| Corn cyst nematode | |
|---|---|
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Nematoda |
| Class: | Secernentea |
| Order: | Tylenchida |
| Family: | Heteroderidae |
| Genus: | Heterodera |
| Species: | H. zeae |
| Binomial name | |
| Heterodera zeae Koshy, Swarup, and Sethi 1970 | |
Heterodera zeae, the corn cyst nematode (CCN), is a plant parasitic nematode that feeds on Zea mays (maize/corn). The CCN has a limited economic impact worldwide due to its high soil temperature requirements. [1]
CCN was first described from a population in Udaipur, India in 1970 by Koshy and his co-workers. It was later reported in Egypt and Pakistan. In India the CCN is considered to be one of the four economically important cyst nematodes. [2] The first report of the species in the Western hemisphere came in 1981 from four colonies in Maryland, Harford, Cecil, Kent, and Queen Anne's counties. These four counties were placed under quarantine. The nematode was later identified from Cumberland Co., VA, over 170 miles from the nearest known infested field in Maryland. In Virginia the nematode was restricted to a 3 by 2.5 mile strip of land along the Appomattox River. [3]
The cysts of CCN are light brown in color and lemon shaped. The cysts also have a zig-zag pattern on the cyst wall with four prominent finger-like bullae below the underbridge. The juveniles have an average stylet length of 20 μm and have a thin finely pointed tail. Females have a vulva slit of approximately 33 μm. [4]
The CCN has been found in India, Pakistan, Egypt, and the United States. In India and Egypt it is considered to be of economic importance. [5] [6] In the United States it is not considered to be of economic importance due to its limited distribution and high soil temperature requirements for reproduction. [7] Surveys have found the nematode in four Maryland counties and one county in Virginia. However, extensive surveys from 2004 to 2011 failed to identify H. zeae from New Jersey, Florida, Wisconsin, Minnesota, South Dakota, North Dakota, and Idaho. [8]
The life cycle of the CCN is similar to other cyst nematodes in the genus Heterodera . Individuals begin as eggs contained within a cyst, the hardened body of a dead female. Juveniles complete the molt from first stage to second stage within the egg, and it is the second stage juvenile or J2, which hatches from the egg. [9] The J2 will seek out the roots of a suitable host plant and penetrate the root in search of a feeding site. The J2 will establish a permanent feeding site known as a syncytium and progress to adulthood. Males have not been described, but are assumed to exist. [10] Female development is highly temperature dependent with development being minimal at 75 °F and steadily increasing in rate from 80 °F to 97 °F. The optimal developmental temperature is ≥ 97 °F, which is considered high for cyst nematodes. In the greenhouse females will produce around 150 eggs when developing on corn. [11] Upon completion of their life adult females will darken in color and become hardened forming protective cysts, which contain their eggs.
The CCN is known to be capable of parasitizing and reproducing on 42 different members of the plant family Poaceae. These include the economically important crops of oat, barley, rice, sorghum, and wheat. [12] Corn is the preferred host with reproduction on corn far exceeding the other crops.
The CCN is a sedentary endoparasitic nematode, establishing feeding sites in the roots of host plants near the vascular tissue. Like other cyst nematodes, CCN feeds from a specialized feeding site known as a syncytium. This feeding site is formed by the deterioration of cell walls of adjoining plant cells in response to elicitors delivered through the nematode's stylet. This cell wall deterioration leads to the formation of a single multi-nucleated feeding cell. Through the diversion of nutrients to the syncytium, CCN can stunt corn plant growth and reduce yield. [13] [14]
The CCN is currently not considered an economically important pest of corn in the United States. [15] If CCN reaches damaging levels crop rotation to non-host crops would be a viable management option as the CCN's host range is limited to grasses and its non-hosts include soybean, alfalfa, and cotton. [16] It has been reported that temperature may influence the susceptibility of poor host plants to infection by H.zeae. [17] At 15 and 23 degrees Celsius the J2's of H.zeae penetrated maize roots but failed to penetrate roots of wheat however, penetration and development on corn and wheat roots was similar at 32 degrees Celsius. [18] Different cultivars of wheat and oats failed to support the reproduction of H.zeae under temperature ranges from 11-22 degrees Celsius however, when the temperature was increased to 33 degrees Celsius in the growth chamber slight nematode reproduction was observed. [19] If CCN is a concern monitoring soil temperatures and alternate hosts and potential host crops may be beneficial. Host plant resistant corn lines have been found and could be used to develop resistant hybrids if needed. [20]
Root-knot nematodes are plant-parasitic nematodes from the genus Meloidogyne. They exist in soil in areas with hot climates or short winters. About 2000 plants worldwide are susceptible to infection by root-knot nematodes and they cause approximately 5% of global crop loss. Root-knot nematode larvae infect plant roots, causing the development of root-knot galls that drain the plant's photosynthate and nutrients. Infection of young plants may be lethal, while infection of mature plants causes decreased yield.
