates of Phaeosphaeria nodorum.
    Fungal genetics and biology : FG & B, 2003
    Co-Authors: R.s Bennett, Barry M. Cunfer, Sung-hwan Yun, Theresa Lee, B. G. Turgeon, E Arseniuk, Gary C Bergstrom
    Abstract:

    Mating type idiomorphs (MAT1-1 and MAT1-2) were identified from the heterothallic loculoascomycete Phaeosphaeria nodorum (wheat biotype) using DNA from a pair of isolates from Poland and Georgia, USA that are known to mate. MAT predicted proteins of P. nodorum are similar in sequence and in phylogenetic relationship to those described for other loculoascomycetes such as Cochliobolus spp., Alternaria alternata, and Didymella zeae-maydis. The organization of the MAT locus of the P. nodorum differs from these species in that its idiomorph begins within an adjacent upstream conserved ORF of unknown function. MAT-specific primers were used to identify isolates of both mating types in field populations, demonstrating that an absence of either mating type is not the reason that the teleomorph has not been found in New York. Portions of MAT1-1 and MAT1-2 were sequenced from geographically diverse isolates, including those from regions where the teleomorph has been reported. MAT was highly conserved and no significant differences in sequence were found.

  • restriction fragment length polymorphisms in the wheat glume blotch fungus Phaeosphaeria nodorum
    Phytopathology, 1992
    Co-Authors: P P Ueng, Gary C Bergstrom, R M Slay, E A Geiger, G Shaner, A L Scharen
    Abstract:

    To develop genetic markers in the fungus Phaeosphaeria nodorum, incitant of leaf and glume blotch of cereals and grasses, genomic DNA from 11 geographically diverse isolates from wheat was used to compare restriction fragment length polymorphisms (RFLPs). An isolate from winter wheat in Cayuga County, New York, was used to construct genomic clones, of which 56 were randomly chosen as probes. Twenty-two of the probes produced unique hybridization patterns with the 11 isolates. RFLP loci exhibited one (13 probes), two (seven probes), three (one probe), or four (one probe) fragment length variants (...)

Tika B Adhikari - One of the best experts on this subject based on the ideXlab platform.

  • Association Mapping of Quantitative Resistance to Phaeosphaeria nodorum in Spring Wheat Landraces from the USDA National Small Grains Collection
    Phytopathology, 2011
    Co-Authors: Tika B Adhikari, Eric W. Jackson, Suraj Gurung, Jana M. Hansen, J. Michael Bonman
    Abstract:

    ABSTRACT Stagonospora nodorum blotch (SNB), caused by Phaeosphaeria nodorum, is a destructive disease of wheat (Triticum aestivum) found throughout the United States. Host resistance is the only economically feasible option for managing the disease; however, few SNB-resistant wheat cultivars are known to exist. In this study, we report findings from an association mapping (AM) of resistance to P. nodorum in 567 spring wheat landraces of diverse geographic origin. The accessions were evaluated for seedling resistance to P. nodorum in a greenhouse. Phenotypic data and 625 polymorphic diversity array technology (DArT) markers have been used for linkage disequilibrium (LD) and association analyses. The results showed that seven DArT markers on five chromosomes (2D, 3B, 5B, 6A, and 7A) were significantly associated with resistance to P. nodorum. Genetic regions on 2D, 3B, and 5B correspond to previously mapped quantitative trait loci (QTL) conferring resistance to P. nodorum whereas the remaining QTL appeared ...

  • Genetics and mapping of resistance to spore inoculum and culture filtrate of Phaeosphaeria nodorum in spring wheat line ND 735
    Crop Protection, 2011
    Co-Authors: Pawan K Singh, Tika B Adhikari, Mohamed Mergoum, Farhad Ghavami, Shahryar F. Kianian
    Abstract:

    Abstract Stagonospora nodorum blotch (SNB), caused by Phaeosphaeria nodorum , is one of the most devastating foliar diseases on wheat ( Triticum aestivum L.) in the northern Great Plains of North America. This study was conducted, under controlled environmental conditions, to elucidate the genetics and map the resistance to SNB caused by spore inoculum and culture filtrate of P. nodorum isolate Sn2000. A hard red spring wheat population was developed from a cross between the susceptible cultivar Steele-ND and the resistant line ND 735 for this study. Two-leaf seedlings of the parents, F 1 and F 2 generations, and F 2:6 recombinant-inbred lines (RILs) were inoculated with spore suspensions while independent two week old seedlings of segregating generations were infiltrated with culture filtrate. Disease reaction was assessed 8 days after inoculation based on a lesion-type scale while plants were evaluated for culture filtrate response four days after infiltration for the presence or absence of necrosis. Genetic analysis revealed that a single recessive gene, Tsn1 , in ND 735 confers resistance to both spore suspension and culture filtrate of P. nodorum isolate Sn2000. Mapping analysis using Diversity Arrays Technology (DArT) and simple sequence repeat (SSR) markers indicates the gene, Tsn1 , is located on the long arm of chromosome 5B and is flanked by the DArt markers wPt-8285 and wPt-3049 at a distance of 7.0 cM and 2.9 cM, respectively. This gene also controls resistance to tan spot caused by Pyrenophora tritici-repentis race 2. Results of this study reveal that wheat- P. nodorum interaction follows the toxin model of gene-for-gene hypothesis. Additionally, the finding of single gene control in the line ND 735 for both tan spot and SNB enhances the utility of the line ND 735 in wheat breeding program as a source of multiple disease resistance.

