Boletus edulis (English: cep, penny bun, porcino) is a basidiomycete fungus, and the type species of the genus Boletus. It is prized as an edible mushroom.
The fungus produces spore-bearing fruit bodies above ground in summer and autumn. The fruit body has a large brown cap which can reach in diameter and in weight. Like other boletes, it has tubes extending downward from the underside of the cap, rather than gills; spores escape at maturity through the tube openings (pores). The pore surface of the fruit body is whitish when young, aging to a greenish-yellow. The stout stipe (or stem) is white or yellowish, up to tall and thick, and partially covered with a raised network pattern (reticulations).
The fungus grows in deciduous and coniferous forests and tree plantations, forming symbiotic ectomycorrhizal associations with living trees by enveloping the tree's underground roots with sheaths of fungal tissue. Widely distributed in the Northern Hemisphere across Eurasia and North America, it does not occur naturally in the Southern Hemisphere but has been introduced to it. Several closely related European mushrooms formerly thought to be varieties or forms of B. edulis have been shown using molecular phylogenetic analysis to be distinct species, while others previously classified as separate species are conspecific with B. edulis. The western North American species commonly known as the California king bolete (B. edulis var. grandedulis) is a large, darker-coloured variant first formally identified in 2007.
B. edulis is held in high regard in many cuisines and is commonly prepared and eaten in soups, pasta, or risotto. The mushroom is low in fat and digestible carbohydrates, while being high in protein, vitamins, minerals and dietary fibre. Although it is sold commercially, it is very difficult to cultivate. Available fresh in autumn throughout Europe and Russia, it is most often dried, packaged, and distributed worldwide. It keeps its flavour after drying and is then reconstituted and used in cooking. B. edulis is also one of the few fungi sold pickled.
Taxonomy
Boletus edulis was first described in 1782 by the French botanist Pierre Bulliard and still bears its original name. The starting date of fungal taxonomy had been set as January 1, 1821, to coincide with the date of the works of the 'father of mycology', Swedish naturalist Elias Magnus Fries, which meant the name required sanction by Fries (indicated in the name by a colon) to be considered valid, as Bulliard's work preceded this date. It was thus written Boletus edulis Bull.:Fr. A 1987 revision of the International Code of Botanical Nomenclature set the starting date at May 1, 1753, the date of publication of Carl Linnaeus' Species Plantarum. Hence, the name no longer requires the ratification of Fries' authority. Early alternate names include Boletus solidus by English naturalist James Sowerby in 1809, This entire work is available in Commons here, but the reference is to plate 419 with textual description on page 697. Sowerby described the same modern species as B. edulis on plate 111 (description on page 57). and Gray's Leccinum edule. Gray's transfer of the species to Leccinum was later determined to be inconsistent with the rules of botanical nomenclature, and he apparently was unfamiliar with the earlier works of Fries when he published his arrangement of bolete species.
Boletus edulis is the type species of the genus Boletus. In Rolf Singer's classification of the Agaricales mushrooms, it is also the type species of section Boletus, a grouping of about 30 related boletes united by several characteristics: a mild-tasting, white flesh that does not change colour when exposed to air; a smooth to distinctly raised, netted pattern over at least the uppermost portion of the stem; a yellow-brown or olive-brown spore print; white tubes that later become yellowish then greenish, which initially appear to be stuffed with cotton; and cystidia that are not strongly coloured. Molecular analysis published in 1997 established that the bolete mushrooms are all derived from a common ancestor, and established the Boletales as an order separate from the Agaricales.
The generic name is derived from the Latin term bōlētus "mushroom", which was borrowed in turn from the Ancient Greek βωλίτης, "terrestrial fungus". Ultimately, this last word derives from bōlos/βῶλος "lump", "clod", and, metaphorically, "mushroom". The βωλίτης of Galen, like the boletus of Latin writers like Martial, Seneca and Petronius,Peter Howell, A Commentary on Book One of the Epigrams of Martial, The Athlone Press, 1980 p.152-3. Howell doubts the identification, and mentions the view advanced by Augusta A. Imholtz Jr., 'Fungi and piace- names, thè origin of boletus,' in AJP Vol.98, 1977 pp.71f., that the Latin word may derive from the Spanish town Boletum, modern-day Boltaña, south of the Pyrenees, which is still famous for its mushrooms. is often identified as the much prized Amanita caesarea. The specific epithet edulis in Latin means "eatable" or "edible".
Common names Common names for B. edulis vary by region. The standard Italian name, porcino (pl. porcini), means porcine; fungo porcino, in Italian, echoes the term suilli, literally "hog mushrooms", a term used by the Ancient RomansPliny, Natural History, Bk. 16, 11, 31: "Such is the multiplicity of products in addition to the acorn that are borne by hard-oaks; but they also produce edible fungi (boletos) and hog mushrooms (suillos)." Pliny, Natural History, 10 vols., tr. H. Rackham, Harvard University Press/Heinemann, (1945) 1968, vol. 4, pp. 408–409. and still in use in southern Italian terms for this species.Neapolitan sillo, and Calabrian sillu/siddu. See Glauco Sanga, Gherardo Ortalli, Nature knowledge: ethnoscience, cognition, and utility, Berghahn Books, 2003 p. 78. The derivation has been ascribed to the resemblance of young fruit bodies to piglets, or to the fondness pigs have for eating them.Carluccio, pp. 36–38. It is also known as "king bolete". The English penny bun refers to its rounded brownish shape.
