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Xiphinema
The genus ''Xiphinema'' are ectoparasitic root nematodes commonly known as dagger nematodes.〔Whitehead, A.G. 1998. Plant Nematode Control〕 The genus is of economic importance on grape, strawberry, hops and a few other crops. Major species include ''X.americanum, X.diversicaudatum, X.index, X.italiae'' and ''X.pachtaicum''.〔Evans, K., Trudgill, D.L., Webster, J.M. 1998. Plant Parasitic Nematodes in Temperate Agriculture.〕 They can be easily recognized by their long bodies and stylets which are long enough to reach the vascular tissue of plants.〔() at Nemaplex, University of California〕 Different members of the genus have been shown to induce moderate to large amounts of root damage through root penetration, which in some species results in the formation of galls.〔 They are of agricultural concern because they are vectors of nepoviruses, transferring them during feeding.〔Taylor, C.E., Robertson, W.M., 1970. Sites of Virus Retention in the Alimentary Tract of the Nematode Vectors, ''Xiphinema diversicaudatum'' (Micol.) and ''X.index'' (Thorne and Allen), Annals of Applied Biology (1970),66, 375-380)〕 Efforts to study these nematodes in more detail have proved problematic in some species due to difficulties in maintaining populations in a greenhouse environment.〔
== Morphology ==
''Xiphinema'' are large nematodes, with an adult length between 1.5mm – 5.0mm.〔 They have a long protrusible odontostyle, with 3 basal flanges at the posterior end of the stylet and a relatively posterior guiding ring when compared to the genus ''Longidorus''.〔 The odontostyle is lined with cuticle and alongside the esophagus serves as a good surface for viruses such as arabis mosaic virus to form a monolayer, which can be vectored to healthy plants.〔 ''Xiphinema'' have a two-part esophagus, which does not contain a metacorpus. A modification in the posterior end of the esophagus forms a muscular posterior bulb, which can generate a pumping action similar to that of a metacorpus in other plant parasitic nematodes.〔 The number of males varies from abundant to sparse depending on the species.〔 Males have paired spicules but the gubernaculum and bursa are absent. Males of different species can be characterized using the varying number and arrangement of papillae.〔 Females have 1 or 2 ovaries.〔
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