Diversity of Microbes and Cryptograms

1 Diversity of Microbes and Cryptograms Fungi – II A.K. Roy University Department of Botany T.M. Bhagalpur University Bhagalpur – 812007 Bihar Date of submission: 28/11//2006 Contents: Basidiomycotina Deuteromycotina Lichens Significant Key words: Basidiomycotina, Deuteromycotina, Lichens 2 FUNGI-II General Characteristics Of Basidiomycotina The members of this Sub Division are usually called as Smuts, Rusts, Mushrooms, Puffballs, Stinkhorns Toadstools, Geasters, Jelly fungi, Shelf fungi or Bracket fungi, Birds nest fungi, Fairy clubs and Earth stars. Kost (1984) has reported several Basidiomycetes inhabiting mosses and called them ‘Bryicole’. They are cosmopolitan in distribution, terrestrial, saprophytic or parasitic and simple to complex in nature. It is considered as 3rd largest group of fungi as it includes about 16,000 species with about 1100 genera. Development of basidium and basidiospores are the distinguishing features of this group of fungi and they are thought to be originated from Ascomycetes. Somatic Structures: Represented by primary, secondary, and tertiary mycelium or pseudo tissue complex • The primary or monokaryotic mycelium which develops after the germination of basidiospores, is septate and uninucleate (Fig.1). • The secondary or dikaryotic mycelium is also septate but having two nuclei in each cell which is developed by the fusion of somatic cells either from the parent primary mycelium or from two different others (Heterothallic). • In heterothallic species cells fuse when the primary mycelium of opposite sex grows together in close association (Fig.2) • • • • • • • • • • • • • • • • • • • • • • • 3 • • In homothallic species the fusion takes place between two hyphae of the single primary mycelium. • The process of formation of primary mycelium to secondary mycelium is called ‘dikaryotization’ or ‘diplodization’ which takes place through fusion of i) vegetative cells of two hyphae of opposite strains; ii) two basidiospores of opposite strains; iii) an oidium (or spermatium) and a cell of primary mycelium of opposite strains; iv) a germinating basidiospore and a haploid cell of a basidium ; v) two haploid cells of basidium and vi) two basidia formed by the germination of smut spores of opposite strains. Clamp connections In dikaryotic mycelium of most of the Basidiomycetes an interesting mechanism appears to ensure that sister nuclei arising from conjugate division of the dikaryon get separated into two daughter cells. This biological phenomenon which is achieved through a special structure is called clamp connection (Fig. 3.1). When a binucleate cell is on way to divide, a short branch (clamp connection) arises between two nuclei i.e., x & y and tends to form a hook. Nuclei then divide, one gets oriented obliquely so as to nucleus y forms in clamp connection and other y1 remains in the dividing cell. The second division (x. nucleus) occurs along the long axis of the cell in such a way that one daughter nucleus remains at end of cell and other near to y1. In the mean time the clamp end gets fused with the cell, in this way it forms a bridge through which y1 passes in the cell near x nucleus. Thereafter a septum develops to separate two cells of mycelium with heterokaryon nuclei ie., x1 y1 and xy. The steps of this biological event are shown in Fig. 3.2 A-G. This clamp connection is, therefore, indicative of dikaryotic condition which was first reported by Uniep (1917) and followed by Bensaude (1918). Dolipore septum It was first reported by Moore and Mc Alear (1962) followed by Thieke (1972) and Moore (1975). In majority of the Basidiomycetes the septum is characterized by the presence of septal pore in the centre is called dolipore septum. This pore remains surrounded by the barrel shaped swellings which is called as parenthesome (Fig 4). Buller phenomenon 4 A dikaryotic hyphae is usually formed by the somatogamy between two monokaryotic hyphae (Primary mycelium), but dikaryotization may also take place between a monokaryotic and a dikaryotic mycelium. This phenomenon which was first discovered by A.H.R. Buller (1931)) in the hyphae of Coprinus cinereus a tetrapolar fungus called as Buller phenomenona (Fig 5, Steps A-G). Tertiary mycelium It is represented by the organized special tissue which composes the sporophores of the higher basidiomycetes. The cells of the tertiary mycelium are binucleate. The sporophore actually originates when the secondary mycelium forms complex tissues. Cell wall Microfibrils of chitin and glucans with 1 – 3 linked and 1 – 6 linked β – D glucosyl units (Bartznicki, 1973) are known to compose the cell wall of higher basidiomyctes. The Basidiocarp The most of the members of Basidiomycetes produce their basidia in highly organized fruiting bodies of various types. These fruiting structures, homologous to the ascocarps of complex Ascomycetes are called Basidiocarps (GR basidion=small base, basidium+karpos = fruit) It may be crust like, gelatinous, cartilaginous, papery, fleshy, spongy, corky, woody or indeed of almost any texture. 