Agaricus bisporus

Common mushroom
Conservation status
Secure
Scientific classification
Kingdom:	Fungi
Division:	Basidiomycota
Class:	Agaricomycetes
Subclass:	Homobasidiomycetidae
Order:	Agaricales
Family:	Agaricaceae
Genus:	Agaricus
Species:	A. bisporus
Binomial name
Agaricus bisporus (J.E.Lange) Imbach

Agaricus bisporus
Mycological characteristics
	gills on hymenium
	cap is convex
	hymenium is free
	stipe has a ring
	spore print is brown
	ecology is saprotrophic
	edibility: choice

Agaricus bisporus—known variously as the common mushroom, button mushroom, white mushroom, table mushroom, portobello mushroom, cremini, crimini mushroom, Swiss brown mushrooms, Roman brown mushrooms, Italian brown, Italian mushroom, or cultivated mushroom is an edible basidiomycete mushroom native to grasslands in Europe and North America. Agaricus bisporus is cultivated in more than 70 countries.^[1]

Taxonomy and naming

The common mushroom has a complicated taxonomic history. It was first described in 1884 as a variety (var. hortensis) of Agaricus campestris.^{[citation needed]} Danish mycologist Jakob Emanuel Lange later reviewed a cultivar specimen, and dubbed it Psalliota hortensis var. bispora in 1926. The epithet bispora distinguished the two-spored basidia from four-spored varieties). In 1938, it was promoted to species status and renamed Psalliota bispora.^{[citation needed]} Emil Imbach renamed imparted the species' current scientific name, Agaricus bisporus, after the genus Psalliota was renamed to Agaricus in 1946.^[1]

Among English speakers, Agaricus bisporus is known by many names. A young specimen with a closed cap and either pale white or light brown flesh is known as a button mushroom or white mushroom. When the flesh darkens, the immature mushroom is variously known as a crimini mushroom, baby portobello, baby bella, mini bella, portabellini, Roman mushroom, Italian mushroom, or brown mushroom. At this stage of maturation, the cap may also begin to open slightly. In maturity, it is called a portobello (frequently misspelled as portabello, or portobella). The French name is champignon de Paris ("Paris mushroom").

Both spellings of portabella and portobello are used. The Mushroom Council, however, uses the former. ^{[2] [3]}

Description

The pileus or cap of the original wild species is a pale grey-brown in color, with broad, flat scales on a paler background and fading toward the margins. It is first hemispherical in shape before flattening out with maturity, and 5-10 cm (2-4 in) in diameter. The narrow, crowded gills are free and initially pink, then red-brown and finally a dark brown with a whitish edge from the cheilocystidia. The cylindrical stipe is up to 6 cm (2⅓ in) tall by 1-2 cm wide and bears a thick and narrow ring, which may be streaked on the upperside. The firm flesh is white though stains a pale pinkish-red on bruising.^[4][5] The spore print is dark brown. The spores are oval to round and measure around 4.5-5.5 x 5-7.5 μm, and the basidia usually two-spored, although two tetrasporic varieties have been described from the Mojave desert and the Mediterranean with predominantly heterothallic and homothallic lifestyles, respectively^[6][7]

Commonly found in fields and grassy areas after rain from late spring through to autumn worldwide, especially in association with manure. It is widely collected and eaten, even by those who would not normally experiment with mushrooming.^[5]

Similar species

The common mushroom could be confused with young specimens of the deadly poisonous destroying angel (Amanita sp.), but the latter can be distinguished by their volva or cup at the base of the mushroom and pure white gills (as opposed to pinkish or brown of Agaricus bisporus). Thus it is important to always clear away debris and examine the base of a mushroom, as well as cutting open young specimens to check the gills. Furthermore, the destroying angel grows in mossy woods and lives symbiotically with spruce.

