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J M Clarkson - One of the best experts on this subject based on the ideXlab platform.
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development of a pcr based diagnostic test for Spongospora subterranea f sp nasturtii the causal agent of crook root of watercress rorippa nasturtium aquaticum
Plant Pathology, 2002Co-Authors: G J Down, J M ClarksonAbstract:The polymerase chain reaction (PCR) technique was utilized to obtain internal transcribed spacer ribosomal DNA (ITS rDNA) and small-subunit (18S) rDNA sequences from UK isolates of Spongospora subterranea f.sp. nasturtii, a plasmodiophorid pathogen of watercress (Rorippa nasturtium-aquaticum). ITS sequence data obtained from S. subterranea isolated from a range of UK sites were found to be identical. PCR primers were designed using these sequences and were shown to be capable of specific amplification of S. subterranea f.sp. nasturtii DNA from plant tissue and from water samples containing zoospores of the pathogen. As little as 5 ng total genomic DNA from infected plant material, or 1000 zoospores, was required for consistently successful amplification of DNA. A filtration-based method for obtaining pathogen DNA for PCR from watercress-bed water was developed.
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Development of a PCR‐based diagnostic test for Spongospora subterranea f.sp. nasturtii, the causal agent of crook root of watercress (Rorippa nasturtium‐aquaticum)
Plant Pathology, 2002Co-Authors: G J Down, J M ClarksonAbstract:The polymerase chain reaction (PCR) technique was utilized to obtain internal transcribed spacer ribosomal DNA (ITS rDNA) and small-subunit (18S) rDNA sequences from UK isolates of Spongospora subterranea f.sp. nasturtii, a plasmodiophorid pathogen of watercress (Rorippa nasturtium-aquaticum). ITS sequence data obtained from S. subterranea isolated from a range of UK sites were found to be identical. PCR primers were designed using these sequences and were shown to be capable of specific amplification of S. subterranea f.sp. nasturtii DNA from plant tissue and from water samples containing zoospores of the pathogen. As little as 5 ng total genomic DNA from infected plant material, or 1000 zoospores, was required for consistently successful amplification of DNA. A filtration-based method for obtaining pathogen DNA for PCR from watercress-bed water was developed.
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The regeneration and screening of watercress somaclones for resistance to Spongospora subterranea f. sp. nasturtii and measurement of somaclonal variation
Plant Cell Tissue and Organ Culture, 1998Co-Authors: J R Claxton, J M Clarkson, D. L. Arnold, D BlakesleyAbstract:A range of watercress (Rorippa nasturtium-aquaticum) explants (stems, hypocotyls, true-leaves, cotyledons and petioles) were tested for their capacity to regenerate adventitious shoots from callus formed using Murashige and Skoog medium containing different concentrations of thidiazuron and 2,4-dichlorophenoxyacetic acid. The highest shoot regeneration rate was a mean of 18 shoots per responding explant from stem callus formed on medium containing 5 μM thidiazuron and 0.05 μM 2,4-dichlorophenoxyacetic acid. A histological study confirmed that shoots originated directly from callus tissue. Twenty five percent of somaclones exhibited somaclonal variation in leaf shape, plant height, axillary branching or ploidy. The variation in 6% of somaclones was heritable to the first selfed generation. A screening protocol was developed to permit the identification of somaclones with increased resistance to the economically damaging watercress root pathogen, Spongospora subterranea f. sp. nasturtii. Although 883 somaclones were screened using this protocol, no significant increase in disease resistance was detected.
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an ultrastructural study of the interaction between Spongospora subterranea f sp nasturtii and watercress roots
Fungal Biology, 1996Co-Authors: J R Claxton, Ursula Potter, D Blakesley, J M ClarksonAbstract:The early stages (up to 72 h) of the infection cycle of Spongospora subterranea f. sp. nasturtii were investigated. Within 48 h, zoospores encysted on roots and produced adhesoria, the cyst wall which formed during zoospore encystment underwent changes in morphology. Cysts contained a dense-staining bullet-like stachel which may be involved in host penetration, this was contained within a long striated tube, the rohr. By 72 h, intracellular uninucleate myxamoebae were observed which apparently engulfed host cell contents with pseudopodia to form ingestion vacuoles. Cell to cell movement of myxamoebae, by host wall penetration appeared to be mediated by enzymic degradation.
