CLASSIFICATION OF FUNGI

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CLASSIFICATION OF FUNGI GAYATHRI.V 1ST SEM M.Sc

What is fungi ? : 

What is fungi ? Fungi is the plural form of fungus which is derived from the latin word fungour means to flurish In common language the fungi may be defined as non green, nucleated thallophytes. According to Alexopoulos {1962} the fungi is nucleated spore bearing achlorophyllous organisms that generally reproduce sexually and whose filamentous branced somatic structers are typically surronded by cell wall contaning cellulose or chitin or both.

classification : 

classification

Phylum chytridiomycota : 

Phylum chytridiomycota Powell in 1993 as shown convincingly that they are an ecologically significant & interesting grp as 110 genera & 575 sps. Chytrids are present in aquatic habitat{like oceans & in fresh water} & in soils. These are the only members of the kingdom fungi that produce motile or zoospore at some stage of their life cycle. Each organisms possess a single posteriorly directed whiplash flagellum. Thallus is coenocytic {no septation}. The cell walls are made up of chitin & glucan. Nuclear divisions is intranuclear {within the nuclear membrane} & centric.

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. Because of their extremely small sizes, most chytrids can be detected only by microscopic examination. It is present either on the cells and tissues of plants & animals or parasitize on the dead organic matter. There is considerable interest in the anaerobic chytrids found in the rumen of cattle and sheep and it is also found in cecum of horses and other herbivores. They play a significant role in degradation of fibers entering the gut. Some of the imp chytrids to humans include a] plant pathogenic sps- synchytrium endobioticum –causes a serious afflication of potatoes known as black wart disease physoderma maydis –causes brown spot of corn & crown wart of alfalfa

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b] various sps of chytrid genus coelomyteces parasitize mosquito larvae & yet it is proved to be valuable as biological control agents. Blastocladiella emer sonii and allomyces macrogynus are free living saprobes that have become popular experimental organisms in cellular and molecular biology laboratories.

Reproductive structures : 

Reproductive structures ENDOBIOTIC- these are the simple form which is present entirely within the cells of their hosts. The nature of thallus is surrounded by a cell wall, although the early may be nacked. EPIBIOTIC- these structures are produce on the surface of either aliving host or some piece of dead organic matter, absorbing structures sunken into the hosts and draw their nutrition. In some speices, both epibiotic and endobiotic sporangia are found eg: physoderma. HOLOCARPIC- entire thallus structures is converted into one or more strutures. eg: olphidium. EUCARPIC- the part of thallus is converted into reproductive structures but not whole. These give raise to zoospores or gametes.

ALLOMYCES : 

ALLOMYCES OCCURRENCE- it was first discovered by in india by Butler{1911}. it is world wide in disturbution, in tropical or warm countries. The genus comprises of 5 sps A. macrogynus &A. javanicus are imp . HABiTAT-all are saprophytes, soil dwellers & are found in wet soil. THALLUS STRUCTURE- it is filamentous & attached to the subtratum by a tuft of delicate but well formed,branced rhizoidal str. On these reproductive organs are born terminally. The hyphal wall constists of chitin, glucan & ash .besides of nuclei & mitrochondria a unique organells are called concentric granules.

REPRODUCTION : 

REPRODUCTION In thallus it is of two types, gametothalli and sporothalli. Towards maturity the gametothalli bear gamatangia & sporothalli baer sporangia. These gametes are motile, uninucleate & post. Unflagellale {whiplash type}. These gametes of both kinds are discharged singly one after the other release into the water at the same time through the papilla. The female gamete produce a harmone called sirenin. These act as chemoattractant .which attract male towards it. Both of them copulate in pairs. This is followed by fusion of cytoplasm called plasmaogamy. Then fusion of nuclei called karyogamy. These resultant fusion of cell forms zygote & germination of zygote takes place . Zygote puts out a slender basal germ tube which grows into branches7 grows as a new allomycses.

LIFE CYCLE OF ALLOMYCES : 

LIFE CYCLE OF ALLOMYCES

OOMYCETES : 

OOMYCETES Sexual repr by means of biflagellate zoospores with a longer tinsel flagellum directed forward & a shorter whiplash type directed backward. Oogamous rper by gametangial contact that results in the production of a thick walled sexual spore called as zoospore. Cell wall is composed of B- glucan, A.A, hydroxyprotien and small amt of cellulose. Mitochondria with tubular cristae. These are present all the world in both fresh & salt water and aslo in terristreial environments. Most of them are aquatic form so called as water moulds. It is of 2 types, parasitic {algae& namatodes} ex: phythium insidiosum causes pythiosis & saprophytic.

