The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Bruce A. Mcdonald - One of the best experts on this subject based on the ideXlab platform.
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two new species
2011Co-Authors: Pascal L. Zaffarano, Bruce A. Mcdonald, Celeste C. LindeAbstract:Rhynchosporium consists of two species, R. secalis and orthosporum. Both are pathogens of grasses with R. secalis infecting a variety of Poaceae hosts and R. orthosporum infecting Dactylis glomerata. Phylogenetic analyses of multilocus DNA sequence data on R. secalis isolates originating from cultivated barley, rye, triticale and other grasses, including Agropyron spp., Bromus diandrus and Hordeum spp., resolved the monophyletic groups into three species according to their respective hosts. Host specificity according to phylogenetic lineages was confirmed with pathogenicity studies. Because R. secalis was described first on rye this name is retained for Rhynchosporium isolates infecting rye and triticale. Rhynchosporium isolates infecting cultivated barley and other Hordeum spp. and Bromus diandrus belong to a distinct species, R. commune. Similarly isolates infecting Agropyron spp. represent a distinct species of Rhynchosporium, namely R. agropyri. A PCR-RFLP assay was developed as a rapid tool for species identification of R. secalis and commune.
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sequence conservation in the mitochondrial cytochrome b gene and lack of g143a qoi resistance allele in a global sample of rhynchosporium secalis
Australasian Plant Pathology, 2009Co-Authors: Stefano F F Torriani, Celeste C. Linde, Bruce A. McdonaldAbstract:Barley scald caused by Rhynchosporium secalis is often controlled by fungicides, most recently by those in the strobilurin-based (QoI) class. Since the launch of QoIs in 1996 a range of important plant pathogens, including Blumeria graminis, Mycosphaerella fijiensis and Plasmopara viticola, developed resistance. Present monitoring data indicate that R. secalis populations remain sensitive. The primary molecular mechanism of QoI resistance in several fungi is a point mutation at codon 143 in the mitochondrial-encoded cytochrome b gene (cytb), which causes the substitution of glycine by alanine (G143A). We characterised the cytb gene of R. secalis, assessed the intraspecific and interspecific sequence diversity, developed a PCR-RFLP diagnostic tool to detect the most common allele associated with QoI resistance, screened a global collection of 841 R. secalis isolates for this allele and tested a representative sample of isolates for QoI resistance in vitro. The results indicated a high degree of conservation for the cytb gene at both intra- and interspecific levels, and complete QoI sensitivity in all R. secalis populations tested.
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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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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.
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Genetic Structure of Rhynchosporium secalis in Australia.
Phytopathology®, 1999Co-Authors: Bruce A. Mcdonald, Jiasui Zhan, Jeremy J. BurdonAbstract:McDonald, B. A., Zhan, J., and Burdon, J. J. 1999. Genetic structure of Rhynchosporium secalis in Australia. Phytopathology 89:639-645. Restriction fragment length polymorphism (RFLP) markers were used to determine the genetic structure of Australian field populations of the barley scald pathogen Rhynchosporium secalis. Fungal isolates were collected by hierarchical sampling from five naturally infected barley fields in different geographic locations during a single growing season. Genetic variation was high in Australian R. secalis populations. Among the 265 fungal isolates analyzed, 214 distinct genotypes were identified. Average genotype diversity within a field population was 65% of its theoretical maximum. Nei’s average gene diversity across seven RFLP loci was 0.54. The majority (76%) of gene diversity was distributed within sampling site areas measuring ≈1 m 2 ; 19% of gene diversity was distributed among sampling sites within fields; and 5% of gene diversity was distributed among fields. Fungal populations from different locations differed significantly both in allele frequencies and genotype diversities. The degree of genetic differentiation was significantly correlated with geographic distance between populations. Our results suggest that the R. secalis population in Western Australia has a different genetic structure than populations in Victoria and South Australia.
Yasukazu Saito - One of the best experts on this subject based on the ideXlab platform.
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hydrogen storage by decalin naphthalene pair and hydrogen supply to fuel cells by use of superheated liquid film type catalysis
Applied Catalysis A-general, 2005Co-Authors: Shinya Hodoshima, Atsushi Shono, Shigeki Takaiwa, Kazumi Satoh, Yasukazu SaitoAbstract:Abstract A catalytic reaction pair of decalin dehydrogenation/naphthalene hydrogenation has been proposed as a storage medium for fuel-cell hydrogen in mobile modes. The hydrogen capacities with decalin (7.3 wt.%, 64.8 kg-H 2 m 3 ) are higher than the target values of the Department of Energy, USA (6.5 wt.%, 62.0 kg-H 2 m 3 ). Platinum–rhenium composite catalysts supported on granular activated carbon in “superheated liquid-film” states gave excellent reactivities for decalin dehydrogenation, where the conversion of almost 100% from decalin to naphthalene was attained within 1 h by heating at 280 °C in a batch-wise reactor. “Superheated liquid-film” conditions were also realized in a continuous-type reactor at the same temperature (280 °C). With the goal of maintaining rapid evolution of hydrogen stationarily, a rather wide range of decalin feed rates was allowable with use of platinum particles supported on activated carbon cloth. Decalin should be evaluated as an organic chemical hydride not only because of its storage densities but also because of its potential power densities for fuel-cell vehicles.
