''Rotylenchulus reniformis'', the reniform nematode, is a species of

parasitic Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson ha ...

nematode of plants with a worldwide distribution in the

tropical The tropics are the regions of Earth surrounding the Equator. They are defined in latitude by the Tropic of Cancer in the Northern Hemisphere at N and the Tropic of Capricorn in the Southern Hemisphere at S. The tropics are also referred to ...

and subtropical regions.Ferris, H
''Rotylenchulus reniformis''.
Nemaplex. Department of Nematology. University of California, Davis. 2012.

Taxonomy

This nematode has a wide host range, infecting many species of plants around the world. It was first observed on the roots of

cowpea The cowpea (''Vigna unguiculata'') is an annual herbaceous legume from the genus ''Vigna''. Its tolerance for sandy soil and low rainfall have made it an important crop in the semiarid regions across Africa and Asia. It requires very few inputs, ...

Hawaii Hawaii ( ; haw, Hawaii or ) is a state in the Western United States, located in the Pacific Ocean about from the U.S. mainland. It is the only U.S. state outside North America, the only state that is an archipelago, and the only state ...

, and was described as new species and new genus in 1940.Robinson, A. F., et al. 1997
''Rotylenchulus'' species: identification, distribution, host ranges, and crop plant resistance.
''Nematropica'' 27(2), 127-80. Its specific epithet, ''reniformis'', was inspired by the

kidney The kidneys are two reddish-brown bean-shaped organs found in vertebrates. They are located on the left and right in the retroperitoneal space, and in adult humans are about in length. They receive blood from the paired renal arteries; blo ...

shape of the adult female. There are now ten species classified in the genus, but ''R. reniformis'' is the only species of major economic importance to agriculture.

Distribution and host range

''R. reniformis'' has been reported from thousands of localities in the Americas, Africa, Europe, Asia, and Australia.Wang, K
Reniform Nematode, ''Rotylenchulus reniformis'' Linford and Oliveira (Nematoda: Tylenchida: Tylenchoidea: Hoplolaimidae: Rotylenchulinae).
EENY-210 (IN367). Entomology and Nematology. Florida Cooperative Extension Service. University of Florida IFAS. Published 2001, revised 2007. It has a wide host range that includes fruit trees,

lentil The lentil (''Lens culinaris'' or ''Lens esculenta'') is an edible legume. It is an annual plant known for its lens-shaped seeds. It is about tall, and the seeds grow in pods, usually with two seeds in each. As a food crop, the largest pro ...

cotton Cotton is a soft, fluffy staple fiber that grows in a boll, or protective case, around the seeds of the cotton plants of the genus '' Gossypium'' in the mallow family Malvaceae. The fiber is almost pure cellulose, and can contain minor pe ...

pigeon pea The pigeon pea (''Cajanus cajan'') is a perennial legume from the family Fabaceae native to the Old World. The pigeon pea is widely cultivated in tropical and semitropical regions around the world, being commonly consumed in South Asia, South ...

tea Tea is an aromatic beverage prepared by pouring hot or boiling water over cured or fresh leaves of ''Camellia sinensis'', an evergreen shrub native to East Asia which probably originated in the borderlands of southwestern China and north ...

tobacco Tobacco is the common name of several plants in the genus '' Nicotiana'' of the family Solanaceae, and the general term for any product prepared from the cured leaves of these plants. More than 70 species of tobacco are known, but the ...

soybean The soybean, soy bean, or soya bean (''Glycine max'') is a species of legume native to East Asia, widely grown for its edible bean, which has numerous uses. Traditional unfermented food uses of soybeans include soy milk, from which tofu a ...

pineapple The pineapple (''Ananas comosus'') is a tropical plant with an edible fruit; it is the most economically significant plant in the family Bromeliaceae. The pineapple is indigenous to South America, where it has been cultivated for many centuri ...

, banana,

okra Okra or Okro (, ), ''Abelmoschus esculentus'', known in many English-speaking countries as ladies' fingers or ochro, is a flowering plant in the mallow family. It has edible green seed pods. The geographical origin of okra is disputed, with su ...

, coconut, cabbage, sweet potato, alfalfa, corn,

asparagus Asparagus, or garden asparagus, folk name sparrow grass, scientific name ''Asparagus officinalis'', is a perennial flowering plant species in the genus '' Asparagus''. Its young shoots are used as a spring vegetable. It was once classified in ...

palm Palm most commonly refers to: * Palm of the hand, the central region of the front of the hand * Palm plants, of family Arecaceae **List of Arecaceae genera * Several other plants known as "palm" Palm or Palms may also refer to: Music * Palm (ba ...

