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R Lowe - One of the best experts on this subject based on the ideXlab platform.

  • detection of spore balls of spongospora subterranea on potato Tubers by enzyme linked immunosorbent assay
    Plant Pathology, 1993
    Co-Authors: J. G. Harrison, E A Rees, H. Barker, R Lowe
    Abstract:

    A rabbit was immunized with a homogenate of spore balls (cystosori) of Spongospora subterranea which also contained some potato Tuber debris. The resultant polyclonal antiserum contained antibodies which reacted against extracts of spore balls and healthy Tubers. Antibodies to the Tuber debris were removed by incubating the blood serum with an extract from a S. subterranea-free Tuber. In enzyme-linked immunosorbent assay (ELISA), the γ-globulin fraction of the absorbed antiserum reacted with dilute Tuber extracts containing the equivalent of as little as 0·08 spore balls per ml. The reaction with spore balls was inhibited in high concentrations of Tuber sap. Extracts of peel from symptomless Tubers which had been stored in contact with scabbed Tubers also reacted with the γ-globulin, presumably because the symptomless Tubers became contaminated with spore balls. However, spore balls in soil were only weakly detected when high numbers were present. The γ-globulin did not react with the plasmodial stage of the pathogen, or with 15 other micro-organisms tested, including resting spores of Plasmodiophora brassicae.

  • Detection of spore balls of Spongospora subterranea on potato Tubers by enzyme‐linked immunosorbent assay
    Plant Pathology, 1993
    Co-Authors: J. G. Harrison, E A Rees, H. Barker, R Lowe
    Abstract:

    A rabbit was immunized with a homogenate of spore balls (cystosori) of Spongospora subterranea which also contained some potato Tuber debris. The resultant polyclonal antiserum contained antibodies which reacted against extracts of spore balls and healthy Tubers. Antibodies to the Tuber debris were removed by incubating the blood serum with an extract from a S. subterranea-free Tuber. In enzyme-linked immunosorbent assay (ELISA), the γ-globulin fraction of the absorbed antiserum reacted with dilute Tuber extracts containing the equivalent of as little as 0·08 spore balls per ml. The reaction with spore balls was inhibited in high concentrations of Tuber sap. Extracts of peel from symptomless Tubers which had been stored in contact with scabbed Tubers also reacted with the γ-globulin, presumably because the symptomless Tubers became contaminated with spore balls. However, spore balls in soil were only weakly detected when high numbers were present. The γ-globulin did not react with the plasmodial stage of the pathogen, or with 15 other micro-organisms tested, including resting spores of Plasmodiophora brassicae.

Dennis A. Johnson - One of the best experts on this subject based on the ideXlab platform.

  • Effects of Tuber Depth and Soil Moisture on Infection of Potato Tubers in Soil by Phytophthora infestans.
    Plant disease, 2005
    Co-Authors: L. D. Porter, Nairanjana Dasgupta, Dennis A. Johnson
    Abstract:

    The effects of Tuber depth, soil type, and soil moisture on potato Tuber infection due to Phytophthora infestans were assessed under greenhouse conditions in soil contained in large pots. Healthy Tubers were used to assess infection and were either hand buried in soil at specific depths or naturally formed from potato plants growing in the soil. A spore suspension of P. infestans was chilled to induce zoospore formation and a suspension of resulting zoospores and sporangia were applied to the soil. Soil depth at which Tubers became infected was used to determine the extent of spore movement in the soils. Tuber infection significantly decreased with increasing soil depth. Most infected Tubers were found at the surface of soil; infection was rare on Tubers at 5 cm or deeper in the soil. Amount of Tuber infection varied among soil types. Significantly less Tuber infection occurred in a Shano silt loam than in medium and fine sands. Only Tubers on the soil surface were infected in the Shano silt loam. Depth in soil at which Tubers became infected did not differ significantly among Quincy fine sand, Quincy loamy fine sand, and Quincy medium sand. Increased soil moisture did not significantly increase the soil depth at which Tuber infection occurred, regardless of the soil type.

  • Control of Potato Tuber Rots Caused by Oomycetes with Foliar Applications of Phosphorous Acid.
    Plant disease, 2004
    Co-Authors: Dennis A. Johnson, Debra Ann Inglis, Jeffrey S. Miller
    Abstract:

    Phosphorous acid for control of Tuber rots caused by Phytophthora infestans, P. erythroseptica, and Pythium ultimum was applied to foliage of potato cultivars at various application timings and rates under growing conditions in the Pacific Northwest at Othello and Mount Vernon, WA, and Bonners Ferry and Aberdeen, ID in 2001 to 2003. Efficacy was assessed by artificially inoculating harvested Tubers. Mean incidence and severity of late blight Tuber rot in Tubers inoculated with US-8 and US-11 isolates of Phytophthora infestans usually were significantly less when the foliage from which the Tubers were obtained was treated with phosphorous acid than when it was not treated at all locations. With two applications of phosphorous acid, late blight Tuber rot in the Tuber-resistant cv. Umatilla Russet was significantly less than for Ranger Russet. For phosphorous acid at a rate of 9.37 kg a.i./ha, late blight Tuber rot control achieved with two applications at 2-week intervals was not consistently improved across locations by making an additional application 2 weeks later. In 2003, incidence and severity of late blight Tuber rot did not differ significantly between the rates of 7.49 and 9.37 kg a.i./ha at both Othello and Mount Vernon. Late blight Tuber rot incidence and severity were significantly less at a rate of 7.49 kg a.i./ha when the application schedule began at initial Tuber bulking rather than when the first application was made 4 weeks after initial Tuber bulking at Othello, but not Mount Vernon. Incidence of pink rot was significantly less in inoculated Tubers from plots treated with three applications of phosphorous acid than in Tubers from nontreated control plots at Mount Vernon in 2002 and 2003, Bonners Ferry in 2002, and Aberdeen in 2003. Pink rot severity was reduced significantly by both two and three phosphorous acid applications at Mount Vernon in 2002. Pink rot incidence, but not severity, was reduced significantly at all timings when either 7.49 or 9.37 kg a.i./ha was applied at Mount Vernon in 2003. Control of Pythium spp. by phosphorous acid was not evident in this study. Total Tuber yield at harvest did not differ significantly among the phosphorous acid treatments and the nontreated control at Othello and Mount Vernon in 2001 and 2002.

  • Incidence of Colletotrichum coccodes in certified potato seed Tubers planted in Washington State
    Plant disease, 1997
    Co-Authors: Dennis A. Johnson, Randall C. Rowe, Thomas F. Cummings
    Abstract:

    Incidence of Colletotrichum coccodes in lots of certified seed Tubers planted in Washington state, originating from nine western and midwestern states in the United State and two provinces in Canada, ranged from 0 to 90% in 1994 and 0 to 53% in 1995. In 1994, significant interactions between state/province and cultivar, and between seed grower and cultivar, were evident. In 1995, incidence of C. coccodes in seed lots did not vary significantly among states and cultivars. C. coccodes was not isolated from nuclear seed Tubers and incidence of infected Tubers was higher with higher seed generations. The fungus was isolated from the Tuber periderm and outer medulla tissues and isolation frequency was greater from Tuber stem ends than from either bud ends or lateral sections. Significantly greater stem infections developed in plants grown from seed Tubers in which C. coccodes had been detected than in plants grown from seed Tubers from which C. coccodes had not been isolated. This study confirms that C. coccodes is distributed among potato-production areas within seed Tubers, and that seed Tuber infection increases the incidence of early-season plant infection.

C R Wilson - One of the best experts on this subject based on the ideXlab platform.

  • qpcr testing seed potato Tubers for pathogens what value for potato seed certification
    XXIX International Horticultural Congress on Horticulture: Sustaining Lives Livelihoods and Landscapes: International Symposium on Root and Tuber Crop, 2016
    Co-Authors: R S Tegg, C R Wilson
    Abstract:

    Utilising certified seed is an important principle in providing a potato crop with the greatest opportunity to grow to its full potential free of disease. Within Australia economically important Tuber blemish diseases affecting potato Tuber quality include Black scurf, Common scab, Powdery scab and Root knot nematode, caused by infections with the pathogens, Rhizoctonia solani , Streptomyces scabies, Spongospora subterranea f. sp. subterranea , and Meloidogyne spp. respectively. All of these pathogens may be carried on seed-Tubers providing inoculum for disease in the subsequent crops, and are assessed in potato seed-Tuber certification schemes world-wide. Typically seedlots are certified by visual subjective assessments of disease but recently developed quantitative polymerase chain reaction (qPCR) tools that detect and enumerate pathogen DNA provide an additional measure of seed Tuber health. We compared both visual and qPCR assessments of potato seedlots passing through the Tasmanian potato certification scheme over a three year period. Further, selected Tubers carrying Tuber-borne inoculum loads of the three pathogens were grown in pathogen-free potting soil to establish whether the concentration of pathogen DNA from the Tuber peel was associated with progeny crop disease. Outcomes suggest that visual assessment, in most circumstances provides an accurate measure of Tuber seed health for certification; however qPCR was able to clearly differentiate difficult to distinguish diseases and identify levels of pathogen DNA present on symptomless Tubers. Additionally, it was shown that planting Tubers with high pathogen inoculum loads led to enhanced progeny disease compared to planting 'certified' Tubers.