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characteristics of decalin dehydrogenation catalysis in the superheated liquid film state for mobile storage of hydrogen
Journal of Chemical Engineering of Japan, 2004Co-Authors: Shinya Hodoshima, Yasukazu SaitoAbstract:Efficient hydrogen evolution from decalin by heating at 210°C and cooling at 5°C was attempted in a batch-wise reactor by the use of “superheated liquid-film-type catalysis”. When the carbon-supported metal catalyst 0.75 g was immersed with decalin 3.0 ml under a reactive distillation conditions, a liquid-film state was realized and the catalytic conversion of decalin was remarkably enhanced in contrast to the ordinary suspended state (e.g., 0.75 g/10 ml). Active sites in the liquid-film state were superheated, being higher in temperatures than the boiling point of the substrate solution, which gave the catalytic abilities of both high reaction rates and accelerated desorption of the reaction products from the catalyst surface, as evident from the Langmuir-type analysis. In addition, scarcity of substrate in the liquid-film state improved the utilization efficiency of heat by allotting it more to the endothermic reaction rather than to inevitable evaporation. According to our repetitive reaction test with the same catalyst, reproducible activities were confirmed well. The adoption of superheated liquid-film-type catalysis for decalin dehydrogenation would make the reaction couple with naphthalene hydrogenation useful for mobile storage of hydrogen.
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liquid film type catalytic decalin dehydrogeno aromatization for long term storage and long distance transportation of hydrogen
International Journal of Hydrogen Energy, 2003Co-Authors: Shinya Hodoshima, Hiroshi Arai, Yasukazu SaitoAbstract:Abstract A new approach for mobile storage of hydrogen has been proposed with the use of a catalytic reaction pair of decalin dehydrogenation/naphthalene hydrogenation. With the complement of the industrialized naphthalene-hydrogenation catalysis, the other endothermic catalysis for decalin dehydrogenation was now performed at around 200°C with carbon-supported platinum-based catalysts. Under liquid-film conditions, hydrogen was evolved from decalin much more efficiently than the suspended ones due to the superheated states of dehydrogenation catalysts. It was confirmed that the catalytic conversions of decalin dehydrogeno-aromatization in the liquid-film states could surpass easily the equilibrium limit, because the conditions of suppressed reactant evaporation and reactive distillation were operative here. Exergy loss in the hydrogen storage system would be reduced tremendously by adopting this catalyst-assisted decalin/naphthalene pair as the medium of hydrogen carrier.
Masayuki Shirai - One of the best experts on this subject based on the ideXlab platform.
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low temperature hydrogenation of tetralin over supported rhodium catalysts in supercritical carbon dioxide solvent
Applied Catalysis A-general, 2006Co-Authors: Norihito Hiyoshi, Eiichi Mine, Chandrashekhar V Rode, Osamu Sato, Masayuki ShiraiAbstract:Hydrogenation of tetralin was studied over supported rhodium catalysts in supercritical carbon dioxide solvent at 333 K. The results were compared with those in an organic solvent and under neat conditions. Higher cis-decalin yield was obtained in supercritical carbon dioxide solvent than under non-supercritical conditions. It was observed that higher hydrogen concentration at the surface in supercritical carbon dioxide solvent led to fast direct hydrogenation of tetralin to cis-decalin; the flipping of the intermediate, octalin, to give trans-decalin could be prevented.
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Tuning cis-decalin Selectivity in Naphthalene Hydrogenation Over Carbon-supported Rhodium Catalyst Under Supercritical Carbon dioxide
Catalysis Letters, 2006Co-Authors: Norihito Hiyoshi, Chandrashekhar V Rode, Osamu Sato, Tomoya Inoue, Masayuki ShiraiAbstract:Catalytic hydrogenation of naphthalene to decalin was studied over a carbon-supported rhodium catalyst in supercritical carbon dioxide solvent at 333 K, and the results were compared with those in an organic solvent. cis -, trans -Decalin and tetralin were formed from the beginning of the reaction in supercritical carbon dioxide. Higher concentration of hydrogen in carbon dioxide solvent and on the active site, and also the suppression of desorption of partially hydrogenated tetralin molecules from the active site would be responsible for higher selectivity to cis -decalin in supercritical carbon dioxide than that in an organic solvent.
Shinya Hodoshima - One of the best experts on this subject based on the ideXlab platform.
