COMMON MUSHROOM: CHARACTERISTICS, PROPERTIES, REPRODUCTION - BIOLOGY - 2025

The common mushroom (Agaricus bisporus) is a fungus of the Basidiomycota division that is characterized, among other aspects, by presenting a rounded whitish carpophor and a large number of lamellae in the hymenium. The latter is protected by a veil that is broken when the fungus reaches its full development.

This is the species of mushroom with the highest production worldwide, due not only to its pleasant taste, but also to the nutritional and medicinal properties it possesses, highlighting that it is low in carbohydrates and rich in B vitamins, potassium, iron, copper and selenium.

Agaricus bisporus. Source: pixabay.com

In addition, it contains substances that can act as aromatase inhibitors, which is why it helps to prevent breast cancer in menopausal women, to keep the prostate healthy, as well as to boost the immune system thanks to its beta-glucans.

The common mushroom has saprophytic habits, therefore it can be cultivated in compost bins. Under these growing conditions, Agaricus bisporus can be attacked by some pathogens and pests, such as Mycogone perniciosa, Pseudomonas spp, and various species of flies.

characteristics

The hat of Agaricus bisporus is initially globose, but later changes to concave or slightly flattened. This hat can reach up to 18 cm in diameter, but generally does not exceed 13 cm. Its surface is covered by a powdery cuticle in which scales and spots can appear with age.

The hymenium (structure that contains the basidia), has numerous lamellae that are not attached to the foot. These lamellae are fleshy and pale white or pink in color, but then turn dark brown or black at maturity.

The basidia are marginal and bisporic, rather than tetrasporic as is normally the case in the genus Agaricus. The spores are brown to slightly purple in color, elliptical to ovoid in shape, smooth and with a size that ranges between 5 and 8 by 4 and 6 microns.

It has a simple and membranous, ascending ring, which in its youth is attached to the bell and is persistent in the middle or lower part of the foot at maturity. It lacks volva.

The foot of Agaricus bisporus is smooth, fibrous, cylindrical, with a height of up to 8 cm long and a diameter of 3 cm, easily removable from the hat.

Taxonomy

The genus Agaricus belongs to the Agaricaceae family, class Agaricomycetes of the Basidiomycota. It was described by Carlos Linneo in 1735, to include a great diversity of terrestrial fungi provided with lamina and foot. This name was renamed Pratella and later Psalliota.

Currently this genus contains more than 300 species worldwide, some of which, including the common mushroom, are edible, but others are very poisonous. The species Agaricus bisporus was described by the Danish mycologist JE Lange and currently has some varieties.

The most commercialized variety is A. bisporus var hortensis, which has a white coloration throughout its surface, with some pink hues in its flesh. Agaricus bisporus var brunnescens is the variety marketed under the names of portobello or crimini, depending on its size and stage of development.

Commercial importance

The common mushroom is the species with the highest production in the world among cultivated species, with estimated annual volumes of more than 4 million tons for 2009. The main producers are China and France.

These volumes, however, should be underestimated due to the ease of cultivation and low space requirements for it.

Artisan cultivation

The common mushroom is easy to grow if its demands for light, humidity, nutrients and temperature are properly controlled. It can be grown in small gardens isolated from sunlight, and even in sacks or boxes. The spores can be purchased in specialized stores.

The interested person can prepare a compost with abundant decomposing organic matter, being horse manure a good compound for this activity. It should be kept moist but not excessively moist, to avoid the proliferation of other unwanted organisms. It also cannot receive sunlight.

Natural enemies

Different organisms act as pathogens or pests of the common mushroom. Among the pathogens are bacteria, as well as fungi and related groups. In turn, its main pests are made up of insects.

Pathogens

The main disease that attacks Agaricus bisporus is called dry bubble and is caused by various species of the genus Verticillum. The vectors are rodents, insects, and humans.

Mycogone perniciosa is one of the most frequent pathogens, which produces the disease called wet bubble or mole, which causes the internal rot of the fungus.

Other pathogens to highlight are Trichoderma spp., Dactylium spp., Diehliomyces spp., Pseudomonas tolaasii and P. aeruginosa.

Pests

The main pests that affect Agaricus bisporus are flies belonging to the species Lycoriella mali, as well as several species of Megaselia and Mycophila. These insects feed on the fungus and can leave necrotic areas at the attack site and in the drill galleries.

Some species of nematodes can feed on the mycelium of the fungus. Mites can also affect the mushroom, and they can be seen as a reddish powder on the mushroom cap when they are concentrated in that area.

Early and juvenile stages of Agaricus bisporus. Taken and edited from: This image was created by user IG Safonov (IGSafonov) at Mushroom Observer, a source for mycological images.You can contact this user here.English - español - français - italiano - македонски - português - +/−

Nutritional properties

Mushrooms are characterized by being very low in carbohydrates, which is why they contribute very few calories to the diet (less than 30 kcal per 100 grams). They are also low in fat, fiber, and protein.