  • genetic structure of Phaeosphaeria nodorum populations in the north central and midwestern united states
    Phytopathology, 2008
    Co-Authors: Tika B Adhikari, Shaukat Ali, Rishi R Burlakoti, Pawan K Singh, Mohamed Mergoum, Stephen B Goodwin
    Abstract:

    Adhikari, T. B., Ali, S., Burlakoti, R. R., Singh, P. K., Mergoum, M., and Goodwin, S. B. 2008. Genetic structure of Phaeosphaeria nodorum populations in the north-central and midwestern United States. Phytopathology 98:101-107. Stagonospora nodorum blotch, caused by Phaeosphaeria nodorum, is considered one of the most destructive foliar diseases of wheat in the United States. However, relatively little is known about the population biology of this fungus in the major wheat-growing regions of the central United States. To rectify this situation, 308 single-spore isolates of P. nodorum were analyzed from 12 populations, five from hard red spring wheat cultivars in Minnesota and North Dakota and seven from soft red winter wheat in Indiana and Ohio. The genetic structure of the sampled populations was determined by analyzing polymorphisms at five microsatellite or simple-sequence repeat (SSR) loci and the mating type locus. Although a few clones were identified, most P. nodorum populations had high levels of gene (HS = 0.175 to 0.519) and genotype (D = 0.600 to 0.972) diversity. Gene diversity was higher among isolates collected from spring wheat cultivars in North Dakota and Minnesota (mean HS = 0.503) than in those from winter wheat cultivars in Indiana and Ohio (HS = 0.269). Analyses of clone-corrected data sets showed equal frequencies of both mating types in both regional and local populations, indicating that sexual recombination may occur regularly. However, significant gametic disequilibrium occurred in three of the four populations from North Dakota, and there was genetic differentiation both within and among locations. Genetic differentiation between the hard red spring and soft red winter wheat production regions was moderate (FST = 0.168), but whether this is due to differences in wheat production or to geographical variation cannot be determined. These results suggest that sexual reproduction occurs in P. nodorum populations in the major wheat-growing regions of the central United States, and that geographically separated populations can be genetically differentiated, reflecting either restrictions on gene flow or selection.

  • Genetic structure of Phaeosphaeria nodorum populations in the north-central and midwestern United States.
    Phytopathology, 2008
    Co-Authors: Tika B Adhikari, Shaukat Ali, Rishi R Burlakoti, Pawan K Singh, Mohamed Mergoum, Stephen B Goodwin
    Abstract:

    Stagonospora nodorum blotch, caused by Phaeosphaeria nodorum, is considered one of the most destructive foliar diseases of wheat in the United States. However, relatively little is known about the population biology of this fungus in the major wheat-growing regions of the central United States. To rectify this situation, 308 single-spore isolates of P. nodorum were analyzed from 12 populations, five from hard red spring wheat cultivars in Minnesota and North Dakota and seven from soft red winter wheat in Indiana and Ohio. The genetic structure of the sampled populations was determined by analyzing polymorphisms at five microsatellite or simple-sequence repeat (SSR) loci and the mating type locus. Although a few clones were identified, most P. nodorum populations had high levels of gene (H(S) = 0.175 to 0.519) and genotype (D = 0.600 to 0.972) diversity. Gene diversity was higher among isolates collected from spring wheat cultivars in North Dakota and Minnesota (mean H(S) = 0.503) than in those from winter wheat cultivars in Indiana and Ohio (H(S) = 0.269). Analyses of clone-corrected data sets showed equal frequencies of both mating types in both regional and local populations, indicating that sexual recombination may occur regularly. However, significant gametic disequilibrium occurred in three of the four populations from North Dakota, and there was genetic differentiation both within and among locations. Genetic differentiation between the hard red spring and soft red winter wheat production regions was moderate (F(ST) = 0.168), but whether this is due to differences in wheat production or to geographical variation cannot be determined. These results suggest that sexual reproduction occurs in P. nodorum populations in the major wheat-growing regions of the central United States, and that geographically separated populations can be genetically differentiated, reflecting either restrictions on gene flow or selection.

