Rev 01/24/2020
Tylenchida Tylenchina Tylenchoidea Pratylenchidae Pratylenchinae
Pratylenchus (Filipjev, 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 a meadow in England. Pratylenchus scribneri was reported from potato in Tennessee in 1889.
Root-lesion nematodes of the genus Pratylenchus are recognised worldwide as major constraints of important economic crops, including banana, cereals, coffee, corn, legumes, peanut, potato and many fruits. Their economic importance in agriculture is due to their wide host range and their distribution in every terrestrial environment on the planet (Castillo and Vovlas, 2007).. There are more than 70 described species, fewer than half of them are known to have males..
Morphological identification of Pratylenchus species is difficult, requiring considerable subjective evaluation of characters and overlapping morphomertrics. Molecular techniques are increasingly important.
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).
Castillo and Vovlas (2007) provide an excellent comprehensive review of the genus.
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).
Gubernaculum plain, not protruding.
[Ref: Luc, (1987) and H. Ferris.]
Distinguishing the species of Pratylenchus based on morphometric characters is not easy but may be important as a basis for management decisions that include resistant varieties, cover crops and crop rotation.
Morphometric Key to the Nine Common Pratylenchus Species in California
Members of this genus are distributed worldwide; individual species are influenced by climate.
C- and D-rated pests in California.
Migratory endoparasites.
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. Fewer than 50% of the described species are recognized asd having males so parthenogenicity is common in the genus.
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.
Castillo, P. and Vovlas, N. 2007. Pratylenchus (Nematoda: Pratylenchidae): diagnosis, biology, pathogenicity and msanagement. Nematology Monographs and Perspectives 6.
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.