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Dennis A. Johnson - One of the best experts on this subject based on the ideXlab platform.
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Evaluation of Solanum sisymbriifolium as a Potential Inoculum Source of Verticillium dahliae and Colletotrichum coccodes
Plant disease, 2017Co-Authors: Z. A. Frederick, C. R. Brown, Thomas F. Cummings, R A Quick, Dennis A. JohnsonAbstract:Solanum sisymbriifolium, the litchi tomato, is a perennial herbaceous plant from South America that is used as a trap crop to reduce soilborne populations of the pale cyst nematode Globodera pallida, an important potato pathogen. Possible interactions of soilborne potato pathogens Verticillium dahliae and Colletotrichum coccodes with litchi tomato are unknown, yet important for potato production if litchi tomato is to be planted as a trap crop. The goal of this research was to quantitatively assess if litchi tomato is a potential inoculum source for C. coccodes and V. dahliae by comparing colony forming units (CFU) observed in litchi tomato to susceptible and resistant potato cultivars. The potato cvs. Alturas (P = 0.0003), Ranger Russet (P = 0.0193), and Russet Norkotah (P = 0.0022) produced more CFUs of the potato pathotype of V. dahliae than litchi tomato the first of two years of greenhouse trials. Significantly more CFUs of the potato pathotype of V. dahliae were quantified from stems and roots of only cv. Russet Norkotah compared with litchi tomato (P = 0.0001) in the second year. The CFUs for C. coccodes varied between litchi tomato and the potato cvs., perhaps due to varying levels of resistance since litchi tomato is from a selected intermated seed source. Based on these data, the effect of litchi tomato in rotation with potato is likely to have limited effect on the proliferation of V. dahliae or C. coccodes populations in the soil when compared with a susceptible potato cultivar.
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Response of Colletotrichum coccodes to Selected Fungicides Using a Plant Inoculation Assay and Efficacy of Azoxystrobin Applied by Chemigation
American Journal of Potato Research, 2011Co-Authors: Jason Ingram, Thomas F. Cummings, Dennis A. JohnsonAbstract:Se desarrolló y utilizó un ensayo de inoculación de plantas para evaluar la eficacia y tiempo de aplicación de fungicida para la reducción de la infección en tallos de papa por Colletotrichum coccodes . La incidencia de tallos infectados tratados con azoxystrobin, pyraclostrobin, fluoxastrobin y mandipropamid + difenoconazole, fue significativamente menor que las plantas testigo no tratadas cuando se aplicaron los fungicidas antes de la inoculación. No obstante, la aplicación del fungicida después de la inoculación no redujo significativamente la infección. Clorotalonil y mancozeb no fueron efectivos en prevenir la infección por C. coccodes . Adicionalmente, se evaluaron aplicaciones de fungicidas al principio del ciclo de cultivo por quimirrigación de pivote central en campos comerciales de papa, como táctica potencial de manejo de la mancha negra. Los tallos subterráneos muestreados de lotes con repeticiones en campos comerciales donde se aplicó azoxistrobin por quimirrigación a 50 y 67 días después de la siembra (DAP), tuvieron significativamente menos área superficial del tallo cubierta con esclerocios a 79 DAP, que los testigos no tratados en dos años. No obstante, no se observó el efecto en ambos años en una colecta posterior a 102 DAP, y solo en uno de los dos años a 140 DAP. Se detectaron infecciones latentes en plantas asintomáticas colectadas en el campo. A plant inoculation assay was developed and used to evaluate fungicide efficacy and application timing for reduction of infection of potato stems by Colletotrichum coccodes . Incidence of infected stems treated with azoxystrobin, pyraclostrobin, fluoxastrobin, and mandipropamid + difenoconazole was significantly less than the non-treated control plants when fungicides were applied prior to inoculation. However, fungicide application after inoculation did not significantly reduce infection. Chlorothalonil and mancozeb were not effective in preventing infection by C. coccodes . Additionally, early season fungicide applications by center pivot chemigation in commercial potato fields were evaluated as a potential black dot management tactic. Below-ground stems sampled from replicated plots in commercial fields where azoxystrobin was applied by chemigation at 50 and 67 days after planting (DAP) had significantly less stem surface area covered with sclerotia at 79 DAP than the non-treated control in two of 2 years. However, the effect was not observed both years at a subsequent collection at 102 DAP and only one of 2 years at 140 DAP. Latent infections were detected in non-symptomatic plants collected from the field.