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the effects of temperature on zoospores of the crook root fungus Spongospora subterranea f sp nasturtii
Plant Pathology, 1995Co-Authors: J R Claxton, D Blakesley, D. L. Arnold, J M ClarksonAbstract:The effect of temperature on the release, survival, encystment and infectivity of Spongospora subterranea f.sp. nasturtii zoospores released from diseased watercress roots was studied. There was rapid, synchronized release of zoospores at 20°C followed by a steep decline in zoospore numbers. A similar trend occurred at 10° C and 15° C, although fewer zoospores were released and the subsequent decline was more gradual. In contrast, at 5°C very low numbers of zoospores were released over the first 5 days. Subsequently, zoospore release increased rapidly over the following 3 days and zoospore numbers were maintained at relatively high levels for a further 6 days. This duration of high zoospore numbers at 5°C was due to prolonged survival rather than continual release. When a uniform zoospore suspension released at IOC was transferred to 20·C zoospore numbers were found to decline rapidly over 6 days; the decline was less rapid at 15° C and IOC, taking 9 and 15 days, respectively. At 5°C zoospore numbers decreased slowly. Few zoospores encysted on roots at 20° C but increased numbers were found at 15°C and 10°C. There were significantly more diseased roots at 10° C than at 5,15 or 20° C. The lowest number of diseased roots was found at 20° C. The correlation between increased seventy of the disease in the field during the winter months and the effect of temperature on zoospores of S. subterranea f.sp. nasturtii is discussed.
U. Merz - One of the best experts on this subject based on the ideXlab platform.
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root infection of potato by Spongospora subterranea knowledge review and evidence for decreased plant productivity
Plant Pathology, 2016Co-Authors: U. Merz, Richard E Falloon, R C Butler, D Curtin, R A Lister, Steve ThomasAbstract:Information is reviewed on root infection of potato by the plasmodiophorid Spongospora subterranea f. sp. subterranea. This pathogen has long been recognized as the cause of root galls (hyperplasia) and the economically important disease powdery scab on tubers (modified stolons). The significance for plant productivity of the zoosporangium stages of the pathogen in potato roots has only recently begun to be documented. Two experiments are described that assessed effects of S. subterranea root infection on potato plant root function and productivity. A greenhouse experiment measured root function and plant parameters for eight potato cultivars with markedly different susceptibilities to tuber powdery scab. Water uptake and plant growth were reduced by S. subterranea inoculation in all eight cultivars. The magnitudes of these negative effects, and intensities of root hyperplasia, differed among the cultivars, but were not related to respective susceptibilities to tuber powdery scab. A field trial assessed root function and plant productivity for a cultivar (Iwa) that is very susceptible to Spongospora tuber and root diseases. Soil water content beneath uninoculated plants was consistently less than for inoculated plants, indicating that inoculation reduced water uptake (root function). Inoculation reduced shoot and root dry weights, and reduced weight of tubers per plant by 42%. Spongospora subterranea causes three diseases of potato: root membrane dysfunction, root hyperplasia and tuber powdery scab. The root diseases caused by the pathogen are likely to be important both for powdery scab management and for deleterious effects on potato crop yields.
