Ergot refers to a group of
fungiA fungus is any member of a large group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. The Fungi are classified as a kingdom that is separate from plants, animals and bacteria...
of the genus
Claviceps (ergot fungi). The most prominent member of this group is
Claviceps purpurea. This fungus grows on
ryeRye is a grass grown extensively as a grain and as a forage crop. It is a member of the wheat tribe and is closely related to barley and wheat. Rye grain is used for flour, rye bread, rye beer, some whiskies, some vodkas, and animal fodder...
and related plants, and can cause
ergotismErgotism is the effect of long-term ergot poisoning, traditionally due to the ingestion of the alkaloids produced by the Claviceps purpurea fungus which infects rye and other cereals, and more recently by the action of a number of ergoline-based drugs. It is also known as ergotoxicosis, ergot...
in humans and other mammals consuming seeds contaminated with the fruiting structure of this fungus, called an ergot
sclerotiumA sclerotium 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...
. There are about 50 known species of
Claviceps, most of them in the tropical regions. Economically important species are
C. purpurea (parasitic on
grassPoaceae or Gramineae is a family in the Class Liliopsida of the flowering plants. Plants of this family are usually called grasses, or, to distinguish them from other graminoids, true grasses; the shrub- or tree-like plants in this family are called bamboo...
es and cereals),
C. fusiformis (on
pearl milletPearl millet is the most widely grown type of millet. Grown in Africa and the Indian subcontinent since prehistoric times, it is generally accepted that pearl millet originated in Africa and was subsequently introduced into India. The earliest archaeological records in India date to 2000 BC, so...
, buffel grass),
C. paspali (on dallis grass), and
C. africana(on
sorghumSorghum is a genus of numerous species of grasses, some of which are raised for grain and many of which are used as fodder plants either cultivated or as part of pasture. The plants are cultivated in warmer climates worldwide. Species are native to tropical and subtropical regions of all continents...
).
C. purpurea most commonly affects
outcrossingOpen pollination is pollination by insects, birds, wind, or other natural mechanisms, and contrasts with cleistogamy, closed pollination, which is one of the many types of self pollination...
species such as
ryeRye is a grass grown extensively as a grain and as a forage crop. It is a member of the wheat tribe and is closely related to barley and wheat. Rye grain is used for flour, rye bread, rye beer, some whiskies, some vodkas, and animal fodder...
(its most common host), as well as
triticaleTriticale is a hybrid of wheat and rye first bred in laboratories during the late 19th century. The grain was originally bred in Scotland and Sweden. Commercially available triticale is almost always a 2nd generation hybrid, i.e. a cross between two kinds of triticale...
,
wheatWheat is a worldwide cultivated grass from the Fertile Crescent region of the Near East. In 2007 world production of wheat was 607 million tons, making it the third most-produced cereal after maize and rice...
and
barleyBarley is a cereal grain derived from the annual grass Hordeum vulgare. It serves as a major animal feed crop, with smaller amounts used for malting and in health food. It is used in soups, stews and barley bread in various countries, such as Scotland and in Africa...
. It affects
oatThe common oat is a species of cereal grain grown for its seed, which is known by the same name . While oats are suitable for human consumption as oatmeal and rolled oats, one of the most common uses is as livestock feed. Oats make up a large part of the diet of horses and are regularly fed to...
s 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
sporeIn biology, a spore is a reproductive structure that is adapted for dispersal and surviving for extended periods of time in unfavorable conditions...
of fungal species of the genus
Claviceps. The infection process mimics a
pollenPollen is a fine to coarse powder containing the microgametophytes of seed plants, which produce the male gametes . Pollen grains have a hard coat that protects the sperm cells during the process of their movement between the stamens to the pistil of flowering plants or from the male cone to the...
grain growing into an
ovaryIn the flowering plants, an ovary is a part of the female reproductive organ of the flower or gynoecium. Specifically, it is the part of the carpel which holds the ovule and is located above or below or at the point of connection with the base of the petals and sepals...
during fertilization. Because infection requires access of the fungal spore to the
stigmaThe gynoecium is a term with several meanings in botanical usage. In reference to mosses; liverworts; and hornworts, gynoecium refers to a cluster of archegonia and any associated modified leaves or stems present on a gametophyte shoot...
, plants infected by
Claviceps are mainly
outcrossingOutcrossing is the practice of introducing unrelated genetic material into a breeding line. It increases genetic diversity, thus reducing the probability of all individuals being subject to disease or reducing genetic abnormalities...
species with
open flowersAnemophily or wind pollination is a form of pollination whereby pollen is distributed by wind. Anemophilous plants may be either gymnosperms or angiosperms ....
