A sclerotium (plural sclerotia) is a compact mass of hardened fungal mycelium containing food reserves. One role of sclerotia is to survive environmental extremes. In some higher fungi such as ergot, sclerotia become detached and remain dormant until a favorable opportunity for growth. Other fungi that produce sclerotia are prominent pathogens for canola crops. These and related fungi are generally controlled through the use of fungicides and crop rotation.
Sclerotium is a dark mass of mycelium that replaces grains which have been infected with the pathogenic fungi Claviceps purpurea. [1] Sclerotium contains alkaloids that, when consumed, can cause ergotism which is a disease that causes paranoia and hallucinations, twitches, spasms, loss of peripheral sensation, edema and loss of affected tissues. [1]
Sclerotia resemble cleistothecia in both their morphology and the genetic control of their development. This suggests the two structures may be homologous, sclerotia being vestigial cleistothecia that lost the capacity to produce spores.[1]
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Sclerotia can be linked back to the Middle Ages where bread were contaminated and led to St Antony’s fire where thousands of people were killed and mutilated. [1]
Louis Rene Tulasne discovered the relationship between infected rye plants and ergotism in the 19th century. [1] With this discovery, more efforts were developed to reduce scerotia from growing on rye and ergotistm became rare. [1] However, in 1879-1881 an outbreak developed in Germany, in 1926-1927 Russia was infected, and in 1977-1978 Ethiopia was infected. [1]
Sclerotia germinate all and form in the spring, and it infects grass and rye plants by releasing ascospores from the perithecia. [1] Although this fungus can infect a wide variety of plants, they are very specific in that they only infect the ovaries. [1] The fungal spores germinate at the anthesis of the plant, and then it penetrates the plant and grows down the pollen tube without branching its hyphae outward. [1] When the fungi reach the bottom of the ovary, it leaves the pollen tube path and enters the vascular tissues where it branches its mycelium. [1] About seven days into the infection, the mycelium takes over the ovary and produces conidia. [1] The conidia are then secreted out of the plant as honeydew where insects can transfer the fungi to other plants causing more infections. [1] After two week of being infected by the fungus, the plant will no longer make honeydew, instead it will to produce sclerotia. [1] Sclerotia is an overwinter structure which contain ergot alkaloids (Haarmann). Claviceps purpurea’s life cycle is an interesting model for plant pathologists and cell biologists because [1]:
In early times, ergot alkaloids have been used for medicinal purposes. [1] For example, ergot was used as a form of abortion in Europe, but it led to hyper-contraction. [1] In the 19th century, it was used to aid in the prevention of bleeding in after childbirth and treatment for migraines and Parkinson’s disease. [1]
Acid hydrolysis is used to convert alkaloids, produced by the fungus Claviceps purpurea, into D-lysergic acid which is the starting material for many pharmaceutical and illegal drugs. [1] In 1938 Albert Hofmann synthesized one of the strongest known hallucinogen, lysergic acid diethylamide (LSD), from ergot alkaloid. [1] Even though this drug had shocking side effects like paranoia, loss of judgment and flashbacks, psychotherapists and psychiatrists still use it to treat patients with neuroses, sexual dysfunctions and anxiety. [1] The secret service may have also used it for interrogation purposes. [1] In 1966 the United State government made LSD illegal and announced that it was dangerous. [1] Recently, clinics have shown an interest in ergoline to treat patients with autism. [1]
Sorghum is a very important cereal crop ranking the 3rd most important in the United States and 5th in the world. [1] This cereal crop can be us for food, livestock feeding, beverage production and industrial purposes. [1] Only non-fertilized ovaries in male sorghum sterile plants are infected with sclerotia caused by three different species of Claviceps fungi: C. africana, C. sorghi and C. sorghicola. [1] C. sorghi was first recognized in India in 1917, and soon after in 1923 C. africana was identified in Kenya. [1] It was not until 1960 when male-sterile sorghum was introduced and became highly susceptible to the Claviceps species causing economic loss. [1] C. Africana has the ability to produce air borne conidia almost out completing C. sorghi. [1] C. Africana also has the ability to produce air borne conidia which traveled to Brazil and spread all through South America and the Caribbean. [1] In 1995 C. Africana infected the Americas and a year later reached Australia infecting 70 000 km2 within one month. [1] This disease spread throughout Asia and Africa causing low production yield and poor seed quality. This worldwide threat has caused losses of up to 80% in India and 25% in Zimbabwe. [1]
Many methods have been created to reduce the growth of sclerotia like changes in crop rotation, deeper ploughing and sifting out sclerotia.[1] Fungicides, breeding disease resistance rye and cross breeding natural rye with hybrid rye have reduced C. purpurea infections.[1]