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response of Colletotrichum coccodes to selected fungicides using a plant inoculation assay and efficacy of azoxystrobin applied by chemigation
American Journal of Potato Research, 2011Co-Authors: Jason Ingram, Thomas F. Cummings, Dennis A. JohnsonAbstract:A plant inoculation assay was developed and used to evaluate fungicide efficacy and application timing for reduction of infection of potato stems by Colletotrichum coccodes. Incidence of infected stems treated with azoxystrobin, pyraclostrobin, fluoxastrobin, and mandipropamid + difenoconazole was significantly less than the non-treated control plants when fungicides were applied prior to inoculation. However, fungicide application after inoculation did not significantly reduce infection. Chlorothalonil and mancozeb were not effec- tive in preventing infection by C. coccodes. Additionally, early season fungicide applications by center pivot chemigation in commercial potato fields were evaluated as a potential black dot management tactic. Below-ground stems sampled from replicated plots in commercial fields where azoxystrobin was applied by chemigation at 50 and 67 days after planting (DAP) had significantly less stem surface area covered with sclerotia at 79 DAP than the non-treated control in two of 2 years. However, the effect was not observed both years at a subsequent collection at 102 DAP and only one of 2 years at 140 DAP. Latent infections were detected in non-symptomatic plants collected from the field.
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Colonization of Potato Roots and Stolons by Colletotrichum coccodes from Tuberborne Inoculum
American Journal of Potato Research, 2010Co-Authors: Jason Ingram, Dennis A. JohnsonAbstract:The rate of colonization by Colletotrichum coccodes was quantified on roots and stolons of the potato cultivar Russet Burbank. Greenhouse grown plants arising from seed-tubers infected with C. coccodes were observed. The distance that C. coccodes colonized potato roots was measured from the seed tuber to the distal edge of microsclerotial development along the roots starting at 21 days after plant emergence and continued at 14 day intervals until crop death. Visual assessment of disease progress was confirmed by isolation from diseased and non-diseased tissues onto nutrient agar. Expansion of C. coccodes foci along the roots in two independent trials resulted in a linear growth model of 1 mm/day (Trial 1 P < 0.011, R 2 = 0.84; Trial 2 P < 0.007, R 2 = 0.87). Colonization radiated from the seed-tuber to form compact foci of infected tissue that was rotationally symmetrical; no secondary foci were observed. The results suggested that C. coccodes expanded linearly from an inoculum source and that for multiple disease foci to develop on a root system, multiple primary infections must occur from sclerotia in the soil.
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Field Resistance to Potato Stem Colonization by the Black Dot Pathogen Colletotrichum coccodes
Plant disease, 2009Co-Authors: Nadav Nitzan, Dallas L Batchelor, Chris Olsen, Dennis A. Johnson, Thomas F. Cummings, Kathleen G Haynes, Marc A. Evans, C. R. BrownAbstract:Potato (Solanum tuberosum) germplasm was tested for resistance to stem colonization by the black dot pathogen Colletotrichum coccodes. Forty-six potato selections were tested in three field trials from 2006 to 2008. Resistance was determined by comparing disease severity on aboveground stems to the mean disease severity of the industry standards Russet Burbank, Ranger Russet, and Umatilla Russet. The potato selections were also tested for genotype*environment interaction to determine their genetic stability. Heritability of resistance was calculated to be 0.13 with confidence intervals between 0.00 and 0.68. The selections A0012-5, PA95B2-4, PA98NM38-1, and PO94A009-7 had less black dot than the standards in all years, and also demonstrated genetic stability. These selections also possess resistance to the root galling stage of the powdery scab pathogen Spongospora subterranea f. sp. subterranea. PA95B2-4, PA98NM38-1, and PO94009-7 were derived from an introgression program to incorporate resistance to the Columbia root-knot nematode Meloidogyne chitwoodi from the Mexican wild species Solanum bulbocastanum, and also have the commercial cultivar Summit Russet in their ancestry. These selections are promising steps toward sustainable management of black dot and powdery scab and will be further tested and used for breeding purposes.
Thomas F. Cummings - One of the best experts on this subject based on the ideXlab platform.
