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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
2011 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 methods and phylogenies. The identification of new species of nematodes and the development of new methods 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 are describing new species of root-knot, cyst, lesion, stunt and insect-associated nematodes. New geographic locations for known species of cyst nematodes and related genera have been discovered through cooperative surveys with federal and state regulatory agencies concerned about recent discoveries of potato cyst nematodes in the western U.S. Nematode DNA sequences from standard and newly introduced molecular markers are being generated for use in building family trees, and DNA sequences from new genes are being evaluated for possible use in family trees. These methods and tools will be used by diagnosticians and extension personnel throughout the world to accurately diagnose and select appropriate controls for a wide variety of crops.

Building the USDA Nematode Collection. 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, ARS scientists at the Nematology Laboratory in Beltsville added 309 slides and vials from worldwide sources to create a total collection of 44,175 slides and vials, loaned 23 slides and vials containing valuable nematode specimens to scientists around the world to enable them to perform accurate nematode identifications, and entered 271 records of specimens into the computerized database, bringing it to a total of 38,227 records. Nematologists throughout the world are using the specimens and related information in the Collection as essential aids in nematode identification and research.


4.Accomplishments
1. Fungus-feeding nematode description. For effective integrated crop pest management, it is important to distinguish nematodes causing crop losses versus nematodes that benefit plant growth indirectly through improving soil properties or causing damage to plant pests. Most crop nematodes are found in or around plant roots, but above-ground plant parts may also harbor nematodes that often supplement their diet with beneficial or harmful fungi. A major problem with accurate assessment of these fungal-feeding nematodes from green plant parts is accessing outdated and often unreliable anatomical descriptions and keys. In this study, ARS scientists from Beltsville, Maryland, and an ecologist from University of Idaho, Moscow, Idaho, identified and described a nematode from cheatgrass weeds, major problems in western wheat and alfalfa fields. Two DNA marker traits to uniquely identify and build a family tree were generated for the first time for this nematode species. New measurements and images of body features were compared with those of their relatives from a slide collection and drawings from old literature. Anatomical features for twenty-three previously described world-wide nematode species were compiled, thereby updating the previous twenty-year-old foreign language key. The impact of this research is that identifiers and ecologists are now able to confidently name these understudied species wherever they may occur in the world.


Review Publications
Carta, L.K., Handoo, Z.A., Lebedeva, N.I., Raina, A.K., Zhuginisov, T.I., Khamraev, A.S. 2010. Pelodera termitis sp. n. and two other rhabditid nematode species associated with the Turkestan termite Anacanthotermes turkestanicus from Uzbekistan. International Journal of Nematology. 20:(2)125-134.

Carta, L.K., Bauchan, G.R., Hsu, C., Yuceer, C.Y. 2010. Description, Low Temperature SEM, and culture of Parasitorhabditis frontali n. sp.(Nemata: Rhabditida) from Dendroctonus frontalis Zimmermann (Coleoptera: Scolytidae). Journal of Nematology. 42(1):46-54.

Hafez, S., Sundararaj, A.P., Handoo, Z.A., Siddiqi, M.R. 2010. Occurrence and distribution of nematodes in Idaho crops. International Journal of Nematology. 20(1):91-98.

Bernard, E.C., Handoo, Z.A., Powers, T.O., Donald, P.A., Heinz, R.D., 2010. Vittatidera zeaphila (Nematoda: Heteroderidae), a new genus and species of cyst nematode parasitic on corn (Zea mays). Journal of Nematology. 42:139-150.

Ibrahim I.K.A., Mokbel A.A., Handoo, Z.A. 2010. Current status of phytoparasitic nematodes and their host plants in Egypt. Nematropica. 40(2):239-262.

Last Modified: 4/18/2014
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