The Experts below are selected from a list of 306 Experts worldwide ranked by ideXlab platform

Richard E Falloon - One of the best experts on this subject based on the ideXlab platform.

  • root infection of potato by spongospora subterranea knowledge review and evidence for decreased plant productivity
    Plant Pathology, 2016
    Co-Authors: U. Merz, Richard E Falloon, R. A. Lister, D Curtin, R C Butler, Steve Thomas
    Abstract:

    Information is reviewed on root infection of potato by the plasmodiophorid Spongospora subterranea f. sp. subterranea. This pathogen has long been recognized as the cause of root galls (hyperplasia) and the economically important disease Powdery Scab on tubers (modified stolons). The significance for plant productivity of the zoosporangium stages of the pathogen in potato roots has only recently begun to be documented. Two experiments are described that assessed effects of S. subterranea root infection on potato plant root function and productivity. A greenhouse experiment measured root function and plant parameters for eight potato cultivars with markedly different susceptibilities to tuber Powdery Scab. Water uptake and plant growth were reduced by S. subterranea inoculation in all eight cultivars. The magnitudes of these negative effects, and intensities of root hyperplasia, differed among the cultivars, but were not related to respective susceptibilities to tuber Powdery Scab. A field trial assessed root function and plant productivity for a cultivar (Iwa) that is very susceptible to Spongospora tuber and root diseases. Soil water content beneath uninoculated plants was consistently less than for inoculated plants, indicating that inoculation reduced water uptake (root function). Inoculation reduced shoot and root dry weights, and reduced weight of tubers per plant by 42%. Spongospora subterranea causes three diseases of potato: root membrane dysfunction, root hyperplasia and tuber Powdery Scab. The root diseases caused by the pathogen are likely to be important both for Powdery Scab management and for deleterious effects on potato crop yields.

  • agronomic factors affect Powdery Scab of potato and amounts of spongospora subterranea dna in soil
    Australasian Plant Pathology, 2014
    Co-Authors: Farhat A. Shah, Richard E Falloon, R. A. Lister, Steve Thomas, R C Butler, D Curtin
    Abstract:

    Severe Powdery Scab (caused by Spongospora subterranea) occurred in potato tubers harvested from a field trial, which measured effects of agronomic treatments (nitrogen fertiliser rates, irrigation intensities, previous crop rotations) on potato yields. Nitrogen application (400 kg N ha−1) increased weight of tubers per plant by 38 %. Incidence and/or severity of Powdery Scab were increased by nitrogen applications. Measurements of S. subterranea DNA in soil at harvest generally reflected the severity of Powdery Scab in harvested tubers. Amounts of DNA were greater after nitrogen application than without nitrogen fertiliser, less after “optimum” irrigation than “low” irrigation, and greater after a potato/wheat rotation than after potato/pea. The field trial area was used for two further growing seasons (without application of treatments) to determine if pre-planting measurements of Spongospora DNA in soil could predict Powdery Scab in harvested potatoes. The disease generally decreased during the next two growing seasons, and effects of the different agronomic treatments on Powdery Scab had disappeared by the second season. However, the greater amounts of pathogen DNA in soil in plots where nitrogen had been applied than where no fertiliser was used continued for the two following growing seasons. Relationships between amounts of pre-planting S. subterranea DNA in soil and Powdery Scab in subsequently harvested tubers were weak in the second growing season, and non-existent in the third. These results demonstrate that agronomic treatments (particularly nitrogen) can increase severity of Powdery Scab in harvested tubers. Furthermore, pre-planting measurements of pathogen DNA in soil did not give good predictions of the incidence or severity of Powdery Scab in harvested potatoes.

  • spongospora subterranea root infection assessed in two potato cultivars differing in susceptibility to tuber Powdery Scab
    Plant Pathology, 2013
    Co-Authors: Richard E Falloon, M Hernandez L Maldonado, A J Conner, R C Butler, Simon Bulman
    Abstract:

    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.

