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

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)

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• • • • • • • • • • • • • • • • • • • • • • 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

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)

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.

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 as cereals, millets and other crops. Out of which some important diseases along with pathogens are listed below:

Host Disease Fungal Pathogen Wheat - Triticum valgare Black stem rust P.graminnis tritici Brown or leaf rust P. recondita (P. triticina) Yellow or stripe rust P. striiformis (P. glumarum) Barley - Hordeum vulgare Brown or leaf rust P. hordei Oat - Avena sativa Crown rust P. coronata Bajra - Pennisetum typhoides Rust P. penniseti Jowar - Sorghum vulgare Rust P. purpurea Maize - Zea mays Rust P.sorghi Cotton - Gossypium sp. Rust P. cacabata Sugarcane - Saccharum officinarum Rust P. erianthi, Groundnut - Arachis hypogea Rust P. arachidis Onoin – Allium cepa Rust P. allii Mint – Piper mentha Rust P. menthae Guava – Psidium guajava Rust P. psidii Sunflower -Helianthus annus Rust P. helianthi Chrysanthemum Rust P. chrysanthemi Safflower - Carthamus tinctorius Rust P. carthami Asparagus racemosus Rust P. aspargi

Somatic Structure

• The mycelium is well developed, septate uninucleate in first phase and binucleate in later stages. • It penetrates the host cells by haustoria through which absorbs nutrient . • Polymorphic in nature i.e. produces more than one type of spores to complete its life cycle .

Reproduction

It has five stages of spores differing in morphological and cytological characters i.e. Stage - 0 . Pycniospores or spermatia. Stage - 1 - Aeciospores Stage - 2 - Uredinospores Stage - 3 - Teliospores & Stage - 4 - Basidiospores Stage - 0 : Spermatia or Pycniospore:

These are monokaryotic gametes produced in spermogonia or pycnia which are variable in form and position. It is produced from haploid primary mycelium formed after germination of basidiospores. Pycnium or spermogonium is usually flask shaped or effused, indefinite structure (Fig. 1). 10

Stage - 1: Aeciospore:

The aecial cups containing the aeciospores are present on the lower surface on the leaves of Berberis vulgaris. The wall of the aecial cup is made up of a sterile protective layer, called peridium. A developing aecium pushes and ruptures the host epidermis and exposes the aeciospores for dispersal. Each aeciospore is a polyhedral binucleate structure having outer thick and smooth exine and inner thin intine(Fig.2)

Stage - 2 : Uredinospores (Uredospores, summer spores, red rust spores): These are repeating vegetative spores or conidia produced on dikaryotic mycelium and give uredinospores again or teliospores. Typical uredinospores are unicellular, pedicillate, deciduous with the pigmented echinulate wall showing two or more germ pores. The uredinospores are produced in uredinia (uredosori, uredia). The uredinia lack peridia but may have paraphysis (Fig.3, A-C). 11

Stage - 3: Teliospores (Teleutospores, winter spores, black rust spores): These are basidia producing spores and are produced in telia. Telia and teliospores which characterize the perfect state (teleomorph) of rust fungi. It may be unicellular or 2 or more celled sessile or pedicillate but not deciduous with a thick wall vigorously ornamented. It may be produced free from each other or may be embedded in a gelatinous matrix (Fig.4, A-C).

Stage - 4: Basidiospore:

These are haploid, unicellular, thin walled, short lived spores produced exogenously on basidia after meiosis. The basidiospores are forcibly discharged from the sterigmata. Upon germination these will either give rise directly to a germ tube or form an auto growth that functions as a sterigma (Fig 5 A-B). 12

Life cycle-3 different types:

Macrocyclic: Rusts which typically produce all the five spores stages are called macrocyclic or long cycled rusts. All the spore stages may be formed on a single host as in Autoecious rust eg. Puccinia helianthi, Uromyces fabae, U .striatus and Phragmidium mucronatum ,or on two alternate hosts as in Heteroecious rust eg. Puccinia graminis tritici and P. penniseti.

