Asexual reproduction in Fungi -Dr C R Meera

This slideshow describes asexual reproduction methods in fungi in detail. Methods like Fission, Budding, Fragmentation, Spore formation (Asexual spores) are explained in detail. Asexual spores and their formation are well explained with examples.

1. Fungi – Asexual Reproduction Dr C R Meera, M Sc ; PhD, Assistant Professor Department of Microbiology St Mary’s College, Thrissur-20 Kerala

2. FUNGI Reproduction by both Sexual and Asexual Methods Yeasts ( Eg: Cryptococcus neoformans ) – Asexual (Budding, fission) and sexual methods Yeast like fungi ( Eg : Candida albicans ) – Asexual (Budding & Fission) Molds : Both asexual and sexual methods Fungi imperfecti : Sporogenesis or Asexual Spore Formation Sexual phase not defined

3. ASEXUAL REPRODUCTION IN FUNGI Somatic or Vegetative reproduction Asexual : No union of nuclei, sex cells or sex organs Fission of somatic cells Budding of somatic cells Fragmentation Spore formation

4. 1. Fission Parental somatic cell Daughter cells Karyokinesis (Nuclear division) followed by Cytokinesis (Cell division) Two identical daughter cells Eg : Schizosaccharomyces pombe , also called "fission yeast "

5. 2. Budding Parental somatic cell Daughter cells Somatic cells produce a small bud like out growth which develops into a new individual Daughter cells pinch or bud from the parental cell Daughter cells are smaller than the mother cell Yeast cells divide once every 90 min Eg : Saccharomyces cerevisiae, Cryptococcus neoformans

6. 3. Fragmentation Disjoining of hyphal cells Disjoined single cells act as the spores and germinate to produce hyphae and mycelium Spores produced by fragmentation are called Oidia or Arthrospores or Thallospore Eg : Erysiphe

7. 4. Asexual Spore Formation Asexual spores are produced from single parental cell Function : Dissemination of the species Mitospores : As these spores are produced by mitosis Pleomorphic or polymorphic fungi : Fungi that produce more than one type of spores   Sporophores : Special spore producing hyphae Name of this special hyphae changes according to the type of spore produced on it. Eg : Hyphae that produce Sporangiospores are called Sporangiophores Hyphae that produce Conidiospores are called Conidiophores

8. EXOGENOUS SPORES Spores are either packed inside special sac-like structures called Sporangium or at the terminal ends Endogenous spores : Spores produced inside the sporangia Exogenous spores : Spores on the terminal ends of sporophores Sporangia is terminal or intercalary in their position. Different asexual spores a) Sporangiospores b) Conidiospores or conidia c) Oidia ( Arthrospores / Thallospores ) d) Chlamydospores e) Blastospores ENDOGENOUS SPORES Sporangium Sporangiospores Columella Apophysis Septum Sporangiophore Mycelium

9. a) Sporangiospores      Single celled spores produced inside the special sac-like structures called Sporangium (Sporangia Pl .) Eg: Mucor and Rhizopus Sporangiophores : Special hyphae producing Sporangia Columella : Sterile dome-like structure at the tip or within a sporangium Apophysis : Funnel-shaped swelling of a sporangiophore , below the columella Sporangiospores can be motile or nonmotile Aplanospores : Non-motile sporangiospores Zoospores : Motile sporangiospores with flagella Sporangium Sporangiospores Columella Apophysis Septum Sporangiophore Mycelium

10. b) Conidiospores or conidia Exogenous spores formed at the tip or side of hyphae Two Forms : Microconidia and Macroconodia Microconidia : Small single celled conidia Macroconidia : Large multi celled spores. The conidia are produced singly Eg : Phytophthora or in chains at the tips of the conidiophores Eg : Aspergillus or at the tips of their branches Eg : Penicillium

11. Oidia and Chlamydospores : single celled spores produced by the disjoining or fragmentation Oidia : Hyphal cells disjoin from the apical regions and each fragmented cell acts as spore. Eg : Erysiphe Chlamydospore : Hyphal Cells become enveloped by a thick wall before fragmentation Chlamydospores can be terminal or intercalary & are highly resistant to adverse conditions Eg . Mucor , Fusarium C & d) Oidia / Oidium ( Arthrospores / Thallospores ) and Chlamydospores Chlamydospore Oidium

12. e) Blastospores Blastospores : Spores formed by budding Also known as a blastoconidium (pl. blastoconidia ) Eg : Candida albicans Blastospores Chlamydospores Pesudomycelia

13. Other Methods of Asexual Reproduction Formation of Sclerotia and Rhizomorphs To overcome unfavourable environmental conditions Structures of perennation and vegetative propagation Sclerotia : Claviceps (Ergot) produce an interwoven compact form of mycelium surrounded by hard covering and is called sclerotium Round , cylindrical, cushion shaped or irregular with a dense mass of thick walled hyphae Rhizomorphs : Rope-like modified mycelium Both forms remain dormant during adverse conditions and can survive for many years They give rise to new mycelia on the return of favourable conditions

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