Northern root-knot nematode

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Northern root-knot nematode
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Nematoda
Class: Secernentea
Order: Tylenchida
Family: Heteroderidae
Genus: Meloidogyne
Species:
M. hapla
Binomial name
Meloidogyne hapla
Chitwood, 1949

Northern root-knot nematode (Meloidogyne hapla) is a species of vegetable pathogens which produces tiny galls on around 550 crop and weed species. They invade root tissue after birth. Females are able to lay up to 1,000 eggs at a time in a large egg mass. By surviving harsh winters, they can survive in cold climates (hence, the name, Northern).

Contents

Hosts and symptoms

Meloidogyne hapla (Northern root-knot nematode) has a wide host range. It is polyphagous and affects over 550 crops and weeds. [1] It feeds on many agricultural and horticultural plants (vegetables, fruits, ornamentals), but few grasses or cereals. A list of known hosts can be found at the bottom of this page.

Symptom of nematode Meloidogyne hapla on carrot Meloidogyne hapla carrot forking.jpg
Symptom of nematode Meloidogyne hapla on carrot

Symptoms can be seen in the roots, leaves, and the overall growth of the infected plant. In roots, there may be stunting, wilting, and the formation of abnormal growths called galls. [3] Galls are usually small and spherical and are situated near many small roots. [1] They are formed when the nematode enters the root and releases chemicals to enlarge root cells, on which they feed. The roots become defective and therefore cannot transport water and nutrients properly. [4] The end result is stunted, wilted, and yellowing plants (characteristic of nutrient deficiency) and a decreased yield. [3] Severity of the symptoms depends on nematode population density and host plant species and cultivar. As the number of nematodes increase in the area, the number and size of root galls increase as well. Each crop responds to Meloidogyne hapla differently. Carrots typically undergo severe forking with galling of the roots, lettuce have beadlike galls, and grasses and onions have small and barely noticeable galls and symptoms. [5] In potato tubers (special stems), brown spots will appear on areas of the tubers where the females have laid their eggs. [1]

If a field has a patchy distribution of symptoms, it usually indicates the presence of nematodes. Most nematodes are not usually distributed uniformly in the soil. To correctly identify Meloidogyne hapla, the infected plant should be sent to a lab for a proper diagnosis. [4] One common method is perineal pattern analysis where the perineum of the female nematode (area between the anus and the vulva) is examined for a specific pattern in ridges and annulations. Another common method is analyzing isozyme (different variations of the same enzyme produced by different genes) electrophoretic profiles using esterase and malate dehydrogenase. [5]

Disease cycle

Northern root-knot nematodes go through six stages in their life cycle (egg stage, four juvenile stages, and then adulthood). They first survive the winter as eggs in the soil. The first juvenile stage occurs while in the egg. When the eggs hatch—usually when the soil temperature is 18 °C—the nematode is in its second juvenile stage, and will start to find, enter, and infect plant roots. [6] The males are able to move freely and leave the root after they become adults, while the females stay sedentary and feed on cells next to the vascular system [4] . Eventually, the females grow to the point where a portion of their bodies pop out of the root surface so that pearly white bodies can be seen. They then start laying thousands of eggs in egg masses outside the root. The life cycle takes about three to four weeks and therefore the population can grow very fast [6] .

Depending on the host and the soil temperature, the life cycle of Meloidogyne hapla can be between 17 and 57 days. [7] Nematodes in cooler regions usually have longer life cycles. Eggs may remain inside root tissue or may be released into the soil matrix and survive for up to one year. [5]

Management

Meloidogyne hapla are one of the most destructive nematodes in agriculture. They are difficult to control due to their wide host range and high rate of reproduction. [8] However, using a combination of control practices, known as integrated pest management plant (IPM), has been proven to be effective. [6] Depending on the control method being utilized, different parts of the root-knot nematode disease cycle is disturbed.

Cultural control

Before planting, one method of control is to leave the land fallow (empty for a duration), soil kept bare, cultivated, and weed controlled for 4–6 months to expose the nematodes to the sun to dry and starve to death. [3] Another control that can be done before the planting season is the use of cover crops such as sudangrass and marigolds which produce chemicals toxic to nematodes. [5] They also stabilize topsoil and improve soil quality which in turn increases microbial competition in the soil. [6] Rotation of nonhost crops (grasses, corn, barley, wheat, oat, rye, asparagus, onions) can also reduce nematode populations. [3] [6] [4]

During growth, soil amendments and maintenance are very important. Adding manure, compost, and organic matter improves soil quality to again increase microbial competition as well as allow the plants to grow stronger and be able to withstand nematode infestation. Controlling weeds can prevent additional hosts. At harvest, if there are infected plants, they should be destroyed and not composted to prevent further contamination. [6]

After harvest, the collecting of crop remains should be destroyed, and soil should never be moved.

Chemical control

A wide range of chemicals have been used to control Meloidogyne hapla. This includes both fumigants (methyl bromide, metham sodium, chloropiocrin), and liquids and granules (fenamiphos, oxamyl, furadan). However, many of these are overly toxic and are now restricted or banned. [3]

Organic control products

There are several OMRI (Organic Materials Reviews Institute) products in the market, but none show any significant effectiveness against Northern root-knot nematodes. [6]

Biofumigation

Some species of the plant genus Brassica can be used as effective biofumigants against the Northern root-knot nematode, however, they can interfere with the effectiveness of biological controls within the IPM. [6]

Biological control

Meloidogyne hapla can be controlled using their natural enemies. Common biological controls of nematodes are fungi and bacteria. Some fungi use mycelial traps or sticky spores to catch nematodes while other fungi parasitize eggs and females. Bacteria consume juvenile nematodes by attaching and penetrating the cuticle. [5]

Resistant varieties

There are no known resistant varieties as of now.

