Agaricus bisporus

Agaricus bisporus, commonly known as the Common Mushroom, Button Mushroom, White Mushroom, or Portobello Mushroom (depending on its stage of maturity), is one of the most widely consumed and cultivated edible mushrooms in the world. It is safe and well-regarded for consumption.

Physical characteristics

Cap
3-16 cm in diameter, globose then hemispherical to convex, sub-spreading to slightly depressed in the center with age, fleshy and thick, dry, slightly silky, ± fibrous-innate, with cuticle sometimes breaking into fine or large fibrous scales appressed, whitish, pale to moderate brown, rarely dark brown, on a white ground, coffee-au-lait to pale vinous, browning with age or on crumpling, margin strongly inrolled at first, long appendixed with a broadly toothed flaky band, often extending beyond the blades

Gills
free at maturity, narrow to wide, up to 12 mm, with lamellae, tight, pinkish to pale brown at first, then chocolate brown to purplish brown, dark blackish brown at the end, with slightly flaky edges, paler

Stem
2-8(10) x 1-3(4) cm, equal, broadened towards base or subbulbous, often stocky and thick, firm, stuffed-hollow, smooth to scaly-cottony below ring, white, becoming dark brownish with age or wrinkling

Partial veil
Fleshy-pulpy, cottony, leaving a median ring on the stipe, double, tufted, narrow but thick, with a serrated edge on the underside, often ridged above, loosely matted below, white, may sag against the stipe with age, rarely perennial with the universal veil.

Flesh
Thick, to 8-25 mm, moderately firm, whitish, often becoming brownish, pinkish-orange to reddish, especially near the pileal surface and laminae, when crumpled or cut, or dull with age, slightly to moderately reddening then browning in the foot.

Smell and flavor
sweet, pleasant, fungal to slightly fruity-spicy odor and pleasant flavor

Spore
chocolate brown, cocoa brown to purple-brown

Basidia
broadly clavate, clavate to cylindrical-clavate, broadly pedicellate, mostly with 2 pointed to narrowly acuminate sterigmata (2)3.5-7 µm long, uncurled at base, hyaline, 17-25 x (4)6.5 -5(9)µm

Spores
broadly ellipsoid, ellipsoid to obovate, obtuse at end, smooth, thickened wall, without distinct germ pore and with often prominent hilar appendage, guttulate, gray-brown to dark brown, (4.9)6.3-7.6(9 ) x (4.5)4.9-5.9(7.1) µm, 6.9 x 5.4 µm average

Cheilocystidia
forming an almost sterile lamellar ridge
scattered or in bundles, polymorphic, clavate, broadly clavate, clavate-truncated to cylindrical, sometimes cylindrical-fusiform, vesicular to spheropedunculate, often appressed, hyaline, (12)20-35 x 6-10.5 (12) µm

Pleurocystidia
absent

Pileipellis
In cutis formed of appressed, parallel hyphae, sometimes slightly erect, not curly, yellowish pigmented, 5-11 µm in diameter.

Mode of growth
Gregarious or cespitous.

Ecology
Saprotrophic in mushroom houses, pastures, on rich and smoky soils, composts, gardens, lawns, vacant lots, heaps of plant and tree litter, also often in forests.

Period
Mid-May to October.

Frequency
 Agaricus bisporus is highly prevalent due to its widespread cultivation and popularity as a food source. It is commercially grown in many countries, making it readily available in grocery stores and markets throughout the year. Its cultivation has made it a common and easily accessible mushroom species for consumers.

Habitat
In its natural habitat, Agaricus bisporus is found in grassy areas, meadows, and pastures. It has a symbiotic relationship with the roots of certain plants, especially grasses. The mushroom forms mycorrhizal associations with the plant roots, benefiting both the mushroom and the plant. Cultivation of Agaricus bisporus primarily occurs in controlled environments such as mushroom farms or cultivation facilities. The mushroom is typically grown on composted materials such as straw, horse manure, and other organic matter. The compost provides the necessary nutrients and environmental conditions for the mushrooms to grow. Agaricus bisporus cultivation involves specific temperature, humidity, and light conditions to mimic its natural habitat and ensure optimal growth. Commercial growers create controlled environments with appropriate temperature and humidity levels to promote mushroom formation. The mushrooms are typically grown in dark or low-light conditions.

Chemical reactions
Negative to KOH on the cap.

Edibility

Edible of choice cultivated, commercially sold and most consumed mushroom. Agaricus bisporus, is one of the most widely consumed and cultivated edible mushrooms in the world. It is safe and well-regarded for consumption.

