Mushroom

A mushroom has two parts: the mycelium and the fruiting body.

The mycelium is the vegetative part, the part that feeds and grows. It lies hidden in the soil (or inside the log or straw), and it is a network of very fine threads called hyphae (singular: hypha). The hyphae absorb water and organic food from their surroundings.

The fruiting body is the part above the ground, the part we call “a mushroom”. It is the reproductive part: its job is to make and scatter spores. It has:

• a stipe, the stalk;
• a pileus, the umbrella-shaped cap on top;
• gills, thin plates like the pages of a book, under the pileus; the spores, called basidiospores, are made on the gills;
• in many kinds, an annulus, a ring of tissue round the stipe, and a volva, a cup at the base of the stipe.

Inside a gill

Cut a gill across and look at it under a microscope, and you see three layers:

1. Trama, the central core of loosely packed hyphae;
2. sub-hymenium, a layer of small cells on each side of the trama;
3. hymenium, the outermost layer, where the spores are made.

The hymenium has two kinds of cells standing side by side, like a fence:

• basidia (singular: basidium), club-shaped cells that make the spores;
• paraphyses (singular: paraphysis), cells between the basidia that make no spores: they are sterile. They hold the basidia apart.

How the spores are made

A young basidium has two nuclei, one of each mating type: a plus (+) strain and a minus (−) strain. (In mushrooms there are no male and female; the two strains are just two mating types that can join.) Then:

1. The two haploid nuclei (each with one set of chromosomes) fuse to make one diploid nucleus (two sets).
2. This nucleus divides by meiosis into four haploid nuclei: two plus and two minus.
3. Four small finger-like stalks, the sterigmata (singular: sterigma), grow out from the tip of the basidium.
4. One nucleus moves into each sterigma, and a basidiospore forms at its tip.

So each basidium makes four basidiospores: two plus and two minus.

From spore to mushroom

1. When the basidiospores are ripe, they are thrown off the sterigmata and carried by the air.
2. A spore that lands in a suitable place (damp, with organic matter, at the right temperature) germinates and grows into a primary mycelium. Its cells have one nucleus each, of one strain only.
3. When a plus and a minus primary mycelium meet, their hyphae fuse. The new mycelium has two nuclei in each cell, one from each strain. It is called the secondary mycelium, or dikaryotic mycelium (di = two, karyon = nucleus).
4. With the right temperature and moisture, the secondary mycelium forms small, round buttons, which grow and open into umbrella-shaped mature mushrooms.
5. Their gills make basidiospores again, and the life cycle is complete.

For thousands of years people have eaten mushrooms and used them as medicine. Modern science shows that mushrooms are a healthy food: they have protein, vitamins, minerals and fiber, and almost no fat, and like all foods from fungi and plants they have no cholesterol. They are tasty, and they are a good source of income.

A. Importance of mushroom for human health

1. A source of protein

Dried mushrooms are 19–35% protein, more than many grains:

Food	Protein
rice (grain)	7.5%
wheat (grain)	12.5%
chicken meat (fresh)	18–20%
mushroom (dried)	19–35%
soybean (dry beans)	38.1%

Mushroom protein contains the amino acids the human body needs to grow and repair itself.

2. A source of vitamins

Mushrooms are a good source of the B vitamins: riboflavin (B₂), niacin (B₃), pantothenic acid (B₅), thiamine (B₁), biotin and folate, and some kinds have a little vitamin B₁₂. That makes them especially useful in a vegetarian diet.

3. A source of minerals

Mushrooms contain potassium, phosphorus, copper, iron, calcium, sodium (only a little) and selenium.

4. As medicine

In China, Japan and Korea, mushrooms have been used as medicine for a very long time, and in Nepal Ayurvedic doctors also advise eating them. Research suggests that eating mushrooms regularly can help the body’s immune system, and may help people with diabetes, high blood pressure and heart disease, because mushrooms are rich in fiber and potassium and low in fat, salt and sugar. Medicines and health products are made from red mushrooms, such as the shiny red-brown Ganoderma (reishi), and people take them for asthma, diabetes, cancer, piles and diseases of the airways. The bright red bracket fungus Pycnoporus cinnabarinus, which grows on dead wood, is another red mushroom whose substances are being studied.

