Ergot or
ergot fungi refers to a group of
fungiA fungus is a member of a large group of eukaryotic organisms that includes microorganisms such as yeasts and molds , as well as the more familiar mushrooms. These organisms are classified as a kingdom, Fungi, which is separate from plants, animals, and bacteria...
of the genus
Claviceps. The most prominent member of this group is
Claviceps purpureaClaviceps purpurea is a fungus that grows on the ears of rye and related cereal and forage plants. Consumption of grains or seeds contaminated with the fruiting structure of this fungus, the ergot sclerotium, can cause ergotism in humans and other mammals.. C...
. 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 whiskeys, some vodkas, and animal fodder...
and related plants, and produces
alkaloidAlkaloids are a group of naturally occurring chemical compounds that contain mostly basic nitrogen atoms. This group also includes some related compounds with neutral and even weakly acidic properties. Also some synthetic compounds of similar structure are attributed to alkaloids...
s that 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 who consume grains contaminated with its fruiting structure (called 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...
).
Claviceps includes about 50 known species, mostly in the tropical regions. Economically significant species include
C. purpurea (parasitic on
grassThe Poaceae is a large and nearly ubiquitous family of flowering plants. Members of this family are commonly called grasses, although the term "grass" is also applied to plants that are not in the Poaceae lineage, including the rushes and sedges...
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 center of diversity, and suggested area of domestication, for...
, buffel grass),
C. paspali (on dallis grass), and
C. africana (on
sorghumSorghum is a genus of numerous species of grasses, one of which is 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 whiskeys, 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 second generation hybrid, i.e., a cross between two kinds of primary triticales...
,
wheatWheat is a cereal grain, originally from the Levant region of the Near East, but now cultivated worldwide. 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 major cereal grain, a member of the grass family. It serves as a major animal fodder, as a base malt for beer and certain distilled beverages, and as a component of various health foods...
. 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...
s only rarely.
C. purpurea has at least three races or varieties, which differ 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
sporeIn biology, a spore is a reproductive structure that is adapted for dispersal and surviving for extended periods of time in unfavorable conditions. Spores form part of the life cycles of many bacteria, plants, algae, fungi and some protozoa. According to scientist Dr...
of fungal species of the genus
Claviceps infects a floret of flowering grass or cereal. 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 from 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 pistil 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. Infection requires that the fungal spore have access to the
stigmaGynoecium is most commonly used as a collective term for all carpels in a flower. A carpel is the ovule and seed producing reproductive organ in flowering plants. Carpels are derived from ovule-bearing leaves which evolved to form a closed structure containing the ovules...
, so 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 of grasses in the Triticeae tribe. The most known member is rye .Other species include:*Secale montanum Guss.*Secale sylvestre Host....
) 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 within many other...
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 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 liquid, 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 a mode of reproduction by which offspring arise from a single parent, and inherit the genes of that parent only, it is reproduction which does not involve meiosis, ploidy reduction, or fertilization. A more stringent definition is agamogenesis which is reproduction without...
spores (conidia), which
insectInsects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...
s disperse to other florets. Later, the sphacelia convert into a hard dry sclerotium inside the husk of the floret. At this stage,
alkaloidAlkaloids are a group of naturally occurring chemical compounds that contain mostly basic nitrogen atoms. This group also includes some related compounds with neutral and even weakly acidic properties. Also some synthetic compounds of similar structure are attributed to alkaloids...
s and
lipidLipids constitute a broad group of naturally occurring molecules that include fats, waxes, sterols, fat-soluble vitamins , monoglycerides, diglycerides, triglycerides, 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* Bunsen Honeydew, a fictional character from The Muppet Show...
. 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 an oval to pearlike shape is formed, to which the contents of the original macroconidium migrates. Secondary conidia form a white, frost-like surface on honeydew drops and spread via the 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 (such as the onset of spring or a rain period). It germinates, forming one or several fruiting bodies with heads and stipe, 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...
). In the head, threadlike
sexualSexual reproduction is the creation of a new organism by combining the genetic material of two organisms. There are two main processes during sexual reproduction; they are: meiosis, involving the halving of the number of chromosomes; and fertilization, involving the fusion of two gametes and the...
spores form, which are ejected simultaneously when suitable grass hosts are flowering. Ergot infection causes a reduction in the yield and quality of grain and hay, and if livestock eat infected grain or hay 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, carry conidia of
Claviceps species, but it is unknown whether insects play a role in spreading the fungus from infected to healthy plants.
