| Rotylenchulus reniformis | |
|---|---|
 | |
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Nematoda |
| Class: | Secernentea |
| Order: | Tylenchida |
| Family: | Hoplolaimidae |
| Genus: | Rotylenchulus |
| Species: | R. reniformis |
| Binomial name | |
| Rotylenchulus reniformis Linford and Oliveira, 1940 | |
Rotylenchulus reniformis, the reniform nematode, is a species of parasitic nematode of plants with a worldwide distribution in the tropical and subtropical regions. [1]
This nematode has a wide host range, infecting many species of plants around the world. It was first observed on the roots of cowpea in Hawaii, and was described as new species and new genus in 1940. [2] Its specific epithet, reniformis, was inspired by the kidney shape of the adult female. [1] There are now ten species classified in the genus, but R. reniformis is the only species of major economic importance to agriculture. [2] Recent studies have demonstrated R. macrosoma is the sister species to R. reniformis. [3]
R. reniformis has been reported from thousands of localities in the Americas, Africa, Europe, Asia, and Australia. [2] [4] It has a wide host range that includes fruit trees, lentil, cotton, pigeon pea, tea, tobacco, soybean, pineapple, banana, okra, coconut, cabbage, sweet potato, alfalfa, corn, asparagus, palm, cucumber, tomato, squash, cassava, radish, eggplant, guava, melon, chickpea, and ginger. [5] [2] [6] Certain plants are considered to be non-hosts of the nematode, such as little barley, common barnyard grass, pangola grass, peppers, and some cultivars of black mustard, oat, spinach, and sugarcane. [6]
The reniform nematode has esophageal glands overlapping the intestine and a short stylet. The dorsal esophageal gland orifice is located posterior to the stylet knobs. [6] [7] The immature female is slender and may be spiral- or C-shaped in death. [8] It is about 0.3 to 0.5 millimeters long. [9] The mature female has a swollen, kidney-shaped body with a short tail, a short, thin stylet with rounded stylet knobs, a three-part esophagus, a long and narrow isthmus, and a well-developed metacarpus. The vulva is just behind the middle of the body. [7] The male is vermiform: with a wormlike appearance. It has a weak stylet, curved spicules, and a pointed tail. The esophagus is reduced. [7] [8]
R. reniformis is sedentary semi-endoparasite on the roots of plants. [4] The female penetrates the root and remains in one position at a permanent feeding site with its posterior end projecting from the root. [4] The immature female is the infective agent, attacking the root and growing to maturity at its feeding site. [10] Males and juveniles live in the soil; males are not parasites and do not feed. [7] Under drought conditions the nematode can persist up to two years outside a host by entering an anhydrobiotic state. [4]
The life cycle is 17 to 29 days long. [6] The juvenile molts once while still inside the egg. [11] The eggs hatch in 8 to 10 days. The juvenile molts three times to reach the immature stage. [11] The immature female parasitizes the root for one to two weeks. [4] During this time the male deposits sperm, which the female stores until her gonads mature. The nematode can also reproduce via parthenogenesis, without fertilization. [4] Upon maturity the female exits the root and lays up to 200 eggs in a gelatinous matrix. [4]
When the immature female penetrates the root, a feeding tube forms from stylet secretions. [8] Reniform nematode infestations can be hard to detect, as they do not cause galls or other obvious symptoms. [12] Instead, it causes symptoms in the host plant that resembles those of moisture and nutrient deficiencies. Reniform nematode cause hypertrophy in the pericycle cells of seedling roots and in the periderm cells of the roots of older plants. [13] Root growth slows and secondary root development is limited. Root necrosis has been observed in pineapple and banana. Shoot growth suppression and reduction of fruit quality has been observed in crops such as pineapple. [10] In sweet potato, early infection of reniform nematodes results in tuber cracking leading to poor storage quality. [14] Infested plants can become stunted and chlorotic. Wilt disease can follow when opportunistic fungi such as Fusarium and Verticillium infect the plants, a process observed in cotton. [4] [7] Secondary fungal infection can also cause root decay. Damage from R. reniformis is directly related to the number of nematodes present when the crop is planted. Variation among nematode populations, hosts, environmental conditions, and soil types may alter the threshold or economic injury level across the geographic distribution of the nematode. [4] [11]
Management can be challenging, as reniform nematodes have been found in depths greater than 1m in soil and appear to become dominant over other nematodes such as southern root knot nematode (M. incognita). [14] Some plants are resistant to this nematode. [6] In susceptible taxa, chemical control is one of the most common management practices. Nematicides before and after planting can be effective. [4] [11] Intercropping and crop rotation, especially with resistant or non-host plants, is used as cultural control to improve soil, increase antagonistic microorganisms, and reduce nematode populations. French marigold (Tagetes patula) and sunn hemp (Crotalaria juncea) are recommended for these uses. [4] [10] Fallowing the land is another cultural practice that can be utilized, but it is much less effective than rotating resistant species, as nematodes can persist in the soil for a long time and feed off of weeds. [15] The fungus Purpureocillium lilacinum and bacteria Bacillus firmus have shown potential to become commercial agents of biological pest control against the nematode in cotton. [16]
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.
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.
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.
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.
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).
Pratylenchus brachyurus is a plant parasitic nematode.
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.
Hirschmanniella oryzae, i.e. rice root nematode (RRN), is among the major pests of rice and is the most common plant-parasitic nematode found on irrigated rice. Recent modifications in cultivation practices have led to a substantial increase in rice production, which has been accompanied by heightened levels of RRN. The proportional increases in RRN with rice production can be explained by the nematode's impeccable adaptation towards constantly flooded conditions in which irrigated rice is often being grown.
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 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.
Mesocriconema xenoplax is a species of plant parasitic nematodes. Nematodes of this particular species are collectively called ring nematodes.
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.
Belonolaimus is a genus of nematodes. They are known commonly as sting nematodes. They are ectoparasites that feed on plant roots, sometimes becoming agricultural pests. They are found in the United States, Mexico, and Puerto Rico.
Hoplolaimus is a genus of nematodes known commonly as lance nematodes. They are parasites of plants, and three species are pests of agricultural crops.
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.
Helicotylenchus is a genus of nematodes in the family Hoplolaimidae. They are known generally as spiral nematodes. They are found worldwide because they can live and survive in a wide range of habitats. They are among the most common parasitic nematodes of plants; found in corn, bananas, grass, soybeans.
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.
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.