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D. D. Clarke - One of the best experts on this subject based on the ideXlab platform.
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diversity and variation in expression of resistance to erysiphe fischeri in Senecio vulgaris
Plant Pathology, 1993Co-Authors: Josie R. Bevan, Ian R. Crute, D. D. ClarkeAbstract:The reactions of 20 inbred lines of Senecio vulgaris (groundsel) to inoculation with up to 10 isolates of Erysiphe fischeri (powdery mildew) were investigated in a number of repeat experiments. There was considerable variation among isolate/plant line reaction phenotypes with examples of both isolate-specific complete resistance and isolate-specific partial resistance. Some plant lines possessed high levels of partial resistance to all isolates tested. Incubation temperature and plant age influenced the infection types of some isolate/plant line combinations. In this pathosystem, complete and partial resistance, together with age-dependent and temperature-dependent resistance, appear to have evolved to facilitate a defence strategy based on a complex mosaic of interacting factors [...]
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Variation for virulence in Erysiphe fischeri from Senecio vulgaris
Plant Pathology, 1993Co-Authors: Josie R. Bevan, Ian R. Crute, D. D. ClarkeAbstract:Variation for virulence was investigated in two populations of Erysiphe fischeri, the cause of powdery mildew of the common annual weed Senecio vulgaris (groundsel). Infection types were recorded on detached leaf segments from 50 inbred lines of S. vulgaris following inoculation with 24 single-conidial-chain isolates of E. fischeri (12 each from two UK sites; one, at Glasgow, located about 480 km north of the other, at Wellesbourne). Mean infection types for each isolate/line combination were categorized by applying several upper limits below which combinations were considered to be incompatible. Regardless of the limit applied, numerous specific virulence and resistance phenotypes could be discriminated. Virulence phenotypes were complex and all isolates were capable of colonizing and reproducing on the majority of groundsel lines. However, all isolates were completely avirulent (no reproduction) on at least one groundsel line, so no isolate was universally virulent. Plants of several groundsel lines exhibiting different resistance phenotypes were exposed to natural infection at Wellesbourne to act as mildew traps, to examine the virulence characteristics of the pathogen population. Common components of the fungus population colonized groundsel lines exhibiting resistance to only a few or none of the single-conidial-chain isolates. Rarer components of the pathogen population colonized groundsel lines with resistance to the majority or all of the isolates previously tested. These latter components of the fungus population also detected resistance in groundsel lines previously recorded as susceptible to all isolates.
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Resistance to Erysiphe fischeri in two populations of Senecio vulgaris
Plant Pathology, 1993Co-Authors: Josie R. Bevan, D. D. Clarke, Ian R. CruteAbstract:The frequency and distribution of different specific phenotypes for resistance to Erysiphe fischeri was studied in two populatoins of the annual weed Senecio vulgaris (groundsel) one located in Glasgow, Scotland the other located about 480 km south at Wellesbourne, England. Progeny of individual plants from the two host populations were tested for their response to up to 10 different isolates of E. fischeri, five from each location; each isolate had a different specific virulence phenotype. Most plants in each sample were susceptible to all 10 isolaes. The proportion of plants whose progeny were resistant to a particular isolate ranged from 1% to 10% with the exception of resistance to one isolate that occurred with a frequency of 37% at Wellesbourne. Overall, resistance to one or more of the 10 isolates appeared to be more common in the plant population sampled at Wellesbourne than at Glasgow. Of the total number of groundsel line/isolate combinations tested, 10% involving Wellesbourne plants and 2% involving Glasgow plants were incompatible, i. e., resistant/avirulent. Both groundsel populations tended to be dominated by one or two resistance phenotypes but they were nevertheless highly heterogeneous when less frequent resistance phenotypes were considered. This was particularly evident at Wellesbourne where 10 different resistance phenotypes were recorded amongst a total of 75 plants growing within an area of 1m 2.
Josie R. Bevan - One of the best experts on this subject based on the ideXlab platform.
