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Ergot refers to a group of fungi of the genus Claviceps (ergot fungi). The most prominent member of this group is Claviceps purpurea. This fungus grows on rye and related plants, and can cause ergotism in humans and other mammals consuming seeds contaminated with the fruiting structure of this fungus, called an ergot sclerotium. There are about 50 known species of Claviceps, most of them in the tropical regions. Economically important species are C. purpurea (parasitic on grass and cereals), C. fusiformis (on pearl millet, buffel grass), C. paspali (on dallis grass), and C. africana(on sorghum). C. purpurea most commonly affects outcrossing species such as rye (its most common host), as well as triticale, wheat and barley. It affects oats only rarely.

There are at least three races or varieties of C. purpurea, differing in their host specificity:
  • G1 — land grasses of open meadows and fields;
  • G2 — grasses from moist, forest, and mountain habitats;
  • G3 (C. purpurea var. spartinae) — salt marsh grasses (Spartina, Distichlis).


Life cycle

An ergot kernel called a sclerotium develops when a floret of flowering grass or cereal is infected by a spore of fungal species of the genus Claviceps. The infection process mimics a pollen grain growing into an ovary during fertilization. Because infection requires access of the fungal spore to the stigma, plants infected by Claviceps are mainly outcrossing species with open flowers, such as rye (Secale cereale) and ryegrasses (genus Lolium). The proliferating fungal mycelium then destroys the plant ovary and connects with the vascular bundle originally intended for seed nutrition. The first stage of ergot infection manifests itself as a white soft tissue (known as sphacelia) producing sugary honeydew, which often drops out of the infected grass florets. This honeydew contains millions of asexual spores (conidia) which are dispersed to other florets by insects. Later, the sphacelia convert into a hard dry sclerotium inside the husk of the floret. At this stage, alkaloids and lipids accumulate in the sclerotium.

Claviceps species from tropic and subtropic regions produce macro- and microconidia in their honeydew. Macroconidia differ in shape and size between the species, whereas microconidia are rather uniform, oval to globose (5x3μm). Macroconidia are able to produce secondary conidia. A germ tube emerges from a macroconidium through the surface of a honeydew drop and a secondary conidium of the oval to pearlike shape is formed to which the contents of the original macroconidium migrates. Secondary conidia form white frost-like surface on honeydew drops and are spread by wind. No such process occurs in Claviceps purpurea, Claviceps grohii, Claviceps nigricans, and Claviceps zizaniae, all from Northern temperate regions.

When a mature sclerotium drops to the ground, the fungus remains dormant until proper conditions trigger its fruiting phase (onset of spring, rain period, etc.). It germinates, forming one or several fruiting bodies with head and stipe, variously coloured (resembling a tiny mushroom). In the head, threadlike sexual spores are formed, which are ejected simultaneously, when suitable grass hosts are flowering. Ergot infection causes a reduction in the yield and quality of grain and hay produced, and if infected grain or hay is fed to livestock it may cause a disease called ergotism.Black and protruding sclerotia of C. purpurea are well known. However, many tropical ergots have brown or greyish sclerotia, mimicking the shape of the host seed. For this reason, the infection is often overlooked.

Insects, including flies and moths, have been shown to carry conidia of Claviceps species, but if insects play a role in spreading the fungus from infected to healthy plants is unknown.

Effects on humans and other mammals



The ergot sclerotium contains high concentrations (up to 2% of dry mass) of the alkaloid ergotamine, a complex molecule consisting of a tripeptide-derived cyclol-lactam ring connected via amide linkage to a lysergic acid (ergoline) moiety, and other alkaloids of the ergoline group that are biosynthesized by the fungus. Ergot alkaloids have a wide range of biological activities including effects on circulation and neurotransmission.

Ergotism is the name for sometimes severe pathological syndromes affecting humans or animals that have ingested ergot alkaloid-containing plant material, such as ergot-contaminated grains. Monks of the order of St. Anthony the Great specialized in treating ergotism victims with balms containing tranquilizing and circulation-stimulating plant extracts; they were also skilled in amputations. The common name for ergotism is "St. Anthony's Fire", in reference to monks who cared for victims as well as symptoms, such as severe burning sensations in the limbs. These are caused by effects of ergot alkaloids on the vascular system due to vasoconstriction of blood vessels, sometimes leading to gangrene and loss of limbs due to severely restricted blood circulation.