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It causes most serious diseases of economically imp plants ex: late bilght of potato, rots of citrus, downy mildew of grapes etc . 2 imp speices are, phytophthora infestans and plasmopara viticola . Oomycota includes both unicelluar,holocarpicforms 7 eucarpic, filamentous sps composed of profusely branched coenocytic hyphae. In addn to distinctive mitochondria & golgi bodies, it possess a unique organelles referred to as either finger print vacuoles or dense body vacuoles. Various function have been proposed in the formation of ooplast: Numerous nuclei are present in hypha of typical oomycete Both mitotic & meiotic divisions in the oomycetes are intranuclear & centric.

Nuclear envelope remains intact.Cell wall composed of B- 1,3 & B- 1,6 glucans and cellulose, chitin is absent . Hydroxy protein has been reproted from cell walls of oomycetes. Hyphae may be either an intracellular or an intercellular fashion. In obligate parasites, tend to remain b/n the host cell, & which give raise to hyphal branches called as HAUSTORIA . Septa are absent expect at the bases of reproductive organs and in highly vacuolate portion of the hyphae of some sps.

Sexual reproduction : 

Sexual reproduction It is heterogametangic: male structures called antheridia & female called oogonia. The eggs/ oospheres have outer periplasm & central ooplast with 1 or more nuclei. Oospores is thick walled, resistant the mature oospore as 3- layers a] exospore b] epispore c] endospore Antheridia is attracted by harmones, & produce a fertilization tubes, when they are closely pressed the male nucleus fuses with nuclus of oosphere 7 develops into oospore.

Asexual reproduction : 

Asexual reproduction It is by heterokant zoospores {one large tensil & whiplash}. Zoospore develops from sporongia in a few sps. Two types of zoospores are produced in oomycete which are biflagellate. 1] primary zoospores- it is of pyriform {pear} with 2 flagella present at the ante end. 2] secondary zoospores- it is of renitype {bean shape} this are inverted laterally into groove of spore surface.tensil is directed at 130 & hairs are present at whiplash flagella. The zoospores will swim for some time for short distances through water, & find substratum & encyst, then give raise to new thalli.

PYTHIUM : 

PYTHIUM CLASS- OOMYCETES ORDER- PERNOSPORALES FAMILY- PYTHIACEAE GENUS- PYTHIUM The family includes both aquatic & terrestrial sps. A few sps paratise on algae & protozoa. Mycelium is non septate & septa are formed only during the formn of reproductive structures. hyphae contains large no of nuclei & reserve food in the form of glycogen. The hyphae in most of the sps are intracellular .haustoria are prtoduced in some sps.

REPRODUCTION : 

REPRODUCTION takes both by sexual & asexual methods. Asexual repr takes by the form of sporangia these are small globular or sac-like structures produced in the aerial hypha and singly at terminal ends. At the maturity a beak like out growth is formed ta the side of zoosporangium. Later it develops & enlarges at distal end and forms a vesicle. By the time zoosporangium divides into uninucleate daughter protoplasts . Then migrate to the vesicles and maturation takes place. It develops into biflagellate zoospore . Flagella is lost after short period of motility & develops a thin layer of cell wall & germination by germ tube.

Sexual reproduction : 

Sexual reproduction Sexual reproduction is by oogonium. Antheridium and oogonium are produced at the end of growing season . pythium is homothallic . Oogonium is spherical and differentiated into outer periplasm & centeral granular portion called ooplasm. Antheridium is of club shaped. It is coenocytic and as many nucleus. The antheridium bends and closely fix to the ooganium . Then it send out a tube fertilisaton tube . This tube pierces through oogonial wall & elongates to reach the tube then it fuses with the egg to form a diploid zygote. Oospores undergoes rest for several months then germination takes place in moisture. The thick wall bursts out and directly mycelium arises from it.

