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Sclerotium can be formed by certain fungal species and consists of a hardened and compact mass of fungal tissue, fungal mycelium and a very small amount of water (5-10%). A sclerotium resembles a cyst with a dark bark-like outer layer. The function is that the fungus should be able to survive under extreme conditions in the form of a sclerotium, which is thus a resting stage, and then begin to grow and thrive again when the conditions return to normal. The fungus can survive during several years in a dry environment in the form of a sclerotium without growing.

Examples of fungi, which can form sclerotia

  • Ergot (Claviceps purpurea) is an example of a plant pathogenic fungus that can form a sclerotium. Substances that can be extracted from the sclerotia have been used for medical purposes, but have often had severe side effects. Certain alkaloids from the sclerotia have been the starting material for the production of LSD (lysergic acid diethylamide).
  • Ophiocordyceps sinensis is a fungus that infects larvae and uses its nutrients to form a mycelium, which then can be transformed into a sclerotium inside the larval body.
  • Inonotus obliquus (chaga mushroom) is a sclerotium that grows mainly on birches in colder climates. It has been used as a tonic and a remedy for thousands of years in Japan, Canada and Russia, among others. The tree sclerotia develops over many years as the mycelium absorbs nutrients from the living tree.


Updated: 2023-01-18.

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Swedish University of Agricultural Sciences