B. Economic importance of mushroom

Because they are nutritious and useful as medicine, mushrooms are grown commercially, and it is a profitable business: they grow fast, in a small space, on cheap farm waste like straw.

• The morel, Morchella (guchi chyau), grows wild in the forests of Jumla and other parts of western Nepal. Dried morels fetch very high prices in the international market, and collecting them is an important income for families in the hills.
• In Nepal, mushroom sukuti (dried mushroom) and mushroom pickles are made and sold, and are good sources of income.
• Kanye chyau, the oyster mushroom (Pleurotus ostreatus), is the mushroom most farmed in Nepal. In the Kathmandu Valley it can be grown for much of the year.
• Gobre chyau, the button mushroom (Agaricus bisporus), is grown commercially in the hills.

There are many ways to farm mushrooms, and the method depends on the kind. Some can be grown at home with simple tools; others need special equipment and rooms. The oyster mushroom (kanye chyau) is the easiest, grown on paddy straw.

Method of kanye chyau farming

1. Collect good, clean paddy straw, and cut it into pieces 1–3 inches (about 2.5–7.5 cm) long.
2. Boil the pieces in water for about 15–20 minutes. This kills the germs and molds in the straw and makes it soft, so the mushroom grows well in it.
3. Drain the boiled straw well and let it cool and dry until it is only damp, not dripping, for about a day.
4. Fill a plastic bag with the straw in layers, sprinkling mushroom spawn (the “seed”: grains covered with the mushroom’s mycelium) on each layer.
5. Usually make 5–6 layers, each about 8–10 cm thick.
6. Press the layers down well with your hand, tie the bag, and make 10–12 small holes in it for air.
7. Keep the bag in a dark room for about seven days. By then, fine white threads (the mycelium) have spread through the straw inside the bag.
8. Make three or four more holes, and sprinkle water on the bag as needed to keep it moist.
9. After about 10 days, the white mycelium has filled the bag. Now make cuts in the plastic (some growers remove it altogether) so that the mushrooms can come out. Around 17 days, tiny mushrooms appear at the cuts and holes.
10. Around 25 days, the mushrooms are fully grown and can be picked.

Fresh mushrooms spoil in a few days, so many ways are used to store them for a long time: drying them into sukuti, or making pickle, ketchup, chutney and soup. Mushroom pickle, ketchup and chutney keep for at least six months at 20–22 °C. Mushrooms are also cooked in curry, pakoda, omelette and sandwiches.

Making mushroom sukuti

1. Wash the mushrooms clean.
2. Cut them into small pieces.
3. Dip them in boiling water for a short time (blanch them).
4. Dry them in the sun, over a fire, or in an oven.
5. When they are completely dry, pack them so that no air gets in.
6. Store the packets in a cool, dry place.

Methods of drying mushrooms

A. Drying with chemicals. Soak the mushrooms for 16 hours in a solution of 1% potassium bisulphite, 0.2% citric acid, 6% sugar and 3% common salt, then dry them at 60–62 °C for 8 hours. This gives good-quality sukuti, which can be ground into a powder and kept in a closed, airtight jar.

B. Drying in the sun. Oyster mushrooms can be dried in the sun when it is warmer than 25 °C, or in a machine at 40–45 °C. Dried this way and kept in a sealed polythene bag, they last up to 120 days.

Almost every monsoon, newspapers in Nepal report people, sometimes whole families, falling ill or dying after eating wild mushrooms. It is very hard to tell an edible mushroom from a poisonous one in the forest, and there is no simple test that can do it. People have always gone by the experience of their elders, but even experienced people make deadly mistakes.

Mushrooms with these features are often thought to be poisonous:

1. a dull gray or light brown color;
2. white gills;
3. a ring (annulus) on the stipe, or a cup (volva) at its base;
4. a bright red color;
5. a red stipe or a red pileus;
6. a smooth, shiny pileus that insects have not eaten;
7. a yellow liquid that oozes out when the pileus is pressed.

But these are only guesses, never a rule. Many poisonous mushrooms break them, and many edible ones have some of these features. Whether a mushroom is poisonous can only be known for sure by an expert or a laboratory test.

1. Choose the correct answer

2. Give reasons

3. Differentiate between

4. Answer the following questions