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infection risk potential of south american Spongospora subterranea f sp subterranea root gall and tuber lesion inoculum on potato solanum tuberosum ssp tuberosum
American Journal of Potato Research, 2015Co-Authors: U. Merz, Richard E FalloonAbstract:Spongospora subterranea f. sp. subterranea causes the potato diseases powdery scab on tubers and galls on roots, and occurs in most potato production areas worldwide. The pathogen was probably introduced to Europe from South America in the 16th century. Three different genotype clusters have been found worldwide: the genetically variable groups from South America (native), and, in contrast, the nearly clonal group outside South America (invasive). An inoculation experiment was carried out with the long-day potato host ‘Agria’ comparing three different native Spongospora resting spore inocula with an invasive one, to determine the infection risk potential on a widely grown potato subspecies. All inocula led to root infection. Invasive tuber lesion sporosori from ‘Agria’ produced the greatest amount of infection, whereas the tuber lesion inoculum from the Venezuelan S. tuberosum ssp. tuberosum host and the root gall inoculum from the Colombian S. phureja host caused the least infections. The inoculum genotypes corresponded to all of the three previously described groups. Most root galls showed the invasive group type, independent of the inoculum. These results suggest that the most successful invasive genotype is still present in native pathogen populations and emphasize the need for continued quarantine vigilance to prevent new virulent recombinants of the pathogen.
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global genetics and invasion history of the potato powdery scab pathogen Spongospora subterranea f sp subterranea
PLOS ONE, 2013Co-Authors: U. Merz, Richard E Falloon, Patrick C BrunnerAbstract:Spongospora subterranea f. sp. subterranea (Sss) causes two diseases on potato (Solanum tuberosum), lesions on tubers and galls on roots, which are economically important worldwide. Knowledge of global genetic diversity and population structure of pathogens is essential for disease management including resistance breeding. A combination of microsatellite and DNA sequence data was used to investigate the structure and invasion history of Sss. South American populations (four countries, 132 samples) were consistently more diverse than those from all other regions (15 countries, 566 samples), in agreement with the hypothesis that Sss originated in South America where potato was domesticated. A substantial genetic differenciation was found between root and tuber-derived samples from South America. Estimates of past and recent gene flow suggested that Sss was probably introduced from South America into Europe. Subsequently, Europe is likely to have been the recent source of migrants of the pathogen, acting as a “bridgehead” for further global dissemination. Quarantine measures must continue to be focussed on maintaining low global genetic diversity and avoiding exchange of genetic material between the native and introduced regions. Nevertheless, the current low global genetic diversity of Sss allows potato breeders to select for resistance, which is likely to be durable.
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first confirmed report of powdery scab caused by Spongospora subterranea f sp subterranea on potato in sri lanka
Plant Disease, 2011Co-Authors: A G C Babu, U. MerzAbstract:White, wart-like outgrowths on roots and stolons – root galls – and blisters and pustules on tubers (lesions) are characteristic symptoms of the potato powdery scab disease caused by Spongospora subterranea (Wallr.) f. sp. subterranea. In Sri Lanka, potato is a major cash crop primarily in two agroecological zones of higher altitude, Nuwara Eliya and Badulla. Approximately 50% of the seed is produced nationally and the other half is imported from the Netherlands, France, Germany, and recently the United States (mainly high quality seed). During the 2002–2003 cultivation season, galls and lesions were observed on certified seed lots of potato cvs. Dura, Desiree, Roko, Cykoda, and Delawae imported from the Netherlands and planted in fields at the Seed Certification Service, Site Eliya near Nuwara Eliya, SriLanka after first inspection. Since then, similar symptoms were also observed on tubers and roots of cv. Granola at seed potato production sites in 2006 at Diagama, in 2007 at Bopathalawa, and in 2007 thr...
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evaluation of the sss agristrip rapid diagnostic test for the detection of Spongospora subterranea on potato tubers
European Journal of Plant Pathology, 2011Co-Authors: K Bouchekmechiche, Francoise Montfort, U. MerzAbstract:Spongospora subterranea, f.sp. subterranea (Sss), which causes powdery scab, is mainly spread through infected seed tubers and survives in contaminated soil for many years. The visual assessment of tuber lots by inspectors carries the risk of misidentification due to the difficulty of distinguishing lesions caused by either Sss or Streptomyces spp.. To avoid this, the “Sss AgriStrip”, a rapid and lab-independent test tool based on a lateral flow immunoassay has been developed, and we assessed its accuracy and sensitivity for detecting Sss. The Sss AgriStrip performed as well as other lab-based identification methods. The Sss AgriStrip, microscopy, ELISA, PCR, and real-time PCR techniques identified infection with S. subterranea in all tubers with typical powdery scab lesions. When lots with tubers showing a mixture of typical and atypical (suspicious) symptoms were tested, the presence of S. subterranea was confirmed in all lesions by all methods. The DNA content was generally lower in atypical than in typical lesions. Diverse and suspicious symptoms, which were difficult to assign to either powdery or common scab, tested negative with Sss AgriStrip and the other methods. This was despite microscopic observation of sporosori-like structures in some samples. Isolation and molecular identification confirmed that these lesions were mostly caused by Streptomyces spp. The Sss AgriStrip is as sensitive as DAS-ELISA with a detection limit between 1 and 10 sporosori per ml buffer. It is ideal for rapid and selective detection of Sss on farms and border inspection points to prevent spread of the pathogen.
