ergot(redirected from Sphacelia segetum)
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ergot(ûr`gət), disease of rye and other cereals caused by the fungus Claviceps purpurea. The cottony, matlike body, or mycelium, of the fungus develops in the ovaries of the host plant; it eventually turns into a hard pink or purple body, the sclerotium, or ergot, that resembles a grain of rye in shape. The sclerotium contains alkaloids (many of which are biologically active) that are toxic to humans and livestock. Ergot poisoning, or ergotism, epidemic in the Middle Ages, results from eating bread made of rye contaminated with ergot. Ergot poisoning is characterized by constriction of blood vessels, resulting in numbness and the development of gangrene in extremities; it may also affect the nervous system. Some of the alkaloids in ergot, e.g., ergotamine and ergonovine, are used as medicines; these alkaloids are chemical derivatives of lysergic acid, which is used in the synthesis of the hallucinogen LSDLSD
or lysergic acid diethylamide
, alkaloid synthesized from lysergic acid, which is found in the fungus ergot (Claviceps purpurea). It is a hallucinogenic drug that intensifies sense perceptions and produces hallucinations, mood changes, and changes in the
..... Click the link for more information. . Ergotamine alleviates migraine headaches. Ergonovine is used medicinally to stop hemorrhage and cause contraction of the uterus; during the 17th cent. midwives used ergot to stop postpartum uterine bleeding.
(1) The parasitic fungus Claviceps purpurea of the class Ascomycetes of the group Pyrenomycetes.
(2) A disease of cereals caused by the fungus Clavicepspurpurea and characterized by the formation of violet sclerotia instead of grains in the spikes. The sclerotia, which represent a resting stage of the fungus, are 1–5 cm long and contain poisonous substances that may cause ergotism, a serious disease of humans and animals contracted by eating contaminated grain or grain products. In the past epidemics and epizooties of ergotism were common in many countries. As a result of advancements in agriculture, the incidence of ergot in cereal crops has decreased.
The causative agent of ergot, which affects more than 170 cultivated and wild cereals, most commonly attacks rye. Sclerotia form, as a rule, in the female sex organs (ovaries). The fungus reproduces by spores, which are distributed during flowering of the cereals by rain, wind, animals, and humans. The disease occurs in regions having a temperate or humid climate. Damage may be substantial: for example, if a spike contains more than 20 sclerotia, only about 20 percent of the nutrient matter entering the spike will be used in grain formation.
Control measures include removing sclerotia from the grains of rye and other cereals; uniform planting of winter and spring cereals to ensure uniform development, flowering, and ripening; inspecting plantations to identify healthy seed-growing plots; shallow plowing of stubble; deep autumn plowing; and selecting varieties with short and uniform periods of flowering.
Z. P. KACHALOVA
(3) Sclerotia of the fungus Claviceps purpurea. The sclerotia contain a large number of alkaloids (derivatives of lysergic acid), biogenic amines (histamine and tyramine), choline, acetylcholine, amino acids, and other substances. The ergot alkaloids are divided into three basic groups: ergotamine, ergometrine (ergobasine), and ergotoxine. Ergot alkaloids and their derivatives exert a complex action on the body (for example, on the uterus, sympathetic nervous system, and central nervous system). The characteristic feature of the alkaloids—mainly of ergometrine and ergotamine—is the ability to induce uterine contractions. The alkaloids are used to sedate the nervous system, lower the basal metabolism, and treat spasms of the blood vessels and hypertension. Ergotamine is effective against migraine.
Sclerotia of ergot are cultivated for medicinal purposes in rye plantings on special farms. The plants are infected during spike formation with the conidiospores of special strains of C. purpurea that produce sclerotia with high alkaloid content.
V. V. PARIN
REFERENCESPshedetskaia, L. I. Biologicheskie osobennosti sporyn’i na kul’turnykh i lugovykh zlakakh, kak material dlia obosnovaniia meropriiatiipo bor’bes nei.
Leningrad, 1953. (Dissertation.) Lekarstvennye rasteniia SSSR (kul’tiviruemye i dikorastushchie). Moscow, 1967.
Peresypkin, V. F. Sel’ skokhoziaistvennaia fitopatologiia. Moscow, 1969.