(10)Salient features of classes

1. Phycomycetes  (Oomycetes/Egg  fungi)  : It is also called lower fungi, mycelium is coenocytic. Hyphal wall may contain chitin or cellulose (e.g., Phytophthora). Asexual reproduction occurs with the help of conidio- sporangia. Under wet conditions they produce zoospores. Under dry conditions, the sporangia directly function as conidia. Zoospores have heterokont flagellation (one smooth, other tinsel). Sexual reproduction is oogamous. It occurs by gametangial contact where male nucleus enters the oogonium through a conjugation tube. The fertilized oogonium forms oospore. e.g., Sapolegnia, Albugo (Cystopus), Phytophthora, Phythium, Sclerospora.
2. Zygomycetes (Conjugation fungi) : Mycelium is coenocytic. Hyphal wall contains chitin or fungal cellulose.  Motile  stage  is  absent.  Spores  (Sporangiospores/aplanospores)  are  born  inside  sporangia.  Sexual reproduction involve fusion of coenogametes through conjugation (Gametangial copulation). It produces a resting diploid Zygospore. On germination, each zygospore forms a germ sporangium at the tip of a hypha called promycelium e.g., Mucor, Rhizopus.
3. Ascomycetes (Ascus : sac, mycete : fungus) : These are unicellular as well as multicellular fungi. In the latter, mycelium is septate. The asexual spores formed in chains are called conidia. The spores are formed exogenously, i.e. outside sporangium. They detach from the parent and form new mycelia. Sexual reproduction is through ascospores, which are formed endogenously (within the mycelium) in a sac like structure called ascus (pl. asci). The gametes involved in sexual reproduction are nonmotile compatible and are generally represented as + and –. The fusion of gametes is followed by reductional division that produces haploid ascospores. The fruiting body called ascocarp.

The ascocarp are of four types :

1. Cleistothecium : It is an ovoid or spherical fruiting body which remains completely closed e.g., Aspergillus.
2. Perithecium : It is a flask shaped fruiting body which opens by a single pore called ostiole. It is lined by sterile hyphae called paraphyses. The asci are also mixed with paraphysis e.g., Cleviceps.
3. Apothecium : It is a saucer-shaped fruiting body. The asci constitute the fertile zone called hymenium

e.g., Peziza.

4. Ascostroma : It is not a distinct fruiting body. It lacks its own well defined wall. The asci arise directly with a cavity (locule) of stroma. It is also called as pseudothecium e.g., Mycosphaerella.

4. Basidiomycetes : They are the most advanced fungi and best decomposers of wood. These are called club fungi because of a club shaped end of mycelium known as basidium. They have septate multinucleated mycelium. Septa possess central dolipores and Lateral clamp connections. The sexual spores called basidiospores are generally four in number. They are produced outside the body (exogenuous) unlike ascomycetes where they are endogenous. Two compatible nuclei fuse to form zygote, which undergoes meiosis and forms four basidiospores. The fruiting body containing basidia is a multicelular structure called basidiocarp. The common members are edible mushrooms (Agaricus). Smut and Rust.
5. Deuteromycetes (Fungi inperfecti) : The group include all those fungi in which sexual or perfect stage is not known. Mycelium is made of septate hyphae. Asexual reproduction commonly occur by means of conidia.

(11)Economic importance

1. Harmful aspects

1. Crop diseases : Several important crop plants are destroyed due to fungi diseases. Some important ones are listed here under :

Some plant disease caused by fungi

2. Diseases in human beings : Several diseases in human beings are found to be caused by fungi infecting different parts of the body. Some of them are given hereunder as :

3. Spoilage of food : Some forms like Rhizopus, Mucor, Aspergillus, Cladosporium grow on food articles and spoil them. Cladosporium grows even at a temperature of – 6°C.
4. Mycotoxins : Some fungi produce toxic metabolites which cause diseases in human beings. They usually contaiminate cereals and oil seed crops. Four types of mycotoxins are generally identified :
   • Aflotoxins : e.g., Aflotoxin B₁, B₂, M₁, M₂, G₁, G₂; They are produced mainly by Aspergillus flavus and A. parasiticus. They are well know for their carcinogenic effect.
   • Zearalenone : It is produced by Fusarium sp.
   • Ochratoxins : They are produced by Aspergillus and Pennicillium sp.
   • Trichothecenes : They are produced by fungi like Cephalosporium, Fusarium etc.
5. Poisonous fungi : Some fungi are extremely poisonous e.g., Amanita phalloides ('death cup'). A. verna, Boletus satanus. Forms like Coprinus, Psilocybe are less poisonous. The fungus Amanita phalloides produces toxins like a-amanitin, phalloidin etc. which are very poisonous.
6. Ergotism :The fungus causing 'ergot' disease of rye (Secale) is Cleviceps purpurea. It contains many poisonous alkaloids in their sclerotia. It causes poisoning in human beings. It's acute condition is called as 'St. Anthony's fire'.
7. Hallucinogenic drugs : The hallucinogenic drug LSD (Lysergic acid Diethylamide) is extracted from

Cleviceps purpurea as also from Inocybe. Besides, the mushroom Amanita muscaria is also hellucinogenic.