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diversity and variation in expression of resistance to erysiphe fischeri in Senecio vulgaris
Plant Pathology, 1993Co-Authors: Josie R. Bevan, Ian R. Crute, D. D. ClarkeAbstract:The reactions of 20 inbred lines of Senecio vulgaris (groundsel) to inoculation with up to 10 isolates of Erysiphe fischeri (powdery mildew) were investigated in a number of repeat experiments. There was considerable variation among isolate/plant line reaction phenotypes with examples of both isolate-specific complete resistance and isolate-specific partial resistance. Some plant lines possessed high levels of partial resistance to all isolates tested. Incubation temperature and plant age influenced the infection types of some isolate/plant line combinations. In this pathosystem, complete and partial resistance, together with age-dependent and temperature-dependent resistance, appear to have evolved to facilitate a defence strategy based on a complex mosaic of interacting factors [...]
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Variation for virulence in Erysiphe fischeri from Senecio vulgaris
Plant Pathology, 1993Co-Authors: Josie R. Bevan, Ian R. Crute, D. D. ClarkeAbstract:Variation for virulence was investigated in two populations of Erysiphe fischeri, the cause of powdery mildew of the common annual weed Senecio vulgaris (groundsel). Infection types were recorded on detached leaf segments from 50 inbred lines of S. vulgaris following inoculation with 24 single-conidial-chain isolates of E. fischeri (12 each from two UK sites; one, at Glasgow, located about 480 km north of the other, at Wellesbourne). Mean infection types for each isolate/line combination were categorized by applying several upper limits below which combinations were considered to be incompatible. Regardless of the limit applied, numerous specific virulence and resistance phenotypes could be discriminated. Virulence phenotypes were complex and all isolates were capable of colonizing and reproducing on the majority of groundsel lines. However, all isolates were completely avirulent (no reproduction) on at least one groundsel line, so no isolate was universally virulent. Plants of several groundsel lines exhibiting different resistance phenotypes were exposed to natural infection at Wellesbourne to act as mildew traps, to examine the virulence characteristics of the pathogen population. Common components of the fungus population colonized groundsel lines exhibiting resistance to only a few or none of the single-conidial-chain isolates. Rarer components of the pathogen population colonized groundsel lines with resistance to the majority or all of the isolates previously tested. These latter components of the fungus population also detected resistance in groundsel lines previously recorded as susceptible to all isolates.
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Resistance to Erysiphe fischeri in two populations of Senecio vulgaris
Plant Pathology, 1993Co-Authors: Josie R. Bevan, D. D. Clarke, Ian R. CruteAbstract:The frequency and distribution of different specific phenotypes for resistance to Erysiphe fischeri was studied in two populatoins of the annual weed Senecio vulgaris (groundsel) one located in Glasgow, Scotland the other located about 480 km south at Wellesbourne, England. Progeny of individual plants from the two host populations were tested for their response to up to 10 different isolates of E. fischeri, five from each location; each isolate had a different specific virulence phenotype. Most plants in each sample were susceptible to all 10 isolaes. The proportion of plants whose progeny were resistant to a particular isolate ranged from 1% to 10% with the exception of resistance to one isolate that occurred with a frequency of 37% at Wellesbourne. Overall, resistance to one or more of the 10 isolates appeared to be more common in the plant population sampled at Wellesbourne than at Glasgow. Of the total number of groundsel line/isolate combinations tested, 10% involving Wellesbourne plants and 2% involving Glasgow plants were incompatible, i. e., resistant/avirulent. Both groundsel populations tended to be dominated by one or two resistance phenotypes but they were nevertheless highly heterogeneous when less frequent resistance phenotypes were considered. This was particularly evident at Wellesbourne where 10 different resistance phenotypes were recorded amongst a total of 75 plants growing within an area of 1m 2.
Thomas Hartmann - One of the best experts on this subject based on the ideXlab platform.
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cloning and expression of homospermidine synthase from Senecio vulgaris a revision
Phytochemistry, 2000Co-Authors: Dietrich Ober, Reiner Harms, Thomas HartmannAbstract:Abstract Homospermidine synthase, which catalyses the first pathway-specific reaction in pyrrolizidine alkaloid biosynthesis, was cloned from root cultures of Senecio vulgaris and expressed in E. coli. The open reading frame encodes a protein of 370 amino acids with a molecular mass of 40,740 Da. The enzyme is strictly dependent on spermidine as aminobutyl donor since it cannot be substituted by putrescine. The homospermidine synthase from S. vulgaris showed 97.9 and 99.3% nucleic acid identity with two HSS sequences from the closely related species Senecio vernalis. This report also revises data from a previous publication (Kaiser, A., 1999. Cloning and expression of a cDNA encoding homospermidine synthase from Senecio vulgaris (Asteraceae) in Escherichia coli. Plant J. 19, 195–201.) that is incorrect.
