Progress 03/12/07 to 03/11/12
Outputs
Progress Report Objectives (from AD-416): (1) Investigate microbe-induced chemical changes on flower surfaces, with particular attention to pH modification, as modes of antagonism towards the fire blight bacterium, Erwinia amylovora; (2) evaluate the contribution and possible relationship of different modes of microbial antagonism toward E. amylovora, including pH reduction, antibiotic production and competitive exclusion; and (3) develop mixtures of antagonists with complimentary mechanisms and ecological niches and integrate their use with other fire blight management strategies. Approach (from AD-416): To accomplish the first objective, we will focus primarily on Pantoea agglomerans strain E325, a patented biocontrol agent recently registered by EPA. This strain was shown in preliminary tests to increase the acidity of stigma exudates based on the pH of exudates extracted from inoculated flowers. Laboratory experiments will be performed with an artificial stigma-based medium (SBM) and detached crab apple flowers prior to conducting field studies. Work with SBM and variations of it will be used to evaluate the relationship between pathogen suppression and pH reduction, determine the pH range and optimum for both pathogen and antagonist bacteria, and evaluate changes in acid production under varying buffer capacities and oxygen conditions. In flower bioassays, pH on stigmatic surfaces will be directly measured using pH-sensitive fluorescent dyes and confocal laser microscopy or with fabricated microelectrodes. In addition, stigma exudates extracted from inoculated flowers will be analyzed for sugar consumption and bacteria-produced organic acids. In field experiments with apple, flowers will be sampled and their stigmas evaluated for bacterial population size, pH and specific organic acids. Similar methods will be used to assess whether biocontrol treatments can be enhanced through the addition of various soft agrochemicals (e.g., foliar nitrogen fertilizers and pH buffers) that may alter acid production by bacteria or directly affect pH on flower surfaces. For the second objective, a collection of antagonist strains, previously shown to be among the best performers in flower bioassays, will be evaluated for mode of action. This will involve a series of laboratory tests with SBM and flowers to determine the importance of acid production, antibiotic production and nutrient depletion as mechanisms of individual antagonist strains. Major extracellular compounds inhibitory to Erwinia amylovora will be identified or characterized. For the third objective, a strategy of enhancing biocontrol with antagonist mixtures will be largely dependent on results of the first two objectives. To fully exploit multiple antagonists and mechanisms, we will evaluate the compatibility of antagonists and avoid or eliminate incompatibilities. Further screening of microbial epiphytes from apple and pear may be necessary to develop the best complement of antagonists. Finally, to further improve the management of fire blight, we will test the integration of antagonist mixtures with other control approaches or agents. This is the final report for the project 5350-22000-015-00D terminated in March 2012. Accomplishments were incorporated in the new inhouse project #5350-22000-018-00D. Fire blight is a potentially devastating disease of apple and pear trees that is generally initiated in flowers by the disease causing bacterium Erwinia amylovora. Disease control historically depended on chemical control measures, but resistance in E. amylovora and safety-related concerns prompted a search for alternative strategies. ARS scientists at Wenatchee, Washington, who previously developed the biocontrol agent Pantoea agglomeran strain E325, now available commercially for fire blight control, and completed studies to understand the biocontrol mechanisms of this beneficial bacterium. Reduction of pH and competition for nutrients on flower stigmas were implicated in biological control, but these mechanisms did not adequately explain the exceptional performance of strain E325. Meanwhile, the chemistry of flower stigmas was characterized and a partial stigma-based medium developed to detect other possible modes of E325 action. This led to the discovery of a unique peptidic compound produced by E325 that is highly inhibitory and specific to E. amylovora. Through collaborations with other researchers, information was generated related to the identity and structure of the peptide and its synthesis by a specific gene located on a plasmid. Involvement of the E325 product in biological control was confirmed by laboratory and field tests showing that mutated bacterial strains lacking the ability to produce the compound were much less effective than the parental strain in suppressing E. amylovora on flowers. Attempts to improve E325 as a biocontrol agent included culturing cells in high-saline media to induce osmoadaptation. This process increased cell survival during freeze drying and subsequent storage, leading to modifications in the commercial production and formulation of E325. Progress was made toward the goal of enhancing biological control of fire blight through the use of microbial mixtures with complementary modes of action in ecological niches. Based on previous evaluations of hundreds of microorganisms screened for biocontrol potential on flowers, effective yeast strains that possibly could complement E325 were selected and field tested. Further research is necessary to assess whether E325 combined with yeast strains are more effective than either type of biocontrol agent alone. The above activities relate to Objective 1 (�Investigate microbe �induced chemical changes on flower�� ), Objective 1B (�Optimize�production and product formulation�), Objective 2 (�Evaluate the contribution and possible relationship of different modes of microbial antagonism toward E. amylovora, including...antibiotic production��), and Objective 3 (�Develop mixtures of antagonists��).