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Evaluation of Solanum sisymbriifolium as a Potential Inoculum Source of Verticillium dahliae and Colletotrichum coccodes
Plant disease, 2017Co-Authors: Z. A. Frederick, C. R. Brown, Thomas F. Cummings, R A Quick, Dennis A. JohnsonAbstract:Solanum sisymbriifolium, the litchi tomato, is a perennial herbaceous plant from South America that is used as a trap crop to reduce soilborne populations of the pale cyst nematode Globodera pallida, an important potato pathogen. Possible interactions of soilborne potato pathogens Verticillium dahliae and Colletotrichum coccodes with litchi tomato are unknown, yet important for potato production if litchi tomato is to be planted as a trap crop. The goal of this research was to quantitatively assess if litchi tomato is a potential inoculum source for C. coccodes and V. dahliae by comparing colony forming units (CFU) observed in litchi tomato to susceptible and resistant potato cultivars. The potato cvs. Alturas (P = 0.0003), Ranger Russet (P = 0.0193), and Russet Norkotah (P = 0.0022) produced more CFUs of the potato pathotype of V. dahliae than litchi tomato the first of two years of greenhouse trials. Significantly more CFUs of the potato pathotype of V. dahliae were quantified from stems and roots of only cv. Russet Norkotah compared with litchi tomato (P = 0.0001) in the second year. The CFUs for C. coccodes varied between litchi tomato and the potato cvs., perhaps due to varying levels of resistance since litchi tomato is from a selected intermated seed source. Based on these data, the effect of litchi tomato in rotation with potato is likely to have limited effect on the proliferation of V. dahliae or C. coccodes populations in the soil when compared with a susceptible potato cultivar.
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Response of Colletotrichum coccodes to Selected Fungicides Using a Plant Inoculation Assay and Efficacy of Azoxystrobin Applied by Chemigation
American Journal of Potato Research, 2011Co-Authors: Jason Ingram, Thomas F. Cummings, Dennis A. JohnsonAbstract:Se desarrolló y utilizó un ensayo de inoculación de plantas para evaluar la eficacia y tiempo de aplicación de fungicida para la reducción de la infección en tallos de papa por Colletotrichum coccodes . La incidencia de tallos infectados tratados con azoxystrobin, pyraclostrobin, fluoxastrobin y mandipropamid + difenoconazole, fue significativamente menor que las plantas testigo no tratadas cuando se aplicaron los fungicidas antes de la inoculación. No obstante, la aplicación del fungicida después de la inoculación no redujo significativamente la infección. Clorotalonil y mancozeb no fueron efectivos en prevenir la infección por C. coccodes . Adicionalmente, se evaluaron aplicaciones de fungicidas al principio del ciclo de cultivo por quimirrigación de pivote central en campos comerciales de papa, como táctica potencial de manejo de la mancha negra. Los tallos subterráneos muestreados de lotes con repeticiones en campos comerciales donde se aplicó azoxistrobin por quimirrigación a 50 y 67 días después de la siembra (DAP), tuvieron significativamente menos área superficial del tallo cubierta con esclerocios a 79 DAP, que los testigos no tratados en dos años. No obstante, no se observó el efecto en ambos años en una colecta posterior a 102 DAP, y solo en uno de los dos años a 140 DAP. Se detectaron infecciones latentes en plantas asintomáticas colectadas en el campo. A plant inoculation assay was developed and used to evaluate fungicide efficacy and application timing for reduction of infection of potato stems by Colletotrichum coccodes . Incidence of infected stems treated with azoxystrobin, pyraclostrobin, fluoxastrobin, and mandipropamid + difenoconazole was significantly less than the non-treated control plants when fungicides were applied prior to inoculation. However, fungicide application after inoculation did not significantly reduce infection. Chlorothalonil and mancozeb were not effective in preventing infection by C. coccodes . Additionally, early season fungicide applications by center pivot chemigation in commercial potato fields were evaluated as a potential black dot management tactic. Below-ground stems sampled from replicated plots in commercial fields where azoxystrobin was applied by chemigation at 50 and 67 days after planting (DAP) had significantly less stem surface area covered with sclerotia at 79 DAP than the non-treated control in two of 2 years. However, the effect was not observed both years at a subsequent collection at 102 DAP and only one of 2 years at 140 DAP. Latent infections were detected in non-symptomatic plants collected from the field.
