Paratylenchus
Contents
Rev 11/11/2008
Paratylenchus |
Contents |
Rev 11/11/2008 |
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| Pin Nematode |
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Classification |
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Hosts |
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Morphology and Anatomy |
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Life Cycle |
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Economic Importance |
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Damage |
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Distribution |
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Management |
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Feeding |
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References |
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Tylenchida
Tylenchina
Criconematoidea
Tylenchulidae
Paratylenchinae
Paratylenchus (Micoletzky, 1922)
Synonyms:
Paratylenchoides (Raski, 1973)
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These nematodes in the family Tylenchulidae are among the smallest plant-parasites, 0.18-0.6 mm long. Cuticular annulation is smooth. Females: Usually less than 0.5 mm long, vermiform, not swollen, except that gravid female may swell anterior to the vulva. Labial framework weakly sclerotized (except in P. israelensis and P. sheri where it is stronger) There is a strong stylet (from 12 to 40 µm, usually about 36 µm) which allows the nematode to feed several cell layers below the root surface. Excretory pore between level of nerve ring and level of esophago-intestinal junction. Females have a single outstretched ovary and the vulva is in the posterior region of the body. Spermatheca appears as a modification of cells, or pouch-like sac, at the anterior end of the uterus. |
| Males: Have reduced feeding structures, with stylet reduced or absent, and
degenerate esophagus.
They probably do not feed. However, they may be common in the population. Juveniles: Juvenile stages resemble the female, but with a smaller stylet. The stylet is usually absent in the J4 stage. The J4 is a dauer (survival) stage, and development will not proceed beyond this stage unless a host plant is present. In a 1987 review, Raski and Luc (1987) recognized 64 species. |
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Size of a Paratylenchus female in relation to some other soil nematodes. Photos by Howard Ferris |
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Paratylenchus procorpus and metacorpus |
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Young female Paratylenchus; body slightly enlarged anterior to vulva. |
| Young female Paratylenchus |
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Common in native and cultivated soils, especially around roots of woody plants and shrubs.
Paratylenchus is the most commonly occurring genus plant-parasitic of nematodes found in California prune orchards (found in 65 of 97 orchards sampled - Lownsbery data).
D-rated pests is California.
Nematode is ectoparasitic but can be somewhat sedentary for periods of time.
Feeds on mature parts of root(?) on epidermal and outer cortical cells; also at wounded areas and lateral root emergence sites.
Wide host range; nematode has been demonstrated to cause damage to celery in New England states and in Holland.
Damage to greenhouse-grown carnations has also been reported.
Life cycle is 30 to 31 days at 25 to 28 C.
J4 is the persistent stage - at least in some species molt of the J4 is stimulated by root diffusates (host presence) - tolerant of cold and desiccation. The J4 do not molt to adults in water, but molt progressively over a 2 week period in root diffusates. In some cases, the root exudates from a host plant did not induce molting of a Paratylenchus species to which it was a host, for example, red clover (Trifolium pratense) is a host for both P. projectus and P. dianthus but only induced molting in P. projectus (Rhoades and Linford, 1959).
In older pot cultures or field soils, the resistant J4 may be 80% of the population.
J4 distinguished from other stages by reduced or absent stylet and esophagus and accumulation of opaque granules in esophagus region (Rhoades and Linford, 1959).
J4 male has no stylet and does not feed.
Female grows after final molt, and may not feed as J4. Gravid females may become quite swollen; the fattening is restricted to that part of the body anterior to the vulva, so that the body posterior to the anus remains slender.
Raski & Luc, 1987. Rev. Nematol. 10(4):409-444
Rhoades, H.L. and M.B. Linford. 1959. Molting of preadult nematodes of the genus Paratylenchus stimulated by root diffusates. Science 130: 1476-1477.
H. Ferris
