Lolium rigidum | |
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Scientific classification | |
Kingdom: | Plantae |
Clade: | Tracheophytes |
Clade: | Angiosperms |
Clade: | Monocots |
Clade: | Commelinids |
Order: | Poales |
Family: | Poaceae |
Subfamily: | Pooideae |
Genus: | Lolium |
Species: | L. rigidum |
Binomial name | |
Lolium rigidum | |
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 (Lolium multiflorum), rigid ryegrass, stiff darnel, Swiss ryegrass and Wimmera ryegrass. [1] 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.
Lolium rigidum is an annual grass that grows in open tussocks. It has fibrous roots and can grow up to a metre tall. The plant form is usually erect but may be prostrate. The stems are often geniculate (with a knee-like bend) and are purplish at the base. The leaves are 5 to 25 cm (2 to 10 in) long, and 3 to 5 mm (0.12 to 0.20 in) wide; the upper surface is glossy dark green, flat and hairless with longitudinal veins, and the underside is shiny and smooth.
The young leaves are rolled when in bud, the auricles are small and the ligule is white and translucent, wider than it is long. The unbranched flower spike is up to 30 cm (12 in) long, with the spikelets on alternating sides and edgeways-on to the rachis (stem), pressed into recesses in the stem.
The spikelets bear up to twelve florets, mostly with a single glume, with only the terminal floret having two. The glumes are up to three-quarters the length of the spikelet; their outer surface is finely ribbed with longitudinal veins. There is no awn, the lemma is oblong and has five nerves and the palea is a similar shape with two nerve and a few fine hairs. The three anthers are yellow. [2]
Lolium rigidum is a native of the Mediterranean area. Its natural range includes Western, Southern and Central Europe, northern Africa, the Near East, western Asia and the Indian sub-continent. It has spread to many other parts of the world and is considered invasive in some regions. It is planted in Australia as a forage crop but not usually in Europe. [3] It was introduced as a forage crop in Australia around 1880, but has since proven to be an economically damaging weed that infests other more important crops, such as canola and wheat. [4]
Lolium rigidum is a diploid grass with a chromosome number of n=7 (2n=14). It exhibits much genetic variability and grows readily in a variety of situations and habitats. It can hybridise with both perennial (L. perenne) and Italian ryegrass (L. multiflorum), as well as some species of Festuca . It propagates solely by seed; freshly shed seed displays dormancy. [2] It is sometimes infected by a rust fungus which has an inhibitory effect on the growth of clovers. [5]
The flower spike of L. rigidum may become infected by a certain species of bacteria, which results in the production of corynetoxins which are toxic to livestock; ingestion of infected material causes a disease, known as annual ryegrass toxicity or annual ryegrass staggers, which is known to occur in the west and south of Australia and in South Africa. [6] The infection is caused by the bacterium Rathayibacter toxicus , which is introduced into the grass by the nematode Anguina funesta . This nematode causes galls on the grass flower spikes and it is in these that the bacteria multiply. Infected galls are present in the winter, but become more toxic as the inflorescence dies in spring. The disease occurs when the pasture is grazed at this toxic stage. Topping the pasture before grazing may prevent the condition, but the seed heads are still toxic when preserved as hay. [7] The symptoms of poisoning are neurological, often causing a mortality rate of forty to fifty percent in infected animals. [6]
L. rigidum is susceptible to infection by ergot (Claviceps purpurea), and also by take-all fungus (Gaeumannomyces graminis) which can cause serious losses in cereal crops. [2]
Lolium rigidum is grown as a forage crop in suitable areas. About 80% of the seed germinates in the autumn, soon after the first significant rains, and about 5% may remain dormant for twelve months. The plant has vigorous growth, and flowering is initiated when the day length is at least eight hours. This means that the crop has a relatively uniform flowering period in late winter/early spring. [5]
Because L. rigidum has been grown as a forage crop in southern Australia since the nineteenth century and seeds readily, it grows ubiquitously in the region with large, genetically diverse populations. Now that arable crops are increasingly been grown, it has become an important weed of these crops. [8] The main reason for its success in competing with crops is its ability to produce prolific numbers of seeds per plant – up to 45,000 seeds per 1 m2 (11 sq ft) – and also its ability to compete with crops at a very early stage of their life cycle. [9]
In addition, it serves as a host for species of the bacteria Clavibacter, which cause annual ryegrass toxicity (ARGT), and can be infected by the poisonous ergot fungus, [9] which causes ergotism in humans and other mammals. [10]
Attempts to control it with herbicide have met with an unexpectedly high level of herbicide resistance. Over 90% of plants in some populations are tolerant to some of the widely used herbicides. Instead of wiping out the L. rigidum, the herbicides have resulted in the selection of resistant genotypes. [8] [9] Possible bioherbicides are being explored, including Pyrenophora seminiperda , a fungus. [4]
L. rigidum has become one of the most serious and economically damaging weeds in southern Australia. A 2021 study listed annual ryegrass as fourth on the list of invasive species which cost Australian farmers the most over a 60-year period, at over a billion Australian dollars. [11]
Weed control is a type of pest control, which attempts to stop or reduce growth of weeds, especially noxious weeds, with the aim of reducing their competition with desired flora and fauna including domesticated plants and livestock, and in natural settings preventing non native species competing with native species.