Impacts
(N/A)
Publications
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Progress 10/01/10 to 09/30/11
Outputs
Progress Report Objectives (from AD-416) (1) Investigate microbe-induced chemical changes on flower surfaces, with particular attention to pH modification, as modes of antagonism towards the fire blight bacterium, Erwinia amylovora; (2) evaluate the contribution and possible relationship of different modes of microbial antagonism toward E. amylovora, including pH reduction, antibiotic production and competitive exclusion; and (3) develop mixtures of antagonists with complimentary mechanisms and ecological niches and integrate their use with other fire blight management strategies. Approach (from AD-416) To accomplish the first objective, we will focus primarily on Pantoea agglomerans strain E325, a patented biocontrol agent recently registered by EPA. This strain was shown in preliminary tests to increase the acidity of stigma exudates based on the pH of exudates extracted from inoculated flowers. Laboratory experiments will be performed with an artificial stigma-based medium (SBM) and detached crab apple flowers prior to conducting field studies. Work with SBM and variations of it will be used to evaluate the relationship between pathogen suppression and pH reduction, determine the pH range and optimum for both pathogen and antagonist bacteria, and evaluate changes in acid production under varying buffer capacities and oxygen conditions. In flower bioassays, pH on stigmatic surfaces will be directly measured using pH-sensitive fluorescent dyes and confocal laser microscopy or with fabricated microelectrodes. In addition, stigma exudates extracted from inoculated flowers will be analyzed for sugar consumption and bacteria-produced organic acids. In field experiments with apple, flowers will be sampled and their stigmas evaluated for bacterial population size, pH and specific organic acids. Similar methods will be used to assess whether biocontrol treatments can be enhanced through the addition of various soft agrochemicals (e.g., foliar nitrogen fertilizers and pH buffers) that may alter acid production by bacteria or directly affect pH on flower surfaces. For the second objective, a collection of antagonist strains, previously shown to be among the best performers in flower bioassays, will be evaluated for mode of action. This will involve a series of laboratory tests with SBM and flowers to determine the importance of acid production, antibiotic production and nutrient depletion as mechanisms of individual antagonist strains. Major extracellular compounds inhibitory to Erwinia amylovora will be identified or characterized. For the third objective, a strategy of enhancing biocontrol with antagonist mixtures will be largely dependent on results of the first two objectives. To fully exploit multiple antagonists and mechanisms, we will evaluate the compatibility of antagonists and avoid or eliminate incompatibilities. Further screening of microbial epiphytes from apple and pear may be necessary to develop the best complement of antagonists. Finally, to further improve the management of fire blight, we will test the integration of antagonist mixtures with other control approaches or agents. Fire blight is a potentially devastating disease of apple and pear trees that is generally initiated in flowers. Disease control historically depended on chemical control measures, but pathogen resistance and safety- related concerns prompted a search for alternative strategies. ARS scientists at Wenatchee, who developed what is now a commercial biocontrol agent for fire blight, completed studies showing that antibiosis is an important mechanism of the biocontrol activity. This was accomplished by comparing the performance of the beneficial bacterium, Pantoea agglomerans strain E325, with mutated derivative strains lacking the ability to produce a unique antibiotic compound. The derivative strains were much less effective than the parental strain in suppressing the disease organism on floral surfaces. Through collaborations with other researchers, new information was obtained relating to the identity and structure of the E325 antibiotic, and the gene for its production was found located on a plasmid. Efforts to improve E325 through a process known as osmoadaptation continued from the previous year, with experiments demonstrating that high salt levels in growth media increase the survival of E325 during freeze drying and subsequent storage prior to application. These results led to modifications in the commercial production and formulation of the biocontrol agent. As another attempt to improve product formulation, collaboration with bioengineering scientists at the University of Illinois led to preliminary data indicating the potential of microencapsulation as a means of protecting biocontrol agents and controlling their release in orchard environments. Also, progress was made toward the goal of enhancing biological control of fire blight through the use of microbial mixtures with complementary modes of action and ecological niches. Based on previous evaluations of hundreds of microorganisms screened for biocontrol potential on flowers, effective yeast strains that possibly could complement E325 were selected and field tested. Further research is necessary