  • low amounts of spongospora subterranea sporosorus inoculum cause severe Powdery Scab root galling and reduced water use in potato solanum tuberosum
    Australasian Plant Pathology, 2012
    Co-Authors: Farhat A. Shah, Richard E Falloon, R C Butler, R. A. Lister
    Abstract:

    This study measured effects of Spongospora subterranea soil inoculum levels on disease of potato tubers and roots, determining relationships between amount of sporosorus inoculum at planting, and both root function during plant growth and Powdery Scab on tubers at harvest. In a series of shadehouse experiments, different amounts of inoculum were applied to soil before planting tubers in large pots, and effects on plant growth and Powdery Scab incidence and severity were determined. In a glasshouse experiment different amounts of inoculum were applied to plants growing in sand/nutrient solution culture, and effects on water use, plant parameters and intensity of S. subterranea root gall formation were measured. In the shadehouse experiments, as few as 25 sporosori mL-1 soil caused Powdery Scab on daughter tubers, and greater amounts of inoculum reduced plant productivity (tuber yields). In the glasshouse experiment, from one to ten sporosori g-1 sand reduced water use by plants and shoot and root dry weights, and caused severe root galling. No consistently strong relationship was found between amount of inoculum at planting and disease incidence or severity at harvest. These results highlight the ability of S. subterranea to cause disease on host plants from low amounts of inoculum when conditions favour disease development, and emphasise the potential for the pathogen to reduce plant growth and tuber yields. They also show that inoculum detection methods should detect low soil inoculum amounts if they are to be useful for Powdery Scab prediction.

  • review Powdery Scab of potato increased knowledge of pathogen biology and disease epidemiology for effective disease management
    Potato Research, 2009
    Co-Authors: Ueli Merz, Richard E Falloon
    Abstract:

    The importance of the potato tuber disease Powdery Scab, caused by the zoosporic pathogen Spongospora subterranea f. sp. subterranea, has increased worldwide, and the disease is one of the most important problems facing potato production in some regions. This soilborne pathogen produces many resting spores which can remain dormant for long periods, are highly resistant to environmental stresses and can spread the disease on seed potatoes and in contaminated soil. The enigmatic nature of this organism exacerbates the development of effective Powdery Scab control methods. Substantial knowledge has been gained in the last decade on the biology of the pathogen and the epidemiology of the disease, but no single effective control measure is, or is likely to be, available. An integrated approach to Powdery Scab management is the aim, with host resistance as a substantial and sustainable component. Further research on the epidemiology of Powdery Scab and population genetics of the pathogen is urgently required. All stakeholders involved in the potato industry must become aware that solution of the Powdery Scab problem is likely to be a long-term goal. When resistant cultivars with all the other characteristics demanded for marketing high-quality potatoes are available, and when disease risk from the pathogen on seed and/or in soil can be accurately determined, then the mission to develop effective Powdery Scab control will become achievable.

Neil C Gudmestad - One of the best experts on this subject based on the ideXlab platform.

  • Chloropicrin Soil Fumigation Reduces Spongospora subterranea Soil Inoculum Levels but Does Not Control Powdery Scab Disease on Roots and Tubers of Potato
    American Journal of Potato Research, 2017
    Co-Authors: Francisco G. Bittara, Gary A Secor, Neil C Gudmestad
    Abstract:

    The effect of chloropicrin fumigation on the soil populations of Spongospora subterranea and the development of Powdery Scab, formation of root galls and tuber yield was investigated in seven field trials conducted in Minnesota and North Dakota. Sixteen potato cultivars, with different levels of susceptibility to disease on roots and tubers, were planted in plots treated with chloropicrin at rates ranging from zero to 201.8 kg a.i. ha−1. The amount of S. subterranea DNA in soil was determined using qPCR. Bioassays were conducted to further assess the effect of chloropicrin fumigation on root colonization by S. subterranea in two potato cultivars with contrasting disease susceptibility. In the field, chloropicrin applied at rates between 70.1 to 201.8 kg a.i. ha−1 significantly decreased S. subterranea initial inoculum in soil but increased the amount of disease observed on roots and tubers of susceptible cultivars. The effect of increasing disease was confirmed in controlled conditions experiments. Although the amount of S. subterranea DNA in roots of bioassay plants increased with increasing chloropicrin rates, it remained similar among potato cultivars. Chloropicrin fumigation significantly increased tuber yield which in cultivars such as Shepody and Umatilla Russet were associated with the amount root galls (r = 0.30; P 

  • chloropicrin soil fumigation reduces spongospora subterranea soil inoculum levels but does not control Powdery Scab disease on roots and tubers of potato
    American Journal of Potato Research, 2017
    Co-Authors: Francisco G. Bittara, Gary A Secor, Neil C Gudmestad
    Abstract:

