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P G Ayres - One of the best experts on this subject based on the ideXlab platform.
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invasion of rust puccinia lagenophorae aecia on Groundsel senecio vulgaris by secondary pathogens death of the host
Fungal Biology, 1992Co-Authors: Steven G. Hallett, P G AyresAbstract:Inoculation of Groundsel (Senecio vulgaris) bearing aecia of the rust Puccinia lagenophorae with isolates of a range of other fungi isolated from naturally occurring rust lesions induced rapidly spreading necrosis and death of the host. In a controlled laboratory environment, the rate of symptom development varied with isolate and species. Death of 50% of plants occurred as soon as 18 d after inoculation with an isolate of Pythium intermedium and as late as 37 d after inoculation with an isolate of Fusarium avenaceum. Three of the eleven species tested caused neither necrosis nor death. In the field in autumn, isolates representing five species that killed Groundsel in the laboratory again caused death of the host, though more slowly than in the laboratory, while a representative of the non-lethal group again had no visible effect on the host (...)
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botrytis cinerea kills Groundsel senecio vulgaris infected by rust puccinia lagenophorae
New Phytologist, 1990Co-Authors: Steven G. Hallett, Nigel D Paul, P G AyresAbstract:Inoculation of healthy Groundsel (Senecio vulgaris L.) with Botrytis cinerea Pers at 1.24 × 106conidia ml −1 caused 10% mortality, and only 40%, mortality when plants were abiotically wounded before inoculation. However, all plants previously infected by rust (Puccinia lagenophorae Cooke) died after inoculation with B. cinerea. Mortality was most rapid it plants were inoculated with B. cinerea as rust colonies first erupted through the host's epidermis. A reduction in the concentration of conidial inoculum increased time to death, and concentrations below 015 × 103 conidia ml−1 failed to cause 100 % mortality within the 32 d of the experiment. Death of plants was associated with the growth of B. cinerea into stem bases; a reduction in the density of rust lesions on leaves had no effect on the time from inoculation to the appearance of foliar symptoms, but increased time-to-kill. There was little variation m virulence between isolates of B. cinerea made from different Groundsel or ragwort (Senecio jacobaea L.) populations. Similar interactions between biotrophic fungi and opportunistic pathogens have occasionally been noted previously; their importance in natural vegetation processes and possible relevance to the biocontrol of weeds is discussed.
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.
Steven G. Hallett - One of the best experts on this subject based on the ideXlab platform.
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Mycoherbicides and other biocontrol agents for Senecio spp
Pesticide Science, 2006Co-Authors: Nigel D Paul, Peter G. Ayres, Steven G. HallettAbstract:Classical biocontrol of Senecio jacobaea (ragwort) has generally utilised herbivorous insects, although the nisi Puccinia expansa has also been considered. Although this rust is specific and damaging in the glasshouse. It has not been used in the field. Research into the ecophysiology of Senecio vulgaris (Groundsel) infected by the rust Puccinia lagenophorae has revealed the extent to which the effects of infection are dependent on environmental factors. The damage caused by rust is enhanced under mild drought conditions, during periods of frost in winter and by competition between Groundsel and neighbouring plants, bui is reduced by nutrient deficiency. Rust injury is also greatly increased by secondary infection of pustules by necrotrophic fungi. Such secondary infection can be achieved artificially with a range of opportunistic necrolrophs and can selectively kill Groundsel: the effective inoculum dose of both fungi is significantly reduced. Attempts to apply our understanding of rust-necrotroph injury to ragwort have been partially successful but we have not succeeded in causing significant mortality of this host.
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invasion of rust puccinia lagenophorae aecia on Groundsel senecio vulgaris by secondary pathogens death of the host
Fungal Biology, 1992Co-Authors: Steven G. Hallett, P G AyresAbstract:Inoculation of Groundsel (Senecio vulgaris) bearing aecia of the rust Puccinia lagenophorae with isolates of a range of other fungi isolated from naturally occurring rust lesions induced rapidly spreading necrosis and death of the host. In a controlled laboratory environment, the rate of symptom development varied with isolate and species. Death of 50% of plants occurred as soon as 18 d after inoculation with an isolate of Pythium intermedium and as late as 37 d after inoculation with an isolate of Fusarium avenaceum. Three of the eleven species tested caused neither necrosis nor death. In the field in autumn, isolates representing five species that killed Groundsel in the laboratory again caused death of the host, though more slowly than in the laboratory, while a representative of the non-lethal group again had no visible effect on the host (...)