Instead they are rich in minerals, such as potassium, which helps in nerve transmission and the flow of nutrients in the body; magnesium, which improves cardiovascular health and controls constipation, and selenium, with anti-cancer properties. It also has iodine, phosphorus, calcium and zinc.

In addition, it contains vitamins A, complex B (B2, B3, B1 and folic acid), C, D and E. For all this, mushrooms are good for losing weight, they increase the body's defenses, help to control the levels of sugar in the blood, have antioxidant, diuretic, hepatoprotective and antianemic properties.

Frequent consumption of mushrooms helps to avoid the effects of free radicals, migraines and fluid retention. It also prevents the growth and proliferation of cancer cells and helps regulate intestinal transit and preserve healthy skin, hair and nails.

Aqueous extracts of carpophores have shown anticancer properties, preventing up to 100% the proliferation of some types of cancer cells in laboratory studies. The mushroom also contains agarithin, a compound with proven carcinogenic properties.

However, the amounts of such a compound in mushrooms are so low that it would be necessary to consume 350 grams of fresh mushrooms daily for a period of 50 years, for the risk of developing tumors to be significant.

Reproduction

Basidomycetes in general exhibit both sexual and asexual reproduction. Sexual reproduction involves the formation of basidiospores. In the latter type, only one parent (homothalic, pseudohomothal) can intervene or more than one intervene (heterothalic).

Asexual reproduction

In Agaricus bisporicus, as in the rest of the basidomycetes, asexual reproduction can occur by fragmentation of the mycelium.

Sexual reproduction

Sexual reproduction in the common mushroom can vary slightly depending on the variety in question. Three taxa are amphiphallic, that is, both heterothallic and pseudohomothallic. The reproductive cycle of Agaricus bisporus var. bisporus is amphiphallic with a predominance of pseudohomotalism.

In that subspecies or variety, a sporophor produces a majority of heterokaryotic spores and a small percentage of homokaryotic spores. In A. bisporus var. burnettii, contrary to the previous one, there is a predominance towards pseudohomotalism, where the spores are mostly homokaryotic.

Agaricus bisporus var. eurotetrasporus is homothalic. The mycelium and sporophor are haploid, fusion of gametic nuclei and meiosis take place in the basidium from identical nuclei.

Spores of the common mushroom Agaricus bisporus. Taken and edited from: Dartmouth Electron Microscope Facility, Dartmouth College.

Lifecycle

A basidiospore germinates to produce a haploid primary mycelium, then a pair of mycelia of a different reproductive type (or two hyphae of a mycelium if it is a homothalic variety) fuse and a secondary mycelium is obtained in which karyogamy does not occur.

The secondary mycelium grows in the soil and when conditions are optimal, it develops the fruiting body that emerges from the soil. This fruiting body (carpophor) is formed by the foot and the cap or crown. At the bottom of the hat is the hymenium with hundreds of lamellae, where the basidia will line up.

After a few days, the two nuclei of each basidium fuse to produce a diploid zygote, which rapidly undergoes meiosis to form haploid spores. Two spores will be produced in each basidium, which is characteristic and gives rise to the name of the species.

Nutrition

Agaricus bisporus is a saprophytic species and it feeds on decomposing organic matter, for which it releases a series of enzymes that allow it to digest said organic matter and then absorb it. In cultivation, this type of feeding of the fungus is used by growing it directly in compost bins.

A combination that is suitable for growing these mushrooms contains oat straw, barley or wheat, sawdust, sandy soil and horse manure.

References

1. Agaricus bisporus. On Wikipedia. Recovered from: en.wikipedia.org.
2. MA Calvo Torras, M. Rodríguez & L. Domínguez (2011). Agaricus bisporus: cultivation, problems and prevention. Annals of the Royal Academy of Doctors of Spain.
3. SP Wasser (2000). A contribution to the taxonomy and species diversity of the Agariceae tribe (Higher Basidiomycetes) of Israel mycobiota. Mediterranean Flora.
4. Mushroom. In Educational Nature. Recovered from: natureduca.com.
5. W. Breene (1990). Nutritional and medicinal value of special mushrooms. Journal of Food Products.
6. G. Mata, R. Medel, P. Callac, C. Billette & R. Garibay-Orijeld (2016). First record of wild Agaricus bisporus (Basidiomycota, Agaricaceae) in Tlaxcala and Veracruz, Mexico. Mexican Journal of Biodiversity.
7. V. Gómez. Basidiomycetes: characteristics, nutrition, habitat and reproduction. Recovered from lifeder.com.