The soybean cyst nematode (SCN), Heterodera glycines, is the most devastating pest to soybean crop yields in the U.S., targeting the roots of soybean and other legume plants. When infection is severe SCNs cause stunting, yellowing, impaired canopy development, and yield loss. The symptoms caused by SCNs can go easily unrecognized by farmers—in some cases there are no warning symptoms before a loss of 40% of the yield. Due to the slight stunting and yellowing, many farmers may mistake these symptoms as environmental problems when in fact they are SCNs. Another symptom of SCNs that may affect farmers' yields is stunted roots with fewer nitrogen-fixing nodules. Due to the fact that soybean cyst nematodes can only move a few centimeters in the soil by themselves, they mostly are spread via tillage or plant transplants. This area of infection will look patchy and nonuniform making diagnosis more difficult for farmers. They can be seen in the roots of summer soybean plants if the roots are taken out very carefully and gently washed with water. The egg masses should be seen as bright white or yellow "pearls" on the roots. The later the roots are pulled the harder it will be to diagnose due to the SCNs female dying and turning a much darker color, forming a "cyst". The best way to know if a field is infected by soybean cyst nematodes is to take a soil sample to a nematologist.
Potato root nematodes or potato cyst nematodes (PCN) are 1-mm long roundworms belonging to the genus Globodera, which comprises around 12 species. They live on the roots of plants of the family Solanaceae, such as potatoes and tomatoes. PCN cause growth retardation and, at very high population densities, damage to the roots and early senescence of plants. The nematode is not indigenous to Europe but originates from the Andes. Fields are free from PCN until an introduction occurs, after which the typical patches, or hotspots, occur on the farmland. These patches can become full field infestations when unchecked. Yield reductions can average up to 60% at high population densities.
Belonolaimus longicaudatus is a common parasite of grasses and other plant crops and products. It is the most destructive nematode pest of turf grass, and it also attacks a wide range of fruit, vegetable, and fiber crops such as citrus, cotton, ornamentals, and forage. The sting nematode is a migratory ectoparasite of roots. It is well established in many golf courses and presents a problem in turf management. The sting nematode is only present in very sandy soils. It cannot reproduce in heavier or clay soils.
Aphelenchoides ritzemabosi is a plant pathogenic nematode. It was first scientifically described in 1890 in England. This nematode has a wide host range. Among the most important species affected are Chrysanthemums and strawberries. A. ritzemabosi is a migratory foliar feeding nematode. It can feed both ectoparasitically and endoparasitically, with the later causing the most significant damage. When adequate moisture is present, this nematode enters the leaves and feeds from inside the tissue. Typical damage is characterized by necrotic zones between the veins of the leaves. Its lifecycle is short; only ten days from egg to mature adult. A single female can lay as many as 3,500 eggs. This pest can be difficult to control. Host plant resistance, hot water treatments, and predatory mites are recommended.
Pratylenchus penetrans is a species of nematode in the genus Pratylenchus, the lesion nematodes. It occurs in temperate regions worldwide, regions between the subtropics and the polar circles. It is an animal that inhabits the roots of a wide variety of plants and results in necrotic lesions on the roots. Symptoms of P. penetrans make it hard to distinguish from other plant pathogens; only an assay of soil can conclusively diagnose a nematode problem in the field. P. penetrans is physically very similar to other nematode species, but is characterized by its highly distinctive mouthpiece. P. penetrans uses its highly modified mouth organs to rupture the outer surface of subterranean plant root structures. It will then enter into the root interior and feed on the plant tissue inside. P. penetrans is considered to be a crop parasite and farmers will often treat their soil with various pesticides in an attempt to eliminate the damage caused by an infestation. In doing this, farmers will also eliminate many of the beneficial soil fauna, which will lead to an overall degradation of soil quality in the future. Alternative, more environmentally sustainable methods to control P. penetrans populations may be possible in certain regions.
