Xiphinema
Contents
Rev 07/26/2012
Xiphinema |
Contents |
Rev 07/26/2012 |
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| Dagger Nematodes |
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Classification |
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Hosts |
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Morphology and Anatomy |
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Life Cycle |
| Return to Xiphinema Menu |
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Economic Importance |
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Damage |
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Distribution |
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Management |
| Return to Longidoridae Menu |
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Feeding |
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References |
Xiphinema
(Cobb, 1913)
Odontostyle
is long, connected to lining of
cheilostome by a cuticular membrane that becomes variously folded, with
refractory qualities - the "guiding ring."
Species in the genus Xiphinema are relatively large nematodes, 2 to 3 mm in length.
The genus is characterized by the presence of a very long odontostyle
or spear (stylet).
The spear and its extension are approximately 150 µm or more in length.
| In Xiphinema, the guiding ring is located near the
base of the odontostyle, just before the junction with the
odontophore.
A flanged odontophore is characteristic of Xiphinema. |
 |
| In Longidorus, the guiding ring is located 2 lip region widths from the anterior end; no flanges occur on the posterior end of the odontophore. |
Xiphinema has a 2-part
esophagus typical of most
Dorylaimida,
with a slender anterior part and swollen glandular and muscular posterior bulb.
The cross-sectional configuration of the stylet is cylindrical and the
cross-section of the odontophore is tri-radiate as in the esophagus. The
esophagus has a tri-questrous lumen.
Males
have paired pre-anal papillae and a ventromedian row of supplementary
papillae. The number and arrangement of these papillae are of importance
in distinguishing species.
Males have paired spicules, but
no gubernaculum;
males have no bursa.
Females of Xiphinema have one or two
ovaries. The ovaries,
when both occur, are opposed and reflexed.
Members of the genus occur worldwide.
Ectoparasites; feed along root, including root tips. Species of Xiphinema feed at root tips and along the length of young roots. Feeding along roots produces symptoms similar to those caused by other cortical feeding nematodes (disintegration of the cortex); those that feed at root tips produce very different symptoms, including root-tip galling and stunting.
The pathogenicity of X. index is well-defined, but that of the other species has not been studied, and several are known only from survey data (Raski, 1988). Xiphinema index is a migratory ectoparasite. All stages feed at the root tip. The odontostyle penetrates deep into the meristematic region of the root tip where secretions of the esophageal glands result in cell hypertrophy and thickening. Kirkpatrick et al. (1965) showed top and root reductions of grape by 65 and 38% respectively in grape pot tests with X. index.
Xiphinema diversicaudatum also feeds at the root tip and causes galling. In contrast, X. americanum sensu stricto feeds behind the root tip and has not been associated with root tip galling.
Many species of Xiphinema have a wide host range.
For an extensive list of host plant species and their susceptibility to this genus, copy the genus name
Xiphinema
select Nemabase Genus Search and paste the name in the Genus box
Relatively little critical biological and ecological work has been done on this important genus - some species are difficult to maintain in greenhouse cultures, e.g. X. americanum, others apparently have a very long life-cycle, e.g., X. diversicaudatum.. All stages occur in the soil.
Eggs, from which first-stage juveniles emerge, are deposited singly in water films around soil particles and are not enclosed in an egg-mass. There are three or four juvenile stages and sexually mature adults. Males are rare in most species and are apparently unnecessary for reproduction.
Species of Xiphinema are primarily problematic in biennial and permanent crop situations. Except for damage to emerging seedlings, they are seldom of major importance in annual crops as they rarely attain high population levels when soil is frequently tilled.
Feeding along roots produces symptoms similar to other cortical feeders (distintegration of cortex); those that feed at root tips produce very different symptoms, i.e., root stunting. There is also ample evidence that the nematode injects substances into roots which causes root swelling. Damage to roots causes foliage to become stunted.
Control of Xiphinema spp. on many annual crops may not be of major importance since species of this nematode seldom attain high population levels when soil is frequently tilled.