Demicyclic: Rust pathogens which lack the uredinal stage are called the demicyclic rusts Gymnosporium juniperi–virginianae is a Heterocious and Gyncomia peckiana, Xenodocus carbonrious are Autoecious demicyclic rust. Microcyclic: In this the teliospore is the only binucleate spore produced eg. Puccinia malvaceanum, P. heterospora, P. chrysanthemi, Endophyllum, etc. Alternation of Generation: There are two distinct generations or phases in the life cycle i.e. dikaryophase on wheat plant and monokaryotic or haplophase on barberry. Dikaryophase initiated by the germination of aeciospores on wheat and multiplied during the growing season of wheat by the formation of uredospores; both are binucleate. In the life cycle dikaryophase and the diplophase constitute the sporophyte generation. It regularly alternates with the haplophase or gametophyte generation vice-versa. One follows the other in a regular sequence. This means that the two generation constituting a single life cycle alternate with each other.

Diagrammatic representation of Life Cycle of Puccinia graminis tritici:

Management of disease.

• To grow the rust resistant varieties. • Crop rotation and mixed cropping. • Early sowing and early harvesting. • Varieties of wheat. • Destruction of self-sown wheat plants, green strubbles and tillers, which carry over the rust in the uredospore stage. • Proper irrigation. • Eradication of alternative host. • Use of fungicides eg. ZnSO4, Diathane, Sulphur dusting, RH-124 and Plantavax etc. • Use of nitrogen fertilizers. • Timely forecast of rust disease, so that effective measures are taken in advance. 14

Mushrooms

AGARICUS

The species of Agaricus with about 200 species commonly known as gill or fleshy fungi are cosmopolitan and found growing widely on ground in pasture. Most of the species of genus are well known table delicacy in many parts of the world, whereas some species are poisonous which may cause gastro intestinal disturbances. These fungi are characterized by the presence of umbrella shaped structure called the pileus undersurface of which plates of tissues are called gills. The pileus alongwith gills are present on stalk like stipe. The cap and stalk together constitutes the fruiting body called the basidiocarp or sporocarp. The most widely cultivated species for food purpose is Agricus bispora. Though it is grown in different parts of India but Solan in Himachal Pradesh is an important centre of Mushroom cultivation.

Habit & Habitat • It is a saprophytic fungus grows in the open fields, grasslands, lawns, wood logs, and manure piles and in soil on cellulose and lignin materials, usually in rainy season. • It is also found growing on the decaying litter on forest floors or on the humus deposited surface of the ground.

Mycelium • The mycelium is differentiated into Primary, Secondary and Tertiary mycelium which is usually septate and branched. • The primary or monokaryotic mycelium which is haploid, develops by the germination of a basidiospore for a short duration. • The secondary or dikaryotic mycelium develops after the fusion of two primary mycelium of different strains. • Dolipore parenthesome septum is present in the secondary mycelium. • The hyphae of the secondary mycelium twist together to form white hyphal cords called Rhizomorphs. • The hypha actually develops in circular rings, from periphery of which arises the fruiting bodies called “Fairy rings.” • Tertiary mycelium develops from secondary mycelium made up of complex tissue of the fruiting bodies. 15

Reproduction

Asexual reproduction:-

• Generally absent except in a few species. • In some species Chlamydospores give rise to mycelia upon germination eg. Agaricus compestris. • Oidia may be formed in some species eg. Coprinus fimetarius, Coprinus lagopus, Collybia conigena etc. Sexual reproduction

• Definite sex organs are absent. • Sexual reproduction takes place by means of hyphal fusion of two different strains. • Majority of the members are heterothallic, bipolar or tetrapolar.

Basidiocarp

• The whole fruiting body of Agaricus is called basidiocarp. • It originates from the underground rhizomorphs and swellings of secondary mycelium. • The primary pseudoparenchymatous stage i.e. hyphal knots develops into stalk region or stipe and a hemispherical upper part called pileus or carp. • The stipe elongates and the button enlarges in the size. • On the upper part of the stipe a membranous structure is present which is called ‘Annulus’. • Numerous pendant gills or lamellae hang down from the underside of the pileus. • A fertile layer of hymenium is present on both the sides of the gill surface. • The basidia and the basidiospores are produced in the hymenium. • Basidia are unicellular and binucleate.

