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United States Department of Agriculture

Agricultural Research Service

2007 Annual Report

1a.Objectives (from AD-416)
The long-term objective of this project is to develop a stable, biologically relevant taxonomy for the genus Alternaria with particular reference to the small-spored members of the genus, which are the taxa most often involved in phytosanitary issues and which are also frequently misidentified. Associated with this objective is the development of molecular protocols for detection and identification of target species of phytosanitary importance that are based upon the systematics work. Certain species of Alternaria (e.g., A. gaisen, A. yaliinficiens) are currently known to have a limited geographic distribution that restricts the movement of deciduous tree fruit to the U.S. and other world markets. Other species, many of which are undescribed or frequently misidentified, occur in the United States and in other countries, and need to be characterized and described so that regulatory actions regarding Alternaria on intercepted plant products can be based upon a firm and scientific understanding of the Alternaria taxa that occur on tree fruits and other substrates in the U.S. Over the next 5 years we will focus on the following objective: Objective 1: Isolate and accumulate sequence data from genomic transcripts of known Alternaria spp. which are detected during development of phenotypic traits that vary among different sub-generic groups sensu Simmons and Roberts (1993) and species within those groups, with particular emphasis on sporulation pattern, conidial morphology and, if necessary, germination-mediated metabolite production.

1b.Approach (from AD-416)
A fundamental understanding of species-diversity (identity) among Alternaria strains associated with tree fruit will be developed using morphological characters and species-specific DNA sequences identified via subtractive hybridization protocols. Research will be conducted as necessary to address market- or issue-specific questions that arise from interactions with trading partners. Replacing 5350-22000-014-00D (11/03).

3.Progress Report
Modifications to operational parameters for two large environmental chambers with tight control of temperature and humidity were made incrementally in an attempt to mimic average lab benchtop conditions used previously to grow cultures for examination. Blind experiments were initiated to validate that different species of Alternaria that produce distinct patterns of sporulation in culture on laboratory benchtops also do so under the conditions provided in the chamber.


5.Significant Activities that Support Special Target Populations

Last Modified: 11/24/2015
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