In this article we will discuss about:- 1. Introduction to Mushroom 2. Origin and Distribution of Mushroom 3. Composition and Uses 4. Botany 5. Morphology 6. Classification.
Introduction to Mushroom:
The food for human beings comes from three different sources, viz. land, water, and microbes. Among microbes used as human food, the fungi comprise the largest and the most important group containing edible mushrooms. Although mushrooms, which appear in nature, are delicious and nutritious but not all the species of mushroom are edible since a few are poisonous.
Mushrooms are the fruiting bodies of some members of a lower group of plants, known as fungi, which are characterized by the absence of chlorophyll (pigment responsible for green colour of plants) and undifferentiated bodies, except the spore bearing structures. The fruiting bodies, mushrooms, are fleshy spore bearing structures of the fungi. They contain numerous spores, which are functionally similar to seeds of higher plants, and are created for the prorogation of fungi.
Origin and Distribution of Mushroom:
The mushrooms have been considered a delicacy for several thousand years. The reference of mushroom is found in the ancient Roman and Greek literature. Historical records about the beginning of human culture are insufficient and the indications of pre-historic people using fungi are very rare. O’Heer (1886) and others have found traces of mushroom on cave walls. In Central America and Gautemala, mushroom-shaped stone carvings have also been found.
The earliest word in Sanskrit for mushroom appears to be Ksumpa, and present day in Hindi, it evolved into Khumbi. The invasion/migration of the Aryans into the Indian sub-continent, which took place around 1500 BC, might have carried with them an intoxicating drink Soma, which was mostly used in Aryan religious rites. In the Rig Veda, there are many songs on Soma and Soma in the Rig Veda refers to Amanita muscaria.
The records are available in the literature that the earliest cultivated edible fungus was a species of Auricularia, which was cultivated about 1000 years ago in China. The next species to be cultivated was Lentinus edodes, almost 900 years ago also in China. The earliest description and expertise of growing mushrooms was Written by Toune Forte, a Frenchman, and published in Paris during 1707, and the method described by him is remarkably similar to that employed today. In fact, no radical change took place until 50 years ago.
In India, the cultivation of edible mushroom is of recent times though the method of cultivation for the same has been known for many years. In 1886, some specimen of mushroom were grown by N.W. Newton and exhibited at the annual show of Horticultural Society of India. Mantel, FAO expert guided the construction of growing facilities and research on spawn production, synthetic compost etc. at Solan (Himachal Pradesh) in 1965.
A coordinated scheme on mushroom was started by ICAR in 1971. In 1974, Hayes, FAO expert guided Himachal Pradesh Horticulture department on improved methods of compost preparation, pasteurization, casing, environment management for yield enhancement etc. and helped in the establishment of mushroom training center at Solan, and in 1997, the Solan was declared as Mushroom city of India.
The cultivation of button mushrooms (A. bisporus) started in the sixteenth century, however, on commercial scale, the cultivation was initiated in Europe around 17th Century. Many farms for the production of button mushrooms were established and this variety still dominates the world production and consumption.
India, with its diverse agro-climatic conditions and abundance of agricultural wastes, has been producing mushrooms, mainly for the domestic market, for more than four decades. Commercial production picked up in the nineties and several hi-tech export oriented farms were set up with foreign technology collaborations but major share of mushroom production is still on small farms.
Composition and Uses of Mushroom:
Composition:
Mushrooms like other vegetables contain about 90% moisture and are low calorie food (approximately 30 kcal/100 g fresh weight). Total carbohydrates, which consist of chitin, hemi- cellulose, and glycogen, are 4-5%. Very little amount of free sugars (0.5%) is present, while the starch is found completely absent.
The fat content is very low (0.3%) but it is rich in linoleic acid (70%). Cholesterol, the dreaded sterol for heart patient, is absent and in its place ergosterol is present, which can be converted into vitamin D by human body. Fiber content is high, which is helpful in excretion of waste and prevention of constipation.
Nutritionally, it is rich in proteins, vitamins, especially vitamin B, C and D, and minerals. Vitamins of B-complex group and vitamin C are present in significant quantities, which include thiamine, riboflavin, niacin, biotin, and pantothenic acid. Folic acid and vitamin B12, which are normally absent in vegetable foodstuffs, are present in mushrooms.
They are also fairly good source of vitamin C (4-8 mg/100 g). Phosphorous and potassium are present in high quantities. They are comparatively deficient in calcium and iron but the latter is present in available form. High potassium to sodium ratio present in mushrooms is desirable for the patients with hypertension. The nutritional composition of mushroom is given below in Table 27.1.