, such as rye (
Secale cerealeSecale is a genus in the Triticeae tribe. The most known member is rye .This is used to treat chilbaines....
) and ryegrasses (genus
Lolium). The proliferating fungal
myceliumthumb|right|Fungal myceliaMycelium is the vegetative part of a fungus, consisting of a mass of branching, thread-like hyphae. The mass of hyphae is sometimes called shiro, especially within the fairy ring fungi. Fungal colonies composed of mycelia are found in soil and on or in many other substrates...
then destroys the plant ovary and connects with the
vascular bundleA vascular bundle is a part of the transport system in vascular plants. The transport itself happens in vascular tissue, which exists in two forms: xylem and phloem. Both these tissues are present in a vascular bundle, which in addition will include supporting and protective tissues...
originally intended for
seedA seed , referred to as a kernel in some plants, is a small embryonic plant enclosed in a covering called the seed coat, usually with some stored food. It is the product of the ripened ovule of gymnosperm and angiosperm plants which occurs after fertilization and some growth within the mother plant...
nutrition. The first stage of ergot infection manifests itself as a white soft tissue (known as
sphacelia) producing sugary
honeydewHoneydew is a sugar-rich sticky substance, secreted by aphids and some scale insects as they feed on plant sap. When their mouthpart penetrates the phloem, the sugary, high-pressure liquid is forced out of the gut's terminal opening. Honeydew is particularly common as a secretion in the Hemipteran...
, which often drops out of the infected grass florets. This honeydew contains millions of
asexualAsexual reproduction is reproduction which does not involve meiosis, ploidy reduction, or fertilization. Only one parent is involved in asexual reproduction. A more stringent definition is agamogenesis which refers to reproduction without the fusion of gametes...
spores (conidia) which are dispersed to other florets by
insectInsects are arthropods, having a hard exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae. They are the most diverse group of animals on the planet and include more than a million species that are already described. Insects represent more than half of all...
s. Later, the sphacelia convert into a hard dry sclerotium inside the husk of the floret. At this stage,
alkaloidAlkaloids are naturally occurring chemical compounds containing basic nitrogen atoms. The name derives from the word alkaline and was used to describe any nitrogen-containing base. Alkaloids are produced by a large variety of organisms, including bacteria, fungi, plants, and animals and are part of...
s and
lipidLipids are a broad group of naturally-occurring molecules which includes fats, waxes, sterols, fat-soluble vitamins , monoglycerides, diglycerides, phospholipids, and others...
s accumulate in the sclerotium.
Claviceps species from tropic and subtropic regions produce macro- and microconidia in their
honeydewHoneydew may refer to:* Honeydew , a cultivar group of melon* Honeydew , a sugar-rich sticky substance secreted by aphids and some scale insects* Honeydew, California, a town* Dr...
. 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
stipethumb|150px|right|Diagram of a [[basidiomycete]] stipe with a [[annulus |annulus]] and [[volva |volva]]In mycology a stipe refers to the stem or stalk-like feature supporting the cap of a mushroom. Like all tissues of the mushroom other than the hymenium, the stipe is composed of sterile hyphal...
, variously coloured (resembling a tiny
mushroomA mushroom is the fleshy, spore-bearing fruiting body of a fungus, typically produced above ground on soil or on its food source. The standard for the name "mushroom" is the cultivated white button mushroom, Agaricus bisporus, hence the word mushroom is most often applied to those fungi that have...
). In the head, threadlike
sexualSexual reproduction is characterized by processes that pass a combination of genetic material to offspring, resulting in diversity. The main two processes are: meiosis, involving the halving of the number of chromosomes; and fertilization, involving the fusion of two gametes and the restoration...
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
ergotismErgotism is the effect of long-term ergot poisoning, traditionally due to the ingestion of the alkaloids produced by the Claviceps purpurea fungus which infects rye and other cereals, and more recently by the action of a number of ergoline-based drugs. It is also known as ergotoxicosis, ergot...
.
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
alkaloidAlkaloids are naturally occurring chemical compounds containing basic nitrogen atoms. The name derives from the word alkaline and was used to describe any nitrogen-containing base. Alkaloids are produced by a large variety of organisms, including bacteria, fungi, plants, and animals and are part of...
ergotamineErgotamine is an ergopeptine and part of the ergot family of alkaloids; it is structurally and biochemically closely related to ergoline. It possesses structural similarity to several neurotransmitters, and has biological activity as a vasoconstrictor...