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effects of rust infection with puccinia lagenophorae on pyrrolizidine alkaloids in Senecio vulgaris
Phytochemistry, 1998Co-Authors: Glenda W Tinney, Claudine Theuring, Nigel D Paul, Thomas HartmannAbstract:The pyrrolizidine alkaloid pattern of Senecio vulgaris, infected with the obligate fungal pathogen Puccinia lagenophorae was analysed quantitatively in comparison to noninfected controls. The fungal infection did not significantly affect the plant's total PA contents and concentrations. In comparison to the controls the fungal-infected plants showed significantly lower PA concentrations in the capitula and roots but not the shoots which contain 90% of total PAs. There was little effect on the PA composition.
Heinz Mullerscharer - One of the best experts on this subject based on the ideXlab platform.
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biological control of Senecio vulgaris in carrots daucus carota with the rust fungus puccinia lagenophorae
Basic and Applied Ecology, 2003Co-Authors: Blair S Grace, Heinz MullerscharerAbstract:Abstract Senecio vulgaris is a troublesome weed in horticulture that is tolerant or resistant to a range of herbicides, and is therefore a candidate for biological control. The rust fungus Puccinia lagenophorae is a potential control agent, but being biotrophic, it is not suitable for use as a mycoherbicide. We tested the effects of induced rust epidemics on S. vulgaris, and investigated the resulting shading dynamics within this system. We sowed carrots at 267 seeds m−2 on five farms in western Switzerland in plots either with or without S. vulgaris seeds (also at 267 seeds m−2, within crop rows), and with or without strong sources of rust spore (four inoculum sources placed every 2 m along crop beds). Plots with S. vulgaris and no inoculum source produced low total carrot yields (18% of yield from S. vulgaris-free plots), whereas plots with S. vulgaris plus rust inoculum sources produced 48% of the yield from S. vulgaris-free plots. There were, however, no significant differences in several commercially important yield parameters such as the number of first grade carrots between S. vulgaris-free plots and those with S. vulgaris plus inoculum sources. Carrots grown with S. vulgaris were smaller and had skewed size distributions compared with the weed-free controls, but adding rust inoculum reduced this effect. This reduced size variability and reduced weed competition have important economic benefits to farmers. Carrots had longer leaves when grown with S. vulgaris, suggesting that carrots and S. vulgaris competed for light. Percent ground cover and height of S. vulgaris relative to carrots was reduced by the presence of rust, and these effects were most obvious one month after placing inoculum sources in the field. Our results are encouraging, even with artificially high weed competition, but further research is needed before this paradigm can be proposed for practical applications. Senecio vulgaris, ein hartnackiges Unkraut im Gartenbau, ist tolerant oder resistent gegenuber mehreren Herbizidgruppen und daher zur biologischen Bekampfung geeignet. Der Rostpilz Puccinia lagenophorae gilt als potentieller Kontrollorganismus, ist aber als biotropher Pilz nicht als Mycoherbizid einsetzbar. Wir untersuchten die Wirkung dieses Rostpilzes auf S. vulgaris durch Induktion und Stimulation einer Epidemie, und analysierten die resultierende Beschattungsdynamik dieses Systems. Wir saten Karotten (Daucus carota) in einer Dichte von 267 m−2 (100 m−1) auf funf Betrieben in der Westschweiz in Parzellen mit und ohne zusatzliche S. vulgaris Samen (ebenfalls 267 m −2 in den Karottenreihen), und mit oder ohne Rostpilzinokulum (je vier Inokulumpflanzen alle 2 m uber die gesamte Parzellenlange). Parzellen mit S. vulgaris und ohne Rostpilzinokulum ergaben einen geringen Karottenertrag (18% des Ertrages der Unkraut-freien Parzellen), wahrend Parzellen mit S. vulgaris und Rostinokulum 48% des Unkraut-freien Ertrages erzielten. In einigen wirtschaftlich wichtigen Ertragsparametern wie Anzahl Karotten erster Qualitat bestanden jedoch keine signifikanten Unterschiede zwischen den Unkraut-freien und denjenigen mit S. vulgaris und Inokulum. Karotten, die mit Unkraut wuchsen, waren kleiner und hatten eine schiefe Grosenverteilung im Vergleich zu den Unkraut-freien Kontrollen, und die Zugabe des Pilzes reduzierte diesen Effekt. Diese reduzierte Heterogenitat und geringere Unkrautkonkurrenz bedeuten einen wichtigen wirtschaftlichen Nutzen fur den Produzenten. Karotten, die in Konkurrenz mit dem Unkraut wuchsen, hatten langere Blatter, was auf Lichtkonkurrenz zwischen Karotten und S. vulgaris hindeutet. Die Anwesenheit des Rostpilzes reduzierte die relative Bodendeckung und Hohe von S. vulgaris im Vergleich zu Karotten, und dieser Unterschied war einen Monat nach dem Transfer der Inokulumspflanzen ins Feld am grobten. Unsere Resultate sind trotz des applizierten, kunstlich hohen Unkrautdruckes ermutigend, weitere Forschung ist jedoch notwendig, bevor dieses Konzept zur Einfuhrung in die Praxis vorgeschlagen werden kann.