Pratylenchus zeae is a plant-pathogenic nematode found on potatoes, maize, cereal, tobacco, coffee, blackberry, and found most often on sugarcane.
Heterodera carotae is a plant pathogenic nematode commonly known as the carrot root nematode or carrot cyst nematode. It is found in Europe, Cyprus and India and is considered an invasive species in the United States. It causes damage to carrot crops and is very specific in its choice of hosts, only infecting Daucus carota and Daucus pulcherrima.
Heterodera goettingiana, the pea cyst nematode, is a plant pathogenic nematode affecting peas.
Heterodera schachtii, the beet cyst eelworm or sugarbeet nematode, is a plant pathogenic nematode. It infects more than 200 different plants including economically important crops such as sugar beets, cabbage, broccoli, and radish. H. schachtii is found worldwide. Affected plants are marked by stunted growth, wilting, yellowing, decreased yields, and death. While there are many methods of control, crop rotation with non-susceptible plants is preferred.
Heterodera trifolii is a plant pathogenic nematode.
Xiphinema americanum, the American dagger nematode, is a species of plant pathogenic nematodes. It is one of many species that belongs to the genus Xiphinema. It was first described by N. A. Cobb in 1913, who found it on both sides of the United States on the roots of grass, corn, and citrus trees. Not only is Xiphinema americanum known to vector plant viruses, but also X. americanum has been referred to as "the most destructive plant parasitic nematode in America", and one of the four major nematode pests in the Southeastern United States.
Tylenchorhynchus claytoni is a plant pathogenic nematode.
Heterodera is a genus of nematodes in the family Heteroderidae. Members of the genus are obligate parasites and different species attack different crops, often causing great economic damage. The genus is unique among nematode genera because of the ability of the female to transform into a tough, brown, cyst which protects the eggs which have been formed within her body. The name heterodera "refers to the different 'skins' of female and cyst."
Heterodera sacchari, the sugarcane cyst nematode, mitotic parthenogenic sedentary endoparasitic nematode. This plant-parasitic nematode infects the roots of sugarcane, and the female nematode eventually becomes a thick-walled cyst filled with eggs. Aboveground symptoms are species specific and are similar to those caused by other Heterodera species. Symptoms include: stunted and chlorotic plants, and reduced root growth. Seedlings may be killed in heavily infested soils.
Pratylenchus is a genus of nematodes known commonly as lesion nematodes. They are parasitic on plants and are responsible for root lesion disease on many taxa of host plants in temperate regions around the world. Lesion nematodes are migratory endoparasites that feed and reproduce in the root and move around, unlike the cyst or root-knot nematodes, which may stay in one place. They usually only feed on the cortex of the root. Species are distinguished primarily by the morphology of the stylets.
Globodera tabacum, commonly known as a tobacco cyst nematode, is a plant parasitic nematode that mainly infests the tobacco plant, but also plants in family Solanaceae.
Pratylenchus alleni is a migratory endoparasitic nematode, living inside of plant roots and feeding on parenchyma cells in the root cortex. P. alleni is an obligate biotroph, meaning it must have a living host in order to survive. Due to their incredibly broad host range, Pratylenchus species fall third in total economic impact, finishing just behind cyst nematodes and root knot nematodes (Meloidogyne). In Canada, it was isolated for the first time in 2011 in a soybean field.
Globodera ellingtonae is one of the potato cyst nematodes and was recently recognized as a new species in the United States. This triggered a quarantine of the fields where it was isolated to prevent the spread of this nematode to other fields.
Pasteuria is a genus of mycelial and endospore-forming, nonmotile gram-positive bacteria that are obligate parasites of some nematodes and crustaceans. The genus of Pasteuria was previously classified within the family Alicyclobacillaceae, but has since been moved to the family Pasteuriaceae.
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