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Richard E Falloon - One of the best experts on this subject based on the ideXlab platform.
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resistance to spongospora subterranea induced in potato by the elicitor β aminobutyric acid
Australasian Plant Pathology, 2015Co-Authors: Richard E Falloon, Loreto Hernandez M Maldonado, A J Conner, R C Butler, 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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spongospora subterranea Root infection assessed in two potato cultivars differing in susceptibility to tuber powdery scab
Plant Pathology, 2013Co-Authors: Richard E Falloon, M Hernandez L Maldonado, A J Conner, R C Butler, 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.
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Nightshade weeds (Solanum spp.) confirmed as hosts of the potato pathogens Meloidogyne fallax and Spongospora subterranea f. sp. subterranea
Australasian Plant Pathology, 2010Co-Authors: Farhat A. Shah, Richard E Falloon, Simon BulmanAbstract:Hairy nightshade ( Solanum physalifolium ) and black nightshade ( S. nigrum ) are common weeds in cropping soils and potato crops ( S. tuberosum ) in New Zealand. Root Galls were found on field-grown plants of hairy and black nightshade, and potato. Microscopic examination indicated that small Galls (approx. 1 mm diameter) were caused by Meloidogyne fallax and larger Galls (1–5 mm diameter) were caused by Spongospora subterranea f. sp. subterranea , and this was confirmed using species-specific PCR primers. Furthermore, infections caused by both pathogens were found simultaneously on individual specimens from all three hosts, and in a few cases, both pathogens occurred in the same individual gall. Mycelia of Rhizoctonia solani were also observed on Galls and Roots. Pathogenicity of M. fallax and Sp. subterranea f. sp. subterranea from field-grown nightshade plants was confirmed by inoculating glasshouse-grown tomato ( Lycopersicon esculentum ) and potato plants. This is the first record of M. fallax infecting S. physalifolium . Nightshade weeds are very likely to be important sources of M. fallax and Sp. subterranea f. sp. subterranea inoculum. Control of these weeds should be an important component of management of soilborne diseases in potato crops, to reduce pathogen inoculum and between-crop perennation.
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susceptibility of potato solanum tuberosum cultivars to powdery scab caused by spongospora subterranea f sp subterranea and relationships between tuber and Root infection
Australasian Plant Pathology, 2003Co-Authors: Richard E Falloon, Andrew R Wallace, R. A. Genet, R C ButlerAbstract:Ninety-nine potato (Solanum tuberosum) cultivars and 13 breeding lines were assessed in field trials for susceptibility to powdery scab (caused by Spongospora subterranea f. sp. subterranea). The trials wer e carried out over 11 growing seasons (each cultivar/line tested in at least two growing seasons) in soil inoculated with S. subterranea and regularly irrigated during crop growth. The cultivars and lines were categorised as ‘very resistant’ (21%). ‘moderately resistant’ (28%). ‘moderately susceptible’ (33%) or ‘very susceptible’ ( 19%). Scaled average severity scores for the cultivars and lines followed a continuum between very resistant and very susceptible, suggesting that resistance to powdery scab is quantitative. In a glasshouse experiment where small plants were inoculated with S. subterranea sporosori, 15 cultivars selected to cover the spectrum of field-assessed susceptibility were assessed for intensity of infection by S. subterranea zoosporangium in Roots and for numbers of Root Galls on Root systems. All of the cultivars developed zoosporangia and Root Galls (i.e. no cultivar was immune from infection), and Root infection was usually related to tuber infection. Field-resistant cultivars (tuber infection) generally had low numbers of Root zoosporangia and Root Galls in the glass house experiment, and cultivars that were very susceptible to tuber infection in the field had high levels of Root infection in the glasshouse experiment. An exception was the early maturing cv. Swift, which had very low levels of tuber infection in the field, but had high numbers of Root zoosporangia and Root Galls in the glasshouse. These results demonstrate the relative reaction of a large number of potato cultivars to powdery scab and reaffirm the potential for using plant resistance as a powdery scab management strategy. Development of S. subterranea in host Roots, even in cultivars with resistance to tuber infection, is likely to be important in the epidemiology of powdery scab.
U. Merz - One of the best experts on this subject based on the ideXlab platform.
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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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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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The Presence of Spongospora Subterranea F.SP. Subterranea in the Northern Areas of Pakistan Confirmed by Microscopy, Serology and Bioassay
Developments in Plant Pathology, 1997Co-Authors: Iftikhar Ahmad, Saman Iftikhar, U. MerzAbstract:During a survey in 1994 in the Skardu region of Northern Areas of Pakistan, potato plants were found in Astak valley with Root Galls and tuber lesions similar to those caused by Spongospora subterranea f.sp. subterranea and these were analysed further. Four months after replanting one plant again showed Root Galls on new Roots and ‘cauliflower’ stage lesions on young tubers, typical of powdery scab. Microscopic preparations of Root Galls showed the presence of the characteristic spongy-like spore balls. The soil gave a high Root infection score for the presence of zoosporangia in a bioassay test. It also reacted very strongly in ELISA. Preparations from Root Galls and the ‘cauliflower’ stage lesions also gave high reactions in ELISA.