to assess whether E325 combined with a yeast strain is more effective than either type of biocontrol agent alone. The above activities relate to Objective 1A (�Optimize�production and product formulation�), Objective 2 (�Evaluate the contribution and possible relationship of different modes of microbial antagonism toward E. amylovora, including...antibiotic production��), and Objective 3 (�Develop mixtures of antagonists��). Accomplishments 01 Fire blight biocontrol agent produces novel antibiotic encoded by gene o plasmid. Biological control of fire blight of apple and pear is a viabl alternative to the use of broad-spectrum antibiotics, which have diminished as an option due to resistance in the causal bacterium and concerns over the possibility of such resistance being transferred to organisms involved in human diseases. ARS scientists at Wenatchee, WA previously discovered biocontrol strain Pantoea agglomerans E325, which now available commercially, and found that it produces an unique antibiotic highly specific to the fire blight organism. Recent collaboration with scientists in Switzerland revealed that the gene encoding the antibiotic compound is located on a plasmid, i.e., DNA independent of the chromosomal DNA. The discovery is significant becaus it opens up new possibilities for studying or enhancing biological contr of fire blight involving microbial production of a novel antibiotic.
Impacts
(N/A)
Publications
- Wang, D., Korban, S.S., Pusey, P.L., Zhao, Y. 2011. Characterization of the RcsC sensor kinase from Erwinia amylovora and other enterobacteria. Phytopathology. 101:710-716.
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Progress 10/01/08 to 09/30/09
Outputs
Progress Report Objectives (from AD-416) (1) Investigate microbe-induced chemical changes on flower surfaces, with particular attention to pH modification, as modes of antagonism towards the fire blight bacterium, Erwinia amylovora; (2) evaluate the contribution and possible relationship of different modes of microbial antagonism toward E. amylovora, including pH reduction, antibiotic production and competitive exclusion; and (3) develop mixtures of antagonists with complimentary mechanisms and ecological niches and integrate their use with other fire blight management strategies. Approach (from AD-416) To accomplish the first objective, we will focus primarily on Pantoea agglomerans strain E325, a patented biocontrol agent recently registered by EPA. This strain was shown in preliminary tests to increase the acidity of stigma exudates based on the pH of exudates extracted from inoculated flowers. Laboratory experiments will be performed with an artificial stigma-based medium (SBM) and detached crab apple flowers prior to conducting field studies. Work with SBM and variations of it will be used to evaluate the relationship between pathogen suppression and pH reduction, determine the pH range and optimum for both pathogen and antagonist bacteria, and evaluate changes in acid production under varying buffer capacities and oxygen conditions. In flower bioassays, pH on stigmatic surfaces will be directly measured using pH-sensitive fluorescent dyes and confocal laser microscopy or with fabricated microelectrodes. In addition, stigma exudates extracted from inoculated flowers will be analyzed for sugar consumption and bacteria-produced organic acids. In field experiments with apple, flowers will be sampled and their stigmas evaluated for bacterial population size, pH and specific organic acids. Similar methods will be used to assess whether biocontrol treatments can be enhanced through the addition of various soft agrochemicals (e.g., foliar nitrogen fertilizers and pH buffers) that may alter acid production by bacteria or directly affect pH on flower surfaces. For the second objective, a collection of antagonist strains, previously shown to be among the best performers in flower bioassays, will be evaluated for mode of action. This will involve a series of laboratory tests with SBM and flowers to determine the importance of acid production, antibiotic production and nutrient depletion as mechanisms of individual antagonist strains. Major extracellular compounds inhibitory to Erwinia amylovora will be identified or characterized. For the third objective, a strategy of enhancing biocontrol with antagonist mixtures will be largely dependent on results of the first two objectives. To fully exploit multiple antagonists and mechanisms, we will evaluate the compatibility of antagonists and avoid or eliminate incompatibilities. Further screening of microbial epiphytes from apple and pear may be necessary to develop the best complement of antagonists. Finally, to further improve the management of fire blight, we will test the integration of antagonist mixtures with other control approaches or agents. Significant Activities that Support Special Target Populations Fire blight is a potentially devastating disease of apple and pear trees that is generally initiated in blossoms. Disease control historically depended on chemical control measures, but pathogen resistance and environmental and safety concerns prompted a search for alternative control strategies. In 2008, ARS scientists in Wenatchee, WA, who developed what is now a commercially available biocontrol agent that suppresses the