Agaricus bisporus mushrooms are known for their mild flavor and versatility in a variety of culinary dishes, including salads, stir-fries, soups, and as a topping for pizzas and burgers. However, it's crucial to ensure that the mushrooms are properly cooked before consuming them, as raw or undercooked mushrooms may be difficult to digest and can cause digestive discomfort for some individuals.

When properly prepared, Agaricus bisporus mushrooms are a delicious addition to many recipes and are appreciated for their taste and texture. These mushrooms are readily available in most grocery stores and are commonly used in both home cooking and the restaurant industry.

Remarks

This agaric is characterized by its often spreading cap, with fibrils which break into fine then large scales, its free, tight gills, pinkish to pale brown at first, its well-developed median ring, its rufescent-browning flesh, its chocolate spore to purple-brown, its basidia with 2 sterigmata and its growth on rich or smoky soils, rarely in lawns.
It is the best-selling cultivated escaped mushroom in supermarkets.
It differs from A. show campestris by its initially globose, more brownish cap, paler lamellar ridges, well-developed annulus, more blushing-browning flesh, basidia with 2 sterigmata, and sparse growth in grass.
A. capellianus has a larger size, a more mechunous cap, an absence of marked browning and basidia with 4 sterigmata.
The genome of var. bisporus is sequenced.

Nutrition value

Agaricus bisporus, commonly known as white button mushrooms or champignon mushrooms, is a widely consumed edible mushroom. Here's the nutritional value of Agaricus bisporus per 100 grams:

• Calories: 22 kcal
• Carbohydrates: 3.3 grams
  • Dietary fiber: 1.0 grams
  • Sugars: 0.5 grams
• Protein: 3.1 grams
• Fat: 0.3 grams
  • Saturated fat: 0.1 grams
  • Monounsaturated fat: 0.0 grams
  • Polyunsaturated fat: 0.1 grams
• Cholesterol: 0 milligrams
• Sodium: 5 milligrams
• Potassium: 318 milligrams
• Vitamin C: 0.0 milligrams
• Calcium: 3 milligrams
• Iron: 0.5 milligrams
• Vitamin D: 0.0 micrograms
• Vitamin B6: 0.1 milligrams
• Magnesium: 9 milligrams

Agaricus bisporus is low in calories, fat, and carbohydrates, making it a suitable option for those who are watching their weight or have dietary restrictions. It also contains some dietary fiber, which can contribute to a healthy digestive system. In terms of vitamins and minerals, Agaricus bisporus is not particularly rich in any specific nutrient. However, it does contain small amounts of iron, potassium, vitamin B6, and magnesium. These nutrients play important roles in various bodily functions, such as oxygen transport, electrolyte balance, and energy metabolism. While Agaricus bisporus is not a significant source of vitamins C, D, or calcium, it is still a valuable addition to a balanced diet due to its low calorie and fat content, as well as its potential contribution to overall nutrient intake.

References

1.  Imbach EJ (1946). "Pilzflora des Kantons Luzern und der angrenzen Innerschweiz". Mitteilungen der naturforschenden Gesellschaft Luzern (in German). 15: 5–85.
2. Arora, David (1986). Mushrooms demystified: a comprehensive guide to the fleshy fungi (Second ed.). Berkeley: Ten Speed Press.
3. Cappelli A. (1984). Fungi Europaei:Agaricus (in Italian). Saronno, Italy: Giovanna Biella. pp. 123–25.
4. Zeitlmayr L (1976). Wild Mushrooms:An Illustrated Handbook. Garden City Press, Hertfordshire. pp. 82–83.
5. Carluccio A. (2003). The Complete Mushroom Book. Quadrille.
6. Callac P, Billette C, Imbernon M, Kerrigan RW (1993). "Morphological, genetic, and interfertility analyses reveal a novel, tetrasporic variety of Agaricus bisporus from the Sonoran Desert of California". Mycologia. 85 (5): 835–851.
7. Callac P, Imbernon M, Guinberteau J, Pirobe L, Granit S, Olivier JM, Theochari I (2000). "Discovery of a wild Mediterranean population of Agaricus bisporus, and its usefulness for breeding work". Mushroom Science. 15: 245–252.
8. Cooke MC (1871). Handbook of British Fungi. Vol. 1. London: Macmillan and Co. p. 138.
9. ange JE (1926). "Studies in the agarics of Denmark. Part VI. Psalliota, Russula". Dansk Botanisk Arkiv. 4 (12): 1–52.
10. Schäffer J, Møller FH (1939). "Beitrag zur Psalliota Forschung". Annales Mycologici (in German). 36 (1): 64–82.
11. "White Button". Fresh Mushrooms. Mushroom Council. n.d. Archived from the original on 29 February 2020.