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response of Colletotrichum coccodes to selected fungicides using a plant inoculation assay and efficacy of azoxystrobin applied by chemigation
American Journal of Potato Research, 2011Co-Authors: Jason Ingram, Thomas F. Cummings, Dennis A. JohnsonAbstract:A plant inoculation assay was developed and used to evaluate fungicide efficacy and application timing for reduction of infection of potato stems by Colletotrichum coccodes. Incidence of infected stems treated with azoxystrobin, pyraclostrobin, fluoxastrobin, and mandipropamid + difenoconazole was significantly less than the non-treated control plants when fungicides were applied prior to inoculation. However, fungicide application after inoculation did not significantly reduce infection. Chlorothalonil and mancozeb were not effec- tive in preventing infection by C. coccodes. Additionally, early season fungicide applications by center pivot chemigation in commercial potato fields were evaluated as a potential black dot management tactic. Below-ground stems sampled from replicated plots in commercial fields where azoxystrobin was applied by chemigation at 50 and 67 days after planting (DAP) had significantly less stem surface area covered with sclerotia at 79 DAP than the non-treated control in two of 2 years. However, the effect was not observed both years at a subsequent collection at 102 DAP and only one of 2 years at 140 DAP. Latent infections were detected in non-symptomatic plants collected from the field.
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Field Resistance to Potato Stem Colonization by the Black Dot Pathogen Colletotrichum coccodes
Plant disease, 2009Co-Authors: Nadav Nitzan, Dallas L Batchelor, Chris Olsen, Dennis A. Johnson, Thomas F. Cummings, Kathleen G Haynes, Marc A. Evans, C. R. BrownAbstract:Potato (Solanum tuberosum) germplasm was tested for resistance to stem colonization by the black dot pathogen Colletotrichum coccodes. Forty-six potato selections were tested in three field trials from 2006 to 2008. Resistance was determined by comparing disease severity on aboveground stems to the mean disease severity of the industry standards Russet Burbank, Ranger Russet, and Umatilla Russet. The potato selections were also tested for genotype*environment interaction to determine their genetic stability. Heritability of resistance was calculated to be 0.13 with confidence intervals between 0.00 and 0.68. The selections A0012-5, PA95B2-4, PA98NM38-1, and PO94A009-7 had less black dot than the standards in all years, and also demonstrated genetic stability. These selections also possess resistance to the root galling stage of the powdery scab pathogen Spongospora subterranea f. sp. subterranea. PA95B2-4, PA98NM38-1, and PO94009-7 were derived from an introgression program to incorporate resistance to the Columbia root-knot nematode Meloidogyne chitwoodi from the Mexican wild species Solanum bulbocastanum, and also have the commercial cultivar Summit Russet in their ancestry. These selections are promising steps toward sustainable management of black dot and powdery scab and will be further tested and used for breeding purposes.
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Field Resistance to Potato Stem Colonization by the Black Dot Pathogen Colletotrichum coccodes
Plant disease, 2009Co-Authors: Nadav Nitzan, Dallas L Batchelor, Chris Olsen, Dennis A. Johnson, Thomas F. Cummings, Kathleen G Haynes, Marc A. Evans, C. R. BrownAbstract:ABSTRACT Potato (Solanum tuberosum) germplasm was tested for resistance to stem colonization by the black dot pathogen Colletotrichum coccodes. Forty-six potato selections were tested in three field trials from 2006 to 2008. Resistance was determined by comparing disease severity on aboveground stems to the mean disease severity of the industry standards Russet Burbank, Ranger Russet, and Umatilla Russet. The potato selections were also tested for genotype*environment interaction to determine their genetic stability. Heritability of resistance was calculated to be 0.13 with confidence intervals between 0.00 and 0.68. The selections A0012-5, PA95B2-4, PA98NM38-1, and PO94A009-7 had less black dot than the standards in all years, and also demonstrated genetic stability. These selections also possess resistance to the root galling stage of the powdery scab pathogen Spongospora subterranea f. sp. subterranea. PA95B2-4, PA98NM38-1, and PO94009-7 were derived from an introgression program to incorporate resista...
S. H. Jabaji-hare - One of the best experts on this subject based on the ideXlab platform.
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Analysis of enriched transcripts induced during velvetleaf - Colletotrichum coccodes interaction
Canadian Journal of Plant Pathology, 2008Co-Authors: Amélie L. Dauch, Danielle C. Morissette, Roland Brousseau, Luke Masson, Martina V. Strömvik, S. H. Jabaji-hareAbstract:We used suppression subtractive hybridization (SSH) and differential screening (DS) to generate cDNA libraries enriched for up-regulated host and pathogen genes following inoculation of velvetleaf leaves with the mycoherbicide Colletotrichum coccodes. A total of 116 expressed sequence tags (EST), representing preferentially expressed genes, were analyzed, of which 89 sequences were assigned putative functions including transcription and translation, energy, cell growth and maintenance, and oxidative stress and defense. The EST sequences were assembled into 20 contigs and 29 singletons/singlets. Except for contig 26 that had the highest hit to fungal Histone 4, all other sequences had top hits to plant sequences. Genes related to oxidative stress and defense formed the largest category corresponding to nine contigs and three singlets (or 48% of the ESTs). The metallothioneins (MT) type 3 proteins were represented by six contigs, three singletons, and two singlets. We also identified genes for the ethylene ...