5 • It may be microscopic to 3 feet or more in diameter. • Most of the basidomycetes bear basidia in basidiocarps (Figs.6,A-G), however, rusts and smuts do not have the same structure. • Some of the members eg. Agaricus compestris forms fairy rings(Fig.7) 6 The Basidium It originates as a terminal cell of a binucleate hypha and separated from the rest of the hypha by a septum over which a clamp connection may also be seen. It is usually simple and club shaped known as holobasidium or forked or septate ie., heterobasidium (Figs.8,A-F) The Basidiospore Typically unicellular, uninucleate, haploid structure may be globose, oval, elongated or sausage shaped colorless or pigmented (green, yellow, orange, ochre, pink, violet, brown or black). The basidiospore often rests on the tip of sterigmata in an oblique fashion (Figs.9, A-E). Discharge of basidiospores The basidiospores are exposed on hymenium and usually perched in an oblique manner (asymetrically) on the tip of sterigmata. They are discharged forcibly in quick succession by the “Water drop mechanism” (Buller, 1909, 22, 24) or “Bubble bursting mechanism” (Olive, 1964; Ingold & Dann, 1968). The spore has a minute projection often referred to as hilar appendix lying very close to the point of its attachment to the sterigmata. Immediately before discharge, a liquid droplet or gas bubble appears at the hilar appendix and grows bigger till attains a certain size, and suddenly pushes off the basidiospores forcibly into the air. The distance of discharge is usually 0.1 to 0.2 mm and rarely more than 1 mm. The surface tension is said to provide the necessary force for such discharge of basidiospore where it carries water drop with it. Moore(1966) has suggested that the gas pressure in bubble might be utilized in the discharge of spores outwards. 7 The gas blister simply collapses to release a jet of gas between inner and outer wall of the spore in the region of hilum which exerts force to push off spores in outward direction away from the sterigma (Figs 10). Germination of Basidiospores Falling on a suitable substratum the basidiospore germinates by giving rise a germ tube (Fig.11). The latter develops into a primary mycelium. In a few species the basidiospores bud off into secondary basidiospores or conidia. Asexual reproduction • It takes place by budding, fragmentation of the mycelium and by the production of conidia, arthrospores or oidia (Fig.12 , A- C). • Smut spore produces conidia and rust produce summer spores uredospores. Sexual Reproduction • Usually sex organs are absent except in the rust eg. Puccinia where the spermatia and receptive hyphae represent the male and female sex organs respectively. • Multiplication is performed by the sexual spores ie., the basidiospores. 8 Classification • Ainsworth(1973) classified the Sub Division Basidiomycotina into three classes i.e. Teliomycetes (2 orders), Hymenomycetes (9 orders) and Gasteromycetes (6 orders). • Allexopoulos & Mims(1979) considered it as Class and further divided into three sub classes i.e. Phragmobasidiomycetidae (3 orders),Holobasidiomycetidae(6 orders) and Teliomycetidae (2 orders). • Khan & Kimbrough (1982) proposed the adoption of four classes based mainly on septal ultrastructure i.e. Teliomycetes, Hemibasidiomycetes, Phragmobasidiomycetes and Holobasidiomycetes. • Hawksworth et.al (1983) divided it into four classes – Hymenomycetes, Gasteromycetes, Uridinomycetes and Ustilaginomycetes. Economic Importance • Crops worth millions of rupees are destroyed annually by rusts and smuts throughout the world. • Several basidiomycetes attack food and ornamental plants as well as forest trees. • Mushrooms are used as delicious food throughout the world eg. Agaricus compestrix, A. brunnescens (A. bisporus), A. rodmani and others, however, some of them are highly poisonous eg. Amanita and Boletus sp. PUCCINIA The term Puccinia is coined by an Italian Scientist T. Puccini. The genus Puccinia with about 3000 sp. out of which 147 species reported from India belongs to the family Pucciniaceae and Order Uredinals. Many species are Autoecious i.e. completes its life cycle on single host (Launea) eg. P. butleri however, some are Heteroecious i.e. completes its life cycle on two different hosts Triticum vulgare (wheat) and Berberis vulgaris (Berbery) e.g. Puccinia graminis. Most of these are obligate parasite attacking diversified group of plants, however, some of them are of great economic importance as they cause destructive rust diseases such

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