Pratylenchus
Contents
Rev 11/13/2008
Pratylenchus |
Contents |
Rev 11/13/2008 |
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| lesion nematodes |
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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
Tylenchoidea
Pratylenchidae
Pratylenchinae
Pratylenchus (Filip'ev, 1936)
Synonyms:
None.
The genus name is derived a a contraction of the words pratum (Latin= meadow), tylos (Greek= knob) and enchos ( Greek=spear).
Originally described as Tylenchus pratensis by De Man in 1880 from
meadow in England. Pratylenchus scribneri
was reported from potato in Tennessee in 1889.
There are about 30 described species.
RFLP techniques have been used as a diagnostic method for Pratylenchus
agilis, P. bolivianus, P. brachyurus, P. coffeae, P. crenatus, P. fallax, P.
goodeyi, P. loosi, P. mediterraneus, P. neglectus, P. penetrans, P. pratensis,
P. pseudocoffeae, P. scribneri, P. subranjani, P. thornei, P. vulnus and P.
zeae. The species could be differentiated by a combination of at least two
enzymes. CfoI differentiated all nematode species with the exception of P.
fallax, P. penetrans and P. pseudocoffeae. P. fallax was
separated by a DdeI restriction, and P. pseudocoffeae by a PstI digestion
(Waeyenberge et al, 2000).
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Nematodes in this genus are 0.4-0.5 mm long (under 0.8
mm).
No sexual dimorphism in the anterior part of the body. Deirids absent. Lip area low, flattened anteriorly, not offset, or only weakly offset, from body contour. SEM reveals that lip area is characterized by fusion of labial disc with submedial lip sectors; lateral lip sectors not reduced. Esophageal glands overlapping intestine ventrally for a moderate distance. Esophago-intestinal valve not well developed. Phasmids located at mid-tail or slightly posterior. Female: Genital tract monovarial with posterior branch reduced to a post-uterine sac. Female is slender. Tail 2 to 3 times the anal body diameter, terminus rounded (rarely pointed). |
| Males: Have caudal
alae (bursa) enveloping tail.
Gubernaculum plain, not protruding. [Ref: Luc, (1987) and H. Ferris.] |
Key to the Nine Common Pratylenchus Species in California
| 1. | Monosexual species, no sperm in spermatheca, males rare or unknown. | 2 |
| Bisexual species, sperm in most spermatheca, males common. | 7 | |
| 2. | Very large, round stylet knobs, stylet averages 19 µm in length; V% 82-89; 2 lip annules | P. brachyurus |
| Stylet knobs oval or flattened, stylet generally less than 19 µm long | 3 | |
| 3. | Tail tip annulated, 3 lip annules | P. crenatus |
| Tail tip smooth | 4 | |
| 4 | Lip annules 2 | 5 |
| Lip annules 3 | 6 | |
| 5 | Average V%=84, lip annules about same width; stylet knobs often flattened; vulval lips somewhat smooth | P. neglectus |
| Average V%=78%, anterior lip annules markedly narrower than posterior; vulval lips protrude somewhat | P. scribneri | |
| 6 | Tail normally truncate, stylet averages 18 µm in length; V% averages 76; normally assumes a "J" or "C" shape when heat killed | P. zeae |
| Tail narrowly rounded, stylet averages 16 µm in length; V% averages 71; normally almost straight when heat killed | P. thornei | |
| 7 | Lip annules 2, occasionally 3 on one side | P. coffeae |
| Lip annules 3, occasionally 4 on one side | 8 | |
| 8 | Spermatheca normally round, posterior uterine branch 1 to 1.5 body widths long; large stylet knobs | P. penetrans |
| Spermatheca normally oval, posterior uterine branch generally greater than 2 body widths long; moderate sized stylet knobs | P. vulnus |
Members of this genus are distributed worldwide; individual species are influenced by climate.
C- and D-rated pests in California.
No distinct infective stage, adults and juveniles of all stages move in and out of roots, entering behind zone of elongation but may feed externally at root tip.
Feeds on parenchyma cells, largely in cortex, but not exclusively.
Move into root by pushing epidermal cells apart, or moving directly through them.
Inserts stylet into cortical cells and withdraws contents associated with pulsating of metacorpus.
Access provided for other pathogens by channels left in cortex.
Most species have quite wide host ranges.
Sexual reproduction probably occurs in those species where males are numerous.
Eggs laid singly in roots and soil; second stage hatches from egg.
Nematodes in soil and roots, lesions in roots.
Actual damage caused by nematode feeding is difficult to ascertain because of associated organisms and secondary infections.
Ref: Luc, Rev. Nematol. 10:203-218 (1987)
Waeyenberge, L.; Ryss, A.; Moens, M.; Pinochet, J.; Vrain,
T.C. 2000. Molecular characterisation of 18 Pratylenchus
species using rDNA restriction fragment length polymorphism. Nematology 2:
135-142.