Clemence Medina - One of the best experts on this subject based on the ideXlab platform.
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characterization of sirnas clusters in arabidopsis thaliana Galls induced by the Root knot nematode meloidogyne incognita
BMC Genomics, 2018Co-Authors: Clemence Medina, Martine Da Rocha, Marc Magliano, Alizee Raptopoulo, Nathalie Marteu, Kevin Lebrigand, Pierre Abad, Bruno Favery, Stephanie JaubertpossamaiAbstract:Root-knot nematodes (RKN), genus Meloidogyne, are plant parasitic worms that have the ability to transform Root vascular cylinder cells into hypertrophied, multinucleate and metabolically over-active feeding cells. Redifferentiation into feeding cells is the result of a massive transcriptional reprogramming of Root cells targeted by RKN. Since RKN are able to induce similar feeding cells in Roots of thousands of plant species, these worms are thought to manipulate essential and conserved plant molecular pathways. Small non-coding RNAs of uninfected Roots and infected Root Galls induced by M. incognita from Arabidopsis thaliana were sequenced by high throughput sequencing. SiRNA populations were analysed by using the Shortstack algorithm. We identified siRNA clusters that are differentially expressed in infected Roots and evidenced an over-representation of the 23–24 nt siRNAs in infected tissue. This size corresponds to heterochromatic siRNAs (hc-siRNAs) which are known to regulate expression of transposons and genes at the transcriptional level, mainly by inducing DNA methylation. Correlation of siRNA clusters expression profile with transcriptomic data identified several protein coding genes that are candidates to be regulated by siRNAs at the transcriptional level by RNA directed DNA methylation (RdDM) pathway either directly or indirectly via silencing of neighbouring transposable elements.
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Characterization of siRNAs clusters in Arabidopsis thaliana Galls induced by the Root-knot nematode Meloidogyne incognita
BMC Genomics, 2018Co-Authors: Clemence Medina, Martine Da Rocha, Marc Magliano, Alizee Raptopoulo, Nathalie Marteu, Kevin Lebrigand, Pierre Abad, Bruno Favery, Stéphanie Jaubert-possamaiAbstract:BackgroundRoot-knot nematodes (RKN), genus Meloidogyne, are plant parasitic worms that have the ability to transform Root vascular cylinder cells into hypertrophied, multinucleate and metabolically over-active feeding cells. Redifferentiation into feeding cells is the result of a massive transcriptional reprogramming of Root cells targeted by RKN. Since RKN are able to induce similar feeding cells in Roots of thousands of plant species, these worms are thought to manipulate essential and conserved plant molecular pathways.ResultsSmall non-coding RNAs of uninfected Roots and infected Root Galls induced by M. incognita from Arabidopsis thaliana were sequenced by high throughput sequencing. SiRNA populations were analysed by using the Shortstack algorithm. We identified siRNA clusters that are differentially expressed in infected Roots and evidenced an over-representation of the 23-24nt siRNAs in infected tissue. This size corresponds to heterochromatic siRNAs (hc-siRNAs) which are known to regulate expression of transposons and genes at the transcriptional level, mainly by inducing DNA methylation.ConclusionsCorrelation of siRNA clusters expression profile with transcriptomic data identified several protein coding genes that are candidates to be regulated by siRNAs at the transcriptional level by RNA directed DNA methylation (RdDM) pathway either directly or indirectly via silencing of neighbouring transposable elements.
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characterization of micrornas from arabidopsis Galls highlights a role for mir159 in the plant response to the Root knot nematode meloidogyne incognita
New Phytologist, 2017Co-Authors: Clemence Medina, Martine Da Rocha, Marc Magliano, Nathalie Marteu, Kevin Lebrigand, Alizee Ratpopoulo, Benoit Revel, Virginie Magnone, Javier Cabrera, Marta BarcalaAbstract:Summary Root knot nematodes (RKN) are Root parasites that induce the genetic reprogramming of vascular cells into giant feeding cells and the development of Root Galls. MicroRNAs (miRNAs) regulate gene expression during development and plant responses to various stresses. Disruption of post-transcriptional gene silencing in Arabidopsis ago1 or ago2 mutants decrease the infection rate of RKN suggesting a role for this mechanism in the plant-nematode interaction. By sequencing small RNAs from uninfected Arabidopsis Roots and from Galls 7 and 14 d post infection with Meloidogyne incognita, we identified 24 miRNAs differentially expressed in gall as putative regulators of gall development. Moreover, strong activity within Galls was detected for five miRNA promoters. Analyses of nematode development in an Arabidopsis miR159abc mutant had a lower susceptibility to RKN, suggesting a role for the miR159 family in the plant response to M. incognita. Localization of mature miR159 within the giant and surrounding cells suggested a role in giant cell and gall. Finally, overexpression of miR159 in Galls at 14 d post inoculation was associated with the repression of the miR159 target MYB33 which expression is restricted to the early stages of infection. Overall, these results implicate the miR159 in plant responses to RKN.