Development of spores

• At the top of the basidium four peg-like out growths develops which is called sterigmata. • The tips of these sterigmata swell and the haploid nuclei migrate into these swellings. • These uninucleate swellings at the tips of the sterigmata develop into uninucleate basidiospores. • According to Miller (1984) the nucleus of each basidiospore undergoes a mitotic division before discharge. Thus each basidiospore becomes binucleate. 16

Discharge and germination of basidiospores

• Mature basidium are discharged explosively, as in many other Basidiomycetes. • A small lateral projection develops at the juncture of the basidiospore and a sterigma i.e. called hilum. • A few seconds before the spore discharge, a drop of the liquid appears at the hilum. This drop increase in size and reaches upto one fifth of the spore size . • The basidiospores are then suddenly shot away from the sterigmata, carrying the drop of liquid with them. • A mature basidiocarp of A. compestris may produce as many as 1.8 billion basidiospores each year. • On falling over a suitable substratum a discharged basidiospore germinates into a primary mycelium of either plus or minus strain. ( Fig. 4)

Economic Importance

• Agaricus compestris, A. brunnescens = (A. bisoprus), A. codamani and larger specimens of many other species are edible and cultivated for commerce. • A. xanthodermus is a poisonous species (Webster, 1980) whereas A. placomyces and A. silvaticus may cause gastrointestinal disturbance in some persons (Alexopoulos & Mims, 1979). 18

PENICILLIUM (Green or Blue mould)

Penicillium commonly known as green or blue mould was first discovered in 1929 by Sir Alexander Fleming which later on got world wide recognition in the field of biomedical research. According to Ainsworth (1973) this genus has been placed under Sub Division- Ascomycotina, Class- Plectomycetes, Order- Eurotiales and Family- Eurotiaceae (syn. Trichochomaceae, Aspergillaceae) having more than 100 species. This fungus is saprophytic in nature and frequently found growing on Citrus fruits, vegetables, preserved foods, jellies, cheese and other food stuffs. Besides, it also grows on apple fruits, leather, fabrics and all kinds of decaying materials and spoiling foods. Some species cause skin and other diseases of man and animals.

Somatic structures

• The mycelium is well developed and copiously branched which is composed of colourless, slender, tubular and septate hyphae. • The aerial hyphae receive nourishment through the haustorial hyphae and produce reproductive structures. • The mycelium in a few species may develop into a sclerotium. • The septa between the cells have a central pore. (Fig.1)

Asexual reproduction:

A. Vegetative method • The hyphae break up into short fragments. Each segment or fragment grows by repeated division into mycelium. • In some species the mycelium forms compact resting bodies the sclerotia which is enable to survive stress or hibernate periods.

B. Sporulation • It takes place by the formation of non-motile asexual spores, the conidia, which are produced exogenously at the tips of long, erect special septate hyphae called conidiophores. • Reaching a certain height the septate conidiophore branches once or twice or even more times, these are termed as primary, secondary or tertiary branches respectively. 19

• In Penicellium thomii conidiophores are unbranched. • The unbranched axis of the later bears a tuft of flask shaped sterigmata. • Flag shaped sterigmata or the phialides are called metulae. • The lower branches which support the metulae when short forms a part of the penicillus are called the rami. • The apical portion of the conidiophore with its branches (metulae) sterigmata and chains of conidia looks like a small artist’s brush known as the Penicillus (Fig. 2, A-E).

C. Development & Germination

• The conidium initial is formed by the distension of the tip of the phialide. • The phialide nucleus undergoes mitosis. One daughter nucleus remains in the phialide and the other migrates into the swollen tip i.e. conidium initial (Fig.3, A-E).

• The conidium initial protoplast is then cut off from the phialide protoplast by a thin perforate septum. • The perforation remains as a channel between the successive conidia in the chain. • On suitable substratum and conditions the conidia germinates and gives rise to a new mycelium.

Sexual Reproduction

It has been studied in a few species as P. vermiculatum (Talaromyces vermiculatus), P. glaucum, P. brefeldianum and a few others (Fig. 4, A-G).

• All of them are reported to be homothallic. • In P. vermiculatum sexual reproduction is oogamous type. • The male and female organs are known as Antheridia and Ascogonia. • The antheridium is a short, terminal, club-shaped uninucleate structure. • The Ascogonium is long, erect multinucleate, aseptate tubular structure. • The uninucleate mycelium forms ascogonium which elongates and gives rise to 64 nuclei after repeated division . • Simultaneously a uninucleate antheridium also develops and coils spirally around the multinucleate ascogonium. • The antheridial tips touch the ascogonoium at one point and the walls of the two, at the point of contact dissolve. • Side by side the ascogonium gets segmented in the form of many binucleate cells.