fire blight organism, conducted studies to examine how the beneficial microorganism prevents fire blight. This has been partly accomplished by comparing the performance of the biocontrol strain with a mutated derivative strain lacking the ability to produce a unique antibiotic compound highly specific to the disease organism. The derivative strain was much less effective than the parent strain in suppressing the disease organism on plant floral surfaces. Studies also showed that the purified antibiotic alone can inhibit the disease organism on blossoms. Collaboration with scientists at Washington State University, Pullman, have provided insight as to the identity of the antibiotic compound. Additional research was performed to increase the survival of the biocontrol agent and other beneficial microorganisms under low relative humidity conditions typical of fruit production areas in the western U.S. Laboratory and field experiments done in cooperation with the commercial producer of the biocontrol agent showed that the addition of certain ingredients to production media, including the commercial fermentation medium, enhances the tolerance of the biocontrol agent to dry environments. This work, still in progress, likely will lead to an improved commercial formulation in 2010. As an additional focus, we revisited a previous survey of microorganisms occurring naturally on tissues of apple blossoms by supplementing earlier identifications with DNA sequence analyses. This information, evaluated in conjunction with prior blossom assays involving hundreds of the same microbes, has allowed us to better select taxonomic groups and specific strains that may enhance biological control through the use of microbial mixtures with complementary modes of action and ecological niches.
Impacts
(N/A)
Publications
- Pusey, P.L., Stockwell, V.O., Rudell Jr, D.R. 2008. Antibiosis and acidification by Panoea agglomerans strain E325 may contribute to suppression of Erwinia amylovora. Phytopathology. 98:1136-1143.
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Progress 10/01/07 to 09/30/08
Outputs
Progress Report Objectives (from AD-416) (1) Investigate microbe-induced chemical changes on flower surfaces, with particular attention to pH modification, as modes of antagonism towards the fire blight bacterium, Erwinia amylovora; (2) evaluate the contribution and possible relationship of different modes of microbial antagonism toward E. amylovora, including pH reduction, antibiotic production and competitive exclusion; and (3) develop mixtures of antagonists with complimentary mechanisms and ecological niches and integrate their use with other fire blight management strategies. Approach (from AD-416) To accomplish the first objective, we will focus primarily on Pantoea agglomerans strain E325, a patented biocontrol agent recently registered by EPA. This strain was shown in preliminary tests to increase the acidity of stigma exudates based on the pH of exudates extracted from inoculated flowers. Laboratory experiments will be performed with an artificial stigma-based medium (SBM) and detached crab apple flowers prior to conducting field studies. Work with SBM and variations of it will be used to evaluate the relationship between pathogen suppression and pH reduction, determine the pH range and optimum for both pathogen and antagonist bacteria, and evaluate changes in acid production under varying buffer capacities and oxygen conditions. In flower bioassays, pH on stigmatic surfaces will be directly measured using pH-sensitive fluorescent dyes and confocal laser microscopy or with fabricated microelectrodes. In addition, stigma exudates extracted from inoculated flowers will be analyzed for sugar consumption and bacteria-produced organic acids. In field experiments with apple, flowers will be sampled and their stigmas evaluated for bacterial population size, pH and specific organic acids. Similar methods will be used to assess whether biocontrol treatments can be enhanced through the addition of various soft agrochemicals (e.g., foliar nitrogen fertilizers and pH buffers) that may alter acid production by bacteria or directly affect pH on flower surfaces. For the second objective, a collection of antagonist strains, previously shown to be among the best performers in flower bioassays, will be evaluated for mode of action. This will involve a series of laboratory tests with SBM and flowers to determine the importance of acid production, antibiotic production and nutrient depletion as mechanisms of individual antagonist strains. Major extracellular compounds inhibitory to Erwinia amylovora will be identified or characterized. For the third objective, a strategy of enhancing biocontrol with antagonist mixtures will be largely dependent on results of the first two objectives. To fully exploit multiple antagonists and mechanisms, we will evaluate the compatibility of antagonists and avoid or eliminate incompatibilities. Further screening of microbial epiphytes from apple and pear may be necessary to develop the best complement of antagonists. Finally, to further improve the management of fire blight, we will test the integration of antagonist mixtures with other control approaches or agents. Significant Activities that Support Special Target Populations Studies have continued with