  • Reaction of Elite Wheat Genotypes from the Northern Great Plains of North America to Septoria Diseases.
    Plant disease, 2007
    Co-Authors: Mohamed Mergoum, Shaukat Ali, Pawan K Singh, Elias M. Elias, James A. Anderson, Karl D. Glover, Tika B Adhikari
    Abstract:

    ABSTRACT Stagonospora nodorum blotch (SNB), caused by Phaeosphaeria nodorum, and Septoria tritici blotch (STB), caused by Mycosphaerella graminicola, are the main pathogens of the Septoria disease complex of wheat (Triticum aestivum) in North America. This study was conducted to determine the disease reaction of 126 elite hard red spring, white, and durum wheat cultivars and advanced breeding lines collected from the northern Great Plains of the United States and Canada to SNB and STB. Seedlings of the 126 wheat genotypes were evaluated for resistance to SNB and STB under controlled environmental conditions. Moreover, these 126 wheat genotypes also were infiltrated with culture filtrate of P. nodorum isolate Sn2000. Based on disease reactions, three cultivars (McNeal, Dapps, and Oklee) and 12 advanced breeding lines (CA-901-580W, 97SO254-8-1, MN03291, MN03308, WA007925, MT0245, ND756, ND801, ND803, ND808, ND809, and ND811) adapted to the northern Great Plains were found to be resistant to both Septoria di...

Arkadiusz Malkus - One of the best experts on this subject based on the ideXlab platform.

  • genetic linkage map of Phaeosphaeria nodorum the causal agent of stagonospora nodorum blotch disease of wheat
    European Journal of Plant Pathology, 2009
    Co-Authors: Arkadiusz Malkus, Edward Arseniuk, Qijian Song, Perry B Cregan, P P Ueng
    Abstract:

    A genetic linkage map of the fungal pathogen Phaeosphaeria nodorum, the causal agent of stagonospora nodorum blotch disease of wheat, was created. A total of 152 ascospore-derived progeny from a single pseudothecium, which resulted from a cross of two opposite mating type isolates, Sn37-1 and S-81-B13B, was analysed with AFLP, RAPD, ISSR, expressed sequence tag (EST)-derived microsatellite primers and sequence tagged site markers developed from specific genes. The genetic linkage map consisted of 276 molecular markers, and included markers developed from five genes [Glyceraldehyde 3-phosphate dehydrogenase (gpd), malate synthase (Mls1), mannitol 1-phosphate dehydrogenase (Mpd1), mating type (MAT1) and RNA polymerase II (RPB2)], which were assigned to 21 major linkage groups (LGs). The total length of the 21 major LGs was 1,932.1 centiMorgans (cM) with an average spacing of 6.88 cM between loci. The idiomorph mating type gene (MAT1) loci was placed in LG 2 and was closely linked to RAPD marker A4-680. On the other hand, 24 molecular markers and four gene loci [β-glucosidase (bgl1), histidinol dehydrogenase (Hdh2), mannitol 1-phosphate dehydrogenase (Mpd2), and xylanase (Xyl 10-2)] were dispersed in 11 minor LGs. The segregation ratio of the xylanase (Xyl 10-1) locus was distorted and not mapped. This is the first genetic linkage map reported for this important foliar pathogen of wheat. In combination with the genomic sequence of P. nodorum strain SN15 (www.broad.mit.edu), the availability of a genetic linkage map of this organism would be an important tool to investigate quantitative trait loci (QTL) of biologically important phenotypes and for positional cloning.

  • RNA polymerase II gene (RPB2) encoding the second largest protein subunit in Phaeosphaeria nodorum and P. avenaria.
    Mycological research, 2006
    Co-Authors: Arkadiusz Malkus, Kuangren Chung, Barry M. Cunfer, Pi-fang Linda Chang, Sabina M Zuzga, Jonathan Shao, Edward Arseniuk, Peter P Ueng
    Abstract:

    A 5586 bp sequence (accession no. DQ278491), which includes the RNA polymerase II gene (RPB2) encoding the second largest protein subunit (RPB2), was obtained from the wheat biotype Phaeosphaeria nodorum (PN-w) by PCR amplification. The 3841 bp full length RPB2 gene contains two exons and a 52 bp intron, and encodes a complete 1262 amino acid protein. Similar to the C-terminals of the beta subunits of prokaryotes and yeast RNA polymerases, the deduced RPB2 protein contained many structural features needed for gene transcription. Based on the phylogenetic analysis with the deduced RPB2 polypeptide sequences, the PN-w was closely related to the maize pathogen Cochliobolus heterostrophus. Size differences were found in the full length RPB2 gene of cereal Phaeosphaeria species, mainly due to differences in intron size. No nucleotide substitutions were found in homothallic P. avenaria f.sp. triticea (Pat1) and barley biotype P. nodorum (PN-b) isolates used in this study. The nucleotide and deduced amino acid sequences of the RPB2 gene in Pat1 were closely related to that in PN-w.