Development of Ascogenous hyphae

• Lateral outgrowths arise from some of the binucleate cells or segments. • The nuclei in the ascogenous hyphae which forms the asci therefore are derived from the original nucleus of the ascogonium (Fig. 5, A- G). • Many sterile hyphae develop and enclose the young asci from all side, the fruiting body i.e. Ascocarp is a cleistothecium type. • Many asci, each with eight uninucleate ascospores are formed within the ascocarp.

• The cleistothecium of Penicillium represents the following three generations:

(i) Parent haplophase: It is represented by the sheath peridium or peridium made up of loosely interwoven hyphae. (ii) Dikaryophase: It is consists of binucleate cells of the ascogonium, ascogenous hyphae and the ascus mother cells. The tertiary diplophase is represented by the young ascus containing a diploid nucleus. (iii) Future haplophase: It is represented by the ascocarp in the asci.

Discharge and Germination of Ascospores :

• At maturity the walls of the asci dissolve and ascospores are liberated. • Ascospores absorb nutrition and mature.The mature ascospores are finally released by the decay of the other wall of the peridium . • On falling on the suitable substratum under suitable conditions (Temp, moisture, and plenty of air) each ascospore germinates and forms the mycelium. (Fig 6, A-F)

Economic Importance

• P. notatum (Fleming 1944) and P. chrysogenum (Raper, 1952, 1978) are used for the production of penicillin throughout the world. • The antibiotic griseofulvin, used in skin and nail infection is prepared from P. griseofulvum. • Decaying and rotting of citrus fruits is done by P. digitatum and P. italicum, whereas apples are decayed by P. expansum. • Some species destroy the leather and fabrics whereas others are associated with some human and animal diseases. • During damp and warm weather this fungus appears on bread, cheese, butter, jam, jelly and cause spoilage of these foodstuffs. • Some species eg. P. roqueforti and P. camemberti are used in food manufacture. • Some species are also used in the production of organic acids such as oxalic, fumaric, gluconic and citric acids.

LICHENS

“A lichen is an association of a fungus and a photosynthetic symbiont, resulting in a stable thallus of specific structure” (International Association for Lichenology, 1981) or “A stable self supporting association of a Mycobiont and a Photobiont” (Dictionary of the fungi, 1983) where fungal partner is known as Mycobiont and the photosysnthetic partner ie., algal member is as Phycobiont. According to the majority of the lichenologist a symbiotic relationship exists between these two partners where fungus parasitizes the algal cells and also lives there saprobically. The algal cells are protected by the fungal cells and in turn getting nutrition and other support from them. The lichens are a small group of cutious plants with about 18,000 species.

Components of Lichens:

Mycobiont is usually a member of Ascomycotina, less commonly of Basidiomycotina and rarely of Deuteromycotina. A majority of the ascomycetous lichens belong to either Discomycetes or Pyrenomycetes, whereas some are of Hemiascomycetes, Plectomycetes and laboulbeniomycetes. Hawksworth and Hill (1984) mentioned that out of about 13,500 lichenized fungi, 13,250 species (98%) belong to Ascomycotina. Further it has also been reported that out of all species of Ascomycotina only 46% are lichen forming species which belong to orders Graphidales, Gyalectales, Peltigerales, Pertusariales and Teloschitales. Lichen forming genera of Basidiomycotina are Dictyonema, Omphalina and Multiclavula whereas only 55 species of Deuteromycotina have been reported so far to form lichen (Hawksworth and Hill, 1984). Phycobiont is usually a member of Cyanophyceae (blue green algae) and less commonly of chlorophyceae (green algae). 37 algal genera have been identified so far as lichen phycobionts. Common lichen-forming blue-green algae are Anabaena, Calothrix, Chroococus, Nostoc, Scytonema, Stigonema and Gileocapsa. Common members of Chlorophyta are Chlorella, Phycopeltis, Trebouxia, Cephaleurus and Trentepohlia.

Occurrence

Lichens grow in a wide variety of situations from the Arctic to Antartic and all regions in between. They are reported growing on leaves, bark of trees, soil, bare rock and many after similar situations.