Pantoea agglomerans strain E325, a fire blight biocontrol agent that originated from our research program and became available commercially for apple and pear beginning in 2007. Strain E325 is antagonistic to Erwinia amylovora on flower stigmas, the primary site of pathogen establishment. In an artificial medium partially formulated based on chemical analyses of exudates from flower stigmas, E325 was shown to produce a compound inhibitory to the pathogen. Characteristics of the compound purified by RP-HPLC distinguished it from antibiotics of other strains of P. agglomerans. The antibacterial compound was active under acidic conditions, sensitive to basic pH and to high phosphate levels conventionally used in buffered media to test for antibiosis, and unaffected by amino acids or proteolytic and other enzymes. Further, the E325 compound exhibited a high specificity to E. amylovora, which may be advantageous in efforts to maximize biological control by integrating E325 with other microbial antagonists with complementary mechanisms or environmental adaptations. Since our research indicates that acidification by E325 is possibly related to antibiosis and may also directly contribute to the antagonism of E. amylovora, screening assays are being done to identify acid-tolerant bacteria or yeast that could potentially complement strain E325 in antagonist mixtures. Efforts are underway to develop a non-antibiotic mutant of E325 to evaluate the role of antibiosis by this antagonist in biological control. Our laboratory has continued to cooperate with the private company marketing E325 by recently evaluating the purity and stability of samples during production scale-up, generating DNA-based identification information required by regulatory agencies in the US and Canada, and sharing research information that may be useful for improving fermentation, formulation and efficacy of the product. As a follow up to our previous biochemical characterization of apple and pear stigmas, a field study was initiated in 2008 to study chemical changes on stigmatic surfaces and in flower tissues in response to colonization by E. amylovora and the antagonist strain E325. Stigma exudates are being evaluated for several chemical components, including free sugars, organic acids, and phenolic compounds, and flower tissues will be evaluated for PR protein gene expression. It is hoped that this data will lead to a better understanding of microbial interactions on apple and pear flowers and improved strategies for fire blight management. This research is part of NP 303, Component 4. Significant Activities that Support Special Target Populations �Responded to farm managers and cooperative extension personnel seeking advice relating to pome fruit diseases, particularly fire blight (this sometimes involved receiving plant specimens for diagnosis). Responded to inquiries from the fruit industry regarding new fire blight biocontrol agent that originated in our lab and is now commercially available. Advised and cooperated with private company in meeting regulatory requirements and scaling up production of the biocontrol agent for use against fire blight in 2008.�
Impacts
(N/A)
Publications
- Pusey, P.L., Smith, T.J. 2008. Relationship of apple flower age to infection of hypanthium by Erwinia amylovora. Plant Disease. 92(1):137-142.
- Temple, T.N., Stockwell, V.O., Pusey, P.L., Johnson, K.B. 2007. Evaluation of Likelihood of Co-occurrence of Erwinia amylovora with Mature Fruit of Winter Pear. Journal of Phytopathology. 97(10):1263-1273.
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Progress 10/01/06 to 09/30/07
Outputs
Progress Report Objectives (from AD-416) (1) Investigate microbe-induced chemical changes on flower surfaces, with particular attention to pH modification, as modes of antagonism towards the fire blight bacterium, Erwinia amylovora; (2) evaluate the contribution and possible relationship of different modes of microbial antagonism toward E. amylovora, including pH reduction, antibiotic production and competitive exclusion; and (3) develop mixtures of antagonists with complimentary mechanisms and ecological niches and integrate their use with other fire blight management strategies. Approach (from AD-416) To accomplish the first objective, we will focus primarily on Pantoea agglomerans strain E325, a patented biocontrol agent recently registered by EPA. This strain was shown in preliminary tests to increase the acidity of stigma exudates based on the pH of exudates extracted from inoculated flowers. Laboratory experiments will be performed with an artificial stigma-based medium (SBM) and detached crab apple flowers prior to conducting field studies. Work with SBM and variations of it will be used to evaluate the relationship between pathogen suppression and pH reduction, determine the pH range and optimum for both pathogen and antagonist bacteria, and evaluate changes in acid production under varying buffer capacities and oxygen conditions. In flower bioassays, pH on stigmatic surfaces will be directly measured using pH-sensitive fluorescent dyes and confocal laser microscopy or with fabricated microelectrodes. In addition, stigma exudates extracted from inoculated flowers will be analyzed for sugar consumption and bacteria-produced organic acids. In field experiments with