| Claviceps purpurea | |
|---|---|
 | |
Scientific classification | |
| Kingdom: | Fungi |
| Division: | Ascomycota |
| Class: | Sordariomycetes |
| Order: | Hypocreales |
| Family: | Clavicipitaceae |
| Genus: | Claviceps |
| Species: | C. purpurea |
| Binomial name | |
| Claviceps purpurea | |
| Ecological races | |
| |
Claviceps purpurea | |
|---|---|
 | Hymenium attachment is not applicable |
| Lacks astipe |
 | Ecology isparasitic |
  | Edibility isdeadly orpsychoactive |
Claviceps purpurea is anergotfungus that grows on theears ofrye and relatedcereal andforage plants. Consumption ofgrains or seeds contaminated with the survival structure of this fungus, the ergotsclerotium, can causeergotism in humans and other mammals.[1][2]C. purpurea most commonly affectsoutcrossing species such asrye (its most common host), as well astriticale,wheat andbarley. It affectsoats only rarely.
Anergot kernel calledSclerotium clavus develops when a floret of flowering grass or cereal is infected by anascospore ofC. purpurea. The infection process mimics apollen grain growing into anovary duringfertilization. Because infection requires access of the fungal spore to thestigma, plants infected byC. purpurea are mainlyoutcrossing species withopen flowers, such as rye (Secale cereale) andAlopecurus.
The proliferating fungalmycelium then destroys the plant ovary and connects with thevascular bundle originally intended for feeding the developingseed. The first stage of ergot infection manifests itself as a white soft tissue (known asSphacelia segetum) producing sugaryhoneydew, which often drops out of the infected grass florets. This honeydew contains millions ofasexual spores (conidia) which are dispersed to other florets byinsects or rain. Later, theSphacelia segetum convert into a hard drySclerotium clavus inside the husk of the floret. At this stage,alkaloids andlipids (e.g.ricinoleic acid) accumulate in the Sclerotium.
When a matureSclerotium drops to the ground, the fungus remains dormant until proper conditions trigger its fruiting phase (onset of spring, rain period, need of fresh temperatures during winter, etc.). It germinates, forming one or severalfruiting bodies with head andstipe, variously colored (resembling a tinymushroom). In the head, threadlikesexual spores (ascospores) are formed inperithecia, 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 calledergotism.
Polistes dorsalis, a species of social wasps, have been recorded as a vector of the spread of this particular fungus. During their foraging behavior, particles of the fungal conidia get bound to parts of this wasp's body. AsP. dorsalis travels from source to source, it leaves the fungal infection behind.[3] Insects, including flies and moths, have also been shown to carry conidia ofClaviceps species, but if insects play a role in spreading the fungus from infected to healthy plants is unknown.[4]
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Early scientists have observedClaviceps purpurea on otherPoaceae asSecale cereale. 1855, Grandclement[5] described ergot onTriticum aestivum. During more than a century scientists aimed to describe specialized species or specialized varieties inside the speciesClaviceps purpurea.
Later scientists tried to determine host varieties as
Molecular biology has not confirmed this hypothesis but has distinguished three groups differing in their ecological specificity.[6]
Morphological criteria to distinguish different groups: The shape and the size of sclerotia are not good indicators because they strongly depend on the size and shape of the host floret. The size of conidia can be an indication but it is weak and it is necessary to pay attention to that, due to osmotic pressure, it varies significantly if the spores are observed in honeydew or in water. The sclerotial density can be used as the groups G2 and G3 float in water.
The compound of alkaloids is also used to differentiate the strains.
Agrostis canina,Alopecurus myosuroides (G2),Alopecurus arundinaceus (G2),Alopecurus pratensis,Bromus arvensis,Bromus commutatus,Bromus hordeaceus (G2),Bromus inermis,[7]Bromus marginatus,Elymus tsukushiense,Festuca arundinacea,[8]Elymus repens (G1),Nardus stricta,Poa annua (G2),Phleum pratense,Phalaris arundinacea (G2),Poa pratensis (G1),Stipa.