Based on their habitat lichens are placed under following groups:-

1. Corticolous: Lichens developing on bark of trees. eg. Species of Parmelia, (Fig.1) Alectoria, Usnea, (Fig. 5) Graphis, etc. 2. Lignicolous: Lichens developing directly on wood e.g. Calicicum, Chaenotheca, Cyphelium etc. 3. Saxicolous: Lichens developing on rocky substrata e.g. Verrucaria, Porina, Dermatocarpon, Xanthora, etc. 4. Terricolous: Lichens growing on the ground e.g. Cladonia floerkeana, (Fig.2) Lecidea granulose, Collema tenax, etc. 5. Marine: Lichens developing on hard siliceous shores of sea e.g. Verrucaria mucosa, Caloplacentum marinae, Caloplaca marina, etc. 6. Fresh water: Lichens developing on hard siliceous rocks in fresh water e.g. Hymenelia lacustris, Epheba lanata, etc. 23

Many man made substrata, such as leather, silk, wool, hairs, bone, glass, fibre, timber, walls, paints, sculpture and asbestos-cement may also be colonized by lichens. Morphology and Anatomy

Formerly only three basic types i.e. Crustose, Foliose and Fructicose (Figs.3A-C) were recognized but on the basis of their detailed studies Hawksworth and Hill (1984) described the following categories and subcategories:- 1. Leprose lichens – This is simplest type of thallus organization in which the fungal hyphae develop either single or small cluster of algal cells. A distinct fungal layer does not envelop the algal cells all over. It appears as powder on the substratum. e.g. Lepraria incana . 2. Crustose lichens – The thallus is very closely adhered to the substratum and provides a crust like appearance. The algal cells are covered by a distinct layer of fungal tissue. e.g. Rhizocarpon.

Some variation in crustose types are mentioned below:- I. Placodioid – When the outer surface is radially striate and contains slightly raised marginal tissues, the lichen is called Placodioid or Placoid e.g. Lacanora and Caloplaca. II. Squamulose – When the outer surface contains overlapping scale-like aquamules, the crustose lichen is called Squamulose. e.g. Psora. 3. Foliose lichens – The thallus is flat, leaf-like, well branched, lobed and attached to the substratum with the help of rhizoid like rhizines. The external appearance is like that of crinkled and twisted leaves e.g. Parmelia, Physcia, Collema, Peltigera, etc. (Figs. 1,4)

Foliose lichens may fall into any of the following categories:

I. Homoiomeros – the algae in some lichens are distributed more or less evently throughout the thallus as e.g. Collema. (Fig.6) II. Heteromeros – the algal cells are in majority of the foliose lichens form a distinct layer (algal zone) within the thallus e.g. Parmelia, Physcia, etc. (Fig.7)

4. Fructicose lichens – These are well branched, generally erect or pendulous structures which provide shrubby appearance e.g. Usnea, Cladonia, Letharia, Bryoria, etc. (Figs. 2,5) 5. Filamentous lichens – In all the above mentioned lichen types (Leprose, Crustose, Foliose, Fructicose) the fungus has the main role in the formation of the structure of the lichen thallus. But in some lichen genera e.g. Coenogonium, Ephebe, Racodium, Cystocoleus the algal partner is filamentous, well developed and remains enseathed or covered by only a few fungal hyphae.

Tissue types in lichens

Cortex like tissues in foliose and fructicose lichens consist of following two main types:-

1. Paraplectenchyma – The cells are oriented randomly and provide a cellular appearance. 2. Prosoplectenchyma – The elongate fungal hyphae are oriented in a particular direction.

However, in some lichens (Parmelia), the cortex is over lined by a thin layer of polysaccharide called, epicortex (Hale, 1973).

Attachment organs in lichens

Lichens remain attached to the substratum by following means:- 1. Medullary hyphae: Some fungal hyphae from the medulla penetrate the substratum in absence of water cortex e.g. majority of the Leprose and Crustose. 2. Rhizinose stand: These are complex, tough, irregularly branched thick strands e.g. Buellia pulchella. 3. Hyphal net: In some cases the fungal hyphae form delicate reticulately branched net like structures e.g. Psora decipines. 26

4. Rhizines: Simple, unbranched or branched attachment organs of foliose lichens are called rhizines. e.g. Physconia pulverulacea. 5. Hypothallus: a thick, black, spongy, algal-free tissue on the lower surface of genera e.g. Anzia. 6. Host fast: It is the basal, black, algal-free persistent region of some lichens e.g. Usnea and Letharia. 7. Hapters: These are the short apical, penetrating branches of some large pendulous lichens which loose their attachment with the point of their origin e.g. Alectoria sarmentosa.