apple, flowers will be sampled and their stigmas evaluated for bacterial population size, pH and specific organic acids. Similar methods will be used to assess whether biocontrol treatments can be enhanced through the addition of various soft agrochemicals (e.g., foliar nitrogen fertilizers and pH buffers) that may alter acid production by bacteria or directly affect pH on flower surfaces. For the second objective, a collection of antagonist strains, previously shown to be among the best performers in flower bioassays, will be evaluated for mode of action. This will involve a series of laboratory tests with SBM and flowers to determine the importance of acid production, antibiotic production and nutrient depletion as mechanisms of individual antagonist strains. Major extracellular compounds inhibitory to Erwinia amylovora will be identified or characterized. For the third objective, a strategy of enhancing biocontrol with antagonist mixtures will be largely dependent on results of the first two objectives. To fully exploit multiple antagonists and mechanisms, we will evaluate the compatibility of antagonists and avoid or eliminate incompatibilities. Further screening of microbial epiphytes from apple and pear may be necessary to develop the best complement of antagonists. Finally, to further improve the management of fire blight, we will test the integration of antagonist mixtures with other control approaches or agents. Significant Activities that Support Special Target Populations Progress was made in understanding mechanisms of the bacterial antagonist Pantoea agglomerans strain E325, which originated from our research program and is now available commercially for use on apple and pear blossoms to reduce fire blight. Studies involving a synthetic medium, which included sugars and amino acids detected in previous chemical analyses of flower stigma exudates, showed a correlation between acidity in the medium and suppression of the disease bacterium (Erwinia amylovora) . This led us to investigate pH modification on flower stigmas as a mode of antagonism. In an experimental apple orchard, blossoms were inoculated with bacteria, and the pH was determined in stigma exudates extracted from pooled samples of flowers. Results indicated a trend consistent with our hypothesis that strain E325 decreases pH to levels negatively affecting growth of E. amylovora, but were not statistically conclusive. To investigate further, we explored methods of directly measuring the pH on flower stigmas using pH-sensitive fluorescent dyes and laser microscopy, but were not successful with this approach. We are making progress, however, with an alternative method involving the fabrication of pH microelectrodes small enough to probe stigmatic surfaces. Meanwhile, we discovered that strain E325 produces an extracellular substance inhibitory to E. amylovora. The active compound is produced in the stigma-based medium when the phosphate buffer concentration is low and pH decreases during bacterial growth to levels between 3 and 5. It is stable when pH is neutralized, but inactivated under basic conditions. The compound has been partially characterized and was recently purified with high-performance liquid chromatography. As part of our effort to enhance biological control by finding antagonists that are compatible and complementary to strain E325, we collected 450 strains of Pseudomonas spp. and screened them for tolerance to acidic conditions. Selected acid-tolerant strains will be tested with E325 in antagonist mixtures applied to blossoms. In other experiments, E325 was evaluated in combination with certain agrochemicals, such as nitrogen fertilizers and pH buffers, but none of the additives significantly improved antagonist performance on flowers. In the past year we also cooperated with private company holding the patent license for strain E325, to improve production and formulation. Accomplishments Phytosanitary concerns about fire blight prohibit export of US-grown pears to some countries without this disease. These concerns were evaluated in a 4-year regional project by scientists with Oregon State University and USDA-ARS, Wenatchee, Washington. We evaluated the potential for co-occurrence of the fire blight bacterium, Erwinia amylovora, with mature symptomless winter pear fruit by inoculation experiments and by survey of commercial orchards. It was concluded that E. amylovora shows similar survival characteristics on both pear and apple fruit, the disease organism does not exist inside mature symptomless pear fruit, its presence is exceptionally rare on commercially-produced fruit, and survival of E. amylovora on fruit surfaces is unlikely during postharvest chilling given the unrealistically high population size required for persistence. The information will be of value in efforts to expand foreign markets for US pears. Research is part of NP 303 (Plant Diseases), supporting Component 2(Biology, Ecology, Epidemiology, and Spread of Plant Pathogens and Their Relationships with Hosts and Vectors) and Problem Statement 2C(Population Dynamics, Spread, and Epidemiology of Pathogens). Technology Transfer Number of Active CRADAS and MTAS: 1 Number of Non-Peer Reviewed Presentations and Proceedings: 2
Impacts
(N/A)
Publications
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