ASEXUAL REPRODUCTION IN FUNGI

ASEXUAL REPRODUCTION IN FUNGI

i) Budding in Yeast

·       In Budding of yeast (Example – Saccharomyces cerevisiae), the parent cell forms a Protuberance (bud) on its outer surface. As the bud elongates, the parent cell’s nucleus divides, and one nucleus migrates into the bud. Cell wall material is then laid down between the bud and parent cell, and the bud eventually breaks away.

·       One yeast cell can in time produce up to 24 daughter cells by Budding.

·       Each bud that separates can grow into a new yeast, and some group together to form colonies.

·       Some yeasts produce buds that fail to detach themselves; these buds form a short chain of cells called a Pseudohypha.

ii) Binary Fission in Yeast

·       Fission yeasts, such as Schizosaccharomyces sp., divide evenly to produce two new cells.

·       During fission, the parent cell elongates, its nucleus divides, and two offspring

cells are produced.

·       Increases in the number of yeast cells on a solid medium produce a colony similar to a bacterial colony.

iii) Fragmentation

·       In Filamentous fungi, the mycelium may fragment into a number of segments, each of which is capable of growing into a new individual.

iv) Asexual spores of Fungi

·       Spore formation is the characteristic feature of fungi.

·       Different fungi forms different types of spore. It includes

a)     Sporangiospore

b)     Conidiospore

c)     Arthrospore

d)     Chlamydospore

e)     Blastospore 

a) Sporangiospore

·   Sporangiospores are the asexual spores produced in a Sac like structure called Sporangia (singular; Sporangium).

·       Sporangium are produced at the end of special Aerial hyphae called Sporangiophore.

·       Sporangium contains large numbers of haploid spores, which are released by rapture of sporangial wall

·       Examples: Rhizopus

b) Conidiospore

·     Conidiospore or Conidia are Single celled, Bicelled or Multicelled structure born on the tip or side of Aerial hyphal structure called Conidiophore.

·      Conidia are different from Sporangiospore as these are not produced inside Sporangium or any sac like structure.

·       Conidia are born singly or in chain

·       Examples: Penicillium and Aspergillus.

c) Arthrospore

·       Arthrospore are very primitive type of spore formed by the breaking up of Fungal mycelium.

·       A spore is formed by Separation followed by Fragmentation of hyphae.

·       Examples: Trichosporium, Geotrichum and Coccididious imitis.

d) Chlamydospore

·   Chlamydospore are usually formed during unfavorable condition and are Thick walled Single celled spore, which are highly resistant to adverse condition.

·   Hyphal cell or portion of hyphae contracts, loose water, round up and develops into thick walled Chalmydospore.

·       When favorable condition returns, each Chlamydospore give rise to a new individual fungi.

·   Examples: Ascomycetes, Basidiomycetes, Zygomycetes, Histoplasma capsulatum and Candida albicans.

e) Blastospore

·       Blastospore is a budding spores usually formed at the terminal end of hyphae.

·       These spores may remains attached to hyphae and bud further to gibe branching chain of Blastospores.

·       Examples: Ascomycetes, Basidiomycetes and Zygomycetes.