The fungi have three main types of reproduction viz. vegetative, sexual, and asexual type. Some fungi show only one known reproduction type. Asexual forms (anamorph) were often described separately and given different names than the sexual form (teleomorph). The complete form having both reproductive forms is called a holomorph (Flowchart and Fig).
(A) Vegetative method:
In this type of reproduction, the new individual is formed
from the somatic portion of the fungal thallus without seed production. There
are some methods by which this propagation method is carried out viz. Fragmentation,
fission, budding, rhizomorphs, and sclerotia.
• Fragmentation: In this process, the mycelium breaks
into similar fragments with the help of external force and gradually turns into
new mycelium.
• Fission: In the case of unicellular fungi, the
single cell is multiplied by this method. The parent cell is divided into two
daughter cells by division of the nucleus followed by division of cytoplasm and
cell wall formation.
• Budding: Sometimes the parent cells produce the
outer growth known as buds. These buds are generally enlarged and slowly
separated out from the parent cells by a cross wall and finally new yeast cell
is formed.
• Rhizomorphs: In some higher fungi, hyphae are
interwoven to form a rope-like structure known as rhizomorphs. Under favorable
conditions, they grow and form fruiting bodies.
• Sclerotia: It occurs in ergot plants where hyphae
become interwoven to form a compact mass surrounded by hard coat. This
structure is known as sclerotia. Under favorable conditions, these sclerotia
germinate and form new mycelia.
(B) Asexual reproduction:
This method is carried out by sporulation where new spores
are formed in reproductive cells by the mitosis process. Each spore develops into
a new mycelium. Usually, spores are unicellular. There are different types of
spores form in various fungi.
• Zoospores: They are flagellated motile spores
produced inside a structure known as zoosporangia. They do not have cell walls
and are produced in the lower fungi. Examples: Achyla and Saprolegnia (Fig.).
Fig: Spores and zoosporangia
• Sporangiospores: They are produced inside the sac-like
structure known as sporangium. They are non-motile and branched. They can
disperse by wind. Examples: Rhizopus and Mucor.
• Chlamydospores: They develop thick walls from
hyphal cells. They store reserve foods and with favorable conditions, they
develop into a new mycelium. Examples: Mucor, and Fusarium.
• Oidia: In some filamentous fungi, the hyphae break
up into individual cells, known as oidia. They are oval-shaped and do not store
reserve food. Example: Rhizopus.
Fungi produce two types of asexual spores viz.
sporangiospores and conidia. Sporangiospores are formed inside the sporangium.
They are of two types viz. motile and non-motile spores. Motile spores are
known as Zoospores and non-motile spores are known as Aplanospores. Zoospores
are three types namely Chytridiomycota, Hypochytridiomycota, and Oomycota.
Conidia are formed at the tip of supporting hyphae known as
conidiophores. They are mainly of two types namely Thallic conidia and Blastic
conidia. Thallic conidia develop by septation and fragmentation of a hypha.
They are of two types Arthrospores (formed by septation and fragmentation of an
existing hyphae) and Chlamydospores (resting spores). Blastic conidia develop
by budding method. They develop as single spores and are classified as
Blastospores (formed by budding of hyphae), Porospores (developed through
distinct pores in the hyphal wall), Aleuriospores (single and terminal spores),
Annellospores (chain spores), Phialospores (pushed up from the tip of the
conidiophore).
Sexual Reproduction:
Sexual reproduction occurs via the fusion of gametes and
gametangia, seen in all groups of fungi. This is the method where fusion occurs
between two compatible sex cells or gametes of opposite strains. Fungal sex
organs are known as gametangia. Reproduction occurs in three phases namely
Plasmogamy, Karyogamy, and Meiosis.
• Plasmogamy: It is the accumulation of protoplast
cells of reproductive hyphae. The nucleus from one male and the other female
are closed together as a pair without fusion. These types of cells are known as
dikaryon. This phase has several methods like Planogametic copulation where
motile gametes undergo fusion; Gametangial contact where gametangia come closer
to each other and form a fertilization tube, Gametangial copulation where
gametangia fuse together and form a zygospore, Spermatization where spermatia
are formed externally on special hyphae and spermatia are develops inside the
cavities known as spermatogonia and finally Somatogamy where fusion between two
somatic cells are occurred.
• Karyogamy: This is the step where two parent nuclei
are fused together. The fusion occurs very fast in lower fungi whereas delayed
in higher fungi so that hyphae remain dikaryotic. This phase is known as
dikaryophase.
• Meiosis: After dikaryophase the next step is
meiosis where after cell division, produce four daughter cells each with half
the number of chromosomes of the parent cell, as in the production of gametes
and plant spores. The production of meiotic spores is known as meiospores.