Xiphinema

''Xiphinema'' is a genus of 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.''Xiphinema''
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.

Taxonomy

There are 296 nominal taxa, including 234 accepted species, 49 synonyms and 13 '' species inquirendae''.(He 2003)

History

''Xiphinema americanum'' was the first species to be described by Nathan Cobb in 1913, who speculated that it was likely a plant pathogen. . This speculation was experimentally confirmed in 1949 and 1952.Schindler, A.F., 1957. Parasitism and Pathogenicity of ''Xiphinema diversicaudatum'', and ectoparasitic nematode. Nematologica, II (1957):25-31)

List of species

:N.B. This list is probably incomplete.

* '' Xiphinema abrantinum'' Roca & Pereira, 1991.
* '' Xiphinema aceri'' Chizhov & al., 1986.
* '' Xiphinema aequum'' Roca & Lamberti, 1988.
* ''Xiphinema americanum'' Cobb, 1913.
* '' Xiphinema artemisiae'' Chizhov & al., 1986.
* '' Xiphinema bakeri''
* '' Xiphinema barense'' Lamberti & al., 1986.
* '' Xiphinema basilgoodeyi'' Coomans, 1965.
* '' Xiphinema belmontense'' Roca & Pereira, 1992.
* '' Xiphinema brevicolle'' Lordello & Da Costa, 1961.
* '' Xiphinema brevisicum'' Lamberti & al., 1994.
* '' Xiphinema cadavalense'' Bravo & Roca, 1995.
* '' Xiphinema coronatum'' Roca, 1991.
* '' Xiphinema coxi'' Tarjan, 1964.
** '' Xiphinema coxi coxi'' Tarjan, 1964.
** '' Xiphinema coxi europaeum'' Sturhan, 1985.
* '' Xiphinema dentatum'' Sturhan, 1978.
* '' Xiphinema diffusum'' Lamberti & Bleve-Zacheo, 1979.
* '' Xiphinema dissimile'' Roca & al., 1988.
* ''Xiphinema diversicaudatum'' (Micoletzky, 1927) — nématode migrant des racines.
* '' Xiphinema diversum'' Roca & al., 1989.
* '' Xiphinema duriense'' Lamberti & al., 1993.
* '' Xiphinema elongatum'' Schuurmans Stekhoven & Teunissen, 1938.
* '' Xiphinema exile'' Roca & al., 1989.
* '' Xiphinema fortuitum'' Roca & al., 1988.
* '' Xiphinema gersoni'' Roca & Bravo, 1993.
* '' Xiphinema globosum'' Sturhan, 1978.
* '' Xiphinema hispidum'' Roca & Bravo, 1994.
* '' Xiphinema histriae'' Lamberti & al., 1993.
* '' Xiphinema horvatovicae'' Barsi & Lamberti, 1999.
* '' Xiphinema illyricum'' Barsi & Lamberti, 1999.
* '' Xiphinema incertum'' Lamberti & al., 1983.
* '' Xiphinema incognitum'' Lamberti & Bleve-Zacheo, 1979.
* ''Xiphinema index'' Thorne & Allen, 1950.
* '' Xiphinema ingens'' Luc & Dalmasso, 1964.
* '' Xiphinema insigne''
* '' Xiphinema intermedium'' Lamberti & Bleve-Zacheo, 1979.
* '' Xiphinema italiae'' Meyl, 1953.
* '' Xiphinema lafoense'' Roca & al., 1988.
* '' Xiphinema lanceolatum'' Roca & Bravo, 1993.
* '' Xiphinema lapidosum'' Roca & Bravo, 1993.
* '' Xiphinema longistilum'' Lamberti & al., 1994.
* '' Xiphinema lupini'' Roca & Pereira, 1993.
* '' Xiphinema lusitanicum'' Sturhan, 1983.
* '' Xiphinema macedonicum'' Barsi & Lamberti, 1999.
* '' Xiphinema macroacanthum'' Lamberti & al., 1989.
* '' Xiphinema madeirense'' Brown & al., 1992.
* '' Xiphinema melitense'' Lamberti & al., 1982.
* '' Xiphinema mesostilum'' Lamberti & al., 1994.
* '' Xiphinema microstilum'' Lamberti & al., 1994.
* '' Xiphinema neovuittenezi'' Dalmasso, 1969.
* '' Xiphinema opisthohysterum'' Siddiqi, 1961.
* '' Xiphinema pachtaicum'' (Tulaganov, 1938).
* '' Xiphinema pachydermum'' Sturhan, 1983.
* '' Xiphinema pombalense'' Bravo & Lamberti, 1996.
* '' Xiphinema porosum'' Roca & Agostinelli, 1986.
* '' Xiphinema pseudocoxi'' Sturhan, 1985.
* '' Xiphinema pyrenaicum'' Dalmasso, 1969.
* '' Xiphinema radicicola'' Goodey, 1936.
* '' Xiphinema riparium'' Chizhov & al., 1991.
* '' Xiphinema rivesi'' Dalmasso, 1969.
* '' Xiphinema rotundatum'' Schuurmans Stekhoven & Teunissen, 1938.
* '' Xiphinema sahelense'' Dalmasso, 1969.
* '' Xiphinema santos'' Lamberti & al., 1993.
* '' Xiphinema silvesi'' Roca & Bravo, 1998.
* '' Xiphinema simile'' Lamberti & al., 1983.
* '' Xiphinema taylori'' Lamberti & al., 1992.
* '' Xiphinema turcicum'' Luc & Dalmasso, 1964.
* '' Xiphinema variurum'' Barsi & Lamberti, 1998.
* '' Xiphinema vuittenezi'' Luc & al., 1964.

Distribution

The genus ''Xiphinema'' is distributed worldwide. Two economically important ''Xiphinema'' species, ''X.index'' and ''X.americanum'', are both commonly found in California and tend to be problematic in vineyards. '' X. diversicaudatum'' is also found in parts of the U.S, as well as Europe and Australia.

Life cycle and reproduction

Eggs are laid singly in thin water layers in the soil and are not part of an egg mass. After the first-stage juvenile emerges from the egg there are 3 or 4 molts, all of which occur in the soil. Males can be abundant or sparse depending on the species, which may suggest the presence of both parthenogenic and amphimictic species.

Host parasite relationship

''Xiphinema'' has a very wide host range including crops of high economic importance such as grape, hops and strawberry. Other documented hosts include: Nectarine, oak, rose, grapevine, raspberry, carrot, cherry, peach, and soybean.

References

Bibliography

Plant parasitic nematodes: Genus ''Xiphinema''. University of North CarolinaYu He. Molecular approach to Longidoridae (Nematoda: Dorylaimida): organelle genomics, phylogeny, population diversity and diagnostics. Doctoral thesis, Applied Biological Sciences, University of Ghent 2003

{{Taxonbar, from=Q3022345

Agricultural pest nematodes
Longidoridae
Enoplea genera