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adaptation of Senecio vulgaris asteraceae to ruderal and agricultural habitats
American Journal of Botany, 2001Co-Authors: Kirsten A Leiss, Heinz MullerscharerAbstract:Adaptation of the annual plant Senecio vulgaris to ruderal and agricultural habitats was investigated. We expected S. vulgaris to be adapted to the agricultural habitat through nutrient-specific differentiation of relatively few genotypes responding to the generally high homogenous nutrient levels at the agricultural habitat caused by constant fertilization. To assess adaptation of S. vulgaris, vegetative and reproductive responses of seed families from various populations of agricultural and ruderal habitats, grown in the greenhouse at high and low nutrient levels, were compared. Data were analyzed with a three-level nested ANOVA based on the levels habitat, population, and family. A significant habitat effect indicated that S. vulgaris from ruderal and agricultural habitats were genetically different with plants from the agricultural habitat having larger leaves and a higher reproduction. A significant habitat by nutrient effect showed a stronger response of reproduction to nutrients at the agricultural habitat, suggesting that genetic differentiation among habitats is nutrient-specific. Contrary to expectations, only the agricultural habitat showed genetic diversity of S. vulgaris. Results suggest that nutrient levels at the agricultural habitat are more heterogeneous as generally proposed leading to a relatively high genetic variation.
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infection process and resistance in the weed pathosystem Senecio vulgaris puccinia lagenophorae and implications for biological control
Botany, 1999Co-Authors: Gabriela S Wyss, Heinz MullerscharerAbstract:The infection process and the level and type of resistance in the pathosystem of a native weed and a naturalized rust fungus, Senecio vulgaris L. - Puccinia lagenophorae Cooke, were examined. Four inbred plant lines from Switzerland (2), The Netherlands, and the United Kingdom, each at two stages of devolpment, were exposed to corresponding rust lines under controlled conditions. Fluorescence and light microscopy were used to assess the infection process and to quantify genotype effects. Component analysis was used to partition disease development and define the infection process. Germinating aeciospores of P. lagenophorae showed all the characteristics of the monokaryotic parasitic stage of rust infection with direct penetration and monokaryotic haustoria formation. Haustoria formed between 3 and 6 days after inoculation at low frequency. The highest level of resistance, for which differences between plant lines were detected, occurred at penetration peg formation. All the studied host-pathogen interacti...
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epidemic spread of the rust fungus puccinia lagenophorae and its impact on the competitive ability of Senecio vulgaris in celeriac during early development
Biocontrol Science and Technology, 1998Co-Authors: Heinz Mullerscharer, Stephanie RiegerAbstract:The 'system management approach' of biological weed control was applied in a small-scale field experiment with celeriac (root celery), intersown with an inbred line of the annual weed Senecio vulgaris L. The naturalized rust fungus Puccinia lagenophorae Cooke (Basidiomycetes: Uredinales), a common and widespread pathogen of S. vulgaris in Europe, was introduced into parts of the plots, and its impact on the competitive balance between the crop and weed in the presence and absence of an additional herbicide treatment was studied. Competition by S. vulgaris (at a realized density of only 50 plants/m2) during the first 10 weeks of growth was substantial, reducing the fresh weight of the celeriac bulbs by 28%. The epidemic spread of the rust fungus was relatively fast, and the time to infection was similar to that in full-area applications. Inoculation with the rust fungus strongly reduced crop losses due to competition with S. vulgaris . The fresh weight of the celeriac bulbs in plots with both S. vulgaris a...