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Molecular Monitoring of Wild-Type and Genetically Engineered Colletotrichum coccodes Biocontrol Strains In Planta.
Plant disease, 2006Co-Authors: A.l. Dauch, A. K. Watson, Byeongseok Ahn, Philippe Seguin, S. H. Jabaji-hareAbstract:Two strains of Colletotrichum coccodes, the wild type (DAOM 183088) and T-20a, engineered with the necrosis- and ethylene-inducing peptide (NEP1) gene for hypervirulence on velvetleaf (Abutilon theophrasti, Medik.), were monitored in planta for the first 2 weeks after infection. Real-time quantitative polymerase chain reaction (QPCR) was used to assess the extent of colonization of both strains on velvetleaf using SYBR Green chemistry. Quantification of both strains was successful as soon as the conidia were sprayed on the leaves and up to 14 days after infection. The increase in fungal DNA amounts corroborated with the appearance of necrotic lesions on velvetleaf leaves infected with the wild-type strain. The wild-type C. coccodes was more efficient at infecting velvetleaf than the transgenic T-20a strain. In addition, detection of host DNA allowed us to quantitatively monitor the decrease in plant DNA amounts in response to wild-type strain infection. Expression of the NEP1 transgene by conventional retro-transcription (RT)-PCR was absent from T-20a growing on either V8 agar or in planta, suggesting that the gene may be silenced. The application of QPCR to monitor fungal growth was proven to detect the target organisms in planta prior to the appearance of symptoms.
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Metallothionein and bZIP Transcription Factor Genes from Velvetleaf and Their Differential Expression Following Colletotrichum coccodes Infection
Phytopathology, 2006Co-Authors: Amélie L. Dauch, S. H. Jabaji-hareAbstract:ABSTRACT Colletotrichum coccodes is a biocontrol agent of velvetleaf (Abutilon theophrasti), a noxious weed of corn and soybean. Metallothioneins (MTs) and basic region/leucine zipper motif (bZIP) are heavy-metal-binding proteins and transcription factors, respectively, that have been related to several plant processes, including the responses of plants to pathogen attack. Previous investigation of the determinants involved in the velvet-leaf-C. coccodes interaction had shed light on particular plant and fungal genes expressed in this pathosystem. Here, we report on the temporal expression patterns of two distinct types (2 and 3) of MT and bZIP transcription factor genes in velvetleaf leaves following infection with C. coccodes using quantitative reverse-transcription polymerase chain reaction. Gene expression ratios were significantly upregulated 1 day after infection (DAI), a time at which velvetleaf leaves appeared symptomless. At 2 DAI, bZIP and type 3 MT expression ratios dropped to levels significantly lower than those estimated for noninfected plants. Necrotic symptoms appeared 5 DAI and increased with time, during which gene expression levels were maintained either below or at levels observed in the control. These findings indicate that C. coccodes altered the expression of type 2 and 3 MT and bZIP genes. In addition, this is the first report on induction of a type 3 MT in plants in response to a pathogen attack.
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Enhancement of Colletotrichum coccodes virulence by inhibitors of plant defense mechanisms
Biocontrol Science and Technology, 2005Co-Authors: Byeongseok Ahn, Timothy C Paulitz, S. H. Jabaji-hare, Alan K WatsonAbstract:Abstract α-Amino-oxyacetic acid (AOA), 2-deoxy-d-glucose (DDG), mannose, and oxalic acid were tested as possible synergizers to enhance the efficacy of Colletotrichum coccodes, as a biological control agent of Abutilon theophrasti. All the chemicals reduced C. coccodes conidia germination and appressoria formation, but the virulence of C. coccodes was significantly enhanced when C. coccodes was applied to A. theophrasti after mannose and oxalic acid were vacuum-infiltrated through the leaf cuticle. Lipophilic analogues, 1-amino-ethyl-phosphonic acid diisopropyl ester of oxalic acid, oxalic acid diammonium salt, and 4,6-di-O-methyl-d-mannose, did not result in more severe disease on velvetleaf and there was no impact on A. theophrasti growth. These results may be due to strong antifungal effects, possible functional changes due to chemical structural changes, size of the chemical molecule, or lack of inhibitory effect of these chemicals on plant defense mechanisms. It is also possible that the defense mech...
Nadav Nitzan - One of the best experts on this subject based on the ideXlab platform.