    The effect of chloropicrin fumigation on the soil populations of Spongospora subterranea and the development of Powdery Scab, formation of root galls and tuber yield was investigated in seven field trials conducted in Minnesota and North Dakota. Sixteen potato cultivars, with different levels of susceptibility to disease on roots and tubers, were planted in plots treated with chloropicrin at rates ranging from zero to 201.8 kg a.i. ha−1. The amount of S. subterranea DNA in soil was determined using qPCR. Bioassays were conducted to further assess the effect of chloropicrin fumigation on root colonization by S. subterranea in two potato cultivars with contrasting disease susceptibility. In the field, chloropicrin applied at rates between 70.1 to 201.8 kg a.i. ha−1 significantly decreased S. subterranea initial inoculum in soil but increased the amount of disease observed on roots and tubers of susceptible cultivars. The effect of increasing disease was confirmed in controlled conditions experiments. Although the amount of S. subterranea DNA in roots of bioassay plants increased with increasing chloropicrin rates, it remained similar among potato cultivars. Chloropicrin fumigation significantly increased tuber yield which in cultivars such as Shepody and Umatilla Russet were associated with the amount root galls (r = 0.30; P < 0.03). Results of these studies contradict earlier reports on the use of chloropicrin fumigation for the control of Powdery Scab. Factors other than inoculum level, such as environmental conditions that affect inoculum efficiency and host susceptibility, may be significant contributors to the development of Powdery Scab and root gall formation.

  • field evaluation of potato genotypes for resistance to Powdery Scab on tubers and root gall formation caused by spongospora subterranea
    American Journal of Potato Research, 2016
    Co-Authors: Francisco G. Bittara, Asunta L Thompson, Neil C Gudmestad, Gary A Secor
    Abstract:

    Spongospora subterranea causes root galls and Powdery Scab on potato tubers (Solanum tuberosum L.). Host resistance represents an economically suitable and long term approach for the management of the disease; however, the relationship between root and tuber symptoms may vary across potato genotypes. To assess susceptibility differences among genotypes, 30 potato cultivars and 83 advanced clones with varying skin type (market class) were evaluated for Powdery Scab and root gall formation. Five field experiments were conducted during 2011 and 2012 on naturally infested soils in Minnesota and North Dakota. Differences among genotypes in the degree of susceptibility to tuber and root symptoms were observed (P < 0.001, n = 33 to 80). Higher Powdery Scab pressure (P < 0.001, n = 90) was observed in North Dakota locations across years. Environmental conditions influenced the formation of root galls and the expression of Powdery Scab, with greatest variability among white- and red-skinned genotypes. Under high disease pressure, the estimates of broad-sense heritability for Powdery Scab incidence and severity were 0.76 and 0.63, respectively. Across environments, russet-skinned genotypes resulted in less disease on tubers, but yielded similar levels of root galls as red-skinned genotypes. Tuber Scab and root gall formation indices were significantly associated (r = 0.42, P < 0.001, n = 80); however, high levels of disease in roots were observed in genotypes ranked resistant to Powdery Scab. Cultivars Dakota Trailblazer, Dakota Russet and Karu ranked highly resistant, whereas Shepody, Kennebec and Red LaSoda were highly susceptible to both phases of the disease. Cultivar selection is highly recommended for disease management.

  • Effect of Soil Moisture Management on the Development of Potato mop-top virus-Induced Tuber Necrosis
    Plant disease, 2015
    Co-Authors: O. Domfeh, Neil C Gudmestad
    Abstract:

