Submitted to: Journal of Nematology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/11/2004
Publication Date: 1/1/2005
Citation: Handoo, Z.A., Carta, L.K., Skantar, A.M., Ye, W., Robbins, R.T., Subbotin, S., Fraedrich, S.W., Cram, M.M. 2005. Morphological and molecular characterization of longidorus americanum n.sp. (nematoda: longidoridae), a needle nematode parasitizing pine in georgia. Journal of Nematology. 37(1): 94-104. Interpretive Summary: Nematodes are microscopic worms that cause ten billion dollars of crop losses in the United States each year. Needle nematodes are an important group of nematodes that damage many kinds of plants directly by feeding on them or indirectly by spreading plant viruses. A specific problem with pine production in the southern United States is the occurrence of a type of needle nematode that causes pine seedlings in plant nurseries to be stunted and yellow. In the present study, ARS scientists led an international collaborative effort to discover methods to distinguish this nematode from other needle nematodes with anatomical and DNA data. Both light and high-powered electron microscope observations indicated that the species is closely related to two other nematode species in the United States and one each in Great Britain and India. The results are significant because they provide the molecular and anatomical details necessary for scientists to identify this species wherever it may occur in the world. This research will be used by scientists, action agencies, and extension agencies engaged in nematode research and control.
Technical Abstract: We describe and illustrate a new needle nematode, Longidorus americanum n. sp., associated with patches of severely stunted and chlorotic loblolly pine (Pinus taeda L.) seedlings in seedbeds at the Flint River Nursery (Byromville, GA, United States). It is characterized in having females with a body length of 6-9 millimeters, lip region slightly swollen, anteriorly flattened, giving the anterior end a rather truncate appearance, long odontostyle that measures 123-165 micrometers, odontophore length 40-67 micrometers, total stylet 182-216 micrometers long, vulva at 46-52% of body length, and tail bluntly rounded to almost hemispherical. Males are rare but present, and are shorter than females. The new species is closely related to L. macrosoma, L. saginus, L. tarjani and L. longicaudatus, but differs from these species either by the body and stylet length or by the shape of the tail. Molecular data of this new species distinguishes it from other available Longidorus species by sequence of the D2-D3 regions of the large subunit (28S) rDNA. Phylogenetic relationships of Longidorus americanum n. sp. with other longidorids based on analysis of this DNA fragment are presented. Additional information regarding the distribution of this species within the region is needed.