Effects on humans and other mammals
The ergot sclerotium contains high concentrations (up to 2% of dry mass) of the
alkaloidAlkaloids are a group of naturally occurring chemical compounds that contain mostly basic nitrogen atoms. This group also includes some related compounds with neutral and even weakly acidic properties. Also some synthetic compounds of similar structure are attributed to alkaloids...
ergotamine, a complex molecule consisting of a tripeptide-derived cyclol-lactam ring connected via
amideIn chemistry, an amide is an organic compound that contains the functional group consisting of a carbonyl group linked to a nitrogen atom . The term refers both to a class of compounds and a functional group within those compounds. The term amide also refers to deprotonated form of ammonia or an...
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 . Ergoline derivatives are used clinically for the purpose of vasoconstriction and in the treatment of migraines and Parkinson's disease...
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 activitiesIn pharmacology, biological activity or pharmacological activity describes the beneficial or adverse effects of a drug on living matter. When a 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...
including effects on
circulationThe circulatory system is an organ system that passes nutrients , gases, hormones, blood cells, etc...
and
neurotransmissionNeurotransmission , also called synaptic transmission, is the process by which signaling molecules called neurotransmitters are released by a neuron , and bind to and activate the receptors of another neuron...
.
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 plant material containing ergot alkaloid, such as ergot-contaminated grains. The
Hospital Brothers of St. AnthonyThe Hospital Brothers of St. Anthony, Order of St. Anthony or Canons Regular of St. Anthony of Vienne , also Antonines, were a Roman Catholic congregation founded in 1095 or so, with the purpose of caring for those suffering from the common medieval disease of St...
(monks) specialized in treating ergotism victims with balms containing tranquilizing and circulation-stimulating plant extracts. 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 systemThe circulatory system is an organ system that passes nutrients , gases, hormones, blood cells, etc...
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 serious and potentially life-threatening condition that arises when a considerable mass of body tissue dies . This may occur after an injury or infection, or in people suffering from any chronic health problem affecting blood circulation. The primary cause of gangrene is reduced blood...
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 or womb is a major female hormone-responsive reproductive sex organ of most mammals including humans. One end, the cervix, opens into the vagina, while the other is connected to one or both fallopian tubes, depending on the species...
contractions,
nauseaNausea , is a sensation of unease and discomfort in the upper stomach with an involuntary urge to vomit. It often, but not always, precedes vomiting...
,
seizureAn epileptic seizure, occasionally referred to as a fit, is defined as a transient symptom of "abnormal excessive or synchronous neuronal activity in the brain". The outward effect can be as dramatic as a wild thrashing movement or as mild as a brief loss of awareness...
s, and unconsciousness. Since the Middle Ages, controlled doses of ergot were used to induce
abortionAbortion is defined as the termination of pregnancy by the removal or expulsion from the uterus of a fetus or embryo prior to viability. An abortion can occur spontaneously, in which case it is usually called a miscarriage, or it can be purposely induced...
s and to stop maternal bleeding after childbirth. Ergot extract has been used in pharmaceutical preparations, including Ergot alkaloids 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 acts as a stimulant drug. Caffeine is found in varying quantities in the seeds, leaves, and fruit of some plants, where it acts as a natural pesticide that paralyzes and kills certain insects feeding on the plants...
and
ergotamine or
ergolineErgoline is a chemical compound whose structural skeleton is contained in a diverse range of alkaloids including a few psychedelic drugs . Ergoline derivatives are used clinically for the purpose of vasoconstriction and in the treatment of migraines and Parkinson's disease...
) 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. The fungi of the genera
PenicilliumPenicillium is a genus of ascomycetous fungi of major importance in the natural environment as well as food and drug production. Members of the genus produce penicillin, a molecule that is used as an antibiotic, which kills or stops the growth of certain kinds of bacteria inside the body...
and
AspergillusAspergillus is a genus consisting of several hundred mold species found in various climates worldwide. Aspergillus was first catalogued in 1729 by the Italian priest and biologist Pier Antonio Micheli...
also produce ergot alkaloids, notably 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 individuals with an immunodeficiency....
, and have been isolated from plants in the family
ConvolvulaceaeConvolvulaceae, known commonly as the bindweed or morning glory family, are 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
ergotamine, 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.