Richard E Falloon - One of the best experts on this subject based on the ideXlab platform.
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root infection of potato by Spongospora subterranea knowledge review and evidence for decreased plant productivity
Plant Pathology, 2016Co-Authors: U. Merz, Richard E Falloon, R C Butler, D Curtin, R A Lister, Steve ThomasAbstract:Information is reviewed on root infection of potato by the plasmodiophorid Spongospora subterranea f. sp. subterranea. This pathogen has long been recognized as the cause of root galls (hyperplasia) and the economically important disease powdery scab on tubers (modified stolons). The significance for plant productivity of the zoosporangium stages of the pathogen in potato roots has only recently begun to be documented. Two experiments are described that assessed effects of S. subterranea root infection on potato plant root function and productivity. A greenhouse experiment measured root function and plant parameters for eight potato cultivars with markedly different susceptibilities to tuber powdery scab. Water uptake and plant growth were reduced by S. subterranea inoculation in all eight cultivars. The magnitudes of these negative effects, and intensities of root hyperplasia, differed among the cultivars, but were not related to respective susceptibilities to tuber powdery scab. A field trial assessed root function and plant productivity for a cultivar (Iwa) that is very susceptible to Spongospora tuber and root diseases. Soil water content beneath uninoculated plants was consistently less than for inoculated plants, indicating that inoculation reduced water uptake (root function). Inoculation reduced shoot and root dry weights, and reduced weight of tubers per plant by 42%. Spongospora subterranea causes three diseases of potato: root membrane dysfunction, root hyperplasia and tuber powdery scab. The root diseases caused by the pathogen are likely to be important both for powdery scab management and for deleterious effects on potato crop yields.
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resistance to Spongospora subterranea induced in potato by the elicitor β aminobutyric acid
Australasian Plant Pathology, 2015Co-Authors: R C Butler, Richard E Falloon, Loreto Hernandez M Maldonado, A J Conner, Simon BulmanAbstract:Induction of resistance in potato to Spongospora subterranea (which causes powdery scab on tubers) was studied in two controlled glasshouse experiments. β-aminobutyric acid (BABA) was applied at different concentrations (1, 2 or 4 mM) to potato plants which were then inoculated with S. subterranea. Amounts of the pathogen in roots and intensity of Spongospora root galling were assessed. Infection was measured at different times during plant growth, at 3 or 6 weeks after inoculation (first experiment), and 2, 4 or 6 weeks after inoculation (second experiment). In the first experiment, growth of plants was reduced in proportion to the BABA application rate, and the plants had high levels of S. subterranea infection. In the second experiment, at 4 weeks after inoculation, plants treated with BABA had less S. subterranea in their roots and fewer root galls compared with non-treated plants. Six weeks after inoculation, plants treated with 1 mM BABA developed S. subterranea infection, almost to the level of non-treated plants. In contrast, 2 and 4 mM BABA treatments greatly reduced the amount of S. subterranea in roots and numbers of root galls compared with non-treated plants. Repeated applications (at 2 weeks intervals) increased the effectiveness of BABA. A third test indicated that BABA was not directly toxic to S. subterranea resting spores. These results demonstrate that chemically induced resistance reduces host root infection by S. subterranea, and may have disease management potential. This is the first report of chemically induced host resistance to Spongospora.
