Laetiporus sulphureus is a species of bracket fungus (fungus that grows on trees) found in Europe and North America. Its common names are crab of the woods, sulphur polypore, sulphur shelf, and chicken of the woods. Its fruit bodies grow as striking golden-yellow shelf-like structures on tree trunks and branches. Like other bracket fungi, they may last many years and fade to pale grey or brown. The undersurface of the fruit body is made up of tubelike pores rather than gills.
Taxonomy and phylogenetics
Laetiporus sulphureus was first described as Boletus sulphureus by French mycologist Pierre Bulliard in 1789. It has had many synonyms and was finally given its current name in 1920 by American mycologist William Murrill. Laetiporus means with bright pores and sulphureus means the colour of sulphur.
Phylogenetic analyses of ITS, nuclear large subunit and mitochondrial small subunit rDNA sequences from a variety of North American species have delineated five distinct clades within the core Laetiporus clade:
- Conifericola clade: contains species that live on conifers, such as L. conifericola and L. huroniensis. All of the other tested species grow on angiosperms.
- Cincinnatus clade: contains L. cincinnatus
- Sulphureus clade I: contains white-pored L. sulfureus isolates.
- Sulphureus clade II: contains yellow-pored L. sulfureus isolates.
- Gilbertsonii clade: contains L. gilbertsonii and unidentified Caribbean isolates
Investigations in North America have shown that there are several similar species within what has been considered L. sulphureus, and that the true L. sulphureus may be restricted to regions east of the Rocky Mountains.
The cap is small and knob-shaped, overlapping in an irregular pattern. Wide, shaped like a fan and attached direct to the trunk of a tree, it has a shelf-like appearance and is sulphur-yellow to bright orange in colour and has a suedelike texture. When it is old the cap fades to tan or white. The shelves often grow in overlapping clumps, and each one may be anywhere from 5 to 60 cm (2 to 24 in) in diameter and 4 cm (1.4 in) thick. The fertile surface is sulphur-yellow with small pores or tubes and has a white spore print.
Distribution and habitat
Laetiporus sulphureus is widely distributed across Europe and North America though may be restricted to east of the Rockies.
The mushroom grows on dead or mature hardwoods such as oak, cherry and beech from August to October or later, sometime as early as June. The species can also be found under conifers. It can usually be found growing in clusters.
The mushroom causes brown cubical rot on the heartwood in the roots, base and stem. At first the wood is discoloured yellowish to red. Later on it becomes reddish-brown and brittle. At the last stage the wood can be rubbed like powder between the fingers.
Guinness world record
A specimen weighing 100 pounds (over 45 kg) was found in the New Forest, Hampshire, United Kingdom, on 15 October 1990.
Because of the taste, the mushroom has been called chicken polypore and chicken-of-the-woods. Many people think that the mushroom tastes like crab or lobster. The authors of Mushrooms in Color said that the mushroom tastes good sauteed in butter or prepared in a cream sauce served on toast or rice. It is highly regarded in Germany and North America. The mushroom is a good substitute for chicken.
Studies have shown severe adverse reactions, including vomiting and fever, in about 10% of the population, but this is now thought to be a result of confusion with morphologically identical species such as Laetiporus huroniensis which grows on hemlock trees, and L. gilbertsonii which grows on Eucalyptus.
The mushroom produces the Laetiporus sulphureus lectin (LSL) which has haemolytic and haemagglutination activities. Haemolytic lectins are sugar-binding proteins that lyse and agglutinate cells. The haemagglutination and haemolytic activity are started by binding carbohydrates.
Compared with species such as Agaricus bisporus (button mushroom) and oyster mushroom, commercial cultivation of Laetiporus is limited. However it can be cultivated; the most dependable and rapid production of this mushroom is cultivation of it indoors. The mushroom does not require the heat and water that gilled mushrooms do. The mushroom is sensitive to carbon dioxide levels and light conditions.
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