| Bentgrass nematode | |
|---|---|
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Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Nematoda |
| Class: | Secernentea |
| Order: | Tylenchida |
| Family: | Anguinidae |
| Genus: | Anguina |
| Species: | A. agrostis |
| Binomial name | |
| Anguina agrostis | |
| Synonyms | |
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Anguina agrostis (Bentgrass nematode, seed-gall nematode) is a plant pathogenic nematode. [1] [2] [3]
Anguina agrostis was one of the first plant parasitic nematodes to be taxonomically described by J.G. Steinbuch in 1799. While on a "botanical walk", Steinbuch collected samples from a grass that resembled Agrostis silvatica. He examined the samples and discovered that the grass was not A. silvatica but was rather a degenerate form of Agrostis capillaris ; he further discovered that A. silvatica is not a true species (or variety) but that the misclassification of the grass was due to the formation of galls by A. agrostis parasitism. [4] Galls caused by A. agrostis have glumes that are 4-5 times longer than normal and can cause yield losses of up to 40-70%. [4] [5] [6] In addition to crop loss, A. agrostis associates with pathogenic bacteria Rathayibacter rathayi (formerly Corynebacterium rathayi) to cause annual ryegrass toxicity in Australia. [4]
A. agrostis infects bentgrasses within the genus Agrostis as well as annual and perennial ryegrasses (Lolium spp.). [3] The nematode can also infect 14 other genera of grasses. [1] [3] A. agrostis has been found in Australia, New Zealand, Western Europe, former USSR, Canada, and the United States. [4] [5]
The lip region is slightly offset (3-4 μm high) and the nematode has a very short stylet (10 μm). A. agrostis has a three-part esophagus. The procorpus is cylindrical with a swelling near its midsection. The metacorpus is ovoid in shape and the isthmus is long and narrow. The postcorpus has three glands and is highly developed, but does not overlap the intestine. [7] On average, infective juveniles (J2) measure 530 μm and dauer juveniles measure 760 μm; the increase in size is due to feeding and the formation of lipid droplets or storage bodies. Females range from 1.5 to 2.7 mm in length, are curved ventrally, and are swollen. The vulva is located near the posterior end and one ovary is present. Males are smaller (1.1-1.7 mm in length), are not as swollen, and have a small bursae that extends subterminally. One testis is present. [4]
Infective second stage juveniles (J2) find a young host, migrate to areas of new growth and are carried up with the growing point of the plant. [8] They may feed ectoparasitically until formation of the inflorescence, at which time the J2 invades the ovule, becomes sedentary, and a gall begins to form. Within the gall, nematodes progress through three molts to reach adulthood (J3, J4, male and female adults). Reproduction is amphimictic and females can lay up to 1000 eggs. The first molt occurs in the egg and the nematode hatches as a J2. These juveniles undergo anhydrobiosis and become the dormant dauer larvae to withstand the hot summer heat of Australia. Autumn rains rehydrate the dauer juveniles which become active to begin the life cycle over again. [4] Only one generation is produced per year. [4] [7]
Infective second stage juveniles colonize plants during the vegetative growth stage and may feed ectoparasitically during this time. When the inflorescence begins to form, the J2s invade the flower ovule and begin to feed endoparasitically. [4] [8] [9] Nematode feeding on floret primordia induces rapid cell division, cell enlargement, and subsequent cell degeneration and collapse. The continuation of this process results in the formation of a large central cavity (in which the now-sedentary nematodes reside) enveloped by a gall wall. Gall size increases rapidly as nematodes grow and reproduce. The gall wall is several cell layers thick. Inner cells of the gall wall (near the cavity) have dense cytoplasm with several mitochondria, indicating high levels of metabolic activity. These cells most likely provide nutrients to the nematodes. The outer layers of the gall wall are unmodified, thereby forming and maintaining the gall structure. As the plant senesces, the galls desiccate and the nematodes undergo anhydrobiosis. [9]
To mitigate the effects of annual ryegrass toxicity, farmers can move their livestock another, uninfected pasture at first sign of toxicity. [4] Hot water treatments or chemical seed treatments have been used to produce clean seed. [5] Infected pastures can be managed by mowing, herbicide treatments, or burning. These techniques eliminate the development of inflorescences and halt the life cycle of the nematode since they only mature to adulthood within the seed gall. [4] [5] A. agrostis cannot survive in the soil for more than one year and thus practices such as crop rotation or fallow have proven to be effective in managing the nematode. [5]
Northern root-knot nematode 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.
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.
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.
Rotylenchulus reniformis, the reniform nematode, is a species of parasitic nematode of plants with a worldwide distribution in the tropical and subtropical regions.
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 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.
Anguina tritici 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.
Tylenchulus semipenetrans, also known as the citrus nematode or citrus root nematode, is a species of plant pathogenic nematodes and the causal agent of slow decline of citrus. T. semipenetrans is found in most citrus production areas and diverse soil textures worldwide. Their feeding strategy is semi-endoparasitic and has a very narrow host range among commonly grown crops. These nematodes are considered as major plant-parasitic nematode because they can cause 10-30% losses reported on citrus trees. They also parasitize other hosts such as olive, grape, persimmon and lilac. The citrus nematode was first discovered in California in 1913 by J. R. Hodges, a horticultural inspector for Los Angeles County, and was later described and named by Nathan Cobb that year. T. semipenetrans is the only species of Tylenchulidae that are economically important to agriculture.
Mesocriconema xenoplax is a species of plant parasitic nematodes. Nematodes of this particular species are collectively called ring nematodes.
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.
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.
Anguina is a genus of plant pathogenic nematodes.
Lolium arundinaceum, tall fescue is a cool-season perennial C3 species of grass that is native to Europe. It occurs on woodland margins, in grassland and in coastal marshes. It is also an important forage grass with many cultivars that used in agriculture and is used as an ornamental grass in gardens, and sometimes as a phytoremediation plant.
Ergovaline is an ergopeptine and one of the ergot alkaloids. It is usually found in endophyte-infected species of grass like Tall fescue or Perennial Ryegrass. It is toxic to cattle feeding on infected grass, probably because it acts as a vasoconstrictor.
A loline alkaloid is a member of the 1-aminopyrrolizidines, which are bioactive natural products with several distinct biological and chemical features. The lolines are insecticidal and insect-deterrent compounds that are produced in grasses infected by endophytic fungal symbionts of the genus Epichloë. Lolines increase resistance of endophyte-infected grasses to insect herbivores, and may also protect the infected plants from environmental stresses such as drought and spatial competition. They are alkaloids, organic compounds containing basic nitrogen atoms. The basic chemical structure of the lolines comprises a saturated pyrrolizidine ring, a primary amine at the C-1 carbon, and an internal ether bridge—a hallmark feature of the lolines, which is uncommon in organic compounds—joining two distant ring carbons. Different substituents at the C-1 amine, such as methyl, formyl, and acetyl groups, yield loline species that have variable bioactivity against insects. Besides endophyte–grass symbionts, loline alkaloids have also been identified in some other plant species; namely, Adenocarpus species and Argyreia mollis.
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.
Rathayibacter toxicus is a phytopathogenic bacterium known for causing annual ryegrass toxicity (ARGT) commonly found in South and Western Australia.
Lolium rigidum is a species of annual grass. Common names by which it is known include annual ryegrass, a name also given to Italian ryegrass, rigid ryegrass, stiff darnel, Swiss ryegrass and Wimmera ryegrass. It is a native of southern Europe, northern Africa, the Middle East and the Indian subcontinent and is grown as a forage crop, particularly in Australia, where it is also a serious and economically damaging crop weed.