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infection risk potential of south american Spongospora subterranea f sp subterranea root gall and tuber lesion inoculum on potato solanum tuberosum ssp tuberosum
American Journal of Potato Research, 2015Co-Authors: U. Merz, Richard E FalloonAbstract:Spongospora subterranea f. sp. subterranea causes the potato diseases powdery scab on tubers and galls on roots, and occurs in most potato production areas worldwide. The pathogen was probably introduced to Europe from South America in the 16th century. Three different genotype clusters have been found worldwide: the genetically variable groups from South America (native), and, in contrast, the nearly clonal group outside South America (invasive). An inoculation experiment was carried out with the long-day potato host ‘Agria’ comparing three different native Spongospora resting spore inocula with an invasive one, to determine the infection risk potential on a widely grown potato subspecies. All inocula led to root infection. Invasive tuber lesion sporosori from ‘Agria’ produced the greatest amount of infection, whereas the tuber lesion inoculum from the Venezuelan S. tuberosum ssp. tuberosum host and the root gall inoculum from the Colombian S. phureja host caused the least infections. The inoculum genotypes corresponded to all of the three previously described groups. Most root galls showed the invasive group type, independent of the inoculum. These results suggest that the most successful invasive genotype is still present in native pathogen populations and emphasize the need for continued quarantine vigilance to prevent new virulent recombinants of the pathogen.
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agronomic factors affect powdery scab of potato and amounts of Spongospora subterranea dna in soil
Australasian Plant Pathology, 2014Co-Authors: Farhat A. Shah, Richard E Falloon, R C Butler, R A Lister, Steve Thomas, D CurtinAbstract:Severe powdery scab (caused by Spongospora subterranea) occurred in potato tubers harvested from a field trial, which measured effects of agronomic treatments (nitrogen fertiliser rates, irrigation intensities, previous crop rotations) on potato yields. Nitrogen application (400 kg N ha−1) increased weight of tubers per plant by 38 %. Incidence and/or severity of powdery scab were increased by nitrogen applications. Measurements of S. subterranea DNA in soil at harvest generally reflected the severity of powdery scab in harvested tubers. Amounts of DNA were greater after nitrogen application than without nitrogen fertiliser, less after “optimum” irrigation than “low” irrigation, and greater after a potato/wheat rotation than after potato/pea. The field trial area was used for two further growing seasons (without application of treatments) to determine if pre-planting measurements of Spongospora DNA in soil could predict powdery scab in harvested potatoes. The disease generally decreased during the next two growing seasons, and effects of the different agronomic treatments on powdery scab had disappeared by the second season. However, the greater amounts of pathogen DNA in soil in plots where nitrogen had been applied than where no fertiliser was used continued for the two following growing seasons. Relationships between amounts of pre-planting S. subterranea DNA in soil and powdery scab in subsequently harvested tubers were weak in the second growing season, and non-existent in the third. These results demonstrate that agronomic treatments (particularly nitrogen) can increase severity of powdery scab in harvested tubers. Furthermore, pre-planting measurements of pathogen DNA in soil did not give good predictions of the incidence or severity of powdery scab in harvested potatoes.