Ian R. Crute - One of the best experts on this subject based on the ideXlab platform.
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diversity and variation in expression of resistance to erysiphe fischeri in Senecio vulgaris
Plant Pathology, 1993Co-Authors: Josie R. Bevan, Ian R. Crute, D. D. ClarkeAbstract:The reactions of 20 inbred lines of Senecio vulgaris (groundsel) to inoculation with up to 10 isolates of Erysiphe fischeri (powdery mildew) were investigated in a number of repeat experiments. There was considerable variation among isolate/plant line reaction phenotypes with examples of both isolate-specific complete resistance and isolate-specific partial resistance. Some plant lines possessed high levels of partial resistance to all isolates tested. Incubation temperature and plant age influenced the infection types of some isolate/plant line combinations. In this pathosystem, complete and partial resistance, together with age-dependent and temperature-dependent resistance, appear to have evolved to facilitate a defence strategy based on a complex mosaic of interacting factors [...]
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Variation for virulence in Erysiphe fischeri from Senecio vulgaris
Plant Pathology, 1993Co-Authors: Josie R. Bevan, Ian R. Crute, D. D. ClarkeAbstract:Variation for virulence was investigated in two populations of Erysiphe fischeri, the cause of powdery mildew of the common annual weed Senecio vulgaris (groundsel). Infection types were recorded on detached leaf segments from 50 inbred lines of S. vulgaris following inoculation with 24 single-conidial-chain isolates of E. fischeri (12 each from two UK sites; one, at Glasgow, located about 480 km north of the other, at Wellesbourne). Mean infection types for each isolate/line combination were categorized by applying several upper limits below which combinations were considered to be incompatible. Regardless of the limit applied, numerous specific virulence and resistance phenotypes could be discriminated. Virulence phenotypes were complex and all isolates were capable of colonizing and reproducing on the majority of groundsel lines. However, all isolates were completely avirulent (no reproduction) on at least one groundsel line, so no isolate was universally virulent. Plants of several groundsel lines exhibiting different resistance phenotypes were exposed to natural infection at Wellesbourne to act as mildew traps, to examine the virulence characteristics of the pathogen population. Common components of the fungus population colonized groundsel lines exhibiting resistance to only a few or none of the single-conidial-chain isolates. Rarer components of the pathogen population colonized groundsel lines with resistance to the majority or all of the isolates previously tested. These latter components of the fungus population also detected resistance in groundsel lines previously recorded as susceptible to all isolates.
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Resistance to Erysiphe fischeri in two populations of Senecio vulgaris
Plant Pathology, 1993Co-Authors: Josie R. Bevan, D. D. Clarke, Ian R. CruteAbstract:The frequency and distribution of different specific phenotypes for resistance to Erysiphe fischeri was studied in two populatoins of the annual weed Senecio vulgaris (groundsel) one located in Glasgow, Scotland the other located about 480 km south at Wellesbourne, England. Progeny of individual plants from the two host populations were tested for their response to up to 10 different isolates of E. fischeri, five from each location; each isolate had a different specific virulence phenotype. Most plants in each sample were susceptible to all 10 isolaes. The proportion of plants whose progeny were resistant to a particular isolate ranged from 1% to 10% with the exception of resistance to one isolate that occurred with a frequency of 37% at Wellesbourne. Overall, resistance to one or more of the 10 isolates appeared to be more common in the plant population sampled at Wellesbourne than at Glasgow. Of the total number of groundsel line/isolate combinations tested, 10% involving Wellesbourne plants and 2% involving Glasgow plants were incompatible, i. e., resistant/avirulent. Both groundsel populations tended to be dominated by one or two resistance phenotypes but they were nevertheless highly heterogeneous when less frequent resistance phenotypes were considered. This was particularly evident at Wellesbourne where 10 different resistance phenotypes were recorded amongst a total of 75 plants growing within an area of 1m 2.