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hydrogen storage by decalin naphthalene pair and hydrogen supply to fuel cells by use of superheated liquid film type catalysis
Applied Catalysis A-general, 2005Co-Authors: Shinya Hodoshima, Atsushi Shono, Shigeki Takaiwa, Kazumi Satoh, Yasukazu SaitoAbstract:Abstract A catalytic reaction pair of decalin dehydrogenation/naphthalene hydrogenation has been proposed as a storage medium for fuel-cell hydrogen in mobile modes. The hydrogen capacities with decalin (7.3 wt.%, 64.8 kg-H 2 m 3 ) are higher than the target values of the Department of Energy, USA (6.5 wt.%, 62.0 kg-H 2 m 3 ). Platinum–rhenium composite catalysts supported on granular activated carbon in “superheated liquid-film” states gave excellent reactivities for decalin dehydrogenation, where the conversion of almost 100% from decalin to naphthalene was attained within 1 h by heating at 280 °C in a batch-wise reactor. “Superheated liquid-film” conditions were also realized in a continuous-type reactor at the same temperature (280 °C). With the goal of maintaining rapid evolution of hydrogen stationarily, a rather wide range of decalin feed rates was allowable with use of platinum particles supported on activated carbon cloth. Decalin should be evaluated as an organic chemical hydride not only because of its storage densities but also because of its potential power densities for fuel-cell vehicles.
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characteristics of decalin dehydrogenation catalysis in the superheated liquid film state for mobile storage of hydrogen
Journal of Chemical Engineering of Japan, 2004Co-Authors: Shinya Hodoshima, Yasukazu SaitoAbstract:Efficient hydrogen evolution from decalin by heating at 210°C and cooling at 5°C was attempted in a batch-wise reactor by the use of “superheated liquid-film-type catalysis”. When the carbon-supported metal catalyst 0.75 g was immersed with decalin 3.0 ml under a reactive distillation conditions, a liquid-film state was realized and the catalytic conversion of decalin was remarkably enhanced in contrast to the ordinary suspended state (e.g., 0.75 g/10 ml). Active sites in the liquid-film state were superheated, being higher in temperatures than the boiling point of the substrate solution, which gave the catalytic abilities of both high reaction rates and accelerated desorption of the reaction products from the catalyst surface, as evident from the Langmuir-type analysis. In addition, scarcity of substrate in the liquid-film state improved the utilization efficiency of heat by allotting it more to the endothermic reaction rather than to inevitable evaporation. According to our repetitive reaction test with the same catalyst, reproducible activities were confirmed well. The adoption of superheated liquid-film-type catalysis for decalin dehydrogenation would make the reaction couple with naphthalene hydrogenation useful for mobile storage of hydrogen.
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liquid film type catalytic decalin dehydrogeno aromatization for long term storage and long distance transportation of hydrogen
International Journal of Hydrogen Energy, 2003Co-Authors: Shinya Hodoshima, Hiroshi Arai, Yasukazu SaitoAbstract:Abstract A new approach for mobile storage of hydrogen has been proposed with the use of a catalytic reaction pair of decalin dehydrogenation/naphthalene hydrogenation. With the complement of the industrialized naphthalene-hydrogenation catalysis, the other endothermic catalysis for decalin dehydrogenation was now performed at around 200°C with carbon-supported platinum-based catalysts. Under liquid-film conditions, hydrogen was evolved from decalin much more efficiently than the suspended ones due to the superheated states of dehydrogenation catalysts. It was confirmed that the catalytic conversions of decalin dehydrogeno-aromatization in the liquid-film states could surpass easily the equilibrium limit, because the conditions of suppressed reactant evaporation and reactive distillation were operative here. Exergy loss in the hydrogen storage system would be reduced tremendously by adopting this catalyst-assisted decalin/naphthalene pair as the medium of hydrogen carrier.
Norihito Hiyoshi - One of the best experts on this subject based on the ideXlab platform.
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low temperature hydrogenation of tetralin over supported rhodium catalysts in supercritical carbon dioxide solvent
Applied Catalysis A-general, 2006Co-Authors: Norihito Hiyoshi, Eiichi Mine, Chandrashekhar V Rode, Osamu Sato, Masayuki ShiraiAbstract:Hydrogenation of tetralin was studied over supported rhodium catalysts in supercritical carbon dioxide solvent at 333 K. The results were compared with those in an organic solvent and under neat conditions. Higher cis-decalin yield was obtained in supercritical carbon dioxide solvent than under non-supercritical conditions. It was observed that higher hydrogen concentration at the surface in supercritical carbon dioxide solvent led to fast direct hydrogenation of tetralin to cis-decalin; the flipping of the intermediate, octalin, to give trans-decalin could be prevented.
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Tuning cis-decalin Selectivity in Naphthalene Hydrogenation Over Carbon-supported Rhodium Catalyst Under Supercritical Carbon dioxide
Catalysis Letters, 2006Co-Authors: Norihito Hiyoshi, Chandrashekhar V Rode, Osamu Sato, Tomoya Inoue, Masayuki ShiraiAbstract:Catalytic hydrogenation of naphthalene to decalin was studied over a carbon-supported rhodium catalyst in supercritical carbon dioxide solvent at 333 K, and the results were compared with those in an organic solvent. cis -, trans -Decalin and tetralin were formed from the beginning of the reaction in supercritical carbon dioxide. Higher concentration of hydrogen in carbon dioxide solvent and on the active site, and also the suppression of desorption of partially hydrogenated tetralin molecules from the active site would be responsible for higher selectivity to cis -decalin in supercritical carbon dioxide than that in an organic solvent.