    Potato mop-top virus (PMTV), transmitted by Spongospora subterranea f. sp. subterranea, the causal agent of Powdery Scab in potato, has become one of the most important tuber necrosis viruses in the United States. The virus has been confirmed in six major potato-producing states in the United States since its identification in 2003. Currently, no control methods are available for PMTV or its vector. A growth-chamber experiment was conducted to investigate the potential of using moisture regime adjustments to manage tuber necrosis caused by PMTV. Two commercial potato cultivars with varying levels of sensitivity to PMTV, 'Dakota Crisp' and 'Ivory Crisp', were grown in soil obtained from a PMTV-infested field. Over the course of the plant growth cycle, plants of each cultivar were subjected to moisture regimes of wet throughout (WT), wet early/dry late (WEDL), dry early/wet late (DEWL), and dry throughout (DT). Soil moisture levels of 90 and 60% field capacity were considered wet and dry, respectively, while early and late refer to first and last 50 days after planting, respectively. Results of visual assessment conducted 3 months after storage showed significant differences in root gall formation, Powdery Scab on tubers, and PMTV tuber necrosis among moisture regimes. Powdery Scab incidence was significantly higher in the WT and DEWL regimes than WEDL and DT regimes. PMTV tuber necrosis incidence did not differ between the WT and DEWL or between DEWL and WEDL moisture regimes. However, PMTV tuber necrosis incidence was significantly higher in WT than under WEDL and DT regimes. The incidence of PMTV tuber necrosis was significantly lower in the DT regime than in the other three moisture regimes. Severity of PMTV tuber necrosis was significantly higher in the WT than the other regimes, which did not differ statistically among themselves. A significant interaction was found between cultivar and moisture regime on root gall formation, with the highest number of galls found on Ivory Crisp grown in the WT moisture regime. A significant correlation was found between Powdery Scab incidence on tubers and PMTV-induced tuber necrosis incidence. The results of this study provide useful basic information upon which further work can be built for formulating irrigation management schemes that have the potential of reducing the likelihood of Powdery Scab infection and PMTV-induced tuber necrosis development in potato.

  • First Report of Potato Powdery Scab, Caused by Spongospora subterranea f. sp. subterranea, in North Dakota
    Plant Disease, 1997
    Co-Authors: M A Draper, Gary A Secor, Neil C Gudmestad
    Abstract:

    Powdery Scab is a serious disease of potatoes (Solanum tuberosum L.) that can cause extensive surface defects on susceptible potato cultivars. The pathogen, Spongospora subterranea (Wallr.) Lagerh. f. sp. subterranea J. A. Tomlinson, is an important concern in seed potato production because current seed certification standards in North Dakota have a zero tolerance for this pathogen. Powdery Scab had not previously been identified in North Dakota. Until recently this disease was not thought to be present in U.S. commercial potato-producing areas. Powdery Scab has now been shown to be more widely distributed than previously thought (1), having been identified in several locations in eastern and western North America. However, environmental conditions in North Dakota, including high soil pH, low rainfall, and high temperatures, are not considered favorable for Powdery Scab development. Diseased potatoes were found in a field from Griggs County, ND, in the fall of 1994 and characteristic cystosori were presen...

Barbara Jane Christ - One of the best experts on this subject based on the ideXlab platform.

  • peter wilcox a new purple skin yellow flesh fresh market potato cultivar with moderate resistance to Powdery Scab
    American Journal of Potato Research, 2015
    Co-Authors: Kathleen G Haynes, Barbara Jane Christ, G C Yencho, M E Clough, M R Henninger, M W Peck, G A Porter, Chad Hutchinson, Douglas Gergela, D E Halseth
    Abstract:

    Peter Wilcox is a new, medium-maturing, purple-skinned, yellow-fleshed potato cultivar for the fresh market. Peter Wilcox also produces light-colored chips, although it is being released primarily as a fresh market potato because of its skin and flesh colors. Tubers are attractive, smooth, with dark purple-skin, oblong shape and moderate size. Yellow-flesh intensity is equal to or slightly darker than Yukon Gold. Marketable yields of Peter Wilcox have averaged 78–97 % of various standard cultivars in multiple years of testing. Specific gravity of Peter Wilcox was lower than Yukon Gold, but higher than standard red-skin cultivars it was compared to at numerous locations. Hollow heart and internal heat necrosis in Peter Wilcox tubers have generally been less than in standard cultivars; however, slight purple-streaks in the flesh have occasionally been reported in Maine. Peter Wilcox is moderately resistant to Powdery Scab. It is susceptible to late blight, early blight, potato virus Y, Verticillium wilt, and common Scab. Peter Wilcox is a publicly released cultivar.

  • multiplex real time pcr taqman assay for the simultaneous detection and discrimination of potato Powdery and common Scab diseases and pathogens
    Journal of Applied Microbiology, 2011
    Co-Authors: Leslie A. Wanner, Barbara Jane Christ
    Abstract:

    Aims:  To develop a multiplex real-time PCR assay using TaqMan probes for the simultaneous detection and discrimination of potato Powdery Scab and common Scab, two potato tuber diseases with similar symptoms, and the causal pathogens Spongospora subterranea and plant pathogenic Streptomyces spp. Methods and Results:  Real-time PCR primers and a probe for S. subterranea were designed based on the DNA sequence of the ribosomal RNA ITS2 region. Primers and a probe for pathogenic Streptomyces were designed based on the DNA sequence of the txtAB genes. The two sets of primer pairs and probes were used in a single real-time PCR assay. The multiplex real-time PCR assay was confirmed to be specific for S. subterranea and pathogenic Streptomyces. The assay detected DNA quantities of 100 fg for each of the two pathogens and linear responses and high correlation coefficients between the amount of DNA and Ct values for each pathogen were achieved. The presence of two sets of primer pairs and probes and of plant extracts did not alter the sensitivity and efficiency of multiplex PCR amplification. Using the PCR assay, we could discriminate between Powdery Scab and common Scab tubers with similar symptoms. Common Scab and Powdery Scab were detected in some tubers with no visible symptoms. Mixed infections of common Scab and Powdery Scab on single tubers were also revealed. Conclusions:  This multiplex real-time PCR assay is a rapid, cost efficient, specific and sensitive tool for the simultaneous detection and discrimination of the two pathogens on infected potato tubers when visual symptoms are inconclusive or not present. Significance and Impact of the Study:  Accurate and quick identification and discrimination of the cause of Scab diseases on potatoes will provide critical information to potato growers and researchers for disease management. This is important because management strategies for common and Powdery Scab diseases are very different.

  • Multiplex real‐time PCR (TaqMan) assay for the simultaneous detection and discrimination of potato Powdery and common Scab diseases and pathogens
    Journal of applied microbiology, 2011
    Co-Authors: Leslie A. Wanner, Barbara Jane Christ
    Abstract:

    Aims:  To develop a multiplex real-time PCR assay using TaqMan probes for the simultaneous detection and discrimination of potato Powdery Scab and common Scab, two potato tuber diseases with similar symptoms, and the causal pathogens Spongospora subterranea and plant pathogenic Streptomyces spp. Methods and Results:  Real-time PCR primers and a probe for S. subterranea were designed based on the DNA sequence of the ribosomal RNA ITS2 region. Primers and a probe for pathogenic Streptomyces were designed based on the DNA sequence of the txtAB genes. The two sets of primer pairs and probes were used in a single real-time PCR assay. The multiplex real-time PCR assay was confirmed to be specific for S. subterranea and pathogenic Streptomyces. The assay detected DNA quantities of 100 fg for each of the two pathogens and linear responses and high correlation coefficients between the amount of DNA and Ct values for each pathogen were achieved. The presence of two sets of primer pairs and probes and of plant extracts did not alter the sensitivity and efficiency of multiplex PCR amplification. Using the PCR assay, we could discriminate between Powdery Scab and common Scab tubers with similar symptoms. Common Scab and Powdery Scab were detected in some tubers with no visible symptoms. Mixed infections of common Scab and Powdery Scab on single tubers were also revealed. Conclusions:  This multiplex real-time PCR assay is a rapid, cost efficient, specific and sensitive tool for the simultaneous detection and discrimination of the two pathogens on infected potato tubers when visual symptoms are inconclusive or not present. Significance and Impact of the Study:  Accurate and quick identification and discrimination of the cause of Scab diseases on potatoes will provide critical information to potato growers and researchers for disease management. This is important because management strategies for common and Powdery Scab diseases are very different.

  • Proceedings from the Symposium
    American Journal of Potato Research, 2008
    Co-Authors: Barbara Jane Christ
    Abstract:

    Spongospora subterranea f. sp. subterranea is the causal agent of Powdery Scab. The research conducted in the US on this disease has been limited. Worldwide, until recently, the research on this disease focused primarily on how to control the mop-top virus, which is vectored by Spongospora subterranea. In recent years, this disease has become a concern in the US and worldwide even in areas where the mop-top virus has not yet occurred. This disease has been difficult to research because it is an obligate parasite and needs a host to complete its life cycle. It is distributed in an aggregated dispersed fashion within a field and is confined to specific production areas where the soil temperature and moisture levels are optimum. There is no single control method for this disease. There is interesting but difficult research to be performed. With the finding of mop-top virus in the US in 2002, there is a need for us to have first hand current knowledge if this disease. The four papers that compromise these proceedings review the biology, epidemiology and control methods and provide the current research areas that are being performed around the world on Powdery Scab, as well as, address the relationship to the mop top virus. S. subterranea f. sp. subterranea: causal agent of Powdery Scab and vector of mop-top virus

Alison K. Lees - One of the best experts on this subject based on the ideXlab platform.

