Fortress Plant by Walters Dale;

Author:Walters, Dale; [Walters, Dale]
Language: eng
Format: epub
Publisher: Oxford University Press, Incorporated
Published: 2017-01-26T00:00:00+00:00

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Tall fescue grass had long been used as a cool season forage crop before reports began to emerge in the 1940s of health problems in livestock fed on this plant. Cattle given hay made from tall fescue grass showed signs of lameness in winter, sometimes leading to loss of the affected foot, giving rise to the name ‘fescue foot’. Subsequently, researchers found that extracts of tall fescue grass obtained from a farm where cattle were exhibiting signs of lameness possessed vasoconstrictive properties. In fact, symptoms of fescue foot were similar to those observed with ergot poisoning, resulting from infection of rye by the fungal pathogen Claviceps purpurea.23 This fungus produces structures called sclerotia (ergots) on cereal heads where grains should form and end up being harvested along with normal rye grains. The sclerotia are produced by the fungus as a survival structure, to help protect it over the winter months. They are packed full of alkaloids as a sort of chemical protection as they lie in the soil waiting for spring. Some of these chemicals, such as ergotamine, are powerful vasoconstrictors, preventing blood flow to tissues and starving them of oxygen in the process. The problem arises when people or animals eat rye grain contaminated with ergots. The ergot fungus causes a disease, known as holy fire or St Anthony’s fire, which was a scourge in the Middle Ages, responsible for the deaths of more than 50,000 people in southern France alone in the period between 990 and 1130. Symptoms of this frightening disease included hallucinations and a feeling of burning skin or insects crawling under the skin. In severe cases, extremities became gangrenous, often resulting in the loss of hands and feet. This dreadful affliction was so frequent that a religious order, the Hospitallers of St Anthony was founded in France in 1095 to help care for victims during their painful suffering. The connection between ergots and the disease was not made until 1670, by a French physician, Dr Thuillier. However, farmers remained unconvinced of this connection for another couple of hundred years and eventually, in 1853, the mycologist Louis Rene Tulasne finally determined that ergots were produced by a fungus and not by the rye plant.24,25

Although the symptoms of fescue foot suggested that a toxin similar to that produced by the ergot fungus (the alkaloid ergotamine) might be involved, it was not until 1977 that an endophytic fungus was found to be the culprit26 and a couple of years later that alkaloid production was found to be responsible for the symptoms. We now know that fescue foot is caused by the endophytic fungus Neotyphodium coenophialum, which produces ergopeptine alkaloids. The symptoms of fescue foot appear to be caused by the most abundant of these alkaloids, ergovaline.27

The curious thing about fescue foot is that the fungus responsible for producing the toxic alkaloids is an endophyte. In other words, this is a fungus that lives within the plant, but unlike the ergot fungus, it is not pathogenic. Fungal endophytes

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