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Spongospora subterranea root infection assessed in two potato cultivars differing in susceptibility to tuber powdery scab
Plant Pathology, 2013Co-Authors: R C Butler, Richard E Falloon, A J Conner, M Hernandez L Maldonado, Simon BulmanAbstract:Infection by Spongospora subterranea of roots of two potato (Solanum tuberosum) cultivars, either very resistant or very susceptible to powdery scab on their tubers, was studied in a glasshouse experiment. Plants grown in sand/nutrient solution culture were inoculated with S. subterranea sporosori 2 weeks after planting. Plant parameters, the intensity of zoosporangium infection in roots, numbers of Spongospora root galls and amounts of Spongospora DNA in roots, measured using quantitative PCR (qPCR), were assessed at sequential harvests. Inoculation with S. subterranea reduced water use (56 days after planting) by 26% in the tuber resistant cultivar compared with uninoculated plants, and by 60% in the susceptible cultivar. Inoculation did not affect growth of the resistant cultivar, nor shoot mass of the susceptible cultivar, but caused a 38% reduction in root mass of the susceptible cultivar. The intensities of zoosporangium development in both cultivars were similar. The susceptible cultivar had approximately four times more Spongospora root galls g ―1 root mass than the resistant cultivar. Quantitative PCR detected S. subterranea DNA in roots 1 week after inoculation, and indicated a twofold greater amount of pathogen DNA in roots of the susceptible than the resistant cultivar. This study suggests that the S. subterranea zoosporangium stage in host roots is affected differently by host resistance factors than the sporosorus (root gall and tuber scab) stages. The study has also demonstrated the usefulness of qPCR for sensitive and consistent detection of S. subterranea across the duration of potato root infection.
C R Wilson - One of the best experts on this subject based on the ideXlab platform.
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susceptibility of opium poppy and pyrethrum to root infection by Spongospora subterranea
Journal of Phytopathology, 2018Co-Authors: Tamara J Clark, Mark A. Balendres, Robert S. Tegg, Luke A Rockliff, Jonathan Amponsah, Tamilarasan Thangavel, Frank Mulcahy, A Wilson, C R WilsonAbstract:Spongospora subterranea, which causes powdery scab of potato, infects a diverse range of plant species. Crop rotation as a powdery scab management tool will be compromised if pathogen hosts exist between potato crops. Opium poppy (Papaver somniferum) and pyrethrum (Tanacetum cinerariifolium) are important crops within intensive vegetable production rotations in NW Tasmania. Measurements of S. subterranea soil inoculum within a commercial field showed pathogen amounts were substantially elevated following an opium poppy crop, which suggested host status. In glasshouse testing, opium poppy and pyrethrum were confirmed as hosts of S. subterranea, with opium poppy the more susceptible of the two. Both species were less susceptible than tomato, a known host. Observations of early growth suggested inoculation impacts on all three plant species, although at 16 (tomato and opium poppy) or 26 (pyrethrum) weeks postinoculation, only tomato had significantly reduced shoot and root development. The role of rotation crops in inoculum persistence and the possible role of S. subterranea as a minor pathogen of nonpotato crops are discussed.
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zoosporangial root infection of tomato by Spongospora subterranea in hydroponic and glasshouse culture results in diminished plant growth
Journal of Phytopathology, 2018Co-Authors: Mark A. Balendres, Robert S. Tegg, Jonathan Amponsah, C R WilsonAbstract:Tomato plants are highly susceptible to root infection by Spongospora subterranea and are commonly used as bioassay hosts. The impacts of root infection with S. subterranea on plant productivity and yield have been debated. Recent experiments with potato, the major economic host of S. subterranea, have indicated significantly reduced plant growth and potato yield following heavy infection. However, there have been very few similar studies that have examined the possible impacts of S. subterranea infection on tomato plant growth. Three tomato cultivars, "Grape," "Roma" and "Truss," were challenged with S. subterranea inoculum in hydroponic culture. Moderate to severe zoosporangial infections were observed with minor but statistically significant differences in susceptibility among the three tomato cultivars. Zoosporangial root infection in the absence of root gall formation resulted in significantly diminished shoot lengths and plant fresh weights in pathogen challenge tests conducted both in hydroponic culture and glasshouse-grown plants in potting mix. Root lengths were reduced, but the differences were statistically significant in a single trial only. The findings from this study demonstrate that, as with potato, root infection by S. subterranea can result in reduced tomato plant growth and that root gall production associated with root infection was not necessary for this retardation of growth response. This further suggests that possible yield impacts in other crop species that are hosts for S. subterranea root infection are worthy of examination.