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 describes itself as the oldest continuously published medical journal in the world.-History:...
includes a paper that documents a British study of more than 11,000
Parkinson's DiseaseParkinson's disease is a degenerative disorder of the central nervous system...
patients. The study found that two ergot-derived drugs,
PergolidePergolide is an ergoline-based dopamine receptor agonist used in some countries for the treatment of Parkinson's disease....
and
CabergolineCabergoline , an ergot derivative, is a potent dopamine receptor agonist on D2 receptors. In vitro, rat studies show cabergoline has a direct inhibitory effect on pituitary lactotroph cells...
, 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 is a periodization of European history from the 5th century to the 15th century. The Middle Ages follows the fall of the Western Roman Empire in 476 and precedes the Early Modern Era. It is the middle period of a three-period division of Western history: Classic, Medieval and Modern...
. 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 20 July to 5 August 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 rumors that bands of armed men were...
in France during the
RevolutionThe French Revolution , sometimes distinguished as the 'Great French Revolution' , was a period of radical social and political upheaval in France and Europe. The absolute monarchy that had ruled France for centuries collapsed in three years...
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 county court trials to prosecute people accused of witchcraft in the counties of Essex, Suffolk, and Middlesex in colonial Massachusetts, between February 1692 and May 1693...
had been the result of consuming ergot-tainted rye. However, Nicholas P. Spanos and Jack Gottlieb, after a review of the historical and medical evidence, later disputed her conclusions. Other authors have likewise cast doubt on ergotism as the cause of the
Salem witch trialsThe Salem witch trials were a series of hearings before county court trials to prosecute people accused of witchcraft in the counties of Essex, Suffolk, and Middlesex in colonial Massachusetts, between February 1692 and May 1693...
.
American author
John Grigsby- Biography :Grigsby received a Bachelor's degree in Prehistoric European Archeology and History and a Master's degree in Celtic Studies. He made contributions to 's Heaven's Mirror and the television series based upon the book, Quest for the Lost Civilization. He is co-author of The Mars Mystery...
contends that the presence of ergot in the stomachs of some of the so called 'bog-bodies' (
Iron AgeThe Iron Age is the archaeological period generally occurring after the Bronze Age, marked by the prevalent use of iron. The early period of the age is characterized by the widespread use of iron or steel. The adoption of such material coincided with other changes in society, including differing...
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...
cult of ancient
GreeceGreece , officially the Hellenic Republic , and historically Hellas or the Republic of Greece in English, is a country in southeastern Europe....
. In his book
Beowulf and GrendelIn Beowulf & Grendel: The Truth Behind England's Oldest Legend , John Grigsby interprets Beowulf as "the recounting in poetic form of a religious conflict between two pagan cults in Denmark around AD 500" . Grigsby argues that the poem reflects the violent ending of the native fertility religion of...
, he argues that the
Anglo-SaxonAnglo-Saxon may refer to:* Anglo-Saxons, a group that invaded Britain** Old English, their language** Anglo-Saxon England, their history, one of various ships* White Anglo-Saxon Protestant, an ethnicity* Anglo-Saxon economy, modern macroeconomic term...
poem
BeowulfBeowulf , but modern scholars agree in naming it after the hero whose life is its subject." of an Old English heroic epic poem consisting of 3182 alliterative long lines, set in Scandinavia, commonly cited as one of the most important works of Anglo-Saxon literature.It survives in a single...
is based on a memory of the quelling of this fertility cult by followers of
OdinOdin is a major god in Norse mythology and the ruler of Asgard. Homologous with the Anglo-Saxon "Wōden" and the Old High German "Wotan", the name is descended from Proto-Germanic "*Wodanaz" or "*Wōđanaz"....
. He writes 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. It was used at the climax of the Eleusinian Mysteries to break a sacred fast, but it was also a favourite drink of Greek peasants.Kykeon is mentioned in Homeric texts: the Iliad describes it as...
, 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...
, 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 known best for being the first person to synthesize, ingest and learn of the psychedelic effects of lysergic acid diethylamide . He authored more than 100 scientific articles and a number of books, including LSD: My Problem Child...
, in 1938.
Claviceps purpurea
Mankind has known about
Claviceps purpurea 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. Temperatures above 37 °C 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 within many other...
, 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, one of which is 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. Symptoms of infection by
C. africana include the secretion of
honeydewHoneydew is a sugar-rich sticky liquid, 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...
(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 the spread of the fungus to uninfected plants.
C. africana caused ergot disease that caused a famine in 1903-1906 in Northern
CameroonCameroon, officially the Republic of Cameroon , is a country in west Central 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...
, 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, as first recognized in the 1960s, and massive losses in seed yield have been noted. Infection is associated with cold night temperatures that are below 12 °C occurring two to three weeks before flowering.
External links