A more common and less dangerous mistake is to confuse Agaricus bisporus with Agaricus xanthodermus, an inedible mushroom found worldwide in grassy areas. Agaricus xanthodermus has an odor reminiscent of phenol; its flesh turns yellow when bruised. This fungus causes nausea and vomiting in some people.

The poisonous Entoloma sinuatum has a passing resemblance but has yellowish gills turning pink and lacks a ring.

Cultivation

Agaricus bisporus being cultivated.

Cultivation of Agaricus bisporus originated in France, when agriculturist Olivier de Serres noted that transplanting mushroom mycelium would lead to more mushrooms. Originally, cultivation was unreliable as mushroom growers would watch for good flushes of mushrooms in fields before digging up the mycelium and replanting in beds of composted manure or inoculating 'bricks' of compressed litter, loam and manure. Spawn collected this way contained pathogens and crops would be commonly infected or not grow at all.^[8]

In 1893 sterilised, or pure culture, spawn was discovered and produced by the Pasteur Institute in Paris.^[9] Today's commercial variety of the common mushroom was originally a light brown color. In 1926, a Pennsylvanian mushroom farmer found a clump of common mushrooms with white caps in his mushroom bed. Like white bread it was seen as a more attractive food item and was very popular.^[10] As was done with the navel orange and Red Delicious apple, cultures were grown from the mutant individuals, and most of the cream-colored store mushrooms we see today are products of this chance natural mutation.

Agaricus bisporus is now cultivated in at least 70 countries around the world.^[1]

Nutritional and medicinal value

Results of an enzyme assay conducted with Agaricus bisporus and the enzyme aromatase.^[11][12]

The common mushroom contains high amounts of Vitamin D^[13] (especially when UV-irradiated^[14][15]) and B vitamins.^[16] It also contains sodium, potassium, and phosphorus.^[16] Agaricus bisporus also contains conjugated linoleic acid^[17] and antioxidants.^[18]

A clinical trial is scheduled to take place at the City of Hope National Medical Center due to earlier research indicating that the common mushroom can inhibit aromatase, and therefore may be able to lower estrogen levels in the human body^[12], which might reduce breast cancer susceptibility.^{[11] [19]} In 2009, a case control study of over 2000 women, correlated a large decrease of breast cancer incidence in women who consumed mushrooms. Women in the study who consumed fresh mushrooms daily, were 64% less likely to develop breast cancer, while those that combined a mushroom diet with regular green tea consumption, reduced their risk of breast cancer by nearly 90%.^[20]

The table mushroom has also been shown to possess possible immune system enhancing properties. An in vitro study demonstrated the mushroom enhanced dendritic cell function.^[21][22]

Research at the Jikei University School of Medicine found that fresh A. bisporus contains small amounts of carcinogenic hydrazine derivatives, including agaritine and gyromitrin.^[23] However, this research also noted when cooked, these compounds were reduced significantly.^[24]

Agaricus bisporus gallery

Portobello mushrooms

Cross-section of a portobello cultivar

Ventral view of a portobello cultivar with a bissected stipe

Two Agaricus bisporus mushrooms which have fused together.

See also

Fungi portal

• Fungiculture
• List of Agaricus species
• Medicinal mushrooms
• Effect of sunlight on mushrooms

Notes

References

• Benjamin, Denis R. (1995). Mushrooms: poisons and panaceas — a handbook for naturalists, mycologists and physicians. New York: WH Freeman and Company. ISBN 0-7167-2600-9. 
• Genders, Roy (1969). Mushroom Growing for Everyone. London: Faber. ISBN 0-571-08992-5. 
• Kuo, M. (2004, January). Agaricus bisporus: The common mushroom Retrieved from the MushroomExpert.Com Web site: [1]
• City of Hope Research[2]

External links

Wikimedia Commons has media related to: Agaricus bisporus

Wikispecies has information related to: Agaricus bisporus

• Complete common mushroom nutrition info
• Mushroom cookbook and information
• Information about a human study with Agaricus bisporus taking place at the City of Hope.