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United States Department of Agriculture

Agricultural Research Service

Research Project: MOLECULAR AND MORPHOLOGICAL SYSTEMATICS AND IDENTIFICATION OF IMPORTANT PLANT PARASITIC NEMATODES
2007 Annual Report


1a.Objectives (from AD-416)
1) Discover, refine, and implement improved microscopic, molecular, and software tools to modernize classification and improve predictive features for plant-parasitic and other agriculturally important nematodes; and.
2)Discover new nematode species, new host associations, and new geographic occurrences among the many nematodes sent to the Nematology Laboratory for identification by various customers.


1b.Approach (from AD-416)
1) Adapt and test recently discovered and potentially promising light and scanning electron microscopic methods to determine if visualization of diagnostically important critical features can be improved in resolution and consistency. Characterize new agriculturally important nematodes with expanded or novel morphological and molecular diagnostic characters for the development of improved diagnostic keys and phylogenetic trees. Identify and prioritize, using phylogenetic methods, potential molecular control targets based on physiologically important peptides within diverse nematodes having analogous phenotypes; and.
2)Characterize unknown or important nematodes by morphology, molecular biology and host range; and continue to computerize and curate the USDA Nematode Collection.


3.Progress Report
New nematode identification targets, methods and compendia: New information and methods to rapidly and accurately identify plant-parasitic nematodes are urgently needed by researchers, regulators, diagnosticians and growers to design the safest, most effective possible plant disease controls. To this end, ARS researchers made descriptions of new species of root-knot, cyst, lesion, and other plant-parasitic nematodes, agricultural soil-associated nematodes and invertebrate parasites. A new microscopic method involving a special high-resolution condenser was also implemented. These pest profiles, host associations and microscopic methods will be used by diagnosticians and extension personnel throughout the world to accurately diagnose and select appropriate controls for a wide variety of crops.

Molecular Diagnostics and Phylogeny: A diagnostic guide to lesion nematodes of coffee using microscopic and molecular features was compiled for an upcoming book chapter. A ribosomal gene molecular family tree of lesion nematodes was also expanded. The value of the heat shock protein gene Hsp90 to diagnose species and predict their family relationships was also expanded to new genera and species of plant-parasitic nematodes. Mycorrhizal spores that look very similar to nematode cysts from regulated areas of Idaho were imaged and prepared for ribosomal gene sequencing to assist regulatory diagnosis.

The USDA Nematode Collection: The researchers and extension personnel that identify nematodes need a source of nematode reference specimens to assure that identifications are accurate. The USDA Nematode Collection at Beltsville, Maryland, is the most important repository of nematode reference specimens in the world. Curatorial services and maintenance are constantly needed to improve the quality and breadth of the Collection. Therefore, scientists at the Nematology Laboratory in Beltsville added 953 slides and vials from worldwide sources to create a total collection of 42,233 slides and vials, loaned 160 slides to scientists around the world to enable them to perform accurate nematode identifications, and entered 781 records of specimens into the computerized database, bringing it to a total of 35,863 records. Nematologists throughout the world are using the specimens and related information in the Collection as essential aids in nematode identification and research.

See also subordinate Project Number: 1275-22000-200-01R/29675, Title: IDENTIFICATION OF PLANT PARASITIC NEMATODES FOR ACTION AGENCIES, Period Covered from 10/01/2006 to 09/30/2007


4.Accomplishments
Compendium of cyst nematodes of grasses New, comprehensive information to rapidly and accurately identify plant-parasitic nematodes are urgently needed by researchers, regulators, diagnosticians and growers to deliver the safest, most effective possible plant disease controls. To this end, ARS researchers produced a compendium of new and conventional anatomical features obtained with light and high-powered electron microscopes, ribosomal DNA sequences, and host ranges were used to clearly identify multiple life stages of several populations of three economically important cyst nematodes of grasses with international collaborators. These nematode species are found on many agricultural and ornamental crops around the world. The results are significant because they provide the details necessary for scientists to identify these widespread species wherever they may occur. This research will be used by scientists, action agencies, and extension agencies engaged in nematode research and control.

This accomplishment directly addresses Component I (Identification and Classification of Pathogens) of National Program 303 (Plant Diseases). The Program states “Effective disease control usually depends on rapid and accurate identification of the pathogens involved so that appropriate control measures may be taken. Accurate identification of pathogens is also critical for making sound decisions regarding quarantines of imported and exported plant materials and commodities. Knowing how pathogens are related to each other can be helpful in suggesting possible control strategies.”

Expansion of Lesion nematode Molecular Family Tree Lesion nematodes are common and important root parasites that seriously damage many economic and other plants worldwide. A major problem with determining the cause of potential crop loss due to these nematodes is delimiting one species from another, using reliable characters. In the present study, ARS scientists from Beltsville, Maryland, discovered with anatomical and DNA sequence data that a common and damaging species worldwide has one predominant identifying sequence among multiple sequences to reliably place it within a revised family tree. Also new sequences of other species provide better definition to the tree. The results are significant because they provide new details important for scientists to more reliably identify these widespread species wherever they may occur. This research will be used by scientists, action agencies, and extension agencies engaged in nematode research and control.

This accomplishment directly addresses Component I (Identification and Classification of Pathogens) of National Program 303 (Plant Diseases).


5.Significant Activities that Support Special Target Populations
None


6.Technology Transfer

Number of non-peer reviewed presentations and proceedings2

Review Publications
Tanha, M., Sturhan, D., Handoo, Z.A., Mor, M., Moens, M., Subbotin, S. 2007. Morphological and molecular studies on heterodera sacchari, h. goldeni, and h. leuceilyma (nematoda: heteroderidae). Nematology. 9(4):483-497.

Last Modified: 10/22/2014
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