, cucumber,

tomato The tomato is the edible berry of the plant ''Solanum lycopersicum'', commonly known as the tomato plant. The species originated in western South America, Mexico, and Central America. The Mexican Nahuatl word gave rise to the Spanish word ...

squash Squash may refer to: Sports * Squash (sport), the high-speed racquet sport also known as squash racquets * Squash (professional wrestling), an extremely one-sided match in professional wrestling * Squash tennis, a game similar to squash but pla ...

cassava ''Manihot esculenta'', commonly called cassava (), manioc, or yuca (among numerous regional names), is a woody shrub of the spurge family, Euphorbiaceae, native to South America. Although a perennial plant, cassava is extensively cultivated ...

radish The radish (''Raphanus raphanistrum'' subsp. ''sativus'') is an edible root vegetable of the family Brassicaceae that was domesticated in Asia prior to Roman times. Radishes are grown and consumed throughout the world, being mostly eaten raw ...

, eggplant, guava,

melon A melon is any of various plants of the family Cucurbitaceae with sweet, edible, and fleshy fruit. The word "melon" can refer to either the plant or specifically to the fruit. Botanically, a melon is a kind of berry, specifically a " pepo". Th ...

, and ginger.MacGowan, J. B
The Reniform Nematode.
Nematology Circular No. 32. Florida Department of Agriculture and Consumer Services. 1977. Certain plants are considered to be non-hosts of the nematode, such as little barley, common barnyard grass, pangola grass,

peppers Pepper or peppers may refer to: Food and spice * Piperaceae or the pepper family, a large family of flowering plant ** Black pepper * ''Capsicum'' or pepper, a genus of flowering plants in the nightshade family Solanaceae ** Bell pepper ** Chili ...

, and some

cultivar A cultivar is a type of cultivated plant that people have selected for desired traits and when propagated retain those traits. Methods used to propagate cultivars include: division, root and stem cuttings, offsets, grafting, tissue culture ...

s of

black mustard ''Brassica nigra'', or black mustard, is an annual plant cultivated for its dark-brown-to-black seeds, which are commonly used as a spice. It is native to tropical regions of North Africa, temperate regions of Europe, and parts of Asia. Desc ...

oat The oat (''Avena sativa''), sometimes called the common oat, is a species of cereal grain grown for its seed, which is known by the same name (usually in the plural, unlike other cereals and pseudocereals). While oats are suitable for human con ...

, spinach, and sugarcane.

Morphology

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.Shurtleff, M. C. and C. W. Averre. ''Diagnosing Plant Diseases Caused by Nematodes''. St. Paul, Minnesota: American Phytopathological Society Press. 2000. The immature female is slender and may be spiral- or C-shaped in death.Dropkin, V. ''Introduction to Plant Nematology''. John Wiley & Sons, Inc. 1980. 293p. It is about 0.3 to 0.5 millimeters long. 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. The male is

vermiform Vermiform (ˈvərməˌfôrm) describes something shaped like a worm. The expression is often employed in biology and anatomy to describe usually soft body parts or animals that are more or less tubular or cylindrical. The word root is Latin, ''ve ...

: with a wormlike appearance. It has a weak stylet, curved

spicule Spicules are any of various small needle-like anatomical structures occurring in organisms Spicule may also refer to: *Spicule (sponge), small skeletal elements of sea sponges *Spicule (nematode), reproductive structures found in male nematodes ( ...

s, and a pointed tail. The esophagus is reduced.

Life cycle

''R. reniformis'' is sedentary semi-endoparasite on the roots of plants. The female penetrates the root and remains in one position at a permanent feeding site with its posterior end projecting from the root. The immature female is the infective agent, attacking the root and growing to maturity at its feeding site.Luc, M., et al. (Eds.
''Plant Parasitic Nematodes in Subtropical and Tropical Agriculture''. 2nd Edition.
CABI Publishing. 2005. pp 38, 39, 709-20. Males and juveniles live in the soil; males are not parasites and do not feed. Under

drought A drought is defined as drier than normal conditions.Douville, H., K. Raghavan, J. Renwick, R.P. Allan, P.A. Arias, M. Barlow, R. Cerezo-Mota, A. Cherchi, T.Y. Gan, J. Gergis, D. Jiang, A. Khan, W. Pokam Mba, D. Rosenfeld, J. Tierney, an ...

conditions the nematode can persist up to two years outside a host by entering an anhydrobiotic state. The life cycle is 17 to 29 days long. The juvenile molts once while still inside the egg.Lawrence, G. W. and K. S. Reniform Nematodes. In: Kirkpatrick, T. L. and C. S. Rothrock. (Eds.) ''Compendium of Cotton Diseases''. 2nd edition. St. Paul, Minnesota: The American Phytopathological Society Press. 2001. pp. 42–44. The eggs hatch in 8 to 10 days. The juvenile molts three times to reach the immature stage. The immature female parasitizes the root for one to two weeks. During this time the male deposits sperm, which the female stores until her gonads mature. The nematode can also reproduce via

parthenogenesis Parthenogenesis (; from the Greek grc, παρθένος, translit=parthénos, lit=virgin, label=none + grc, γένεσις, translit=génesis, lit=creation, label=none) is a natural form of asexual reproduction in which growth and developmen ...