Economic importance : 

Economic importance P. aphanadermatum – soft rot in ginger and also in papaya. Damping of in tobacco, tomato & chilles. Wheat rot in a wheat. Soft rot in turmeric by p. graminicola

ZYGOMYCETES : 

ZYGOMYCETES This produces a thick walled resting spores called zygospores later develops into zygosporangium. it as coenocytic mycelium[ no septation]. The cell wall is made up of chitin and polyglucuronic acid. Asexual reproduction is by sporangiospores & absence of flagellate cells. Some sps produces chlamydospores and athrospores in addition. Nutritional modes from saprophytes and facultative parasitism . Few sps forms mycorrhizal partners with plants.

Sexual reproduction : 

Sexual reproduction This as both homothalli and heterothalli sps that produce zygospora. Zygospores of opp types grow towards another in a dirtected fashion. The tips swells up & froms progametangia . Then this fuses where plasmogamy & karyogamy occurs. A zygote forms in which a single zygospore develops

RHIZOPUS : 

RHIZOPUS OCCURRENCE: it is the commonest & best known fungus found on bread & known as bread mould. It is exclusively saprophtye and grown in moist & damp places. THALLUS: long, slender and freely branched filaments. Hyphae form a fiuffy white mass makes up the thallus of fungi & also called as mycelium . Black, pin head like structures develop on the mycelium hence popularly called as black mould. It is attached to the substratum. stolons are produced on it called as aerial hyphae , grows horizontally. These stolons give raise to roots like structures known as rhizoid.

Slide 30: 

RHIZOPUS

ASEXUAL REPRODUCTION : 

ASEXUAL REPRODUCTION It occurs by chlamydospores. {thick walled}.. They contain sufficient amt of resever food & are resistant to desiccation . On substraum mycelium starts drying & spores germinate. By oidia formation- mycelium is in sugar medium a coenocyctic hyphae develop & divide into short segments then forms oidia. By sproluation- small, non- motile & black spores.

Sexual reproduction : 

Sexual reproduction

ASCOMYCETES : 

ASCOMYCETES It is also called as sac fungi. The ascospores are produced in a sac like structure called ascus. the cell wall as B- 1,3 glucans & polysaccharide. The somatic structures are well developed & as branched mycelium. The origin of dikaryophaes, distinguish b/n ascomycetes & phycomycetes. Croos wall is common, but it is not coenocyctic, septal spoers are called woranin bodies [crystalline protein}. There is complete absence of motile cells.

ASEXUAL REPRODUCTION : 

ASEXUAL REPRODUCTION BY Budding: By fragmentation. By conidia.

Sexual reproduction : 

Sexual reproduction

Fruiting bodies : 

Fruiting bodies 1] cleistothecium 2] perithecium 3] apothecium

BASIDIOMYCETES : 

BASIDIOMYCETES Basidomycetes are filamentous with both uninucleate and or dikaryotic hyphae depending on stage. These group includes both saprophytic and parasitic sps {wood , roots barks of trees}. Basidiomycetes produce a highly complicated fruiting bodies called basidiocarps. The well developed, filamentous, mycelium mass, septate hyphae in a fan shaped manner. The cell wall is chitinous. Most of them are heterothallic{+, -}. The two nuclei fuses to form a dikaryon. Somatic structures are yeast like.

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Motile cells are abesent in the life cycle. The clamp connections on the dikaryotic hyphae . Aseual reproduction spores which latter it develops into uredospores and aeciospores in the rusts. The sex organs are lacking in basidiomycetes. The sexual proces is by plasmogamy & karyogamy . Basidium is the reproductive organ in which basidiospores germinates to produce the mycelium

Life cycle : 

Life cycle The life cycle is as follows: Spores germinate into uninucleate hyphae. Two different hyphal strands can fuse to form a dikaryotic hyphae. To insure that each new cell contains a nucleus of each type a clamp connection must be formed - see diagram beneath (b). The dikaryotic tissue forms the basidiocarp. As they develop, basidia form on the gills, which makes up the cap.As the basidia form the 2 nuclei fuse to form a 2N nucleus and then goes meiosis to form the 1N spores which are dispersed to the wind.

CONCLUSION : 

CONCLUSION Fungi is achlorophyllus. Fungi used as food.[agaricus biporus} As biological assay.{ assay of drugs] As biological controling agents. As single cell proteins. Fungi used as antibiotics.

REFERENCES : 

REFERENCES A TEXTBOOK OF FUNGI - VASHISTA AN INTRODUCTION TO MYCOLOGY - MEHOROTRA MYCOLOGY - ALEXOPOULUS WEB ADDRESS: WWW.GOOGLE.CO.IN

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THANK YOU

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