  • relationship between spongospora subterranea f sp subterranea soil inoculum level host resistance and Powdery Scab on potato tubers in the field
    Plant Pathology, 2013
    Co-Authors: Jennifer L. Brierley, L. Sullivan, A. J. Hilton, D. T. Kiezebrink, S J Wale, Alison K. Lees
    Abstract:

    The relationship between initial soil inoculum level of Spongospora subterranea f. sp. subterranea (Sss) and the incidence and severity of Powdery Scab on potato tubers at harvest was investigated. In all experiments soil inoculum level of Sss (sporeballs ⁄g soil) was measured using a quantitative real-time PCR assay. Of 113 commercial potato fields across the UK, soil inoculum was detected in 75%, ranging from 0 to 148 Sss sporeballs ⁄g soil. When arbitrary soil inoculum threshold values of 0, 10 sporeballs ⁄g soil were set, it was observed that the number of progeny crops developing Powdery Scab increased with the level of inoculum quantified in the field soil preplanting. In four field trials carried out to investigate the link between the amount of inoculum added to the soil and disease development, disease incidence and severity on progeny tubers was found to be significantly (P <0 AE01) greater in plots with increasing levels of inoculum incorporated. There was a cultivar effect in all years, with disease incidence and severity scores being significantly greater in cvs Agria and Estima than in Nicola (P <0 AE01).

  • Relationship between Spongospora subterranea f. sp. subterranea soil inoculum level, host resistance and Powdery Scab on potato tubers in the field
    Plant Pathology, 2012
    Co-Authors: Jennifer L. Brierley, L. Sullivan, A. J. Hilton, D. T. Kiezebrink, S J Wale, Alison K. Lees
    Abstract:

    The relationship between initial soil inoculum level of Spongospora subterranea f. sp. subterranea (Sss) and the incidence and severity of Powdery Scab on potato tubers at harvest was investigated. In all experiments soil inoculum level of Sss (sporeballs ⁄g soil) was measured using a quantitative real-time PCR assay. Of 113 commercial potato fields across the UK, soil inoculum was detected in 75%, ranging from 0 to 148 Sss sporeballs ⁄g soil. When arbitrary soil inoculum threshold values of 0, 10 sporeballs ⁄g soil were set, it was observed that the number of progeny crops developing Powdery Scab increased with the level of inoculum quantified in the field soil preplanting. In four field trials carried out to investigate the link between the amount of inoculum added to the soil and disease development, disease incidence and severity on progeny tubers was found to be significantly (P

  • Powdery Scab resistance in Solanum tuberosum: an assessment of cultivar × environment effect
    Plant Pathology, 2011
    Co-Authors: Ueli Merz, L. Sullivan, Alison K. Lees, T. Hebeisen, H. G. Kirk, R. Schwärzel, K. Bouchek-mechiche, H. R. Hofferbert
    Abstract:

    Publication Inra prise en compte dans l'analyse bibliométrique des publications scientifiques mondiales sur les Fruits, les Légumes et la Pomme de terre. Période 2000-2012. http://prodinra.inra.fr/record/256699International audiencePowdery Scab of potato caused by Spongospora subterranea is one of the main disease problems in many potato production regions of the world. However, no efficient and economically sound control method is currently available. Host resistance will be a key component of the integrated management of Powdery Scab, but there are discrepancies in published Powdery Scab resistance ratings of cultivars between countries. In order to identify the main factors causing such discrepancies, 10 reference cultivars thought to have a range of susceptibility to Powdery Scab and potato mop-top virus were cropped over 4 years in four to six locations across Europe and disease levels on roots and tubers were assessed using standardized scoring scales. Soil contamination was tested using real-time PCR and ELISA. The cultivars performed as expected according to previous characterization, with one exception. No relationship was found between tuber and root susceptibility. Assessment of Powdery Scab symptoms 1 month before harvest gave results comparable to those assessed 2 months after harvest. Neither real-time PCR nor ELISA soil test results were closely related to disease index data. The field trial results indicate that different scoring methods are the main factor for the discrepancy in resistance ratings, and that environmental conditions and/or soil inoculum level play a minor role. Furthermore, there was either no difference between the pathogen populations in each location or the resistance of most of the cultivars is polygenic

  • The use of molecular diagnostics to investigate the epidemiology of potato diseases
    Australasian Plant Pathology, 2005
    Co-Authors: Alison K. Lees, S J Wale, P. Van De Graaf, J. L. Brierley
    Abstract:

