The purple-brown ergot fungus (Claviceps purpurea) is a tubular fungus that grows parasitically on host plants such as rye, wheat, oats, and barley. It is also often found on wild grasses such as couch grass, lolch grass, and field foxtail grass. There, it can survive on the field margin after grain harvest and resprout with the upcoming seeding. The ergot fungus produces purple to black sclerotia (permanent mycelia) called ergot. This name is explained by its use in childbirth, which was common in the past. Various constituents acted supportively in inducing labor. At times, the poisonous mushroom was even cultivated to be used for abortions. Regionally, the terms beggar monk, hungry grain and red club head are common. In the fields, the ripe sclerotia fall to the ground along with the cereal grains to get through the winter. Widely distributed Claviceps purpurea in areas with temperate climate.
What is claviceps purpurea?
The ergot fungus can reproduce both sexually and asexually. Several stalked fruiting bodies, which have a head-like shape, develop from a sclerotium during the growing season. They are formed by fusion of several filamentous fungal cells. The fruiting bodies develop numerous tubes (asci) inside, where the ascospores (seeds) are produced. As grass and grain flowers begin to bloom, the ascospores are released and dispersed by the wind. They enter the ovaries through the stigmas of unfertilized flowers. This sexual reproduction is defined as primary infection. In secondary (asexual) infection, conidiospores (conidia) develop from the mycelium of the ergot fungus by strangulation of cells. They are released by contact from ear to ear and via rain and wind. Insects, which are attracted by the so-called honeydew, also perform an important function. This is a sweet liquid that the purple ergot fungus forms by decomposing grain seeds. The conidiospores eventually enter the fruiting body of, for example, flowering grasses, similar to the ascospores.
Occurrence, distribution and characteristics
In the fruiting body of the colonized plant, the spores germinate into a fungal mycelium that eventually decomposes the ovary. Honeydew emerges from a newly formed soft mass. Later, the mycelium matures into a horn-like sclerotium, which acquires the typical dark purple appearance. Instead of seeds, the grasses or plants attacked by the ergot fungus then produce only sclerotia. However, they contain alkaloids (“plant ash“), which are toxic to the human organism. In their effect they can be compared with morphine, strychnine and solanine. If a person ingests sclerotia in large quantities, limbs may die under certain circumstances, as certain blood vessels are constricted. Muscle spasms may also occur due to central nervous system disorders. Gastrointestinal disorders are also likely. Even in the Middle Ages, when sclerotia were ground into flour together with cereal grains in ignorance of the risks, terrible consequences of the toxic substances were recorded. Because of these hazards, limit values for the sclerotia content in cereals were set some time ago. With today’s standard cleaning processes for grain, however, the toxic substances can be sorted out with a high degree of certainty in the milling plants. However, dangers still exist for domestic animals and livestock when they graze grassy areas that may have been contaminated with ergot.
Significance and function
The sclerotia of the purple ergot fungus are usually slightly curved, grow up to six centimeters long, and often protrude a significant distance from the husks of the cereal plant. The ears or panicles affected by the black fungi are very sticky because of the honeydew secreted. The sclerotia can withstand cold and drought relatively well. After surviving the winter in or on the ground, they enter the germination stage at the flowering time of the grasses. Ergot fungus has the best chance of spreading when the weather is rainy and cool. On the other hand, very hot and dry conditions are dangerous for the grain, as this leaves more flowers unfertilized. Then they can be infected by Claviceps purpurea.A major risk of infection is also posed by grasses that are already infested and are located at the edges of the cereal fields. If cereal stands flower unevenly and rye follows rye in the crop, for example, it is easier for the ergot fungus to spread.
Diseases and ailments
Medically, it is now considered proven that alkaloids of ergot fungus can cause intestinal spasms, hallucinations, and the death of fingers and toes. These abnormalities are triggered by circulatory disturbances. From ancient times, the term Antony’s fire was used for this strangulation of limbs. Later the word ergot burn was added. Technically, the clinical picture is called ergotism today. The metabolism of an adult human being is so severely affected by eating five to ten grams of fresh ergot that respiratory paralysis and circulatory failure follow, with a potentially fatal outcome. Reliable studies warn of health damage in humans when around ten milligrams of ergot alkaloids per kilogram of flour occur. Two milligrams per kilogram is the legal limit for safety. However, the alkaloids can also be used beneficially in medicine. For example, they have hemostatic properties during and after childbirth. They also help against orthostatic hypotension (low blood pressure) and dizziness immediately after getting up, as well as migraine. From the purple ergot mushroom can be obtained the so-called lysergic acid, which can be used to produce the drug LSD.
