Agaricus

Agaricus
A. campestris
Scientific classification
Kingdom:	Fungi
Phylum:	Basidiomycota
Subphylum:	Agaricomycotina
Class:	Agaricomycetes
Order:	Agaricales
Family:	Agaricaceae
Genus:	Agaricus L.:Fr. emend Karst.
Type species
Agaricus campestris L.:Fr.
Species
List of Agaricus species

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Agaricus is a large and important genus of mushrooms containing both edible and poisonous species, with possibly over 300 members worldwide^[1][2]. The genus includes the common ("button") mushroom (Agaricus bisporus) and the field mushroom (Agaricus campestris), the dominant cultivated mushrooms of the West.

Members of Agaricus are characterized by having a fleshy cap or pileus, from the underside of which grow a number of radiating plates or gills on which are produced the naked spores. They are distinguished from other members of their family, Agaricaceae, by their chocolate-brown spores. Members of Agaricus also have a stem or stipe, which elevates the pileus above the object on which the mushroom grows, and a partial veil, which protects the developing gills and later forms a ring or annulus on the stalk.

Taxonomy

For many years members of the genus Agaricus were given the generic name Psalliota, and this can still be seen in older books on mushrooms. All proposals to conserve Agaricus against Psalliota or vice versa have so far been considered superfluous.^{[citation needed]}

Several origins of Agaricus have been proposed; It possibly derives "from Agarica of Sarmatica, a district of Russia" (!).^{[citation needed]} Note also Greek ἀγαρικ^[3] όν "a sort of tree fungus" (There's been an Agaricon Adans. genus, treated by Donk in Persoonia 1:180)

Donk reports Linnaeus' name is devalidated (so that the proper author citation apparently is "L. per Fr., 1821") because Agaricus was not linked to Tournefort's name (Linnaeus places both Agaricus Dill. and Amanita Dill. in synonymy), but truly a replacement for Amanita Dill., which would require that A. quercinus, not A. campestris be the type. This question compounded by the fact that Fries himself used Agaricus roughly in Linnaeus' sense (which leads to issues with Amanita), and that A. campestris was eventually excluded from Agaricus by Karsten and was apparently in Lepiota at the time Donk wrote this, commenting that a type conservation might become necessary.^[4]

The alternate name for the genus, Psalliota, derived from the Greek psalion/ψάλιον, "ring", was first published by Fries (1821) as trib. Psalliota. The type is Agaricus campestris (widely accepted, except by Earle, who proposed A. cretaceus). Paul Kummer (not Quélet, who merely excluded Stropharia) was the first to elevate the tribe to a genus. Psalliota was the tribe containing the type of Agaricus, so when separated, it should have caused the rest of the genus to be renamed, but this did not happen. It seems to be currently not considered valid, or a junior homotypic synonym, anyway the explanation is that it was raised by (in retrospect) erroneously maintaining the tribe name.^[4]

Phylogenetics

The use of phylogenetic analysis to determine evolutionary relationships amongst Agaricus species has increased our understanding of this taxonomically difficult genus, although there remains much work to be done to fully delineate infrageneric relationships. Prior to these analyses, the genus Agaricus, as circumscribed by Rolf Singer (1986), was divided into 42 species grouped into five sections based on reactions of mushroom tissue to air or various chemical reagents, as well as subtle differences in mushroom morphology.^[5] Restriction fragment length polymorphism analysis demonstrated that this classification scheme needed revision.^[6]

Sections

This genus is divided into several sections:

• Section Agaricus
• Section Arvense Konrad & Maubl.

Contains 19 species in six subgroups similar to the horse mushroom, A. arvensis, and with versatile heterothallic life cycles.^[7]

• Section Xanthodermatei

Outlined by Singer in 1948, this section includes species with various characteristics similar to the type species A. xanthodermus.^[8] The section forms a single clade based on analysis of ITS1+2.^[9]

• Section Chitonioides
• Section Sanguinoletti
• Section Spissicaules (Hainem.) Kerrigan
• Section Duploannulatae

Based on DNA analysis of ITS1, ITS2, and 5.8S sequences, the section Duploannulatae (also known as section Hortenses) may be divided into six distinct clades, five of which correspond to well-known species from the temperate Northern Hemisphere: A. bisporus, A. subfloccosus, A. bitorquis, A. vaporarius and A. cupressicola. The sixth clade comprises the species complex A. devoniensis.^[10]

Edibility

The genus contains the most widely consumed and best known mushroom today, Agaricus bisporus, with A. campestris also well known. The most notable inedible species is the yellow-staining mushroom A. xanthodermus.^{[citation needed]} All three are found worldwide.

One species reported from Africa, A. aurantioviolaceus, is reportedly deadly poisonous.^{[citation needed]}

See also

Fungi portal

List of Agaricus species

Footnotes

External links

• MycoKey - The Genus Agaricus
• Mushroom Expert - The Genus Agaricus
• Varieties of California, USA on MYKOWEB .com
• Agaricus page at Index Fungorum
• On-line nomenclature of Agaricus from Royal Botanic Garden, Madrid. CSIC

• Multilingual taxonomic information from the University of Melbourne