Described about general characters of fungi which include sexual and asexual reproduction with diagram, so it will be easy for undergraduates to understand the various concepts

1. General characters of fungi
N. H. SHANKAR REDDY
1st , Ph.D Plant Pathology
Annamalai University

2. • Fungi are eukaryotic, achlorophyllous, non motile, unicellular or
multicellular organism, which reproduce by means of asexual or
sexual spores
• Nutrition – Heterotrophic (lack of preparation of own food
material) and absorptive (ingestion rare)
• Thallus – Unicellular, filamentous, septate or non-septate
typically non motile (protoplasmic flow) but motile stages
(Zoospores) may occur
• Cell wall – Well defined and typically chitinised (cellulose in
Oomycota)
• Sexuality – Asexual or sexual and homothallic or heterothallic
• Habitat – Ubiquitous as saprobes, symbionts, parasites or
hyperparasites.

3. • They reproduce sexually by means of spores asexually by means of
budding, fragmentation etc.
• Fungi lack chlorophyll and hence cannot perform photosynthesis.
• Fungi produce sex hormones play a major role in sexual
reproduction.
• The majority of fungi belonging to the phylum Ascomycota,
basidiomycota, zygomycota etc.
• Eg - Mushrooms, moulds, yeast

4. Thallus – Vegetative/ somatic body (entire body) of fungus. Thallus is
not differentiated into distinct parts. Thallus is divided into two
• Holocarpic thallus – The entire thallus at maturity become converted
into single or several reproductive organs.
• Eg – Olphidium and Synchytrium
• Eucarpic thallus – The mature thallus is differentiated at the time
of reproduction, into a vegetative part (which absorb nutrinets) and
reproductive part.
• Eg – Pythium and Phytophthora

5. • Hyphae – It is a microscopic, thread like
filamentous and structure. Hyphae is
divided into
Septate hyphae – Presence of cross walls
Aseptate hyphae/ coenocytic hyphae/ non-
septate hyphae – Absence of cross walls
• Mycelium – Group of hyphae collectively
called as mycelium.
• Rhizoid – It is anchoring or absorbing
organ of Rhizopus

6. Somatic structures produced by fungi
• In mycelial thallus, the differention of hyphae
may occur to form specialized structures
adapted to particular functions. The following
specilized structures are
• Rhizoids – A rhizoid is a short, root like
filamentous branch of the thallus, generally
formed in turfts at the base of the thallus.
Rhizoids function as anchoring and absorbing
organ. (eg – Rhizopus)
• Appresorium – It is simple or lobed swollen
structure to germ tube or infecting hyphae.
They adhre/ attach to host surface and provide
strong anchoring to infecting hyphae in
penetration. Eg – Rust, powdery mildews etc.
(simply attachment organ or anchoring organ)

8. • Haustorium – It is a nutrient
absorbing organ of fungi from host
cells without killing it. Haustorium is
intracellular sac like, filamentous or
branched structure and is a
characteristic of obligate parasites
(Uredinales, Erysiphales,
Pernosporales).
• Hyphal traps – The fungi which
capture the nematodes (predacious
fungi), develop a number of
modifications by their hyphae. These
modifications are known as snares or
hyphal traps. Eg – Dactylaria candida,
Arthrobotrys robusta, Monacrsporium.

9. Hyphal modifications in fungi or mycelial aggregations in fungi
• The fungal structure as resting bodies, fruiting bodies, migratory
strands etc. are formd by the aggregation of hyphae to various
extents.
• The mycelium becomes organized into loosely or compactly woven
tissues called as plectenchyma, used to designate all organized
fungal tissues. Plectenchyma basically of two types
• Prosenchyma - Loosely woven tissue in which the individual hyphae
lie more or less parallel to one another and their elongated cells are
easily distinguished from each another.
• Pseudoparenchma – It consists of loosely packed, more or less
isodiametric oval cells recembling the parenchyma of higher plants
in cross section.
• Prosenchyma and pseudoparenchyma makes various types of
somatic or reproductive structures are produced below

11. Somatic or reproductive strutcture of fungi
1. Stromata – A stroma is a compact mass of tissues.
This somatic structure is like a mattress on which
fructifications are formed.
2. Sclerotia – Hyphal aggregations with determinate
growth. This is made of pseudoparenchymatous
tissues. These types of resting bodies are produced by
the pathogenic members of Sclerotinia, Claviceps,
Rhizoctonia etc. they contains huge amount of reserve
food material (in the form of mannitol, trehalose,
glycogen and lipids) for long term survival.
3. Mycelial strands – The formation of aggregates of
parallel, relatively undifferentiated hyphae. A strand
is formed around one or more leader hyphae which
grow out of the margin of the thallus. They are
capable of translocating materials in both directions.
Commonly observed in Basidiomycotina and some
Ascomycotina and Deuteromycotina.

12. Rhizomorphs – The root like aggregation of hyphae.
Certain fungi have highly differentiatiated
aggregations of hyphae with well developed apical
meristem and a central core of thick walled
elongated cells. They are about 4 mm and having
4000 hyphae aggregations togeather.
Eg – Armillariella mellea (honey fugus or honey
agaric)
Do u know – The sclerotium of the Australian
Polyporus milittae can reach the size of man’s head
(about 15 kg) and is known as native bread or black
fello’s bread.