Propagules associated with Lichen thallus

Breathing pores – These are the area in the cortex where loosely inter woven hyphae are present e.g. Oropogon. Cyphellae – These are the circular depression present only on the lower surface of certain lichens. e.g. Sticta sylvatica Pseudocyphellae – In some cases loose hyphal medullary tissue comes to the surface of the lichen thallus in the form of discrete patches e.g. Alectoria, Bryoria, Coelocaulon and Pseudocyphellaria. Cephalodia – A special external or internal swellings by the segregation of blue green algae in three membered (2 algae + 1 fungus) lichen is called Cephalodia e.g. Lobaria amplissima, L. pulmonaria and Solorina crocea. (Fig.8 A-B). Isidia – An isidium is a small and corticated outgrowth present on the upper surface of lichen thallus. It is made up of both fungal hyphae and algal cells. (Fig. 9) Soredia – A soredium is a small but noncorticated bud like outgrowth present on the upper surface of the lichen thallus. It is made up of only a few algal cells, enclosed by only a few fungal hyphae. (Figs.10)

Both Isidia and Soredia are meant for the vegetative reproduction.

Nutrition The algal cells obtain water and minerals from the thallus of which they form a part. They provide themselves with carbon from the carbon dioxide of the air. From these raw materials they synthesize the necessary carbohydrates with the help of their chloroplast. A part of these carbohydrates the alga uses in nutrition, the rest is supplied to the fungal partner. The actual mechanism of interchange of food between the two symbionts is still obscure. The movement of food materials probably occurs by diffusion. The soluble food material diffuses out from the alga and is absorbed by the fungal partner. In addition the fungus may augment its food supply by annexing. It may also consume the dead bodies of algal cells in due course of time.

Reproduction

A. Reproduction of Lichen thallus

It multiplies by:-

1. Fragmentation:- It consists in the breaking up of the established thalli into segments which are distributed to start new growths e.g. Cladomia uncialis, C. stellaris and Bryoria capillaries. 2. Isidium:- a detached isidium develops into a new lichen thallus e.g. Parmelia, Pseudoevernia, Bryoria and Usenea, etc. 3. Soredia:- each soredium may develop into a new lichen thallus e.g. Parmelia and Bryoria.

Asexual spores:-

1. Conidia: The conidia of different shape and size develop in special multi hyphal structures in many lichens e.g. Anthonia, Lecanactis, Peltigera, Roccella, Cladonia, Lobaria and Xanthoria etc. which germinate in contact with an appropriate phycobiont to give rise to new lichen. 2. Oidia: according to Smith (1921) the hyphae of certain lichens breakup into bodies, called oidia which may germinate into hyphae.

B. Sexual reproduction of Mycobiont

In Ascolichens – It takes place by means of:- 28

Ascogonium:- it is multicellular with coiled lower portion which develops from the certain hyphae situated deep in algal layer. Cells are usually uninucleate. The upper portion of the multicellular ascogonium usually projects Trychogyne (Fig.11).

Spermatium:- The conidia produced in pycnidia which is called spermatia i.e. male cells. Fertilization:-At the time of fertilization many spermatia are lodged against the sticky tips of the trichogne. The cytological process involved in fertilization and further development of ascocarp are difficult to observe, due to minute nuclei and chromosomes. Ascocarp:- After fertilization many small ascogenous hyphae develop from the basal portion of the ascogonium which finally develops into an ascocarp. A number of asci are formed within the ascocarp each having eight haploid nuclei. The ascocarp may be either an apothecium e.g. Lacidella, Arthonia, Graphis, Physcia, Baeomyces, Umbilicaria etc. or a peritheci type e.g. Pyrenula, Vernicaria, Acrocordia etc (Fig.12).

Hamathecia:- The tissue that separate the asci are called hamathecia (Hawksworth and Hill, 1984). According to Erickson (1981) the hamathecial elements may be any of the following types :-

(i) Paraphyses – Originates from the base of the ascocarp and grow upwards. (ii) Paraphysoides – Originates from the tissues of the ascocarp before the development of asci. (iii) Periphysoides – Originates from above the asci and grow downwards. (iv) Periphyses – These line the ostiolar canal and grow upwards.

