BOLETUS: CHARACTERISTICS, CLASSIFICATION, HABITAT, SPECIES - BIOLOGY - 2025

Boletus is a genus of Basidiomycota fungi of the Boletaceae family that is characterized by presenting a fruiting body with its internal part (context) white or pale yellow, yellow-brown or green-brown spores and smooth surface, reticulated foot and base. enlarged, with a mantle that covers the pores of the tubes of immature organisms.

Until recent years, mycologists had included within this genus more than 300 species of fungi that were characterized by presenting pores instead of sheets in the hymenium. However, recent studies showed that the genus was polyphyletic, for which it was redefined and most of the species were relocated to other genera.

Boletus edulis. Taken and edited from: H. Krisp.

They are widely distributed and all of them form mycorrhizal-type associations with different plant species. These are mutualistic symbiotic associations, that is, they provide benefits to both the fungus and the plant involved in the relationship.

The genus has more than 100 species of fungi, some of which are edible, while others are not. Among the edible species are the famous porcini mushrooms, while among the inedible species there are some poisonous and others simply unpleasant in taste.

Edible species not only taste good, but also provide significant amounts of vitamins, essential amino acids, minerals, fiber, and some even have medicinal properties that strengthen the immune system and help prevent some diseases.

characteristics

Boletus are mushrooms with a fruiting body in the shape of a mushroom, with a well developed hat and fleshy foot. The hat is generally small, although exceptionally it can reach about 35 centimeters in diameter in some species. Its shape can be hemispherical in young specimens to convex in adults.

A defining characteristic of the gender (although it is not exclusive to it) is the presence of a hymenium composed of tubes of light colors and joined together. The tubes, in older organisms, open to the outside through pores that present various shapes, being able to present angles or be circular or elliptical.

In younger organisms the pores of the hymenium are covered by a mantle. The tubes of the hymenium form a more or less compact tissue and generally easy to separate from the flesh of the hat.

The cuticle presents varied colors, but generally nuanced, with a smooth texture and devoid of volva remains.

The foot or stipe is fleshy and can measure up to 12 cm, but it generally has a little less than half this length, and its diameter can be up to 5 cm. It is generally cross-linked and ring-free.

In some species the stipe may be widened and even as wide as the cap, with the fungi acquiring a plump appearance.

The spores are generally smooth and yellow-brown or greenish-brown in color.

All species of the genus form ectomycorrhiza-like associations with various plant species.

Taxonomy

Boletus is a genus of Basidiomycota fungi belonging to the Boletales order and the Boletaceae family. The fungi of this family are characterized by the lack of laminae and the hymenium is made up of tubes that open through pores.

The genus was described by Linnaeus in 1753 to contain all the fungi that possessed pores rather than laminae in the hymenium, however, this feature proved over time that it was not enough to define the genus, which is why it had become a polyphyletic group, made up of more than 300 species.

Recently, and thanks to molecular biology and phylogenetic studies, the genus was circumscribed and about two thirds of the species were rearranged into other genera.

The genus Boletus, in its strict sense, was thus formed by fungi, which in addition to presenting pores instead of laminae in the hymenium, have them covered by a mantle in juvenile organisms and their stipe is reticulated and widened at the base.

Among the new and / or resurrected genera to relocate the excluded species of Boletus are for example: Suillus, Xerocomus, Leccinum, Tylopilus, Baorangia, Buchwaldoboletus, Butyriboletus, Caloboletus, Hemileccinum. Imleria and Rubroboletus.

Traditionally, mycologists divided the genus into the following sections:

Edules Section

It contains edible species and a sweet taste, with the reticulated stem on the upper part and the white pores of the hymenium, for example Boletus edulis, B. pinophilus, B. aereus and B. reticulatus.

Calopodes Section

The species in this section have yellow pores and in some of them the flesh turns blue when cut due to the presence of a substance called boletol. Its taste is bitter. For example Boletus calopus and B. radicans.

Appendiculati section

Like the mushrooms in the Calapodes section, those in this section have yellow pores and some may turn blue when cut, but this blue is less intense. Its flavor is sweet. Examples: Boletus appendiculatus, B. regius and B. flesneri, among others.

Fragrant Section

Species with very intense yellow pores, some capable of secreting bullet. The foot is not reticulated. Some species can turn blue when touched. Both its taste and its smell are pleasant. Among the species located in this section are Boletus fragans (currently Lanmaoa fragans) and B. aemilli.

Satan Section

It includes poisonous species, with red pores and a whitish to pink hat, which do not turn blue when touched but when cut. Some of the species in this section, such as Boletus satanas, have been relocated to other genera.

Luridi Section

Mushrooms with webbed feet, red pores, and leathery brown hat that turns blue when touched, but then turns black. For example, Boletus luridus, B. torosus and B. purpureus, among others.

Erythropodes Section

They have red or yellow pores and non-reticulated foot, such as Boletus erythopus and B. queleti, for example.

Boletus aereus. Taken and edited from: Roberto1974.

Classification according to use (types of

Boletus species can be classified for utilitarian purposes into two large groups, edible and inedible. Edible species include some of the most popular mushrooms in international cuisine.

Its flavor, in most cases, is slightly smoky and some species also give off a very attractive smell. Boletus edulis, the main representative of this group, has been classified as the wild mushroom par excellence by prestigious international chefs.

Among the inedible species, some of them are considered as such due to their unpleasant taste, generally very bitter. However, there are also species that present some degree of toxicity. Although it is true that none of them are considered fatal, they can cause very strong intestinal discomfort.

Habitat and distribution

Boletus species are adapted to thrive in different types of soil, although they show a certain predilection for acid soils with high moisture content. They are abundant in coniferous forests and in deciduous forests of species such as oak, beech and chestnut.