Forage is a plant material eaten by grazing livestock. Historically, the term forage has meant only plants eaten by the animals directly as pasture, crop residue, or immature cereal crops, but it is also used more loosely to include similar plants cut for fodder and carried to the animals, especially as hay or silage.
Lolium is a genus of tufted grasses in the bluegrass subfamily (Pooideae). It is often called ryegrass, but this term is sometimes used to refer to grasses in other genera.
Paspalum is a genus of plants in the grass family.
Annual ryegrass toxicity (ARGT) is the poisoning of livestock from toxin contained in bacterially infected annual ryegrass. The toxin is produced by the bacterium Rathayibacter toxicus, which is carried into the ryegrass by the nematode Anguina funesta.
Pendimethalin is an herbicide of the dinitroaniline class used in premergence and postemergence applications to control annual grasses and certain broadleaf weeds. It inhibits cell division and cell elongation. Pendimethalin is listed in the K1-group according to the Herbicide Resistance Action Committee (HRAC) classification and is approved in Europe, North America, South America, Africa, Asia and Oceania for different crops including cereals, corn, soybeans, rice, potato, legumes, fruits, vegetables, nuts as well as lawns and ornamental plants.
Lolium perenne, common name perennial ryegrass, English ryegrass, winter ryegrass, or ray grass, is a grass from the family Poaceae. It is native to Europe, Asia and northern Africa, but is widely cultivated and naturalised around the world.
Lolium pratense, meadow fescue is a perennial species of grass, which is often used as an ornamental in gardens, and is also an important forage crop. It grows in meadows, roadsides, old pastures, and riversides on moist, rich soils, especially on loamy and heavy soils.
Epichloë is a genus of ascomycete fungi forming an endophytic symbiosis with grasses. Grass choke disease is a symptom in grasses induced by some Epichloë species, which form spore-bearing mats (stromata) on tillers and suppress the development of their host plant's inflorescence. For most of their life cycle however, Epichloë grow in the intercellular space of stems, leaves, inflorescences, and seeds of the grass plant without incurring symptoms of disease. In fact, they provide several benefits to their host, including the production of different herbivore-deterring alkaloids, increased stress resistance, and growth promotion.
Anguina agrostis is a plant pathogenic nematode.
Annual ryegrass is a common name for several species of ryegrass and may refer to:
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.
Lolium multiflorum is a ryegrass native to temperate Europe, though its precise native range is unknown.
A weed is a plant considered undesirable in a particular situation, growing where it conflicts with human preferences, needs, or goals. Plants with characteristics that make them hazardous, aesthetically unappealing, difficult to control in managed environments, or otherwise unwanted in farm land, orchards, gardens, lawns, parks, recreational spaces, residential and industrial areas, may all be considered weeds. The concept of weeds is particularly significant in agriculture, where the presence of weeds in fields used to grow crops may cause major losses in yields. Invasive species, plants introduced to an environment where their presence negatively impacts the overall functioning and biodiversity of the ecosystem, may also sometimes be considered weeds.
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.
Plant use of endophytic fungi in defense occurs when endophytic fungi, which live symbiotically with the majority of plants by entering their cells, are utilized as an indirect defense against herbivores. In exchange for carbohydrate energy resources, the fungus provides benefits to the plant which can include increased water or nutrient uptake and protection from phytophagous insects, birds or mammals. Once associated, the fungi alter nutrient content of the plant and enhance or begin production of secondary metabolites. The change in chemical composition acts to deter herbivory by insects, grazing by ungulates and/or oviposition by adult insects. Endophyte-mediated defense can also be effective against pathogens and non-herbivory damage.
Rathayibacter toxicus is a phytopathogenic bacterium known for causing annual ryegrass toxicity (ARGT) commonly found in South and Western Australia.
Perennial ryegrass staggers is poisoning by peramine, lolitrem B, and other toxins that are contained in perennial ryegrass, and produced by the endophyte fungus Epichloë festucae which can be present in all parts of the grass plant, but tends to be concentrated in the lower part of the leaf sheaths, the flower stalks and seeds. This condition can affect horses, cattle, sheep, farmed deer and llamas. It regularly occurs in New Zealand and is known spasmodically from Australia, North and South America, and Europe.
Lolitrem B is one of many toxins produced by a fungus called Epichloë festucae var. lolii), which grows in Lolium perenne. The fungus is symbiotic with the ryegrass; it doesn't harm the plant, and the toxins it produces kill insects that feed on ryegrass. Lolitrem B is one of these toxins, but it is also harmful to mammals. The shoots and flowers of infected ryegrass have especially high concentrations of lolitrem B, and when livestock eat too much of them, they get perennial ryegrass staggers. At low doses the animals have tremors, and at higher doses they stagger, and at higher yet doses the animals become paralyzed and die. The blood pressure of the animals also goes up. The effect of the lolitrem B comes on slowly and fades out slowly, as it is stored in fat after the ryegrass is eaten. The condition is especially common in New Zealand and Australia, and plant breeders there have been trying to develop strains of fungus that produce toxins only harmful to pests, and not to mammals.