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germinate to exterminate chemical stimulation of Spongospora subterranea resting spore germination and its potential to diminish soil inoculum
Plant Pathology, 2018Co-Authors: Mark A. Balendres, Robert S. Tegg, T J Clark, C R WilsonAbstract:Hoagland’s solution (HS), a defined nutrient supplement for plants, has been previously reported to stimulate zoospore release from resting spores of the potato pathogen Spongospora subterranea f. sp. subterranea. This study obtained direct empirical evidence for an increase in zoospore release with HS treatment, and identified Fe-EDTA as the stimulant component of HS. Stimulation of resting spores by HS and Fe-EDTA resulted in greater and earlier zoospore release compared to a distilled water control, and in the presence of a susceptible tomato host plant resulted in enhanced root infection. Given the labile nature of S. subterranea zoospores, it was postulated that stimulation of premature release of zoospores from the dormant resting spores in absence of susceptible hosts could reduce soil inoculum levels. In two glasshouse trials in the absence of host plants, both Fe-EDTA and HS soil treatments reduced S. subterranea soil inoculum levels, providing proof of concept for the ‘germinate to exterminate’ approach to inoculum management.
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resting spore dormancy and infectivity characteristics of the potato powdery scab pathogen Spongospora subterranea
Journal of Phytopathology, 2017Co-Authors: Mark A. Balendres, Robert S. Tegg, C R WilsonAbstract:The soil-borne potato pathogen Spongospora subterranea persists in soil as sporosori, which are aggregates of resting spores. Resting spores may germinate in the presence of plant or environmental stimuli, but direct evidence for resting spore dormancy is limited. A soilless tomato bait plant bioassay and microscopic examination were used to examine features of S. subterranea resting spore dormancy and infectivity. Dried sporosori inocula prepared from tuber lesions and root galls were infective after both short- and long-term storage (1 week to 5 years for tuber lesions and 1 week to 1 year for root galls) with both young and mature root galls inocula showing infectivity. This demonstrated that a proportion of all S. subterranea resting spores regardless of maturity exhibit characteristics of stimuli-responsive dormancy, germinating under the stimulatory conditions of the bait host plant bioassay. However, evidence for constitutive dormancy within the resting spore population was also provided as incubation of sporosorus inoculum in a germination-stimulating environment did not fully exhaust germination potential even after 2.4 years. We conclude that S. subterranea sporosori contain both exogenous (stimuli-responsive) and constitutively dormant resting spores, which enables successful host infection by germination in response to plant stimuli and long-term persistence in the soil.
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potato root exudation and release of Spongospora subterranea resting spore germination stimulants are affected by plant and environmental conditions
Journal of Phytopathology, 2017Co-Authors: Mark A. Balendres, David Nichols, Robert S. Tegg, C R WilsonAbstract:Variation in plant and environmental conditions were studied to determine the effect thereof on the exudation of low-molecular-weight organic compounds by potato roots. The results of the phytochemical analyses showed that among the conditions investigated, root vigour, potato cultivar, nutrients in incubation solution and temperature influenced the number and the type of primary metabolites released. Moreover, these conditions influenced our detection of compounds known to stimulate germination of resting spores of the pathogen Spongospora subterranea, causal agent of powdery scab and root diseases of potato. We conclude that changes in plant and environmental conditions can affect the release of specific compounds that stimulate germination of S. subterranea resting spores. The impact of the factors affecting potato root exudation on subsequent disease development is discussed.
J. A. Walsh - One of the best experts on this subject based on the ideXlab platform.
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Detection of Resting Spores of Spongospora subterranea F.SP. subterranea Using Serological Techniques
Developments in Plant Pathology, 1997Co-Authors: J. A. Walsh, U. MerzAbstract:A polyclonal antiserum has been produced against spore balls of Spongospora subterranea f.sp. subterranea prepared from potato tubers. It was able to detect as little as 0.02 spore balls in enzyme-linked immunosorbent assay (ELISA). It detected spore balls of different cultivar origin equally well. It also detected spores from different geographical origins. Western blot analysis revealed that the antiserum detected a number of different proteins, the most distinct of which had a molecular weight of slightly less than 6.5 kDa. In indirect FITC immunofluorescence, discrete bright fluorescent spots were visualised using the specific serum. With the non-specific serum only a very dull background fluorescence was evident.