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botrytis cinerea kills Groundsel senecio vulgaris infected by rust puccinia lagenophorae
New Phytologist, 1990Co-Authors: Steven G. Hallett, Nigel D Paul, P G AyresAbstract:Inoculation of healthy Groundsel (Senecio vulgaris L.) with Botrytis cinerea Pers at 1.24 × 106conidia ml −1 caused 10% mortality, and only 40%, mortality when plants were abiotically wounded before inoculation. However, all plants previously infected by rust (Puccinia lagenophorae Cooke) died after inoculation with B. cinerea. Mortality was most rapid it plants were inoculated with B. cinerea as rust colonies first erupted through the host's epidermis. A reduction in the concentration of conidial inoculum increased time to death, and concentrations below 015 × 103 conidia ml−1 failed to cause 100 % mortality within the 32 d of the experiment. Death of plants was associated with the growth of B. cinerea into stem bases; a reduction in the density of rust lesions on leaves had no effect on the time from inoculation to the appearance of foliar symptoms, but increased time-to-kill. There was little variation m virulence between isolates of B. cinerea made from different Groundsel or ragwort (Senecio jacobaea L.) populations. Similar interactions between biotrophic fungi and opportunistic pathogens have occasionally been noted previously; their importance in natural vegetation processes and possible relevance to the biocontrol of weeds is discussed.
R Abbott - One of the best experts on this subject based on the ideXlab platform.
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routes of origin of two recently evolved hybrid taxa senecio vulgaris var hibernicus and york radiate Groundsel asteraceae
American Journal of Botany, 2000Co-Authors: Andrew J Lowe, R AbbottAbstract:The possible pathways of origin of two recently arisen introgressant forms of Senecio vulgaris (i.e., var. hibernicus and York radiate Groundsel) were investigated in experimental crosses between tetraploid S. vulgaris var. vulgaris and the normally diploid S. squalidus. Comparison of the morphology of synthesized hybrid progeny with established taxa, by discriminant function analysis, revealed that fertile hybrid offspring similar in morphology to S. vulgaris var. hibernicus and York radiate Groundsel could be synthesized: (1) following formation of genomically stable diploid gametes by the triploid hybrid; (2) through the production of unreduced gametes by diploid S. squalidus; and (3) when a tetraploid form of S. squalidus acted as one of the parents. It was evident that hybrid offspring similar in morphology to the two introgressant taxa were more often produced in backcrosses to S. vulgaris than in segregating F2 or F3 generations (53% as opposed to 36%), and that fertile hybrid progeny were formed within two generations. Because hybridization between S. vulgaris and S. squalidus occurs regularly, although at very low frequency, in natural mixed populations in the British Isles, there is the potential for multiple origins to occur in the wild of both S. vulgaris var. hibernicus and York radiate Groundsel.
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introgressive origin of the radiate Groundsel senecio vulgaris l var hibernicus syme aat 3 evidence
Heredity, 1992Co-Authors: R Abbott, Paul A Ashton, David G ForbesAbstract:A survey of allelic variation at the Aat-3 locus in Senecio squalidus and S. vulgaris revealed that the Aat-3c allele, which was present at high frequency in British populations of S. squalidus, was also common in British radiate Groundsel (S. vulgaris var. hibernicus) but was rare among individuals of the non-radiate Groundsel (S. vulgaris var. vulgaris) which co-occurred with var. hibernicus and was absent from British, Irish and mainland European populations monomorphic for var. vulgaris. This evidence is taken as confirmation of an introgressive origin of S. vulgaris var. hibernicus across a chromosome barrier following hybridization between S. vulgaris var. vulgaris (2n = 40) and radiate S. squalidus (2n = 20) and backcrossing to S. vulgaris var. vulgaris. Genetic analysis showed that the Aat-3 locus, which is duplicated in S. vulgaris is not linked to the ray floret locus controlling capitulum type. It is suggested that the close association between the Aat-3c allele and the radiate allele in populations of S. vulgaris polymorphic for capitulum type may be maintained by selection favouring a co-adapted complex of genes introgressed from S. squalidus, although alternative explanations are not ruled out. The introgression of the Aat-3c allele and associated genetic material from S. squalidus into S. vulgaris is likely to have enhanced the level of genetic variation present within S. vulgaris and may have been a factor that has favoured the spread of S. vulgaris var. hibernicus in Britain following its origin last century.
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.