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Partial Resistance to Potato Black Dot, Caused by Colletotrichum coccodes in Solanum tuberosum Group Andigena
American Journal of Potato Research, 2010Co-Authors: Nadav Nitzan, Richard A. Quick, Will D. Hutson, John Bamberg, Chuck R. BrownAbstract:La mancha negra es producida por el hongo Colletotrichum coccodes (Wallr.) S.J. Hughes. La enfermedad es prevalente en los campos de papa y puede ser de importancia económica de por sí, o es parte del síndrome de muerte temprana de la papa. Se sabe poco respecto de la resistencia a esta enfermedad. En el presente estudio se probó la resistencia a la mancha negra de la papa en Solanum tuberosum grupo Andígena . Se seleccionaron y evaluaron cuarenta accesiones al azar de la colección principal. Las accesiones fueron originarias de Perú, México, Bolivia, Colombia, Ecuador, Argentina y Costa Rica. Cinco accesiones tuvieron menos enfermedad (P ≤ 0.05) en raíces y tallos que un juego de estándares comerciales. Estas accesiones fueron: PIs 189473, 230475, 161683, 243367 y 230470. Se volvieron a probar para validar su resistencia parcial. Quince plantas, cada una de un genotipo único, se seleccionaron de cada accesión y se propagaron en múltiples clones que se inocularon con el patógeno. Se identificaron tres genotipos con menos enfermedad (P ≤ 0.05) en raíces y tallos que los estándares de la industria. Estos genotipos se originaron de las accesiones Pl-243367 y Pl230475. Los clones de los genotipos resistentes se agregaron a la colección de germoplasma de papa ubicada en el Laboratorio de Mejoramiento de Papa del USDA-ARS cerca de Prosser, WA, para usarse en el desarrollo de variedades comerciales resistentes a la mancha negra. Black dot is caused by the fungus Colletotrichum coccodes (Wallr.) S.J. Hughes. The disease is prevalent in potato fields and can be of economic concern by itself, or as a part of the potato early dying syndrome. Little is known about resistance to this disease. In the present study resistance to potato black dot was tested in Solanum tuberosum Group Andigena . Forty accessions were chosen randomly from the core collection and screened. The accessions originated from Peru, Mexico, Bolivia, Columbia, Ecuador, Argentina and Costa Rica. Five accessions had less ( P ≤ 0.05) disease on roots and stems than a set of commercial standards. These accessions were: PIs 189473, 230475, 161683, 243367 and 230470. They were retested to validate their partial resistance. Fifteen plants, each a unique genotype, were selected from each accession and were propagated into multiple clones that were inoculated with the pathogen. Three genotypes were identified with less ( P
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Partial Resistance to Potato Black Dot, Caused by Colletotrichum coccodes in Solanum tuberosum Group Andigena
American Journal of Potato Research, 2010Co-Authors: Nadav Nitzan, Richard A. Quick, Will D. Hutson, John Bamberg, C. R. BrownAbstract:Black dot is caused by the fungus Colletotrichum coccodes (Wallr.) S.J. Hughes. The disease is prevalent in potato fields and can be of economic concern by itself, or as a part of the potato early dying syndrome. Little is known about resistance to this disease. In the present study resistance to potato black dot was tested in Solanum tuberosum Group Andigena. Forty accessions were chosen randomly from the core collection and screened. The accessions originated from Peru, Mexico, Bolivia, Columbia, Ecuador, Argentina and Costa Rica. Five accessions had less (P ≤ 0.05) disease on roots and stems than a set of commercial standards. These accessions were: PIs 189473, 230475, 161683, 243367 and 230470. They were retested to validate their partial resistance. Fifteen plants, each a unique genotype, were selected from each accession and were propagated into multiple clones that were inoculated with the pathogen. Three genotypes were identified with less (P < 0.05) disease on roots and stems than the industry standard. These genotypes originated from the accessions PI-243367 and PI-230475. Clones of the resistant genotypes were added to the potato germplasm collection located at the Potato Improvement Laboratory of the USDA-ARS near Prosser, WA, to be used in the development of black dot resistant commercial varieties.