Jutta Ludwig-müller - One of the best experts on this subject based on the ideXlab platform.
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New kid on the block – the clubRoot pathogen genome moves the plasmodiophorids into the genomic era
European Journal of Plant Pathology, 2016Co-Authors: Arne Schwelm, Christina Dixelius, Jutta Ludwig-müllerAbstract:Plasmodiophora brassicae causes clubRoot on cruciferous plants and causes worldwide huge economical losses on important Brassica crops. P. brassicae infection produces large Root Galls, the clubRoots, which can also affect the upper plant parts by reduced water and nutrient uptake and redirection of assimilates from leaves to Roots. P. brassicae is an obligate biotrophic protist in the plasmodiophorids within the eukaryote supergroup of Rhizaria and is unrelated to other known plant pathogens. Plasmodiophorids can be parasites of plants and oomycetes. The recently released genome of P. brassicae is only the third in the poorly studied Rhizaria and the first plant pathogenic genome of this eukaryotic group. The P. brassicae genome was estimated to be 25.5 Mb in size and predicted to contain 9730 gene models. A transcriptome of P. brassicae and Spongospora subterranea , the potato scab pathogen was also presented. Consequently, for the first time large scale data for a eukaryotic plant pathogen group outside the fungi and oomycetes are now available. This review highlights selected characteristics of the P. brassicae genome including molecular events shown or predicted to take place in each phase of its life-cycle, such as manipulation of: 1) host primary metabolism, 2) plant hormone homeostasis, and 3) plant defense. Further, future directions and challenges in the P. brassicae and plasmodiophorid genomic research are discussed.
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Flavonoid accumulation in Arabidopsis thaliana Root Galls caused by the obligate biotrophic pathogen Plasmodiophora brassicae
Molecular Plant Pathology, 2010Co-Authors: Susanne Päsold, Ina Siegel, Claudia Seidel, Jutta Ludwig-müllerAbstract:SUMMARY Three different flavonoids—naringenin, quercetin and kaempferol—accumulate in Root Galls of Arabidopsis thaliana after infection with the obligate biotrophic pathogen Plasmodiophora brassicae. In addition, high-performance liquid chromatography and thin layer chromatography analysis indicated that these flavonoids and their glycosides were induced in Galls rather than in healthy Roots. The transcripts of selected genes involved in the biosynthesis of flavonoids were up-regulated during the time course of the disease. Some, such as chalcone synthase and chalcone isomerase, were up-regulated at both times investigated in this study, whereas up-regulation was observed only at later times for others, such as a flavonol synthase-like gene. Plants with mutations in different flavonoid biosynthesis genes were slightly more tolerant to clubRoot at low infection pressure. However, flavonoid treatment of either leaves or Roots did not reduce gall development. The possibility that flavonoids might influence auxin levels by regulating auxin transport or auxin degradation in Roots was investigated by measuring auxin levels and response in Roots of flavonoid-deficient mutants and the wild-type after inoculation with P. brassicae, as well as the antioxidative potential of flavonoids in the peroxidase-catalysed degradation of indole-3-acetic acid. In addition, the auxin transport rate from the shoots to the Roots was measured in infected wild-type or flavonoid mutant plants compared with controls. In conclusion, our results indicate a role of flavonoids in the modulation of auxin efflux in Root Galls.
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Metabolism and Plant Hormone Action During ClubRoot Disease
Journal of Plant Growth Regulation, 2009Co-Authors: Jutta Ludwig-müller, Els Prinsen, Stephen A. Rolfe, Julie D. ScholesAbstract:Infection of Brassicaceae with the obligate biotrophic pathogen Plasmodiophora brassicae results in the development of Root Galls (clubRoots). During the transformation of a healthy Root to a Root gall a plethora of changes in primary and secondary metabolism occur. The upper part of an infected plant is retarded in growth due to redirection of assimilates from the shoot to the Root. In addition, changes in the levels of plant growth regulators, especially auxins and cytokinins, contribute to the hypertrophy of infected Roots. Also, defense reactions are manipulated after inoculation of suitable host plants with P. brassicae . This review summarizes our current knowledge on the changes in these parameters. A model is presented for how primary metabolism and secondary metabolism, including plant hormones, interact to induce clubRoot formation.