The neurotropic activities of the ergot alkaloids may also cause hallucinations and attendant irrational behaviour, convulsions, and even death. Other symptoms include strong uterine contractions, nausea, seizures, and unconsciousness. Since the middle ages, controlled doses of ergot were used to induce abortions and to stop maternal bleeding after childbirth.Ergot extract has been used in pharmaceutical preparations, including Ergot alkaloids in products such as Cafergot (containing caffeine and ergotamine or ergoline) to treat migraine headaches, and ergometrine, used to induce uterine contractions and to control bleeding after childbirth.In addition to ergot alkaloids, Claviceps paspali also produces tremorgens (paspalitrem) causing "paspalum staggers" in cattle. Ergot alkaloids are also produced by fungi of the genera Penicillium and Aspergillus, notably by some isolates of the human pathogen Aspergillus fumigatus, and have been isolated from plants in the family Convolvulaceae, of which morning glory is best known.

Ergot contains no lysergic acid diethylamide (LSD) but instead contains ergotamine, which is used to synthesize lysergic acid, an analog of and precursor for synthesis of LSD. Moreover, ergot sclerotia naturally contain some amounts of lysergic acid.

In the January 4, 2007 issue of the New England Journal of Medicine, a paper was published documenting a British study of over 11,000 Parkinson's Disease patients. The study found that two ergot-derived drugs, Pergolide and Cabergoline, commonly used to treat Parkinson's Disease may increase the risk of leaky heart valves by up to 700%.

History

Ergot on wheat spikes


Human poisoning due to the consumption of rye bread made from ergot-infected grain was common in Europe in the Middle Ages. The epidemic was known as Saint Anthony's fire, or ignis sacer, and some historical events, such as the Great Fear in France during the Revolution have been linked to ergot poisoning. Linnda R. Caporael posited in 1976 that the hysterical symptoms of young women that had spurred the Salem witch trials had been the result of consuming ergot-tainted rye. However, her conclusions were later disputed by Nicholas P. Spanos and Jack Gottlieb, after a review of the historical and medical evidence. Other authors have likewise cast doubt on ergotism having been the cause of the Salem witch trials.

British author John Grigsby claims that the presence of ergot in the stomachs of some of the so called 'bog-bodies' (Iron Age human remains from peat bogs N E Europe such as Tollund Man) is indicative of use of ergot in ritual drinks in a prehistoric fertility cult akin to the Eleusinian Mysteries cult of ancient Greecemarker. In his book Beowulf and Grendel he argues that the Anglo-Saxon poem Beowulf is based on a memory of the quelling of this fertility cult by followers of Odin. He states that Beowulf, which he translates as barley-wolf, suggests a connection to ergot which in German was known as the 'tooth of the wolf'.

Kykeon, the beverage consumed by participants in the ancient Greek cult of Eleusinian Mysteries, might have been based on hallucinogens from ergot, and lysergic acid diethylamide (LSD) is a potent hallucinogen, which was first synthesized from ergot alkaloids by the Swiss chemist, Albert Hofmann, in 1938.

Claviceps purpurea

Claviceps purpurea has been known to mankind for a long time, and its appearance has been linked to extremely cold winters that were followed by rainy summers.

The sclerotial stage of C. purpurea conspicuous on the heads of ryes and other such grains is known as ergot. Favorable temperatures for growth are in the range of 18-30°C, while temperatures above 37°C will cause rapid germination of conidia. Sunlight has a chromogenic effect on the mycelium with intense coloration. Cereal mashes and sprouted rye are suitable substrates for growth of the fungus in the laboratory.

Claviceps africana

Claviceps africana infects sorghum and was first observed in south Texas in 1997. It only infects unfertilized ovaries, so self-pollination and fertilization can decrease the presence of the disease, but male-sterile lines are extremely vulnerable to infection by this fungus. Symptoms of infection by C. africana include the secretion of honeydew (a fluid with high concentrates of sugar and conidia), which attracts insects like flies, beetles, and wasps that feed on it. This in turn contributes to spread of the fungus to uninfected plants.

C. africana caused ergot disease resulting in a famine in 1903-1906 in Northern Cameroonmarker, West Africa, and also occurs in eastern and southern Africa, especially Zimbabwe and South Africa. Male sterile sorghums (also referred to as A-lines) are especially susceptible to infection, first recognized in the 1960s, and massive losses in seed yield have been noted. Infection is associated with cold night temperatures that are below twelve degrees Celsius occurring two to three weeks before flowering.

References

  1. ergot, online medical dictionary
  2. ergot, Dorland's Medical Dictionary
  3. Microbiology in Action. P115. By J. Heritage, Emlyn Glyn Vaughn Evans, R. A. Killington. Cambridge University Press, 1999.
  4. [1]
  5. Untersuchungen über das Verhalten der Secalealkaloide bei der Herstellung von Mutterkornextrakten. Labib Farid Nuar. Universität Wien - 1946 - (University of Vienna)
  6. NEJM - Dopamine Agonists and the Risk of Cardiac-Valve Regurgitation
  7. "Mixing the Kykeon", ELEUSIS: Journal of Psychoactive Plants and Compounds, New Series 4, 2000


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