, a complex molecule consisting of a tripeptide-derived cyclol-lactam ring connected via
amideIn chemistry, an amide is usually an organic compound that contains the functional group consisting of an acyl group linked to a nitrogen atom . The term refers both to a class of compounds and a functional group within those compounds...
linkage to a
lysergic acidLysergic acid, also known as D-lysergic acid and -lysergic acid, is a precursor for a wide range of ergoline alkaloids that are produced by the ergot fungus and some plants. Amides of lysergic acid, lysergamides, are widely used as pharmaceuticals and as psychedelic drugs...
(ergoline) moiety, and other alkaloids of the
ergolineErgoline is a chemical compound whose structural skeleton is contained in a diverse range of alkaloids including a few psychedelic drugs...
group that are
biosynthesizedBiosynthesis is an enzyme-catalyzed process in cells of living organisms by which substrates are converted to more complex products. The biosynthesis process often consists of several enzymatic steps in which the product of one step is used as substrate in the following step...
by the fungus. Ergot alkaloids have a wide range of
biological activitiesPharmacological or biological activity is an expression describing the beneficial or adverse effects of a drug on living matter. When the drug is a complex chemical mixture, this activity is exerted by the substance's active ingredient or pharmacophore but can be modified by the other constituents....
including effects on
circulation- [Headline text]--75.137.171.242 01:21, 21 October 2009 :bThe circulatory system is an organ system that passes nutrients , gases, hormones, blood cells, nitrogen waste products, etc. to and from cells in the body to help fight diseases and help stabilize body temperature and pHb to maintain...
and
neurotransmissionNeurotransmission , also called synaptic transmission, is an electrical movement within synapses caused by a propagation of nerve impulses...
.
ErgotismErgotism is the effect of long-term ergot poisoning, traditionally due to the ingestion of the alkaloids produced by the Claviceps purpurea fungus which infects rye and other cereals, and more recently by the action of a number of ergoline-based drugs. It is also known as ergotoxicosis, ergot...
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 GreatAnthony the Great , , also known as Saint Anthony, Anthony the Abbot, Anthony of Egypt, Anthony of the Desert, Anthony the Anchorite, Abba Antonius , and Father of All Monks, was a Christian saint from Egypt, a prominent leader among the Desert Fathers...
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- [Headline text]--75.137.171.242 01:21, 21 October 2009 :bThe circulatory system is an organ system that passes nutrients , gases, hormones, blood cells, nitrogen waste products, etc. to and from cells in the body to help fight diseases and help stabilize body temperature and pHb to maintain...
due to
vasoconstrictionVasoconstriction is the narrowing of the blood vessels resulting from contraction of the muscular wall of the vessels, particularly the large arteries, small arterioles and veins. The process is the opposite of vasodilation, the widening of blood vessels. The process is particularly important in...
of blood vessels, sometimes leading to
gangreneGangrene is a complication of necrosis or cell death characterized by the decay of body tissues, which become black and malodorous. It is caused by infection or ischemia, such as from thrombosis. It is usually the result of critically insufficient blood supply and is often associated with...
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
uterineThe uterus is a major female hormone-responsive reproductive sex organ of most mammals, including humans. It is within the uterus that the fetus develops during gestation. The term uterus is used consistently within the medical and related professions; the Germanic term, womb is more common in...
contractions,
nauseaNausea is the sensation of unease and discomfort in the stomach with an urge to vomit.-Causes:...
,
seizureAn epileptic seizure is a transient symptom of excessive or synchronous neuronal activity in the brain. It can manifest as an alteration in mental state, tonic or clonic movements, convulsions, and various other psychic symptoms...
s, and unconsciousness. Since the middle ages, controlled doses of ergot were used to induce
abortionAn abortion is the termination of a pregnancy by the removal or expulsion from the uterus of a fetus or embryo. An abortion can occur spontaneously due to complications during pregnancy or can be induced, in humans and other species...
s and to stop maternal bleeding after childbirth. Ergot alkaloids are also used in products such as
CafergotCafergot is the proprietary name of a medication consisting of ergotamine tartrate and caffeine. This combination is used for the treatment of vascular headaches, such as migraine headache.-Use:...
(containing
caffeineCaffeine is a bitter, white crystalline xanthine alkaloid that is a psychoactive stimulant drug. Caffeine was discovered by a German chemist, Friedrich Ferdinand Runge, in 1819. He coined the term kaffein, a chemical compound in coffee, which in English became caffeine...
and
ergotamineErgotamine is an ergopeptine and part of the ergot family of alkaloids; it is structurally and biochemically closely related to ergoline. It possesses structural similarity to several neurotransmitters, and has biological activity as a vasoconstrictor...
or
ergolineErgoline is a chemical compound whose structural skeleton is contained in a diverse range of alkaloids including a few psychedelic drugs...