List of known hosts [3] [1]

Related Research Articles

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<i>Radopholus similis</i> Species of roundworm

Radopholus similis is a species of nematode known commonly as the burrowing nematode. It is a parasite of plants, and it is a pest of many agricultural crops. It is an especially important pest of bananas, and it can be found on coconut, avocado, coffee, sugarcane, other grasses, and ornamentals. It is a migratory endoparasite of roots, causing lesions that form cankers. Infected plants experience malnutrition.

<i>Meloidogyne incognita</i> Nematode worm, plant disease, many hosts

Meloidogyne incognita, also known as the southern root-nematode or cotton root-knot nematode is a plant-parasitic roundworm in the family Heteroderidae. This nematode is one of the four most common species worldwide and has numerous hosts. It typically incites large, usually irregular galls on roots as a result of parasitism.

<span class="mw-page-title-main">Soybean cyst nematode</span> Species of roundworm

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.

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Clubroot is a common disease of cabbages, broccoli, cauliflower, Brussels sprouts, radishes, turnips, stocks, wallflowers and other plants of the family Brassicaceae (Cruciferae). It is caused by Plasmodiophora brassicae, which was once considered a slime mold but is now put in the group Phytomyxea. It is the first phytomyxean for which the genome has been sequenced. It has as many as thirteen races. Gall formation or distortion takes place on latent roots and gives the shape of a club or spindle. In the cabbage such attacks on the roots cause undeveloped heads or a failure to head at all, followed often by decline in vigor or by death. It is an important disease, affecting an estimated 10% of the total cultured area worldwide.

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<i>Rotylenchulus reniformis</i> Species of roundworm

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<i>Meloidogyne arenaria</i> Species of roundworm

Meloidogyne arenaria is a species of plant pathogenic nematodes. This nematode is also known as the peanut root knot nematode. The word "Meloidogyne" is derived from two Greek words that mean "apple-shaped" and "female". The peanut root knot nematode, M. arenaria is one of the "major" Meloidogyne species because of its worldwide economic importance. M. arenaria is a predominant nematode species in the United States attacking peanut in Alabama, Florida, Georgia, and Texas. The most damaging nematode species for peanut in the USA is M. arenaria race 1 and losses can exceed 50% in severely infested fields. Among the several Meloidogyne species that have been characterized, M. arenaria is the most variable both morphologically and cytologically. In 1949, two races of this nematode had been identified, race 1 which reproduces on peanut and race 2 which cannot do so. However, in a recent study, three races were described. López-Pérez et al (2011) had also studied populations of M. arenaria race 2, which reproduces on tomato plants carrying the Mi gene and race 3, which reproduces on both resistant pepper and tomato.

<i>Meloidogyne javanica</i> Species of roundworm

Meloidogyne javanica is a species of plant-pathogenic nematodes. It is one of the tropical root-knot nematodes and a major agricultural pest in many countries. It has many hosts. Meloidogyne javanica reproduces by obligatory mitotic parthenogenesis (apomixis).

<i>Pratylenchus penetrans</i> Species of roundworm

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.

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<i>Paratylenchus hamatus</i> Species of roundworm

Paratylenchus hamatus, the fig pin nematode, is a species of migratory plant endoparasites, that causes lesions on plant roots resulting in symptoms of chlorosis, wilting and ultimately yield losses. They move and feed on different parts of host tissue throughout their life cycle in order to find enough susceptible host tissue to survive and reproduce. A wide range of host plant species are susceptible to the fig pin nematode, including many valuable fruit and vegetable crops such as figs, carrots and celery. They are also commonly found associated with woody perennials in California. P. hamatus inhabits soils in both Europe and North America, and was originally isolated from fig in central California in 1950.

Xiphinema diversicaudatum is an amphimictic ectoparasitic nematode species. This species has a characteristically long stylet capable of penetrating into a host's vascular tissue. They have a wide host range with some of the extensively studied ones being strawberry, hops and raspberry, due to their economic importance. The direct root damage caused through penetration near the root tip and formation of galls is a secondary concern when compared with the damage caused by vectoring the Arabis mosaic virus. The virus attaches to the interior cuticle lining and can be transferred from infected to uninfected root tissue as the nematode feeds and sheds. Management of this particular nematode relies on nematicides such as 1,3-Dichloropropene (Telone) at 40 gpa.or methyl bromide at 1000 lb/ac to control to 28 in deep.

There are many plant-parasitic species in the root-knot nematode genus (Meloidogyne) that attack coffee such as M. incognita, M. arenaria, M. exigua, M. javanica and M. coffeicola. Study has already shown interspecific variability coffee, in which show how this species can be adapting to new hosts and environments.

Arabis mosaic virus is a viral plant pathogen that is known to infect multiple hosts. The pathogen, commonly referred to as ArMV, is from the family Secoviridae, and it causes yellow dwarf of raspberry and is one of the causes of mosaic of rhubarb. Arabis mosaic virus infects multiple hosts, including strawberries, hops, hemp, grape, geraniums, raspberries, sugar beets, celery, horseradish, lilac, peach, and lettuces.

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 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.

References

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