  • QPCR testing seed potato Tubers for pathogens – what value for potato seed certification?
    Acta Horticulturae, 2016
    Co-Authors: R S Tegg, C R Wilson
    Abstract:

    Utilising certified seed is an important principle in providing a potato crop with the greatest opportunity to grow to its full potential free of disease. Within Australia economically important Tuber blemish diseases affecting potato Tuber quality include Black scurf, Common scab, Powdery scab and Root knot nematode, caused by infections with the pathogens, Rhizoctonia solani , Streptomyces scabies, Spongospora subterranea f. sp. subterranea , and Meloidogyne spp. respectively. All of these pathogens may be carried on seed-Tubers providing inoculum for disease in the subsequent crops, and are assessed in potato seed-Tuber certification schemes world-wide. Typically seedlots are certified by visual subjective assessments of disease but recently developed quantitative polymerase chain reaction (qPCR) tools that detect and enumerate pathogen DNA provide an additional measure of seed Tuber health. We compared both visual and qPCR assessments of potato seedlots passing through the Tasmanian potato certification scheme over a three year period. Further, selected Tubers carrying Tuber-borne inoculum loads of the three pathogens were grown in pathogen-free potting soil to establish whether the concentration of pathogen DNA from the Tuber peel was associated with progeny crop disease. Outcomes suggest that visual assessment, in most circumstances provides an accurate measure of Tuber seed health for certification; however qPCR was able to clearly differentiate difficult to distinguish diseases and identify levels of pathogen DNA present on symptomless Tubers. Additionally, it was shown that planting Tubers with high pathogen inoculum loads led to enhanced progeny disease compared to planting 'certified' Tubers.

  • Modeling Pathogen DNA Content and Visual Disease Assessment in Seed Tubers to Inform Disease in Potato Progeny Root, Stolon, and Tubers
    Plant disease, 2015
    Co-Authors: R S Tegg, Ross Corkrey, Herdina Herdina, Alan C. Mckay, Nigel S Crump, Rudolf F De Boer, Tonya J Wiechel, C R Wilson
    Abstract:

    Measurement of pathogens on seed Tubers is essential for informing likelihood of subsequent potato disease. Here we utilized quantitative PCR assessment of pathogen DNA and visual assessment of disease to measure seed Tuber inoculum and used this to model development of disease in potato grown in pathogen-free soil. Analysis by recursive partitioning and modeling using receiver operating curves indicated both abundance of Rhizoctonia solani AG3 and Streptomyces scabies DNA, and disease symptoms associated with these pathogens on seed Tubers could predict subsequent disease in progeny Tubers and for R. solani, stolons. In contrast, abundance of Spongospora subterranea DNA and disease symptoms on seed Tubers were not consistently associated with powdery scab in progeny Tubers. The relationship between S. subterranea DNA and seed Tuber symptoms on root galling was stronger. Symptomless seed Tubers that carried high levels of S. subterranea DNA were also associated with greater root galling than those with low pathogen DNA levels. There was a modest association between root galling and powdery scab in progeny Tubers. These results highlight the importance of using certified seed Tubers, and demonstrate a statistical tool for measuring the impact of seed Tuber-borne inoculum.

  • A comparison of potato seed-Tuber sampling strategies using visual and DNA analyses to estimate incidence of major seed Tuber-borne pathogens
    European Journal of Plant Pathology, 2014
    Co-Authors: R S Tegg, Ross Corkrey, C R Wilson
    Abstract:

    Potato seed certification is a disease management tool that minimises the risk of spreading seed Tuber-borne inoculum of infectious diseases. Traditionally, certification sampling strategies have relied upon visual assessment of a seedlot from samples taken at one or two points within the load of seed Tubers. However methodologies in selection of Tuber samples have not been critically assessed for their precision in estimating disease load. This study presents an analysis of 37 potato seedlots over a 3 year period. Analysis of sample data using receiver operating curves (ROCs) indicates that point sampling taking two samples of 100 Tubers at the beginning and end of a seedlot gives equivalent disease estimation as a continuous sampling strategy taking ten samples of 20 Tubers randomly throughout the seedlot, although at lower statistical precision. This was confirmed both by visual assessment of Tuber-borne disease and by analysis of pathogen DNA content from Tuber peel. Across the 3 years of study, powdery scab and black scurf were the major seed Tuber-borne diseases recognised and this corresponded with high levels of pathogen DNA from peel analysis for both Spongospora subterranea and Rhizoctonia solani AG3 respectively.

