Location: Foreign Disease-weed Science Research2007 Annual Report
1a. Objectives (from AD-416)
Develop pathogen detection arrays in support of certification programs for Prunus and Citrus crops and provide innovative diagnostic systems for new and emerging plant pathogens; investigate molecular and biological factors in pathogen/host/vector systems that affect host adaptation, vector adaptation, and evolution of new pathogenic forms; and, investigate critical factors that influence developmental and circulative processes of vector transmission in new or emerging plant pathogenic diseases (pathogen ingestion and fate in persistent and non-persistent transmission systems) i.e., Huanglongbing and citrus psyllids, Soybean dwarf virus and soybean aphid, Plum pox virus and aphid vectors, Citrus tristeza virus and brown citrus aphid, and other foreign and emerging plant pathogens. Contribute to curation of microbial collections for all CRIS projects at the unit, perform physical audits of pathogens, monitor APHIS permit status, oversee and track regulations regarding transport and storage of APHIS Select Agents, and liaison with APHIS for containment inspections and certifications. PER PDRAM NAA2 FY07 Program Redirection for Plum Pox Research Adding this objective: Investigate virus adaptation to changing hosts using plum pox as a working model and develop a fluorescent viral labeling system for tracking viruses in aphids.
1b. Approach (from AD-416)
Establish and maintain foreign (exotic) and emerging insect-transmitted plant pathogens under quarantine containment and determine factors involved in pathogen change and adaptation, mechanisms of transmission, and novel detection strategies. Specific approaches will include using microarray format to select optimal probes for multiple Prunus pathogen detection macroarrays and adaptation of TIGER diagnostics for the detection of potyviruses. Viral adaptation to host and vector will be studied experimentally using repeated passages of Plum pox virus and Soybean dwarf virus as model systems. Virus/vector interactions will be studied using fluorescently tagged virions of PPV and SbDV to study viral movement in aphids. The presence or absence of transovarial transmission of HLB by the citrus psyllid will be determined by following the developmental stages of hundreds of progeny of infective psyllids from egg to adult on non-HLB hosts using Real-time PCR and specific primers for HLB. The presence, pathway, and location of HLB in citrus psyllids will be monitored by real-time PCR on whole psyllids, dissected psyllid organs, and use of fluorescently tagged HLB bacteria.
3. Progress Report
1920-22000-034-01S – Specific Cooperative Agreement with Pennsylvania State Univ: Objectives included developing methods for studying mechanisms regulating PPV transmission by aphids, identifying sites of virus binding to aphid tissues, identification of efficient vector species, and methods of virus detection. Two aphid species, the green peach and the Spirea aphid, were shown to be efficient vectors. Limited transmission electron microscopy did not reveal specific sites of virus attachment in these vectors. Fruit and leaves were sources of virus inoculum. No infected fruit samples were found in international shipments of stone fruits from Chile. Progress was monitored by frequent site visits, interactive research at ARS site, emails, seminars, workshops, etc. For a complete report on the progress of this agreement, see the report for 1920-22000-034-01S. 1920-22000-034-02R - NRI-Funded Agreement - USAMRIID: The objective of this work was to transition TIGER, a universal diagnostic tool that combines broad range PCR with mass spectrometry for the identification of any and all bacteria in a given sample, to plant pathogens. The TIGER system proved successful at detecting bacteria, both individually and in mixtures, at the general level (93%) and the species level (70%). Research progress was monitored by bi-weekly meetings and reports at National and Local meetings. For a complete report see the report for 1920-22000-034-02R. 1920-22000-034-03S - Specific Cooperative Agreement - Pennsylvania State Univ: The objectives of this work are to develop a protocol for tracking labeled viral particles in aphids and use these tools to study virus transmission. Due to the lack of appropriate graduate student candidates the only work done on this project this year was planning work (choosing the appropriate labeling system, acquiring necessary equipment and interviewing potential graduate students). Progress was monitored by regular site visits, telephone calls and e-mails. For a complete report refer to report for 1920-22000-034-03S.
Since the project was just initiated (on 4/16/07) there are no accomplishments.
5. Significant Activities that Support Special Target Populations