    In recent years, quantitative molecular diagnostic assays based on real-time PCR have been developed for many pests and pathogens of potato. In addition, simple sequence repeat markers have been developed and used to track isolates of Phytophthora infestans. These diagnostic assays are now being used as tools to study unresolved questions in the epidemiology of potato diseases including late blight, Powdery Scab and black dot. Examples of various investigations designed to examine the relative contribution of seed and soil-borne inoculum in causing black dot and Powdery Scab on progeny tubers, the effect of environmental factors on the incidence and severity of Powdery Scab and the survival of asexual and sexual inoculum of P. infestans in soil are described. Consideration is given to the development of appropriate diagnostic assays, their use in conjunction with relevant and robust sampling techniques, and the interpretation of results to inform disease risk assessment and control strategies through industry collaboration.

Ueli Merz - One of the best experts on this subject based on the ideXlab platform.

  • Powdery Scab resistance in Solanum tuberosum: an assessment of cultivar × environment effect
    Plant Pathology, 2011
    Co-Authors: Ueli Merz, L. Sullivan, Alison K. Lees, T. Hebeisen, H. G. Kirk, R. Schwärzel, K. Bouchek-mechiche, H. R. Hofferbert
    Abstract:

    Publication Inra prise en compte dans l'analyse bibliométrique des publications scientifiques mondiales sur les Fruits, les Légumes et la Pomme de terre. Période 2000-2012. http://prodinra.inra.fr/record/256699International audiencePowdery Scab of potato caused by Spongospora subterranea is one of the main disease problems in many potato production regions of the world. However, no efficient and economically sound control method is currently available. Host resistance will be a key component of the integrated management of Powdery Scab, but there are discrepancies in published Powdery Scab resistance ratings of cultivars between countries. In order to identify the main factors causing such discrepancies, 10 reference cultivars thought to have a range of susceptibility to Powdery Scab and potato mop-top virus were cropped over 4 years in four to six locations across Europe and disease levels on roots and tubers were assessed using standardized scoring scales. Soil contamination was tested using real-time PCR and ELISA. The cultivars performed as expected according to previous characterization, with one exception. No relationship was found between tuber and root susceptibility. Assessment of Powdery Scab symptoms 1 month before harvest gave results comparable to those assessed 2 months after harvest. Neither real-time PCR nor ELISA soil test results were closely related to disease index data. The field trial results indicate that different scoring methods are the main factor for the discrepancy in resistance ratings, and that environmental conditions and/or soil inoculum level play a minor role. Furthermore, there was either no difference between the pathogen populations in each location or the resistance of most of the cultivars is polygenic

  • First Confirmed Report of Powdery Scab Caused by Spongospora subterranea f. sp. subterranea on Potato in Sri Lanka.
    Plant disease, 2011
    Co-Authors: A G C Babu, Ueli Merz
    Abstract:

    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 through 2010 at Pedru. In 2009 and 2010, blister-like lesions on tubers and root galls were again observed on seed of cvs. Calwhite, Keuka Gold, Red la Soda, and Chieftain imported from the United States and planted at the Agricultural Research Station, Site Eliya. In February 2004, a bioassay was carried out using healthy tubers of cvs. Roko, Cykoda, Delawae, and Isna to evaluate the potential contamination of field soils. Clay pots filled with soil samples collected from the suspected contaminated fields were planted with seed of the above cultivars. The pots were arranged in a complete random design with three replicates per cultivar in a place isolated from any potato-production location. Seventy-five days after planting, all varieties were recorded with white root galls but no lesions on the tubers. With light microscopy, suspected root and tuber tissue was examined to confirm the presence of the characteristic sporosori of the soilborne pathogen S. subterranea (Wallr.) f. sp. subterranea with their unique sponge-like structure (1). Additionally, two root galls and three tuber lesions were prepared for diagnostics by ELISA using antiserum produced against S. subterranea (Wallr.) f. sp. subterranea (3) and reactions were positive. Furthermore, in a lab-based bioassay (2), sporosori obtained from a single root gall and a single tuber lesion were used to inoculate tomato bait plants, cv. Marmande. Eight days postinoculation, zoosporangia were observed microscopically in roots at frequencies of 10 of 12 and 11 of 12 plants for the root gall and the tuber lesion, respectively. To our knowledge, the results presented here are the first confirmed report of the presence of S. subterranea (Wallr.) f. sp. subterranea, the causal agent of potato Powdery Scab in Sri Lanka. Powdery Scab currently occurs at several places in Sri Lanka. Therefore, more attention should be paid to this disease in the seed certification process and seed import regulations concerning Powdery Scab should be strictly enforced. References: (1) C. H. Lawrence and A. R. McKenzie. Powdery Scab. Page 35 in: Compendium of Potato Diseases. The American Phytopathological Society, St, Paul, MN, 1981. (2) U. Merz et al. Eur. J. Plant Pathol. 110:71, 2004. (3) U. Merz et al. Eur. J. Plant Pathol. 111:171, 2005.