Spartina,Distichlis (G3)
Claviceps purpurea has been known to humankind for a long time, and its appearance has been linked to extremely cold winters that were followed by rainy springs.[citation needed]
The sclerotial stage ofC. purpurea conspicuous on the heads of ryes and other such grains is known as ergot. Sclerotia germinate in spring after a period of low temperature. A temperature of 0-5 °C for at least 25 days is required. Water before the cold period is also necessary.[9] Favorable temperatures for stroma production are in the range of 10-25 °C.[10] Favorable temperatures for mycelial growth are in the range of 20-30 °C with an optimum at 25 °C.[10]
Sunlight has a chromogenic effect on themycelium with intense coloration.[11]
The disease cycle of the ergot fungus was first described in 1853,[12] but the connection with ergot and epidemics among people and animals was reported already in a scientific text in 1676.[13]The ergot sclerotium contains high concentrations (up to 2% of dry mass) of thealkaloidergotamine, a complex molecule consisting of a tripeptide-derived cyclol-lactam ring connected viaamide linkage to alysergic acid (ergoline) moiety, and other alkaloids of theergoline group that arebiosynthesized by the fungus.[14] Ergot alkaloids have a wide range ofbiological activities including effects oncirculation andneurotransmission.[15]
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[16] with balms containing tranquilizing and circulation-stimulating plant extracts; they were also skilled in amputations.[citation needed] The common name for ergotism is "St. Anthony's Fire",[16] in reference to monks who cared for victims as well as symptoms, such as severe burning sensations in the limbs.[17] These are caused by effects of ergot alkaloids on thevascular system due tovasoconstriction of blood vessels, sometimes leading togangrene and loss of limbs due to severely restricted blood circulation.
The neurotropic activities of the ergot alkaloids may also causehallucinations and attendant irrational behaviour, convulsions, and even death.[14][15] Other symptoms include stronguterine contractions,nausea,seizures, and unconsciousness. Since the Middle Ages, controlled doses of ergot were used to induceabortions and to stop maternal bleeding after childbirth.[18] Ergot alkaloids are also used in products such asCafergot (containingcaffeine andergotamine[18] orergoline) to treat migraine headaches. Ergot extract is no longer used as apharmaceutical preparation.[citation needed]
Ergot contains nolysergic acid diethylamide (LSD) but rather ergotamine, which is used to synthesizelysergic acid, an analog of and precursor for synthesis of LSD. Moreover, ergot sclerotia naturally contain some amounts of lysergic acid.[19]
Potato dextrose agar, wheat seeds or oat flour are suitable substrates for growth of the fungus in the laboratory.[20]
Agricultural production of Claviceps purpurea on rye is used to produce ergot alkaloids.[citation needed] Biological production of ergot alkaloids is also carried out by saprophytic cultivations.
During theMiddle Ages, human poisoning due to the consumption of rye bread made from ergot-infected grain was common in Europe. These epidemics were known asSaint Anthony's fire,[16] orignis sacer.
Gordon Wasson proposed that the psychedelic effects were the explanation behind the festival ofDemeter at theEleusinian Mysteries, where the initiates drankkykeon.[21]
Linnda R. Caporael posited in 1976 that the hysterical symptoms of young women that had spurred theSalem witch trials had been the result of consuming ergot-tainted rye.[22] However, her conclusions were later disputed by Nicholas P. Spanos and Jack Gottlieb, after a review of the historical and medical evidence.[23] Other authors have likewise cast doubt on ergotism having been the cause of the Salem witch trials.[24]
TheGreat Fear in France during theRevolution has also been linked by some historians to the influence of ergot.[citation needed]
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 asTollund Man), reveals that ergot was once a ritual drink in a prehistoric fertility cult akin to theEleusinian Mysteries cult of ancientGreece. In his bookBeowulf and Grendel he argues that theAnglo-Saxon poemBeowulf is based on a memory of the quelling of this fertility cult by followers ofOdin. He states that Beowulf, which he translates asbarley-wolf, suggests a connection to ergot which in German was known as the 'tooth of the wolf'.[citation needed]
An outbreak of violent hallucinations among hundreds of residents ofPont St. Esprit in 1951 in the south of France has also been attributed to ergotism.[25] Shortly after the event at least four people had been declared dead,[25] although some claim the total number of deaths to be five or seven.[26]