The German name Steinpilz (stone mushroom) refers to the species' firm flesh. (online ) In Austria, it is called Herrenpilz, the "noble mushroom", while in Mexico, the Spanish name is panza, meaning "belly". Another Spanish name, rodellon, means "small round boulder", while the Dutch name eekhoorntjesbrood means "squirrel's bread". Russian names are belyy grib (:ru:белый гриб; "white mushroom" as opposed to less valuable "black mushrooms") and borovik (:ru:боровик; from bor—"pine forest"). The vernacular name cep is derived from the Catalan cep or its French name cèpe, although the latter is a generic term applying to several related species. In France, it is more fully cèpe de Bordeaux, derived from the Gascon cep "trunk" for its fat stalk, ultimately from the Latin cippus "stake". Ceppatello, ceppatello buono, ceppatello bianco, giallo leonato, ghezzo, and moreccio are names from Italian dialects, and ciurenys or surenys is another term in Catalan. The French-born King Charles XIV John popularised B. edulis in Sweden after 1818, and is honoured in the local vernacular name Karljohanssvamp, as well as the Danish name Karl Johan svamp. The monarch cultivated the fungus about his residence, Rosersberg Palace.
Description
The cap of this mushroom grows up to wide, sometimes more. Viscid when moist, the cap is convex when young and flattens with age. The colour is generally reddish-brown, sometimes with a paler margin. The stipe grows up to tall and thick—rather large in comparison to the cap. The stem is usually enlarged at the base when young, becoming more cylindrical in age. It is finely reticulate on the upper portion or sometimes the whole. The flesh of the stem is sometimes dark yellow near the base.
The undersurface of the cap consists of thin tubes, the site of spore production; they are deep, and whitish in colour when young, but mature to a greenish-yellow. The angular pores, which do not stain when bruised, are small—roughly 2 to 3 pores per millimetre. In youth, the pores are white and appear as if stuffed with cotton (which are actually mycelia); as they age, they change colour to yellow and later to brown. The spore print is olive brown. The flesh of the fruit body is white, thick and firm when young, but becomes somewhat spongy with age. When bruised or cut, it either does not change colour, or turns a very light brown or light red. Mature specimens can weigh about . A huge specimen collected on the Isle of Skye, Scotland, in 1995 weighed ; its cap was wide and the stipe was tall and wide. A similarly sized specimen found in Poland in 2013 made international news.
The spores are elliptical to spindle-shaped, with dimensions of 12–17 by 5–7 μm. The basidia, the spore-bearing cells, are produced in a layer lining the tubes, and arrange themselves so their ends are facing the center of the tube; this layer of cells is known technically as a hymenium. The basidia are thin-walled, mostly attached to four spores, and measure 25–30 by 8–10 μm. Another cell type present in the hymenium is the cystidia, larger sterile cells that protrude beyond the basidia into the lumen of the hymenium and act as air traps, regulating humidity. B. edulis has pleurocystidia (cystidia located on the face of a pore) that are thin-walled, roughly spindle-shaped to ventricose, and 30–45 by 7–10 μm; the "stuffed" feature of the hymenium is caused by cheilocystidia—cells found on the edges of the pores. The hyphae of B. edulis do not have clamp connections.
Similar species
Boletus edulis is considered one of the safest wild mushrooms to pick for the table, as few poisonous species closely resemble it and those that do may be easily distinguished by careful examination. The most similar poisonous mushroom may be the devil's bolete (Rubroboletus satanas), which has a similar shape, but has a red stem and stains blue on bruising. It is often confused with the very bitter and unpalatable Tylopilus felleus, but can be distinguished by the reticulation on the stalk; in porcini, it is a whitish, net-like pattern on a brownish stalk, whereas it is a dark pattern on white in the latter. Porcini have whitish pores while the other has pink. If in doubt, tasting a tiny bit of flesh will yield a bitter taste. It can also resemble the "bolete-like" Gyroporus castaneus, which is generally smaller, and has a browner stem. Boletus huronensis, an uncommon mushroom of northeastern North America, is another recognized look-alike known to cause severe gastrointestinal disorders.
Related species
Several similar brownish-coloured species are sometimes considered subspecies or forms of this mushroom. In Europe, in addition to B. edulis (or cèpe de Bordeaux), the most popular are: Cèpe bronzé ("dark cep"; Boletus aereus), much rarer than B. edulis, is more highly regarded by gourmets and consequently more expensive. Usually smaller than B. edulis, it is also distinctively darker in colour. It is especially suited to drying. Cèpe des pins ("pine tree cep"; Boletus pinophilus or Boletus pinicola) grows among pine trees. Rarer than B. edulis, it is less appreciated by gourmets than the two other kinds of porcini, but remains a mushroom rated above most others. Cèpe d'été ("summer cep"; Boletus reticulatus), also less common and found earlier.
Molecular phylogenetic analyses have proven these three are all distinctive and separate species; other taxa formerly believed to be unique species or subspecies, such as B. betulicola, B. chippewaensis, B. persoonii, B. quercicola and B. venturii, are now known to be part of a B. edulis species complex with a wide morphological, ecological and geographic range, and that the genetic variability in this complex is low. Similar molecular technology has been developed to rapidly and accurately identify B. edulis and other commercially important fungi.