Uses:
The economic importance of mushroom lies primarily in the use as food for human consumption. The exotic flavor, taste, and fleshiness of mushroom have made it an important delicacy in human diet. The productivity of mushroom is higher than any other crop. Food, nutritional and medicinal values apart, mushroom growing can be efficient means of waste disposal (agricultural, industrial, and family wastes) since it can use then wastes as medium of growth, hence, it could be considered as eco-friendly.
Mushrooms have long been considered to have medicinal value. In fact, the early herbalists were more interested in medicinal properties of mushroom than in their basic value as a source of food. Due to unique chemical composition, mushrooms are suited to specific groups suffering with some ailments/disorders.
As a low calorie high protein diet with almost no starch and sugars, mushrooms are the ‘delight of the diabetic’. Cholesterol content of mushroom is low. It is also known to have medicinal values and certain varieties of mushroom can inhibit growth of cancerous tumors.
Due to high potassium to sodium ratio, few calories and low fat (rich in linoleic acid and lacking cholesterol), mushrooms are suited to persons suffering from obesity, hypertension, and arthrosclerosis. Alkaline ash and high fiber contents make them suitable for those suffering from hyper-acidity and constipation. The medicinal properties of some of the common edible mushroom species are given below in Table 27.2.
The following medicinal products of mushrooms are available in the market:
i. Concord Sunchih:
The Concord International Trading Pvt. Ltd., Australia is preparing Concord Sunchih from fresh cultivated Gandoderm fruit-bodies. It improves immunity, anti-hypertensive, and remedy for hepatitis, bronchitis, piles, asthma, and diabetes. Its prescribed dosages are 1 to 2 caps twice a day for healthy and three caps thrice a day for individuals suffering from afore said ailments.
ii. Griferon:
The Maitake products Inc. New Jersey, USA prepares it from Grifola frondosa. It combines well with conventional chemotherapeutic drugs against cancer. The prescribed dosages are 5-6 drops TDS for general healthy individuals, and the therapeutic dose is 0.5-1.0 mg/kg of body weight.
The use of mushroom as food is as old as human civilization. However, not all the mushrooms are edible. Some are mild to deadly poisonous but there is no visible sign of any mushroom nor there is any thumb rule, which indicates weather it is toxic or not. In olden days, before people could differentiate between edible and non-edible mushrooms, eating poisonous mushrooms perhaps lost many lives.
Some of the traditional methods for identification of edible and non- edible species are unreliable. It was believed that the edible fungus peeled off easily and did not change a silver spoon black while cooking. This belief is incorrect as Amanita phalloides (death cap), which is poisonous, peels off easily and the silver spoon remains unaffected.
The followings are the species of mushroom that cause mild to fatal reactions and hallucinogenic effect:
Agaricus species- A. pilatianaus and A. xanthoidermus
Amanita species- A. aspera, A. brunescens and A. muscaria
Boletus species- B. purpureus, B. rhodoxanthus and B. satanus.
Botany of Mushroom:
The vegetative mycelium is composed of many inter-woven sepatate hyphae. The reproductive phase is initiated by the formation of small knob like swellings at different points of interwoven mycelial strands. These swellings increase in size and break through the surface of the substratum as small balls constituting the button stage.
A matured basidiocarp (fruit body) is whitish in colour and consists of thick short stipe with an annulus. The stipe supports the pileus, which appears as a hat like expansion. On the underside of the pileus, a number of radiating gills or lamellae are present which are pink when young but purple-brown when mature.
Morphology of Mushroom:
In general, the term mushroom is the fruiting body of the fleshy fungi and consists of two portions, one the fruiting body or the mushrooms itself, and another is the thread like structures growing extensively in substrate comparable to the roots of higher plants. These thread-like structures are known as mycelium, which supplies nutrients from substrate to fruiting bodies. Most of the mushrooms have caps and stalks, whereas, there are some other varieties with different shapes and sizes and are devoid of stalks.
Mushroom has following different parts:
1. Cap or Pileus:
The cap or pileus is the expanded portion of the carpophore, which may be thick, fleshy, membranous, or corky, and it varies greatly in shape, size, and colour. The surface of the pileus may be smooth, hairy, or rough.
The Gills or lamellae are situated on the underside of the pileus starting from the apex of the stalk and radiating out towards the margin. These gills bear spores on their surface and exhibit a change in colour corresponding to that of the spores. The attachment of the gill to the stipe helps in the identification of mushroom. When the gills do not touch the stipe or only do so by a fine line they are known as free.
When they are attached directly to the stem, forming nearly a right angle with the latter, they are termed as adnate. If the attachment is only by a part of the width of the gills, they are adnexed. When the gills extend down the stem to a greater or lesser degree they are known as decurrent and when they are near the stalk in a deep notch they are termed as sinuate.
