''Helicotylenchus'' is a genus of
nematode
The nematodes ( or ; ; ), roundworms or eelworms constitute the phylum Nematoda. Species in the phylum inhabit a broad range of environments. Most species are free-living, feeding on microorganisms, but many are parasitic. Parasitic worms (h ...
s in the family
Hoplolaimidae.
They are known generally as spiral nematodes.
[O'Bannon, J. H. and R. N. Inserra]
''Helicotylenchus'' species as crop damaging parasitic nematodes.
Nematology Circular 165. Florida Department of Agriculture and Consumer Services. 1989. They are found worldwide because they can live and survive in a wide range of habitats.
[Subbotin, S. A., et al. (2011)]
Diversity and phylogenetic relationships within the spiral nematodes of ''Helicotylenchus'' Steiner, 1945 (Tylenchida: Hoplolaimidae) as inferred from analysis of the D2-D3 expansion segments of 28S rRNA gene sequences.
''Nematology'' 13(3), 333-45. They are among the most common
parasitic
Parasitism is a close relationship between species, where one organism, the parasite, lives (at least some of the time) on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The ent ...
nematodes of plants; found in corn, bananas, grass, soybeans.
[
]
Description
The female is wormlike and straight or spiral-shaped. The male is similar, but with a smaller anterior end. The body may take a spiral shape after death, if not in life. This ''habitus mortis'' gives the nematodes their common name.[
]
Behavior
Most are ectoparasites of plant roots.. They insert their stylets into root epidermis
The epidermis is the outermost of the three layers that comprise the skin, the inner layers being the dermis and Subcutaneous tissue, hypodermis. The epidermal layer provides a barrier to infection from environmental pathogens and regulates the ...
to feed. Some species live half-buried in the root tissue, and others penetrate the root and live inside. They lay eggs on, around, or inside the roots, and within two or three days the juveniles emerge to feed.[ The genus is found on a wide variety of host plant taxa.][ Males can be rare, suggesting the nematode often reproduces by ]parthenogenesis
Parthenogenesis (; from the Greek + ) is a natural form of asexual reproduction in which the embryo develops directly from an egg without need for fertilization. In animals, parthenogenesis means the development of an embryo from an unfertiliz ...
.Genus ''Helicotylenchus''.
Plant Parasitic
Nematodes: An Introduction. North Carolina State University.
Most species are not very damaging to the plant. Nematodes of this genus have been noted to be ubiquitous in soil samples in Florida
Florida ( ; ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It borders the Gulf of Mexico to the west, Alabama to the northwest, Georgia (U.S. state), Georgia to the north, the Atlantic ...
with no plant damage nearby. Four species out of over 200 are known as destructive plant pests
PESTS was an anonymous American activist group formed in 1986 to critique racism, tokenism, and exclusion in the art world. PESTS produced newsletters, posters, and other print material highlighting examples of discrimination in gallery represent ...
that suppress plant growth: ''H. dihystera'', ''H. multicinctus'', ''H. pseudorobustus'', and ''H. digonicus''. A few others are potential pests.[
]
Impacts
Plants infested with aggressive species may become stunted and yellowed, but usually there is no sign of infestation in the herbage. An exception is in parasitism by ''H. multicinctus'', which can cause enough root necrosis
Necrosis () is a form of cell injury which results in the premature death of cells in living tissue by autolysis. The term "necrosis" came about in the mid-19th century and is commonly attributed to German pathologist Rudolf Virchow, who i ...
that it seriously weakens the plant. This species may be the most economically important, occurring in crops such as banana
A banana is an elongated, edible fruit – botanically a berry – produced by several kinds of large treelike herbaceous flowering plants in the genus '' Musa''. In some countries, cooking bananas are called plantains, distinguishing the ...
s of the Cavendish group. Other species have caused occasional damage to maize
Maize (; ''Zea mays''), also known as corn in North American English, is a tall stout grass that produces cereal grain. It was domesticated by indigenous peoples in southern Mexico about 9,000 years ago from wild teosinte. Native American ...
and Kentucky bluegrass
''Poa pratensis'', commonly known as Kentucky bluegrass (or blue grass), smooth meadow-grass, or common meadow-grass, is a perennial species of grass native to practically all of Europe, North Asia and the mountains of Algeria, Morocco, and Tuni ...
.[
]
Species
There are over 200 species.[ They can be difficult to tell apart because many species are very similar, individuals in a particular species can be variable, and species bounds are not entirely clear. Genetic analysis has helped to define several ]clade
In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...
s within the genus.[
Species include:
* '' Helicotylenchus canadensis'' Waseem, 1961]Helicotylenchus dihystera
''Helicotylenchus dihystera'' (Steiner's spiral nematode) is a plant pathogenic nematode. It is known to inhabit sugarcane, rice, potatoes, corn, peanut, millet, sorghum, banana and forest trees.
See also
* Sodium azide
Sodium azide is an i ...
'' (Cobb, 1893) Sher, 1961
* '' Helicotylenchus labiatus''
References
External links
''Helicotylenchus pseudorobustus''
on the UF / IFAS Featured Creatures website.
{{Taxonbar, from=Q3719010
Tylenchida
Plant pathogenic nematodes
Grape pest nematodes
Secernentea genera