) to treat migraine headaches. Ergot extract is no longer used as a pharmaceutical preparation.
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
PenicilliumPenicillium is a genus of ascomycetous fungi of major importance in the environment, food and drug production...
and
AspergillusAspergillus is a genus of a few hundred molds found throughout much of nature worldwide. Aspergillus was first catalogued in 1729 by the Italian priest and biologist Pier Antonio Micheli. Viewing the fungi under a microscope, Micheli was reminded of the shape of an aspergillum , and named the genus...
, notably by some isolates of the human pathogen
Aspergillus fumigatusAspergillus fumigatus is a fungus of the genus Aspergillus, and is one of the most common Aspergillus species to cause disease in immuno-compromised individuals....
, and have been isolated from plants in the family
ConvolvulaceaeThe Convolvulaceae, known commonly as the bindweed or morning glory family, is a group of about 60 genera and more than 1,650 species of mostly herbaceous vines, but also trees, shrubs and herbs.- Description :...
, of which
morning gloryMorning glory is a common name for over 1,000 species of flowering plants in the family Convolvulaceae, whose current taxonomy and systematics is in flux...
is best known.
Ergot contains no lysergic acid diethylamide (LSD) but instead contains
ergotamineErgotamine is an ergopeptine and part of the ergot family of alkaloids; it is structurally and biochemically closely related to ergoline. It possesses structural similarity to several neurotransmitters, and has biological activity as a vasoconstrictor...
, which is used to synthesize
lysergic acidLysergic acid, also known as D-lysergic acid and -lysergic acid, is a precursor for a wide range of ergoline alkaloids that are produced by the ergot fungus and some plants. Amides of lysergic acid, lysergamides, are widely used as pharmaceuticals and as psychedelic drugs...
, 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 MedicineThe New England Journal of Medicine is an English-language peer-reviewed medical journal published by the Massachusetts Medical Society. It is the oldest continuously published medical journal in the world, and is the most widely read, cited, and influential general medical periodical in the...
, a paper was published documenting a British study of over 11,000
Parkinson's DiseaseParkinson's disease is a degenerative disorder of the central nervous system that often impairs the sufferer's motor skills, speech, and other functions....
patients. The study found that two ergot-derived drugs,
PergolidePergolide is an ergoline-based dopamine receptor agonist used for the treatment of Parkinson's disease.Parkinson's disease is associated with low levels of the neurotransmitter dopamine in the brain...
and
CabergolineCabergoline , an ergot derivative, is a potent dopamine receptor agonist on D2 receptors. It also acts on dopamine receptors in lactophilic hypothalamus cells to suppress prolactin production in the pituitary gland...
, commonly used to treat Parkinson's Disease may increase the risk of leaky heart valves by up to 700%.
History
Human poisoning due to the consumption of rye bread made from ergot-infected grain was common in Europe in the
Middle AgesThe Middle Ages of European history is a period of European history covering roughly a millennium in the 5th century through 16th centuries. More specific starting and ending points are sometimes adopted by scholars to suit their respective specializations or current focus...
. The epidemic was known as
Saint Anthony's fireErgotism is the effect of long-term ergot poisoning, traditionally due to the ingestion of the alkaloids produced by the Claviceps purpurea fungus which infects rye and other cereals, and more recently by the action of a number of ergoline-based drugs. It is also known as ergotoxicosis, ergot...
, or
ignis sacer, and some historical events, such as the
Great FearThe "Great Fear" occurred from July 20 to August 5, 1789 in France at the start of the French Revolution. Rural unrest had been present in France since the worsening grain shortage of the spring, and the grain supplies were now guarded by local militias as bands of vagrants roamed the countryside...
in France during the
RevolutionThe French Revolution was a period of political and social upheaval and radical change in the history of France, during which the French governmental structure, previously an absolute monarchy with feudal privileges for the aristocracy and Catholic clergy, underwent radical change to forms based...
have been linked to ergot poisoning.
Linnda R. CaporaelLinnda Caporael is a professor at the Science and Technology Studies Department at Rensselaer Polytechnic Institute.-Educational background:Caporael studied psychology at the University of California, Santa Barbara and received both her B.A. and PhD. She studied human ethology at the Institute of...
posited in 1976 that the hysterical symptoms of young women that had spurred the
Salem witch trialsThe Salem witch trials were a series of hearings before local magistrates followed by county court trials to prosecute people accused of witchcraft in Essex, Suffolk and Middlesex counties of colonial Massachusetts, between February 1692 and May 1693...