8. Rotting of wood : Rotting of wood is caused due to degradation of lignin and cellulose. It is brought about fungi like Polyporus sp., Fomes sp. and Ganoderma sp., Forms like Fusarium, Penicillium leave stains on the wood.
9. Allergies : Spores of Mucor, Aspergillus, Penicillium, Puccinia etc., present in the atmosphere cause allergies.
10. Deterioration of articles : Forms like Aspergillus, Cladosporium, Rhizopus, Chaetomium, Alternaria

deteriorate cork, rubber, leather, textile and even plastics.

(ii)Useful aspects

1. Food : Forms like Agaricus bisporus, Morchella esculenta, Lentinus edodes, Clavatia gigantia, Volvariella volvacea are edible. The yeast Saccharomyces cerevisiae is used for making 'yeast cake'. When mixed with cereal flour, the yeasts produce a preparation called incaparina. The Single Cell Protein (SCP) obtained from yeasts, Penicillium, Fusarium etc. are used as substitute of protein food, Rhizopus oligosporus, when processed with soybeans yield a food preparation called 'tempeh'. It has high protein contents.
2. Flavoring of food : Penicillium roquefortii and P. camemberti are employed for flavoring cheese.
3. Brewing and baking : Yeasts are generally used in bakeries and breweries. The sugars are fermented by yeasts into alcohol and CO₂. While the former in main product of breweries CO₂ is mainly useful in bakeries.
4. Organic acids : Several organic acids are commercially produced by fungi, some of which are given hereunder :

5. Antibiotics : The antibiotics are chemicals produced by living organisms that kill other living organisms. The first known antibiotic is penicillin that was extracted from Penicillium notatum by A. Fleming, (1944). Raper (1952) also extracted the same antibiotic from P. chrysogenum. Besides, several other antibiotics have been extracted since then.

6. Other chemicals : Various chemicals have been obtained from different kinds of fungi. Yeast are good source of glycerol and enzymes like zymase, invertase and lipase. Cellulases are obtained from Aspergillus. Some alkaloids are also obtained from fungi e.g., Ergotinine, Ergotetrine and Ergobasine from Cleviceps purpurea. Gibberellins (plant hormones) are obtained from Gibberella fujikuroi. Another hormone, trisporic acid is obtained from Mucor mucedo.
7. Biological assays : The fungi can detect the presence of certain chemicals present in the medium even in traces e.g., Aspergillus niger for Mn, Pb, Zn, Cu, Mo etc.
8. Vitamins : Various vitamins have been obtained from different kind of fungi.

(i)Other uses

• Nitrogen fixation by yeasts like Saccharomyces and Rhodotorula.
• Production of latex by Mycena galopus.
• Soil building by Rhizopus, Cladosporium, Aspergillus etc.
• Along with bacteria, the fungi work as decomposers.
• Biological control of growth of hyperparasites like insects, nematodes, bacteria and even other fungi.
• Neurospora is a good research material for geneticists and Physarum for molecular biologists for the study of DNA.

Important Tips

• Fungus : The term was used by Gaspard Bauhin (1560–1624).
• Father of Mycology : Pier Antonio Micheli. In 1729 he wrote 'Nova Genera Plantarum' in which 900 fungi were described.
• Father of Systematic Mycology : E.M. Fries (1794–1878). He wrote 'Systema Mycologicum' in three volume.
• Father of Modern Mycology and Plant Pathology : H.A. de Bary.
• Father of Indian Mycology and Plant Pathology: E.J. Butler.
• Smallest Fungus : Yeast with a size of 3–15 mm × 2–10 mm.
• Largest Fungus : Lignocolous Shelf Fungus/Bracket Fungus Ganoderma applanatum (fruiting body 60 cm across). Glant Puffball/Clavatia is 90–120 cm across. It possesses anticancer properties.
• Millardet discovered fungicide Bordeaux mixture. Which is solution of copper sulphate and calcium hydroxide (CaSO₄ + Ca(OH)₂).
• Pseudogamy : Fusion between unrelated cells.
• Pedogamy : Fusion between mature and immature cells.
• Adelphogamy : Fusion between mother and daughter cells or sister cells.
• Non-ciliated spores called 'aplanospores'.