The causal agent of fire blight of pear and apple. Alyssa Carey Dr. Joyce Loper Dr. Virginia Stockwell Erwinia amylovora 1 to 2 μm long rod-shaped bacterial

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  • The causal agent of fire blight of pear and apple. Alyssa Carey Dr. Joyce Loper Dr. Virginia Stockwell Erwinia amylovora 1 to 2 m long rod-shaped bacterial cells
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  • Fire Blight Most severe bacterial disease of pear and apple First discovered in Hudson Valley 1780. Spread across US, and to Europe, the Middle East and New Zealand Economically devastating in all areas. Pacific Northwest 1988 - $89 million (Central WA) 1998 - $68 million (Hood River Valley) 2002 Worst epidemic in 100 years Medford, OR
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  • Spring Cankers activate, Erwinia amylovora spread by bees and rain and grows on flower tissues Early Summer Infection of blossoms Shoot and fruit infection Summer and Fall Pathogen kills branches and forms cankers Winter Pathogen overwinters in cankers Disease Cycle of Fire BlightX
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  • Research Opportunities Periodic fire blight epidemics continue to damage orchards causing great losses There are few options for disease control Erwinia amylovora long considered homogeneous but recent findings indicate that the pathogen may be more diverse
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  • Summer Research Characterize isolates of Erwinia amylovora from orchards in the Pacific Northwest Determine if the plasmid pEA29 is ubiquitous in Northwest isolates Determine if other extrachromosomal DNA is present in Northwest isolates of fire blight pathogen ovora.gif
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  • pEA29 Considered near ubiquitous in Erwinia amylovora. Associated with virulence/fitness, but not essential Target for some PCR methods for identification/detection of E. amylovora
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  • Hypothesis Erwinia amylovora isolates from the Pacific Northwest contain extrachromosomal DNA in addition to pEA29
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  • Goals Isolate and characterize plasmids of Erwinia amylovora from the Pacific Northwest Determine if there is a correlation of plasmid content and orchard location 1162548310
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  • Procedure Obtain samples from orchards Dilution series Plate onto agar medium for growth Confirm identity as Erwinia amylovora PCR reactions AgriStrip test Sequencing of 16S rRNA Isolate plasmid DNA using alkaline lysis method PCR reactions for pEA29 Restriction digest or RFLP analysis
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  • RFLP (Restriction Fragment Length Polymorphism) Analysis of Plasmids Using restriction enzyme digests to identify unique and characteristic patterns EcoRI BamHI
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  • pEA29 Use restriction enzymes to examine plasmid preparations 28,185 bpsuse sequence to predict fragment sizes If extra bands Mutations Other incorporated DNA in pEA29 Other extrachromosomal DNA (plasmid) in isolate BamHIEcoRI
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  • Isolates without pEA29 pEA29 considered ubiquitous in United States A few isolates lacking pEA29 recorded in Iran, Egypt and EU From our collection Six isolates of 205 examined (3%) lack this plasmid
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  • Locations of orchards with isolates of E. amylovora lacking pEA29 Yakima Valley, WA Sampled orchard Orchard with E. amylovora without pEA29
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  • Additional Plasmids? About half of 205 isolates have more bands in addition to those from pEA29 in RFLP Unique banding patterns indicate that additional plasmid(s) exist within PNW isolates of Erwinia amylovora EcoRI digest
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  • pEU30 Another plasmid in Utah strain of E. amylovora found by Foster et al. pEU30 was sequenced and primers for detection developed by Foster 27 (13%) of our strains were positive with primers designed to this plasmid Isolates with pEU30 also had pEA29 Foster, McGhee, Jones, and Sundin. 2004. Appl. Environ. Microbiol. 70:7539-7544.
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  • Locations of orchards with isolates that were PCR positive for pEU30 Yakima Valley, WA Sampled orchard Orchard with E. amylovora with pEU30
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  • Current Research Activities Sequencing an uncharacterized plasmid(s) from my collection Four isolates with unique RFLP patterns were selected Isolates were cured of pEA29 using eviction mutagenesis
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  • Summary 205 isolates of E. amylovora Over half had altered plasmid profiles 6 lacked pEA29 27 were positive for pEU30
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  • Acknowledgments Mentor Virginia Stockwell Lab Members Joyce Loper Marcella Henkels Brenda Shaffer HHMI Kevin Ahern Gayle McGhee Michigan State University Larry Pusey USDA-ARS, Wenatchee, WA Krishna Mohan University of Idaho, Parma Kathleen McNamara Bear Creek Orchards, Medford, OR