Domain: Eukarya
Kingdom: Fungi
Phylum: Ascomycota
Class: Sordariomycetes
Order: Hypocreales
Family: Clavicipitaceae
Genus: Claviceps

Claviceps purpurea, commonly known as Ergot, lives most of its life as an ndophyte inside the cells of graminaceous plants, particularly rye. This fungus infects rye through the stigma of its flower and produces a mycelial mat that replaces the plant’s ovarian tissues. This mycelial mat develops into conspicuous brownish-black sclerotia that can be found growing from the inflorescence of the plants. C. purpurea induces hypertrophy and hyperplasia in the plant cells (parasitic behavior), resulting in the relatively large sclerotia. Sclerotia are over-wintering structures that germinate in spring to form small, mushroom-like stromata that produce ascospores in perithecia. These spores are released and infect new plants.

Sclerotia are elongated, 1.5-3.5cm long, cylindrical, rounded at the ends, and firm. They are often curved and have slight longitudinal grooves. Usually dark brown to black on the outside and a lighter grayish-white on the inside. One to several sclerotia may be found growing from a single grass inflorescence (Image 1 & Image 2).

When Spring comes, small, mushroom-like stromata emerge from sclerotia that have fallen to the ground. A short stalk elevates a globose head that is approximately 2mm in diameter. Along the head perithecia form. Inside these structures, needle-like sexually formed ascospores develop in elongated asci. Each ascus contains 8 ascospores. The hyaline ascospores are approximately 65-100um x 0.5-1um. The tips of the asci turn blue in Melzer’s reagent. The ascospores are forcibly ejected through a long neck-like ostiole. (Image 3 & Image 4).

The ascospores are wind disseminated and germinate when they land on the flowers of rye (or other susceptible plants in bloom). Germ tubes infect the ovary, destroying tissue and replacing it with mycelium. Short conidiophores bearing tiny oval conidia form. Insects visiting the flower can transfer these asexually produced conidia to uninfected flowers and transfer the fungus.

Image 1: sclerotia on rye

Image 2: sclerotium on rye

Image 3: perithecia

Image 4: perithecium

Temperate regions worldwide, notably in the eastern US and in Europe.

Graminaceous plant species, particularly rye. C. purpurea grows best in wet conditions.

Superficially, some smuts may look similar, but 2 seconds under the microscope will easily distinguish Claviceps with its perithecia, or even just the structure of the sclerotia.

Besides parasitizing rye, this fungus affects animals as well. The sclerotia produced by Claviceps purpurea contain many powerful alkaloids (ergotamine, ergometrin, ergonovin), some that are useful to people and some that are very harmful to people.

Ergotism:
Cattle are often poisoned by grazing on infected grasses, but people can also be infected. Ergotism is also known as St. Anthony’s Fire. Some of the alkaloids produced by Claviceps purpurea cause vasoconstriction in blood vessels, resulting in a burning sensation, blackening, and eventually the loss of gangrenous limbs. Other symptoms include the feeling of insects crawling under the skin, paralysis, convulsions, vomiting, diarrhea, and abortions. Ingestion also results in hallucinations. Ergotism is thought to be responsible for the deaths of hundreds of thousands of people and animals in the last millennium as a result of accidental ingestion of contaminated grain.

It’s been hypothesized that ergot poisoning was responsible for the strange behavior and sickness associated with the Salem Witch Trials in Salem, Massachusetts in the 1600s (see Caporael 1976 for more information).

Childbirth:
The same alkaloid that causes abortions can be administered clinically in low dosages to actually aid in child birth by helping to induce uterine contractions and to prevent post partum hemorrhage.

Headaches:
Another alkaloid produced by this fungus has been successful in treating migraine headaches.

LSD:
The hallucinogenic compound LSD, commonly known as “Acid,” can be synthesized directly from lysergic acid (LSA), which is naturally produced in the ergot sclerotia. LSA has similar psychoactive properties when compared with LSD, which provides a good explanation for the hallucinations associated with Ergotism.

C. purpurea can be easily grown in culture, however, production of sclerotia has not been successful. Regardless, many alkaloid-forming strains have been isolated which produce the desired alkaloids in their mycelium, negating the need for sclerotia. Also, some of the alkaloids can now be produced synthetically.

For additional information see Tom Volk’s fungus of the month page on Claviceps purpurea

Alexopoulos, C.J., & C.W. Mims. Introductory Mycology Third Edition. John Wiley & Sons Inc. New York, NY. 1979.

Bessette, A.E., A.R. Bessette, & D.W. Fisher. Mushrooms of Northeastern North America. Syracuse University Press. Syracuse, NY. 1997.

Caporael, L.R. 1976. “Ergotism: The Satan Loosed in Salem?” Science. 192: 21-26.

Kwon-Chung, K.J., & J.E. Bennett. Medical Mycology. Lea & Febiger. Malvern, PA. 1992.

Pacioni, G. Simon & Schuster’s Guide to Mushrooms. Simon & Schuster Inc. New York, NY. 1981.

Schumann, G.L. Plant Diseases: Their Biology and Social Impact. The American Phytopathological Society. St. Paul, MN. 1991.

Volk, T.J. 1999. “Tom Volk’s Fungus of the Month for October 1999: Claviceps purpurea, cause of ergotism— and likely contributor to the Salem Witch Trials.” Tom Volk’s Fungi. http://botit.botany.wisc.edu/toms_fungi/oct99.html

Matthew Foltz
UW-La Crosse Medical Mycology
April 2009