, without fertilization. Upon maturity the female exits the root and lays up to 200 eggs in a gelatinous matrix.

Host-parasite relationship

Sweetpotato infected by reniform nematodes14618951783

When the immature female penetrates the root, a feeding tube forms from stylet secretions. Reniform nematode infestations can be hard to detect, as they do not cause galls or other obvious symptoms. Instead, it causes symptoms in the host plant that resembles those of moisture and nutrient deficiencies. Reniform nematode cause hypertrophy in the

pericycle The pericycle is a cylinder of parenchyma or sclerenchyma cells that lies just inside the endodermis and is the outer most part of the stele of plants. Although it is composed of non-vascular parenchyma cells, it's still considered part of the va ...

cells of seedling roots and in the

periderm Bark is the outermost layers of stems and roots of woody plants. Plants with bark include trees, woody vines, and shrubs. Bark refers to all the tissues outside the vascular cambium and is a nontechnical term. It overlays the wood and consist ...

cells of the roots of older plants.Oteifa, B. A. (1970). The reniform nematode problem of Egyptian cotton production. ''Journal of Parasitology'' 56, 255. 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. In sweet potato, early infection of reniform nematodes results in tuber cracking leading to poor storage quality. Infested plants can become stunted and

chlorotic In botany, chlorosis is a condition in which leaves produce insufficient chlorophyll. As chlorophyll is responsible for the green color of leaves, chlorotic leaves are pale, yellow, or yellow-white. The affected plant has little or no ability to ...

Wilt disease A wilt disease is any number of diseases that affect the vascular system of plants. Attacks by fungi, bacteria, and nematodes can cause rapid killing of plants, large tree branches or even entire trees. Wilt diseases in woody plants tend to fal ...

can follow when opportunistic

fungi A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from ...

such as ''

Fusarium ''Fusarium'' is a large genus of filamentous fungi, part of a group often referred to as hyphomycetes, widely distributed in soil and associated with plants. Most species are harmless saprobes, and are relatively abundant members of the soil mi ...

'' and ''

Verticillium ''Verticillium'' is a genus of fungi in the division Ascomycota, and are an anamorphic form of the family Plectosphaerellaceae. The genus used to include diverse groups comprising saprobes and parasites of higher plants, insects, nematodes, mo ...

'' infect the plants, a process observed in cotton. 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.

Management

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).'' Some plants are resistant to this nematode. In susceptible taxa, chemical control is one of the most common management practices.

Nematicide A nematicide is a type of chemical pesticide used to kill plant-parasitic nematodes. Nematicides have tended to be broad-spectrum toxicants possessing high volatility or other properties promoting migration through the soil. Aldicarb (Temik), a ca ...

s before and after planting can be effective.

Intercropping Intercropping is a multiple cropping practice that involves growing two or more crops in proximity. In other words, intercropping is the cultivation of two or more crops simultaneously on the same field. The most common goal of intercropping is ...

and

crop rotation Crop rotation is the practice of growing a series of different types of crops in the same area across a sequence of growing seasons. It reduces reliance on one set of nutrients, pest and weed pressure, and the probability of developing resistant ...

, especially with resistant or non-host plants, is used as

cultural control In agriculture cultural control is the practice of modifying the growing environment to reduce the prevalence of unwanted pests. Examples include changing soil pH or fertility levels, irrigation Irrigation (also referred to as watering) is t ...

to improve soil, increase antagonistic microorganisms, and reduce nematode populations. French marigold (''Tagetes patula'') and sunn hemp (''Crotalaria juncea'') are recommended for these uses. The fungus ''

Purpureocillium lilacinum ''Purpureocillium lilacinum'' is a species of filamentous fungus in the family Ophiocordycipitaceae. It has been isolated from a wide range of habitats, including cultivated and uncultivated soils, forests, grassland, deserts, estuarine sedime ...

'' has been used as an agent of biological pest control against the nematode in chickpea.

References

{{Taxonbar, from=Q7370726 Tylenchida Plant pathogenic nematodes Nematodes described in 1940