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 trialsThe Salem witch trials were a series of hearings before local magistrates followed by county court trials to prosecute people accused of witchcraft in Essex, Suffolk and Middlesex counties of colonial Massachusetts, between February 1692 and May 1693...
.
British author
John Grigsby John Grigsby is a British author of two books on prehistory and mythology: Warriors of the Wasteland and Beowulf and Grendel .- Background :...
claims that the presence of ergot in the stomachs of some of the so called 'bog-bodies' (
Iron AgeIn archaeology, the Iron Age is the prehistoric period in any area during which cutting tools and weapons were mainly made of iron or steel. The adoption of this material coincided with other changes in society, including differing agricultural practices, religious beliefs and artistic styles.The...
human remains from peat bogs N E Europe such as
Tollund ManThe Tollund Man is the naturally mummified corpse of a man who lived during the 4th century BC, during the time period characterised in Scandinavia as the Pre-Roman Iron Age. He was found in 1950 buried in a peat bog on the Jutland Peninsula in Denmark, which preserved his body. Such a find is...
) is indicative of use of ergot in ritual drinks in a prehistoric fertility cult akin to the
Eleusinian MysteriesThe Eleusinian Mysteries were initiation ceremonies held every year for the cult of Demeter and Persephone based at Eleusis in ancient Greece. Of all the mysteries celebrated in ancient times, these were held to be the ones of greatest importance. These myths and mysteries, begun in the Mycenean...
cult of ancient
GreeceGreece , officially the Hellenic Republic , is a country in southeastern Europe, situated on the southern end of the Balkan Peninsula....
. In his book
Beowulf and GrendelIn Beowulf & Grendel: The Truth Behind England's Oldest Legend , British author John Grigsby interprets Beowulf as "the recounting in poetic form of a religious conflict between two pagan cults in Denmark around AD 500" . Joining scholars such as Catherine M...
he argues that the
Anglo-SaxonAnglo-Saxon may refer to:* historically, the Anglo-Saxons, a Germanic people inhabiting parts of England during the Dark Ages** their Anglo-Saxon language, commonly referred to as Old English** anything pertaining to the History of Anglo-Saxon England...
poem
BeowulfBeowulf is an Old English heroic epic poem of unknown authorship, dating as recorded in the Nowell Codex manuscript from between the 8th and the early 11th century, set in Denmark and Sweden...
is based on a memory of the quelling of this fertility cult by followers of
OdinOdin , is considered the chief god in Norse paganism and the ruler of Asgard. Homologous with the Anglo-Saxon Wōden and the Old High German Wotan, it is descended from Proto-Germanic *Wōđinaz or *Wōđanaz.The name Odin is generally accepted as the modern translation; although, in some cases, older...
. 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'.
KykeonKykeon was an Ancient Greek drink made mainly of water, barley and naturally occurring substances. Mysteries say it was derived from ergot...
, the beverage consumed by participants in the ancient Greek cult of
Eleusinian MysteriesThe Eleusinian Mysteries were initiation ceremonies held every year for the cult of Demeter and Persephone based at Eleusis in ancient Greece. Of all the mysteries celebrated in ancient times, these were held to be the ones of greatest importance. These myths and mysteries, begun in the Mycenean...
, 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 HofmannAlbert Hofmann was a Swiss scientist best known for having been the first to synthesize, ingest and learn of the psychedelic effects of lysergic acid diethylamide . Hofmann authored more than 100 scientific articles and wrote a number of books, including LSD: My Problem Child...
, 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
myceliumthumb|right|Fungal myceliaMycelium is the vegetative part of a fungus, consisting of a mass of branching, thread-like hyphae. The mass of hyphae is sometimes called shiro, especially within the fairy ring fungi. Fungal colonies composed of mycelia are found in soil and on or in many other substrates...
with intense coloration. Cereal mashes and sprouted rye are suitable substrates for growth of the fungus in the laboratory.
Claviceps africana
Claviceps africana infects
sorghumSorghum is a genus of numerous species of grasses, some of which are raised for grain and many of which are used as fodder plants either cultivated or as part of pasture. The plants are cultivated in warmer climates worldwide. Species are native to tropical and subtropical regions of all continents...
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
honeydewHoneydew may refer to:* Honeydew , a cultivar group of melon* Honeydew , a sugar-rich sticky substance secreted by aphids and some scale insects* Honeydew, California, a town* Dr...
(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
CameroonThe Republic of Cameroon is a unitary republic of central and western Africa. It is bordered by Nigeria to the west; Chad to the northeast; the Central African Republic to the east; and Equatorial Guinea, Gabon, and the Republic of the Congo to the south. Cameroon's coastline lies on the Bight of...
, 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.
External links