Your Learning Point

Explain the different types of reproduction in Fungi ?

REPRODUCTION:

Most fungi can reproduce asexually as well as sexually.

(Except imperfect fungi in which sexual reproduction has not been observed).

Asexual Reproduction:

Asexual reproduction takes place by

(i) Spores (ii) Conidia (iii) Fragmentation and (iv) Budding

(i) Spores:

Spores are produced inside the reproductive structures called sporangia, which are cut off from the hyphae by complete septa.

Spores may be produced by sexual or asexual process, are haploid, non-motile and not needing water for their dispersal, are small, produced in very large number and dispersed by wind to great distance and cause wide distribution of many kinds of fungi, including many plant pathogens.

When spores land in a suitable place, they germinate, giving rise to new fungal hyphae.

Spores may also be dispersed by insects and other small animals and by rain splashes.

Spores are a common means, of reproduction in fungi.

(ii) Conidia:

Conidia (singular conidium) are non-motile.

Asexual spores which are cut off at the end of modified hyphae called conidiophores, and not inside the sporangia, usually in chains or clusters.

These may be produced in a very large number,

Can survive for weeks and cause repaid colonization of new food.

(iii) Fragmentation:

Fragmentation is simple breaking of mycelium of some hyphal fungi, each broken fragment rise to a new mycelium.

(iv) Budding

Unicellular yeasts reproduce by budding (an asymmetric division in which tiny outgrowth or bud is produced which may separate and grow or By simple, relatively equal cell division.

Sexual Reproduction:

Details of sexual reproduction vary in different groups of fungi but fusion of haploid nuclei and meiosis is common to all.

When fungi reproduce sexually, hyphae of two genetically different but compatible mating types come together, their cytoplasm fuse followed by nuclear fusion.

(i) Karyogamy and Plasmogamy:

In two of the three main groups of fungi (Basidiomycetes, Ascomycetes) fusion of nuclei (Karyogamy) does not take place immediately after the fusion of cytoplasm (Plasmogamy); instead, the two genetic types of haploid nuclei from two individuals may coexist and divide in the same hyphae for most of the life of the fungus.

(ii) Dikaryotic (Heterokaryotic):

Such a fungal hypha/cell having 2 nuclei of different genetic types is called dikaryotic (also heterokaryotic) hypha/cell.

(iii) Haploid Sexual Spores:

Different groups of fungi produce different types of haploid sexual spores, such as basidiospores and ascopores, subsequent upon meiosis in zygote.

These spores may be produced by their characteristics structure/fruiting bodies such as basidia/basidiocarps and asci/ascocarps.