13. REPRODUCTION IN FUNGI
• Reproduction is the formation of new individuals with all
characteristics.
• Types
Vegetative reproduction
Asexual reproduction
Sexual reproduction

14. Vegetative reproduction
• It does not involve in the the union of nuclei, no sex cells (gamaates)
or sex organs (gametangia) are produced. The asexual spores are
also called as mitospores.
• Fragmentation - A bit of broken fragment of hyphae detchd and
establishes a new colony..
• Budding – It is the production of a small outgrowth (bud) from a
parent cell or spore. Each bud produces a new individual. As the bud
is formed, the nuclei of parent cell divides and one daughter nucleus
migrates into bud. Budding can be observed in yeast.
• Fission – The splitting of a cell into two daughter cells by
constriction. The nucleus divides mitotically along with the
formation of a cell wall. Although, it is a characteristic of bacteria
and it also occurs in fission yeasts.

15. Asexual reproduction
• Production of asexual spores – Spore is a reproductive structure of
fungi. There are two major kinds of asexual spores in fungi.
1. Sporangiospores – Produced within the sporangium. The
sporangiospore are two types
• Aplanospores – They are non motile spores having typical cell wall
around them. They ar uni or multinucleate, unicellular, smooth
walled, globose or ellipsoid in shape. The number of aplanospores per
sporangium ranges from one to several thousands.
Eg – Zygomycotinai (Mucorales)
• Zoospores – These are motile spore and are self propelled by means of
flagella. They lack cell walls and contains cell envelope in a
membrane. Eg - Mastigomycotina

16. 2. Conida or condisospores – They are asexual reproductive
structure producd by different groups of fungi especially
Ascomycotina and Deuteomycotina. Conidia are produced
exogenously on condiophores.
• Arthrospores – They are formed by close separation in basipeta
succession. Each cells rouds off and sets free as a thin-walled
arthrospores. It is also called as oidia.
• Eg – Oidium, Endomyces
• Chlamydospores – It is a thick walled resting spore surrounded
by pigmented wall and is formed from terminal or intercalary
cells of hyphae. They contains enormous amount of food
reserves in the form of glycogen or oil. They may be dispersed in
water currents and then known as gemmae.

18. Asexual fruiting bodies produced by fungi
Particulars Pycnidium Sporadachium Acervulus Synemma
Descrption Hallow, flask
shaped
globose
fruiting body
with narrow
circular mouth
It is
hemispherical
or barrel
shaped
compound
conidiophore
Saucer
depressed
pseudoparen-
chymatous
aggregation
of hyphae
Loose
aggregation
of branched
or
unbranched
erect
conidiophore
Examples Macrophomin
a phaseolina,
Fusarium,
Tubercularia
and
Epicoccum
Colletotrichu
m and
Pestalotia
Ceratocystis,
Graphium

19. • Flagella – Small hair like structure, which is helpful for locomotion
Anterior flagella – Episthocont
Posterior flagella – Opisthocont
• Types of flagella in fungi–
Whiplash (Acronematic) – Flagella without hair/ flimmers
Tinsel (Pantonematic) – Flagella with hair/ flimmers
Types of flagella

20. Sexual reproduction
Sexual reproduction – Union of two opposite nuclei. Three phases maily
occurs in the order of sexual reproduction in fungi
• Plasmogamy – Sexual reproduction begins with plasmogamy which
involves the union of two protoplasts bringing the opposite nuclei close
togeather within in the same cell.
• Karyogamy – Fusion of two opposite nuclei. The process fusion of
nuclei is known as syngamy or diploidizaion and it takes place in
zeuguites.
• Meiosis – Reeduction division where chromosome number become half
(diploid become haploid). Meiosis takes place in gonotoconts.
• Thus plasmogamy brings to haploid nuclei togeather in a cell,
karyogamy results in a diploid zygote nucleus and meiosis by
reducing the chromosome number restores the haploid condion.

21. Types of plasmogamy
1. Gametogamy (Planogametic copulation) – Fusion of morphologically
or physiologically differentiated gamates.
• Isogamy - Fusion of isogamates of same size and shape.
Eg – Olphidium and Synchytrium
• Anisogamy – Fusion of aniosogametes of morophologically similar but
differ in size.
Eg – Allomyces and Blastocladiales
• Heterogamy (= oogamy) – Fusion of motile male gamtes with non
motile female gamates.
Eg – Monoblephariales (Monoblepharis)

22. 2. Gametangiogamy (Gametangial contact) -
Copulation of morphologically or
physiologically differentiated gamatangia.
Where gamates are passed form male to
female through fertilization tube developed
by male gametangium and trichogyne is
developed by female gametangium. The
purpose or fertiziation tube or trichogyne is
to facilitate a passage for fertilization.
• Eg – Albugo, Pythium and Phytophthora

23. 3. Gametangy (Gametagial copulation) – Fusion of entire
content of two gametangia. Fusion takes in different ways
• Hologamy - Whole content of one gametangium passes into
another gametangium
Eg – Chytridis and Yeast (Polyphogus and Rhizophidium)
• Direct fusion - Fusion of two morphologically similar
gametangia and become a single cell
Eg – Mucor and Rhizopus
• Anisogametangial population – Fusion between unequa
gametangia
Eg – Mucorales

24. 4. Spermatization - This method of sexual reproduction can be
observed in ruts. Rust produce numerous, tiny, uninucleate, non-
motile, spore like male sex cells called spermatia. They form flask
shaped organs called spermogonia developed on the upper surface of
leaf of the second host. The spermatia are carried by various agencies,
generally by insects, wind or water to the receptive hyphae of opposite
strains produced in another spermagonium. At the point of contact the
wall was dissolved and a pore is formed, the content of spermatium
(male gamates) migrates through the pore into the receptive hypha
and become binucleate. The union of hyphae with the receptive hyphae
is known as spermatization.
• Eg – Puccinia graminis and Podospora

25. 5. Somatogamy - Fusion of vegetative cells/ somatic cells which
are not sexully differentiated (Hyphae or conidia). Fusion takes
between somatic hyphae of the primary mycelia of opposite
strains come in contact. Also known as pseudomixis.

26. Sexual reproduction in fungi