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Field Resistance to Potato Stem Colonization by the Black Dot Pathogen Colletotrichum coccodes
Plant disease, 2009Co-Authors: Nadav Nitzan, Dallas L Batchelor, Chris Olsen, Dennis A. Johnson, Thomas F. Cummings, Kathleen G Haynes, Marc A. Evans, C. R. BrownAbstract:Potato (Solanum tuberosum) germplasm was tested for resistance to stem colonization by the black dot pathogen Colletotrichum coccodes. Forty-six potato selections were tested in three field trials from 2006 to 2008. Resistance was determined by comparing disease severity on aboveground stems to the mean disease severity of the industry standards Russet Burbank, Ranger Russet, and Umatilla Russet. The potato selections were also tested for genotype*environment interaction to determine their genetic stability. Heritability of resistance was calculated to be 0.13 with confidence intervals between 0.00 and 0.68. The selections A0012-5, PA95B2-4, PA98NM38-1, and PO94A009-7 had less black dot than the standards in all years, and also demonstrated genetic stability. These selections also possess resistance to the root galling stage of the powdery scab pathogen Spongospora subterranea f. sp. subterranea. PA95B2-4, PA98NM38-1, and PO94009-7 were derived from an introgression program to incorporate resistance to the Columbia root-knot nematode Meloidogyne chitwoodi from the Mexican wild species Solanum bulbocastanum, and also have the commercial cultivar Summit Russet in their ancestry. These selections are promising steps toward sustainable management of black dot and powdery scab and will be further tested and used for breeding purposes.
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Field Resistance to Potato Stem Colonization by the Black Dot Pathogen Colletotrichum coccodes
Plant disease, 2009Co-Authors: Nadav Nitzan, Dallas L Batchelor, Chris Olsen, Dennis A. Johnson, Thomas F. Cummings, Kathleen G Haynes, Marc A. Evans, C. R. BrownAbstract:ABSTRACT Potato (Solanum tuberosum) germplasm was tested for resistance to stem colonization by the black dot pathogen Colletotrichum coccodes. Forty-six potato selections were tested in three field trials from 2006 to 2008. Resistance was determined by comparing disease severity on aboveground stems to the mean disease severity of the industry standards Russet Burbank, Ranger Russet, and Umatilla Russet. The potato selections were also tested for genotype*environment interaction to determine their genetic stability. Heritability of resistance was calculated to be 0.13 with confidence intervals between 0.00 and 0.68. The selections A0012-5, PA95B2-4, PA98NM38-1, and PO94A009-7 had less black dot than the standards in all years, and also demonstrated genetic stability. These selections also possess resistance to the root galling stage of the powdery scab pathogen Spongospora subterranea f. sp. subterranea. PA95B2-4, PA98NM38-1, and PO94009-7 were derived from an introgression program to incorporate resista...
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Disease Potential of Soil- and Tuberborne Inocula of Colletotrichum coccodes and Black Dot Severity on Potato.
Plant disease, 2008Co-Authors: Nadav Nitzan, Thomas F. Cummings, Dennis A. JohnsonAbstract:Inoculum of Colletotrichum coccodes, the cause of potato black dot, is soil- or tuberborne. Understanding the disease potential of sources of inocula is crucial for developing disease management strategies and resistance screening techniques. Two hypotheses were tested in this study: (i) soilborne inoculum causes more disease than tuberborne inoculum and (ii) black dot severity is related to the concentration of soilborne inoculum. Trials were conducted in the greenhouse with standardized inoculum. Plants grown in infested soil had more sclerotia on roots than plants grown from infected tubers in three of four trials. In general, plants grown in infested soil produced fewer tubers and lower yields than the noninoculated plants. Plants grown from infected tubers produced similar numbers of tubers as the noninoculated plants in all trials, and had reduced yields in one of the four trials. Increasing concentrations of soilborne inoculum had a nonlinear association with disease development. Foliar symptoms, sclerotial density on roots, and sclerotial development on stems did not increase when soil inoculum exceeded 0.5 or 1.7 g/liters of soil. In this study, soilborne inoculum caused more disease than tuberborne inoculum and disease severity remained constant above a threshold of soilborne inoculum.
Dov Prusky - One of the best experts on this subject based on the ideXlab platform.
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Ammonium secretion during Colletotrichum coccodes infection modulates salicylic and jasmonic acid pathways of ripe and unripe tomato fruit.