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Plant defence — what can we learn from clubRoots?
Australasian Plant Pathology, 2009Co-Authors: Jutta Ludwig-müllerAbstract:The interaction of the obligate biotrophic pathogen Plasmodiophora brassicae with host plants of the family Brassicaceae leads to the formation of Root Galls which create a strong metabolic sink, and reprograms host growth and development. Ultimately, the plant succumbs to the loss of both Root nutrients and water, and assimilates are redirected from leaves to Roots. Central regulators of these changes are the plant hormones auxins and cytokinins. Plant hormones such as abscisic acid might be involved in drought protection of the host Roots during late stages of pathogen development. However, other signalling molecules might play important roles in defence reactions. It is long known that salicylic acid is induced in plants during defence responses with a methyl systemic signal that confers resistance to the upper parts of the plant, but whether this plays a role in the establishment of the clubRoot pathogen is not yet clear. Jasmonic acid and ethylene might also play a role in the intricate relationship between the obligate biotrophic pathogen and its host.
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Glucosinolates and the clubRoot disease: defense compounds or auxin precursors?
Phytochemistry Reviews, 2009Co-Authors: Jutta Ludwig-müllerAbstract:The clubRoot disease is caused by the obligate biotrophic protist Plasmodiophora brassicae and is one of the most damaging for the family of Brassicaceae. Since many economically important crops belong to this plant family, the understanding of mechanisms how the disease is developing, are of high importance. Glucosinolates, a group of secondary plant products in the family of Brassicaceae, have long been associated with clubRoot disease symptoms. Measurements showed that several glucosinolates are induced in Root Galls. While aliphatic glucosinolates are regarded as defense compounds, analysis of Brassica cultivars as well as Arabidopsis thaliana mutants provided correlative evidence between disease severity and indole glucosinolate content. The latter have been discussed as precursors for auxin biosynthesis. Since high auxin levels are associated with large Root Galls, indole glucosinolates could contribute directly or indirectly to the extent of disease development. Transcriptome and proteome experiments have revealed evidence for the involvement of genes from the glucosinolate and auxin pathway in gall formation. These data have been complemented by expression and mutant analysis. It can be concluded that regulation of glucosinolate and IAA biosynthesis might differ in Brassica and Arabidopsis .
Simon Bulman - One of the best experts on this subject based on the ideXlab platform.
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resistance to spongospora subterranea induced in potato by the elicitor β aminobutyric acid
Australasian Plant Pathology, 2015Co-Authors: Richard E Falloon, Loreto Hernandez M Maldonado, A J Conner, R C Butler, 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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spongospora subterranea Root infection assessed in two potato cultivars differing in susceptibility to tuber powdery scab
Plant Pathology, 2013Co-Authors: Richard E Falloon, M Hernandez L Maldonado, A J Conner, R C Butler, 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.
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Nightshade weeds (Solanum spp.) confirmed as hosts of the potato pathogens Meloidogyne fallax and Spongospora subterranea f. sp. subterranea
Australasian Plant Pathology, 2010Co-Authors: Farhat A. Shah, Richard E Falloon, Simon BulmanAbstract:Hairy nightshade ( Solanum physalifolium ) and black nightshade ( S. nigrum ) are common weeds in cropping soils and potato crops ( S. tuberosum ) in New Zealand. Root Galls were found on field-grown plants of hairy and black nightshade, and potato. Microscopic examination indicated that small Galls (approx. 1 mm diameter) were caused by Meloidogyne fallax and larger Galls (1–5 mm diameter) were caused by Spongospora subterranea f. sp. subterranea , and this was confirmed using species-specific PCR primers. Furthermore, infections caused by both pathogens were found simultaneously on individual specimens from all three hosts, and in a few cases, both pathogens occurred in the same individual gall. Mycelia of Rhizoctonia solani were also observed on Galls and Roots. Pathogenicity of M. fallax and Sp. subterranea f. sp. subterranea from field-grown nightshade plants was confirmed by inoculating glasshouse-grown tomato ( Lycopersicon esculentum ) and potato plants. This is the first record of M. fallax infecting S. physalifolium . Nightshade weeds are very likely to be important sources of M. fallax and Sp. subterranea f. sp. subterranea inoculum. Control of these weeds should be an important component of management of soilborne diseases in potato crops, to reduce pathogen inoculum and between-crop perennation.