The ascospores are discharged and germinate by producing hyphal branches which comes in contact with a suitable alga to form a lichen thallus.

In Basidiolichens No basidiolichens have sexual cycle. However, it is presumed that basidiospores are formed in mycobiont belonging to Aphylophorales or Agaricales.

C. Reproduction in Phycobiont

Blue green algae reproduce by akinetes, hormogonia, heterocysts and cell division in laboratory. Green algae are known to multiply by vegetative cell division and formation of aplanospores and biflagellate zoospores. The sexual reproduction in phycobionts has not been observed in nature.

Ecological Importance

The lichens are of considerable ecological importance. They are slow but efficient soil farmers. They are the pioneers to grow on barren, nacked, rocky surface where no other plants can grow. Leprose and Crustose are usually the first to appear and they are followed by the Foliaceous and the Fructicose types. The lichen thalli secrete certain organic acids which gradually dissolve and disintegrate the rocks to which they cling. The rock particles together with decaying and dead lichen thalli form a soil fertile enough for other plants to make appearance. The successors are the Mosses. Sooner or later flowering plants begin to grow in the soil.

Economic Importance

Biochemical weathering & pedogenesis:- The Crustose lichens affect the chemistry of the rocks on which they grow producing a series of activities, which are collectively called “Biological weathering”. After biological weathering new soil forms this phenomenon is called “Pedogenesis”.

Natural products:- Lichens are known to produce over 550 natural products, including locanoric acids, Salazinic acid, Squamatic acid, lichenin, zeorin and many other aliphatic acids, benzyl exters, xanthones, terpenoides, etc.

Drugs from lichens:- • Usnic acids produced from many lichens, have antibiotic properties and are effective against many Gram (+)ve bacteria. • Many antiseptic creams, such as ‘Usno’ and ‘Evosin’ are available in the market and well known for their tumor inhibiting spasmolytic and virucidal properties. • Erythrin obtained from Roccella montagnei is used in angina a serious heart disease. • Some lichens have protolichesterinic acid, a compound used in the preparation of some anti-cancer drugs. • Some lichen compounds (Lichenin and isolichenin) have anti-tumour properties. 30

• Use of Lobaria pulmonaria and Cetaria islandica in tuberculosis and other lung diseases is known since very early times. • Some lichens are used with tobacco because of their hallucinogenic effects.

Perfumes from lichens:- Pseudevernia furfuracea and Evermia prunastri are widely used in the manufacture of perfumes. The remainder, left after the preparation of perfumes from lichens, contains compounds such as naphthalene, camphor, geraniol and borneol.

Dyes from lichens:- • Red and purple dyes are obtained from Ochrolechia androgyna and O. tartaria. • Litmus paper is prepared from Rocella montagnei and lasallia pustulata. • Brown dye obtainedParmelia omphalodes is used to dye wool and silk fibres. • Lecanoric acid, erythrin and gyrophoric acid is responsible for different colours.

Foods from lichens:- • Cladonia rangifernia (reindeer moss) serves as a common food in Tundra regions for many animals, including reindeer and musk ox. • Species of Parmelia lacanora and Cetraria are eaten by man, horses, cattles etc. in some form or other.

Materials for religious purposes from lichens:- The perfume obtained from lichen is also used in the manufacture of “Dhoop” and “Havan samagries” at the time of religious ceremonies.

Poison from lichens:- Letharia vulpine (Wolf moss) is used as a poison for wolves when mixed with powdered glass. Vulpinic acid, present in this lichen is responsible for its poisonous nature.

CERCOSPORA

The genus Cercospora with about 3800 species (Chupp, 1953) belongs to class Deuteromycotina order Moniliales and family Dematiaceae. Of all more than 260 species are reported from India (Vasudeva, 1963). Over 700 common species are known to cause leaf spot diseases of higher plants of economic value like tomato, lettuce, potato, cotton, rice groundnut, chillies, pigeonpea, beet, tobacco, etc. Some common leaf spot diseases caused by the species of Cercospora, are listed below:

1. Tikka disease of groundnut (Arachis hypogea) - C. personata C. arachidicola 2. Leaf spot of Gossypium herbarum - C. gossypina C. oryzae 3. Leaf spot disease of rice - C. oryzae 4. Leaf spot disease of Solanum nigrum - C. nigri

Some species also cause severe lesions on the human face making it horrible (Emmons et. al.,1957) e.g. C. apii. The perfect state of both C. personata and C. arachidicola is Microsphaerella berkleyi.

