Laetiporus sulphureus is a species of bracket fungus (fungi that grow 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. Old fruitbodies fade to pale beige or pale grey. The undersurface of the fruit body is made up of tubelike pores rather than gills.
Laetiporus sulphureus is a saprophyte and occasionally a weak parasite, causing brown cubical rot in the heartwood of trees on which it grows. Unlike many bracket fungi, it is edible when young, although adverse reactions have been reported.
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.
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. Phylogenetic analyses of ITS, nuclear large subunit and mitochondrial small subunit rDNA sequences from North American collections 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.
The fruiting body emerges directly from the trunk of a tree and is initially knob-shaped, but soon expands to fan-shaped shelves, typically growing in overlapping tiers. It is sulphur-yellow to bright orange in color and has a suedelike texture. Old fruitbodies fade to tan or whitish. Each shelf may be anywhere from 5 to 60 cm (2 to 23.5 in) across and up to 4 cm (1.5 in) thick. The fertile surface is sulphur-yellow with small pores or tubes and produces a white spore print. When fresh, the flesh is succulent with a strong fungal aroma and exudes a yellowish, transparent juice, but soon becomes dry and brittle.
Distribution and habitat
Laetiporus sulphureus is widely distributed across Europe and North America, although its range may be restricted to areas east of the Rockies. It grows on dead or mature hardwoods and has been reported from a very wide variety of host trees, such as Quercus, Prunus, Pyrus, Populus, Salix, Robinia, and Fagus, occasionally also from conifers, from August to October or later, sometimes as early as June. In the Mediterranean region, this species is usually found on Ceratonia and Eucalyptus. It can usually be found growing in clusters.
The fungus causes brown cubical rot of heartwood in the roots, tree base and stem. After infection, the wood is at first discolored yellowish to red but subsequently becomes reddish-brown and brittle. At the final stages of decay, 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.
Due to its taste, Laetiporus sulphureus has been called the 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.
Severe adverse reactions can occur, including vomiting and fever, in about 10% of the population, but this is now thought to be the result of confusion with morphologically similar species such as Laetiporus huroniensis, which grows on hemlock trees, and L. gilbertsonii, which grows on Eucalyptus.
The fungus produces the Laetiporus sulphureus lectin (LSL) which exhibits haemolytic and haemagglutination activities. Haemolytic lectins are sugar-binding proteins that lyse and agglutinate cells. These biochemical activities are promoted when bound to carbohydrates.
Compared with species such as Agaricus bisporus (button mushroom) and the oyster mushroom, commercial cultivation of Laetiporus is limited. However, it can be cultivated; the most dependable and rapid production of this mushroom is indoor cultivation. The mushroom may or may not require the heat and moisture that gilled mushrooms do, depending on the strain. Fungal development is sensitive to carbon dioxide levels and light conditions. Artificial cultivation on synthetic substrates has been achieved.
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