J. G. Harrison - One of the best experts on this subject based on the ideXlab platform.

  • detection of spore balls of spongospora subterranea on potato Tubers by enzyme linked immunosorbent assay
    Plant Pathology, 1993
    Co-Authors: J. G. Harrison, E A Rees, H. Barker, R Lowe
    Abstract:

    A rabbit was immunized with a homogenate of spore balls (cystosori) of Spongospora subterranea which also contained some potato Tuber debris. The resultant polyclonal antiserum contained antibodies which reacted against extracts of spore balls and healthy Tubers. Antibodies to the Tuber debris were removed by incubating the blood serum with an extract from a S. subterranea-free Tuber. In enzyme-linked immunosorbent assay (ELISA), the γ-globulin fraction of the absorbed antiserum reacted with dilute Tuber extracts containing the equivalent of as little as 0·08 spore balls per ml. The reaction with spore balls was inhibited in high concentrations of Tuber sap. Extracts of peel from symptomless Tubers which had been stored in contact with scabbed Tubers also reacted with the γ-globulin, presumably because the symptomless Tubers became contaminated with spore balls. However, spore balls in soil were only weakly detected when high numbers were present. The γ-globulin did not react with the plasmodial stage of the pathogen, or with 15 other micro-organisms tested, including resting spores of Plasmodiophora brassicae.

  • Detection of spore balls of Spongospora subterranea on potato Tubers by enzyme‐linked immunosorbent assay
    Plant Pathology, 1993
    Co-Authors: J. G. Harrison, E A Rees, H. Barker, R Lowe
    Abstract:

    A rabbit was immunized with a homogenate of spore balls (cystosori) of Spongospora subterranea which also contained some potato Tuber debris. The resultant polyclonal antiserum contained antibodies which reacted against extracts of spore balls and healthy Tubers. Antibodies to the Tuber debris were removed by incubating the blood serum with an extract from a S. subterranea-free Tuber. In enzyme-linked immunosorbent assay (ELISA), the γ-globulin fraction of the absorbed antiserum reacted with dilute Tuber extracts containing the equivalent of as little as 0·08 spore balls per ml. The reaction with spore balls was inhibited in high concentrations of Tuber sap. Extracts of peel from symptomless Tubers which had been stored in contact with scabbed Tubers also reacted with the γ-globulin, presumably because the symptomless Tubers became contaminated with spore balls. However, spore balls in soil were only weakly detected when high numbers were present. The γ-globulin did not react with the plasmodial stage of the pathogen, or with 15 other micro-organisms tested, including resting spores of Plasmodiophora brassicae.

E A Rees - One of the best experts on this subject based on the ideXlab platform.

  • detection of spore balls of spongospora subterranea on potato Tubers by enzyme linked immunosorbent assay
    Plant Pathology, 1993
    Co-Authors: J. G. Harrison, E A Rees, H. Barker, R Lowe
    Abstract:

    A rabbit was immunized with a homogenate of spore balls (cystosori) of Spongospora subterranea which also contained some potato Tuber debris. The resultant polyclonal antiserum contained antibodies which reacted against extracts of spore balls and healthy Tubers. Antibodies to the Tuber debris were removed by incubating the blood serum with an extract from a S. subterranea-free Tuber. In enzyme-linked immunosorbent assay (ELISA), the γ-globulin fraction of the absorbed antiserum reacted with dilute Tuber extracts containing the equivalent of as little as 0·08 spore balls per ml. The reaction with spore balls was inhibited in high concentrations of Tuber sap. Extracts of peel from symptomless Tubers which had been stored in contact with scabbed Tubers also reacted with the γ-globulin, presumably because the symptomless Tubers became contaminated with spore balls. However, spore balls in soil were only weakly detected when high numbers were present. The γ-globulin did not react with the plasmodial stage of the pathogen, or with 15 other micro-organisms tested, including resting spores of Plasmodiophora brassicae.

  • Detection of spore balls of Spongospora subterranea on potato Tubers by enzyme‐linked immunosorbent assay
    Plant Pathology, 1993
    Co-Authors: J. G. Harrison, E A Rees, H. Barker, R Lowe
    Abstract:

    A rabbit was immunized with a homogenate of spore balls (cystosori) of Spongospora subterranea which also contained some potato Tuber debris. The resultant polyclonal antiserum contained antibodies which reacted against extracts of spore balls and healthy Tubers. Antibodies to the Tuber debris were removed by incubating the blood serum with an extract from a S. subterranea-free Tuber. In enzyme-linked immunosorbent assay (ELISA), the γ-globulin fraction of the absorbed antiserum reacted with dilute Tuber extracts containing the equivalent of as little as 0·08 spore balls per ml. The reaction with spore balls was inhibited in high concentrations of Tuber sap. Extracts of peel from symptomless Tubers which had been stored in contact with scabbed Tubers also reacted with the γ-globulin, presumably because the symptomless Tubers became contaminated with spore balls. However, spore balls in soil were only weakly detected when high numbers were present. The γ-globulin did not react with the plasmodial stage of the pathogen, or with 15 other micro-organisms tested, including resting spores of Plasmodiophora brassicae.