  • Powdery Scab effect on the potato Solanum tuberosum ssp. andigena growth and yield
    Tropical Plant Pathology, 2011
    Co-Authors: Elizabeth Gilchrist, Ueli Merz, Juliana Soler, Sebastián Reynaldi
    Abstract:

    Powdery Scab affects most potato production zones in the world. The causal organism Spongospora subterranea f. sp. subterranea forms galls in roots and lesions on tubers during its replication. Recent researches suggest that S. subterranea could cause harmful effects on the host plant and potentially on yield.In order to quantify the disease impact on plant growth and yield, potato Solanum tuberosum ssp. andigena, cv. Diacol Capiro was grown in a soil infested with S. subterranea and compared to a healthy control soil. Data was taken at the flowering stage and at harvest. S. subterranea caused a plant length reduction of 23%, a foliar dry weight reduction of 32% and a tuber weight reduction of 30%, whereas S. subterranea did not reduce the number of tubers or stems.

  • review Powdery Scab of potato increased knowledge of pathogen biology and disease epidemiology for effective disease management
    Potato Research, 2009
    Co-Authors: Ueli Merz, Richard E Falloon
    Abstract:

    The importance of the potato tuber disease Powdery Scab, caused by the zoosporic pathogen Spongospora subterranea f. sp. subterranea, has increased worldwide, and the disease is one of the most important problems facing potato production in some regions. This soilborne pathogen produces many resting spores which can remain dormant for long periods, are highly resistant to environmental stresses and can spread the disease on seed potatoes and in contaminated soil. The enigmatic nature of this organism exacerbates the development of effective Powdery Scab control methods. Substantial knowledge has been gained in the last decade on the biology of the pathogen and the epidemiology of the disease, but no single effective control measure is, or is likely to be, available. An integrated approach to Powdery Scab management is the aim, with host resistance as a substantial and sustainable component. Further research on the epidemiology of Powdery Scab and population genetics of the pathogen is urgently required. All stakeholders involved in the potato industry must become aware that solution of the Powdery Scab problem is likely to be a long-term goal. When resistant cultivars with all the other characteristics demanded for marketing high-quality potatoes are available, and when disease risk from the pathogen on seed and/or in soil can be accurately determined, then the mission to develop effective Powdery Scab control will become achievable.

  • Powdery Scab of potato occurrence life cycle and epidemiology
    American Journal of Potato Research, 2008
    Co-Authors: Ueli Merz
    Abstract:

    Powdery Scab of potato, caused by the zoosporic pathogen Spongospora subterranea f.sp. subterranea (Sss), is an often underestimated disease, which has lead to lack of appropriate control strategies. A new wave of increasing importance of this disease has occurred in the last 30 years in many countries, among them France, Pakistan, Japan, Australia, New Zealand, Costa Rica, USA, and, very recently, Colombia, Korea and China. A consequence is that occurrence of, and research on, Powdery Scab has shown a cyclic pattern. Additionally to its importance as a pathogen, Sss is a vector of potato mop top virus which itself can cause substantial damage. Factors such as intensification of potato production, increasing use of susceptible cultivars, more frequent irrigation and banning of mercury, previously used as an efficient seed tuber treatment, have all contributed to greater incidence of Powdery Scab. Since 1842, when Wallroth first described the disease in the scientific literature, many researchers, particularly before 1960, started to work with Sss, mostly because Powdery Scab became a problem in their respective countries. Today we know many aspects of the biology of the biotrophic protozoan organism that causes Powdery Scab, but we still lack basic knowledge on the etiology and epidemiology of the disease. We lack sufficient knowledge of the factors that affect survival of the resting structures, potato and alternative host infection and disease development. This knowledge is essential in predicting disease risk and developing effective Powdery Scab management strategies.