Molecular plant-microbe interactions : MPMI, 2012Co-Authors: Noam Alkan, Robert Fluhr, Dov PruskyAbstract:The postharvest pathogens Colletotrichum coccodes remains quiescent after infection of unripe fruit. However, during fruit ripening, the pathogen assumes a necrotrophic life style, rapidly colonizing the tissue. C. coccodes secretes ammonium during germination and colonization of host tissue that induces host programmed cell death. We further examined the role of ammonia in the infection process by analyzing transcriptome expression from infected and ammonia-treated fruit tissue compared with healthy tissue. The analysis revealed 82 and 237 common upregulated and downregulated genes, respectively. Quantitative reverse-transcriptase polymerase chain reaction analysis of select transcripts in normal and transgenic NADPH oxidase antisense plants revealed that their expression was NADPH oxidase dependent. Common-upregulated genes showed overrepresentation of salicylic acid (SA)-dependent genes as well as genes related to biotic stress. The downregulated genes showed overrepresentation of jasmonic acid (JA)-dependent genes. Indeed, direct application of SA to the fruit enhanced C. coccodes necrotrophic colonization, whereas the application of JA delayed colonization. Importantly, green fruit and red fruit displayed similar gene expression patterns although only red fruit is susceptible to colonization. Thus, it is likely that the resistance of green fruit to C. coccodes colonization is due to additional factors.
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Ammonium Secretion by Colletotrichum coccodes Activates Host NADPH Oxidase Activity Enhancing Host Cell Death and Fungal Virulence in Tomato Fruits
Molecular plant-microbe interactions : MPMI, 2009Co-Authors: Noam Alkan, Olga Davydov, Moshe Sagi, Robert Fluhr, Dov PruskyAbstract:Colletotrichum pathogens of fruit and leaves are known ammonium secretors. Here, we show that Colletotrichum coccodes virulence, as measured by tomato (Solanum lycopersicum cv. Motelle) fruit tissue necrosis, correlates with the amount of ammonium secreted. Ammonium application to fruit tissue induced hydrogen peroxide (H2O2) accumulation. To examine whether the tomato NADPH oxidase, SlRBOH, is a source for the ammonium-induced H2O2, wild-type and antisense lines abrogated for SlRBOH (SlRBOH-AS) were examined. Wild-type lines produced 7.5-fold more reactive oxygen species when exposed to exogenous ammonium than did SlRBOH-AS lines. C. coccodes colonization of wild-type tomato lines resulted in higher H2O2 production and faster fungal growth rate compared with colonization in the SlRBOH-AS mutant, although the amount of ammonium secreted by the fungi was similar in both cases. Enhanced ion leakage and cell death of fruit tissue were correlated with H2O2 accumulation, and treatment with the reactive oxygen ...
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Role of ammonia secretion and pH modulation on pathogenicity of Colletotrichum coccodes on tomato fruit.
Molecular plant-microbe interactions : MPMI, 2008Co-Authors: Noam Alkan, Robert Fluhr, Amir Sherman, Dov PruskyAbstract:Colletotrichum coccodes was found to alkalinize the decaying tissue of tomato fruit via accumulation and secretion of ammonia. Alkalinization dynamics caused by ammonia secretion from growing hyphae was examined microscopically using the pH-sensitive fluorescent dye 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein. Values of pH of 7.9 observed in the host tissue close to the hyphal tips declined to pH 6.0 at 10 mm away from the hyphal tip, which was a value that was still higher than that detected in the healthy tissue, pH 4.2. Ammonia accumulation at the infection site depended on the initial environmental pH. Treatments with low (4.0) pH buffer at the infection site resulted in high levels of ammonia secretion and increased virulence of C. coccodes compared with similar treatments with buffer at pH 7.0. Significantly, mutants of C. coccodes defective in nitrogen utilization, nit-, and areA- were impaired in ammonia secretion and showed reduced decay development. The reduced infection rate of nit- mutants could be complemented by adding glutamine at the infection site. Thus, ammonia accumulation is a critical factor contributing to C. coccodes pathogenicity on tomato fruit. The results show that the initial acidic pH of the fruit is conducive to ammonia secretion and the subsequent alkalinization of the infection site, and facilitates fungal virulence and the transformation from the quiescent-biotrophic to active-necrotrophic state.
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Expression of an Antifungal Peptide in Saccharomyces: A New Approach for Biological Control of the Postharvest Disease Caused by Colletotrichum coccodes
Phytopathology, 2002Co-Authors: Richard W. Jones, Dov PruskyAbstract:ABSTRACT A cecropin A-based peptide inhibited germination of Colletotrichum coccodes at 50 μM. The DNA sequence encoding the peptide was cloned in pRS413, using the Saccharomyces cerevisiae invertase leader sequence for secretion of the peptide, and expressed in yeast. Yeast transformants inhibited the growth of germinated C. coccodes spores and inhibited decay development caused by C. coccodes in tomato fruits. Expression of the antifungal peptide in yeast therefore represents a new approach for the biological control of postharvest diseases.