In young fruit bodies, the gill remains covered by a tissue that extends from the margin of the cap (pileus) to the stipe and this tissue in called the veil. It is very delicate, and can easily be rubbed off or may even be washed away by rains.
A ring formed around the stipe is known as annulus, which may be present or absent in different varieties.
The stalk supporting the pileus is also known as stipe. Its presence or absence and mode of its attachment to the cap are an important character for the identification of genera. Mostly the stem is centrally attached to the cap, however, in some cases, the attachment may not be exactly in the middle or lateral, and then, it is known as eccentric.
A cup/saucer like structure at the base of stem/stipe is known as volva, and it may or may not be present.
Classification of Mushrooms:
1. Epigenous:
It forms as fruiting bodies entirely above the surface of substrate, e.g., cup fungi (Pizza species) and morels (Marchella species).
2. Hypogenous:
Such mushrooms usually grow underground and form fruiting bodies therein. Species of family Tuberaceae such as Tuber species may be cited as an example. These species are also known as true truffles.
B. Natural Habits:
(i) Humicolous: Humus Inhabiting:
(a) Saprophytic: Volvariella species and Polyporus tuberaster
(b) Symbiotic: Boletus and Tricholoma species
(ii) Lignicolous: Wood Inhabiting:
(a) Saprophytic: Agrocybe, Pleurotus, Auricularia and Lentinus
(b) Parasitic: Armellariella mellea and Cyttaria
(iii) Coprophilous (Dung Inhabiting):
Agaricus species, Coprinus species
C. Spore Colour:
White Spored:
Amanita, Armillaria, Cantharellus, Clitocybe, Lacterius, Lentinus, Lepiota, Pleurotus, Russula and Tricholomai
Pink Spored:
Flammulina, Inocybe and Paxillus
Black Spored:
Entoloma and Volvariella
Purple Brown Spored:
Agaricus, Hypholoma and Stropharia
Yellow Brown Spored:
Coprinus and Panaeolus
D. Morphology:
Group-I: Basidiomycetous Mushrooms:
Fruiting Layers Exposed to the Air:
This sub group has further been divided into five categories
Gill Fungi:
Characterized by presence of gills
Pore Fungi:
Absence of gills and presence of tubes or pores
Teeth Fungi: Fungi without gills or pores but with prickles or teeth
Club or Coral Fungi: Fungi without gills, pores or teeth, but are club or coral like in shape
Jelly Fungi: Fungi without gills, pores, or teeth, forming soft jelly like masses when moist.
Group II: Ascomycetous:
Morchella, Gyromitra, Helvella, Plicaria, Pustularia and Sarcoscypha
E. Fruit Bodies:
Gilled (Family-Agaricaceae):
Agaricus and Amanita
Pore (Family-Polyporaceae):
Fistulina, Trametes, Favolus Candensis and Polyporus
Tooth (Family-Hydnaceae):
Hydnum Corailoides and Hynum Caputursi
Club Shaped (Family-Clavariaceae):
Clavaria
Boletaceous (Family-Boletaceae):
Boletinus and Boletus
Cup-Shaped: Morchella
F. Fruit Bodies and Spores:
Ainsowrh et al. (1973) classified mushrooms into two subdivisions, i.e., Ascomycotina and Basidiomycotina. These two groups contain most of the edible fungi.
Mushrooms belonging to these subdivisions may be described as under:
(i) Subdivision: Ascomycotina, Class: Discomycetes and Species: Morchella and Terfezia
(II) Subdivision: Basidiomycotina, Class: Gasteromycetes. There are six economically important orders of this class. These are orders Podaxales, Phallales, Sclerodermatales, Pymenoganterales, Melanogastrales and Lycoperdales.
Latest Classification:
Ainsworth and Bisby’s Dictionary of Fungi has been published during the year 1995 from International Mycological Research Institute. According to this classification, the genera has been placed within families all under eleven fungal phyla.
Subdivision: Basidiomycotina
Class: Hymenomycetes
Subclass: Holobasidiomycetidae
Order: Agaricales
Genus: Agaricus, Coprinus, Lentinus, Pleurotus, Tricholoma, Flammulina, Calocybe, Stropharia, Plliota, Kuehneromycetes, Hypholoma
Subclass: Aphyllophorals Phragmobasidiomycidae
Order: Auricularials, Tremellales
Genus: Auricularia, Tremella
Subdivision: Ascomycotina
Class: Discomycetes species
Subclass: Hymenoascomycetidae
Order: Tuberales
Genus: Tuber