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Spongospora subterranea f sp nasturtii ultrastructure of the plasmodial host interface food vacuoles flagellar apparatus and exit pores
Fungal Biology, 1997Co-Authors: C M Clay, J. A. WalshAbstract:Ultrastructural details of sporangial plasmodia and zoosporangia of Spongospora subterranea f. sp. nasturtii infecting the roots of watercress were observed using transmission electron microscopy. The plasmodial envelope, the interface between host and parasite, was found to be convoluted, having a large surface area. Pseudo-food vacuoles, formed by convolutions of the plasmodial envelope, contained portions of host cytoplasm. True-food vacuoles containing the remains of host organelles were seen within plasmodia. Similar remains also were seen in the central vacuole. The flagellar apparatus including the kinetosome, with microtubular rootlets, the transition zone, the flagellum and the tapering end-piece were examined and described. These observations are discussed in terms of the nutrition of S. subterranea f. sp. nasturtii, its original classification within the fungi (latterly Plasmodiophoromycetes) and affinities with the protists.
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Spongospora subterranea f. sp. nasturtii, ultrastructure of the plasmodial–host interface, food vacuoles, flagellar apparatus and exit pores
Fungal Biology, 1997Co-Authors: C M Clay, J. A. WalshAbstract:Ultrastructural details of sporangial plasmodia and zoosporangia of Spongospora subterranea f. sp. nasturtii infecting the roots of watercress were observed using transmission electron microscopy. The plasmodial envelope, the interface between host and parasite, was found to be convoluted, having a large surface area. Pseudo-food vacuoles, formed by convolutions of the plasmodial envelope, contained portions of host cytoplasm. True-food vacuoles containing the remains of host organelles were seen within plasmodia. Similar remains also were seen in the central vacuole. The flagellar apparatus including the kinetosome, with microtubular rootlets, the transition zone, the flagellum and the tapering end-piece were examined and described. These observations are discussed in terms of the nutrition of S. subterranea f. sp. nasturtii, its original classification within the fungi (latterly Plasmodiophoromycetes) and affinities with the protists.
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serological detection of spore balls of Spongospora subterranea and quantification in soil
Plant Pathology, 1996Co-Authors: J. A. Walsh, U. Merz, G HarrisonAbstract:A polyclonal antiserum produced against spore balls of Spongospora subterranea f.sp. subterranea prepared from potato tubers was able to detect as little as 0.02 spore balls in an enzyme-linked immunosorbent assay (ELISA). In spiked soil samples, the antiserum detected 100 spore balls per g soil. However, the different spore ball contamination levels were discriminated better in ELISA tests at concentrations above 2000 spore balls per g soil than at lower concentrations. In contrast, a bioassay test based on baiting soils with tomato seedlings gave good discrimination of spore ball contamination levels in spiked soils containing 2000 spore balls per g soil. Tests on a limited number of field soils suggested ELISA may be capable of predicting disease levels on tubers grown in such soils better than the bioassay. The antiserum did not react with 30 other micro-organisms tested, including many that are saprophytes or pathogens on potatoes and resting spores of the taxonomically related Plasmodiophora brassicae. It detected spore balls of different cultivar origin equally well. It also detected spores from different geographical origins. An attempt to improve the sensitivity of the serological detection through concentrating spore balls from field soils by sieving was unsuccessful. Cross-absorption of the antiserum with uncontaminated field soil increased the sensitivity of detection of spore balls in spiked soil samples four-fold. The ability of the antiserum to discriminate contaminated field soils from an uncontaminated soil was much improved by using the gamma-globulin fraction or cross-absorbed serum. Western blot analysis revealed that the antiserum detected a number of different proteins the most distinct of which had a molecular weight of slightly less than 6.5 kDa. A technique was developed to suppress autofluorescence of spore balls, allowing immunofluorescence studies to be carried out. Using this technique in conjunction with indirect FITC immunofluorescence. discrete bright fluorescent spots were visualized using the specific serum. With the non-specific serum, only a very dull background fluorescence was evident.