Somatic structure • The mycelium is well developed, branched and consists of septate, slender intercellular hyphae. • Branched haustoria are present in C. personata whereas both the internal and external mycelium are found in C. arachidicola. • The young hyphae are hyaline which becomes brown at maturity. Some of the hyphae aggregate in the stomatal cavity and form stroma.

Asexual Reproduction • It takes place by means of long cylindrical usually hyaline, multi septate conidia, which are abstracted successively at the tips of unbranched, dark conidiophores. The latter arise in tufts from a stroma lying in a substomatal cavity and emerge by rupturing the overlying epidermis. The conidiophores are hyaline to dark brown septate or non septate, sometimes branched straight or flexuous and show geniculate (Knee like) bends. • The conidium as it falls off, leaves a scar on the conidiophore. • The conidia develop on septate, dark-coloured conidiophores. • The conidia are long, slender, narrow, tapering and contain many transverse septa. • The conidia are dispersed effectively by rain splash. • Under ambient temperature and moisture each conidium germinates into a new mycelium. 32

Disease Management/Control Measures • Crop rotation. • Seed treatment. • Disposal of infected host debris by burning or burying in deep pits to eliminate chances of primary infection from the soil borne inoculum. • The seeds within the shells are disinfected with sulphuric acid. • Without shells they are soaked for half an hour in 0.5% copper sulphate solution. • Agrosan GN dressing of naked seeds. • Field spraying by suitable fungicides e.g. Bordeux mixture, Diathan, Red oxide, copper dust + sulphate in the ratio 1:1. • Uses of disease resistant and early maturing varieties.

COLLETOTRICHUM

The genus Colletotrichum with about 11 species (Von Arx, 1957) and more than 1000 form species (Alexopoulos and Mims, 1979) are parasites and saprophytes on terrestrial vascular plants. • It belongs to Class- Coelomycetes, Order- Melanconiales and Family- Melan coniaceae, having acervular type of fruiting bodies. • The form genus which includes a number of species viz., C. gloeosporoides, C. dematicum, C. coccodia, C. graminicola, C. falcatum, C. capsici produce a alike symptom is known as anthracnose cause serious diseases to economically important plants. The common examples are: 33

o Colletotrichum falcatum incitant of red rot of sugarcane. o C. capsici incitant of ripe fruit rot and die back of chillies. o C. gloeosporioides incitant of mango, citrus and banana. o C. coffeanum incitant of coffee berry. • The common species Colletotrichum gloeosporides having its perfect stage i.e. Glomerella cingulata an ascomycetous fungus.

Somatic structures • Mycelium is endophytic and consists of slender, branched colourless, septate, intercellular as well as intracellular hyphae. • Mycelium is hyaline in young stage which becomes dark at maturity.

Reproduction Colletotrichum reproduces only asexually by conidia which are born on saucer shaped, flat or black velvety structure ie., acervulus • It may be sub-cuticular, sub-epidermal or epidermal with a characteristic peripheral ring or black, long and stiff setae consisting of a dense, palisade-like layer of short, hyaline conidiophores. • The conidiophores are unseptate, usually unbranched and rarely branched which bears many unicellular, folcate or sickle-shaped, hyaline conidia. • Setae may be present in some species which is long, stiff, pointed, unbranched and multicellular bristle like. • Sclerotia are also formed in some species of Colletotrichum. • Moist weather is essential for conidia formation. • The conidia are dispersed by wind spattering rain or irrigated water. • The conidia are short lived and thus germinate readily under suitable conditions of moisture and temperature by one or more germ tubes to form mycelium. • Terminal or intercalary thick walled chlamydospores are formed by the septation of hyphae which persist in the soil for a long-time. 34

Control Measures

• Removal and sanitation of the diseased plants. • Long crop rotation. • Uses of disease resistant variety. • Use of fungicides is example 1% solution of copper oxychloride (50% copper). • Aerial spray with Perenox (0.2%) 3-4 times.