Because they establish mycorrhizae with different tree species, they do not develop in arid areas or in mountainous areas devoid of arboreal vegetation.

They have representatives in practically all countries worldwide, however, they are more common in the northern hemisphere, both in America, as well as in Europe and Asia.

Nutrition

All Boletus species establish ectomycorrhizal mutualistic associations with tree roots. These are associations in which the mycelium of the fungus produces a highly branched network of hyphae that will grow around the roots of the trees, forming a structure called the mantle.

This mantle projects hyphae towards the roots of the plant that do not penetrate into the root cells, but do grow between them, forming a structure that is called the Hartig network. In this network, the exchange of water, nutrients and other substances between both members of the association will occur.

Poisonous species

Boletus satanas

Known by the name of Satan's boletus, it is the species of Boletus considered with the highest toxicity. Currently this species has been relocated to the genus Rubroboletus. When eaten raw it causes severe gastrointestinal disturbances, without being fatal in any case. After cooking it loses toxicity but is still indigestible.

This species is typical of temperate regions of Europe and probably North America, where it preferably thrives in limestone soils of deciduous forests. It is characterized by presenting a hat of up to 30 cm, initially hemispherical and then convex.

Hymenium pores are originally yellow, turning orange and then red as the fungus matures. The foot is short and plump in appearance, red in color that turns blue when touched.

The species Rubroboletus dupainii, R. legaliae, R. lupinus, R. pulchrotinctus, R. rhodoxanthus, R. rubrosanguineus that were previously located in the genus Boletus, are all also toxic and cause gastrointestinal disorders.

Boletus rubroflammeus

Its consumption produces gastrointestinal disorders. This species, native to the eastern United States and Mexico, grows in mycorrhizal association with trees from wooded areas, such as conifers. It has a dark red or purple hat up to 12 centimeters in diameter and is strongly convex.

The pores are also dark red. The foot is up to 6 cm long by 2 in diameter, it is covered almost entirely with dark red reticulations. All mushrooms can quickly turn blue when touched or cut.

Boletus luteocupreus

Currently called Imperator luteocupreus. It has a velvety cuticle, yellow or orange in color that over time acquires purple tones. The pores are yellow to reddish and turn blue to the touch. The foot is swollen, reticulated reddish and purple-red near the base.

Other species of toxic Boletus that have been relocated to the genus Imperator are Boletus rhodopurpureus and Boletus torosus.

Edible species

Boletus edulis

This species is one of the wild mushrooms most appreciated by international haute cuisine. It receives several common names, including porcini mushroom and pumpkin mushroom. The hat can measure up to 20 cm in diameter and its long stipe can reach this same length.

The cap is fleshy, solid, initially hemispherical in shape and then convex; its initial coloration is more or less dark brown, with a lighter edge, the colors darken slightly as the organism ages.

The pores are closed in young organisms and are white or slightly grayish in color. When opened they are yellow and then turn greenish.

This species forms ectomycorrhizae with pine trees. Its flavor is reminiscent of hazelnuts and is consumed both fresh and canned.

Boletus pinophilus

Species eaten raw, cooked, fresh or dried, with a pleasant smell. It is a robust and large mushroom, with a cap that reaches 30 cm in diameter, hemispherical at first and then becomes convex or somewhat flattened. The margins are flat or somewhat curved.

The cuticle is smooth, very slightly velvety. It does not separate easily from the meat, its color is mahogany or reddish brown and it does not turn blue when touched.

The stem can be thicker than the hat, especially in younger specimens, with a light yellow color that later turns reddish-brown.

The tubes are white, detachable, turning yellow or olive green. The pores are initially closed and are whitish in color and when opened they acquire a greenish-yellow color.

This species forms mycorrhizae with different species of trees, mainly pine and beech.

Boletus reticulatus

Common European species in deciduous forests throughout the continent, where it forms mycorrhizal associations with oaks. It is particularly abundant in France. It receives the common name of reticulated boleto or summer boleto, the latter name because the fruiting bodies emerge during the summer months.

The hat can exceed 35 cm in diameter, covered by a uniform and velvety dark brown cuticle, with a bulbous, swollen stem, which can exceed the diameter of the hat, without a ring.

The meat is white and thick, firm and with a pleasant aroma. This species is attacked by various species of insects that feed on its meat. The spores are olive green in color.

Boletus coniferarum. Taken and edited from: Ron Pastorino (Ronpast).

Boletus aereus

Pleasant tasting mushroom that grows in North America, as well as in central and southern Europe. The fruiting body appears between autumn and summer, in forests of species such as oak, chestnut, holm oak, among others.

The hat is convex slightly flared, with measurements that can reach 20 cm in diameter, dark brown in color, while the foot is lighter and can measure up to 8 cm long by 1.5 in diameter.

References

1. ME Nuhn, M. Binder, AFS Taylor, RE Halling & DS Hibbett (2013). Phylogenetic overview of the Boletineae. Mycological Research.
2. Boletus. On Wikipedia. Recovered from: en.wikipedia.org.
3. Boletus. In Mycological files. Recovered from: amanitacesarea.com.
4. Characteristics: biology, ecology, uses, cultivation. In Wild edible fungi a global overview of their use and importance to people. Recovered from: fao.org.
5. JM Martínez. Main edible and toxic species of Boletus SL (3/3). Recovered from: Cestaysetas.com.
6. Boletaceae. On Wikipedia. Recovered from. en.wikipedia.org.
7. C. Lyre. Ectomycorrhizae and endomycorrhizae. Recovered from: lifeder.com.