  • the tri functional histidine biosynthesis gene his in wheat stagonospora nodorum blotch pathogen Phaeosphaeria nodorum
    Plant Pathology Bulletin, 2006
    Co-Authors: Arkadiusz Malkus, Kuangren Chung, Chungjan Chang, Peter P Ueng
    Abstract:

    The histidine biosynthesis gene (his) sequence was obtained from wheat-biotype Phaeosphaeria nodorum genomic DNA using a ”step down” PCR amplification technique. The 2700-bp his gene fragment contained two exons and a 51-bp intron. The two exons of this gene encoded a complete 881-amino acid protein. Like the histidine synthesis proteins in other filamentous ascomycetes, the deduced protein contained the conserved domains for three biosynthetic activities: phosphoribosyl-AMP cyclohydrolase (PRA-CH; EC 3.5.4.19), phosphoribosyl-ATP pyrophosphohydrolase (PRA-PH; EC 3.6.1.31), and histidinol dehydrogenase (HDH; EC 1.1.1.23). The substrate and zinc ion binding location in this tri-functional histidine biosynthesis protein is discussed.

  • RNA polymerase II gene (RPB2) encoding the second largest protein subunit in Phaeosphaeria nodorum and P. avenaria
    Mycological Research, 2006
    Co-Authors: Arkadiusz Malkus, Kuangren Chung, Barry M. Cunfer, Pi-fang Linda Chang, Sabina M Zuzga, Jonathan Shao, Edward Arseniuk, Peter P Ueng
    Abstract:

    A 5586 bp sequence (accession no. DQ278491), which includes the RNA polymerase II gene (RPB2) encoding the second largest protein subunit (RPB2), was obtained from the wheat biotype Phaeosphaeria nodorum (PN-w) by PCR amplification. The 3841 bp full length RPB2 gene contains two exons and a 52 bp intron, and encodes a complete 1262 amino acid protein. Similar to the C-terminals of the beta subunits of prokaryotes and yeast RNA polymerases, the deduced RPB2 protein contained many structural features needed for gene transcription. Based on the phylogenetic analysis with the deduced RPB2 polypeptide sequences, the PN-w was closely related to the maize pathogen Cochliobolus heterostrophus. Size differences were found in the full length RPB2 gene of cereal Phaeosphaeria species, mainly due to differences in intron size. No nucleotide substitutions were found in homothallic P. avenaria f.sp. triticea (Pat1) and barley biotype P. nodorum (PN-b) isolates used in this study. The nucleotide and deduced amino acid sequences of the RPB2 gene in Pat1 were closely related to that in PN-w. (c) 2006 The British Mycological Society. Published by Elsevier Ltd. All rights reserved

  • Sequence diversity of β-tubulin (tubA) gene in Phaeosphaeria nodorum and P. avenaria
    FEMS microbiology letters, 2005
    Co-Authors: Arkadiusz Malkus, Chungjan Chang, Pi-fang Linda Chang, Edward Arseniuk, Ewelina Reszka, Peter P Ueng
    Abstract:

    Full-length coding sequences of the beta-tubulin gene (tubA) were PCR-amplified and sequenced from 42 Phaeosphaeria isolates, including 16 P. nodorum and 23 P. avenaria species from cereals, two Polish isolates from rye (Secale cereale L.), and one isolate from dallis grass (Paspalum dilatatum Poir). A tubA gene of size 1556bp was identified in wheat- and barley-biotype P. nodorum (PN-w and PN-b), P. avenaria f. sp. avenaria (Paa), homothallic P. avenaria f. sp. triticea (P.a.t.) (Pat1) and the P.a.t. isolate (Pat3) from the State of Washington. The tubA gene length polymorphisms were detected in two P.a.t. isolates (Pat2) from foxtail barley (Hordeum jubatum L.), one from dallis grass and two Polish isolates from rye. These size differences were due to the variation of intron lengths among these three Phaeosphaeria species. All Phaeosphaeria isolates have identical 1344bp exons that can be translated into a 447 amino acid beta-tubulin. Like glyceraldehyde-3-phosphate dehydrogenase, the beta-tubulin amino acid sequence was identical in all Phaeosphaeria species used in this study, with the exception of the two Pat2 isolates. Six amino acid differences were evident in the beta-tubulin of these Pat2 isolates.