01._Chytridiomycota_Zygomycota_and_Ascomycota_Tentative.pptx

Semester – I
KARNATAK UNIVERSITY DHARWAD
KITTEL SCIENCE COLLEGE DHARWAD - 580001
Subject: Botany
DSC (Discipline Specific Course) : (01) Fungi, Microbiology and Plant Pathology (Unit – 01)
Total Hrs: 56
Lecture By: PRASHANT KARADAKATTI M.Sc B.Ed
Discipline-Specific Course (DSC)

Unit – I :
(A): Introduction to fungi and classification.
(B): Chytridiomycota, Zygomycota, Ascomycota.
(C): Basidiomycota, Oomycota and allied fungi.
(A):
(About Fungi)
 General charactaristics.
 Affinities with plants and animals.
 Thallus organisation.
 Cell wall composition.
 Nutrition.
 Classification (Alexopoulos).
(B):
(Chytridiomycota and Zygomycota)
 Charectaristic features.
 Ecology and Significance.
 Thallus Organization.
 Reproduction.
 Life cycle with reference to Synchytrium, Rhizopus sp.
 Ascomycota –
1) General charectaristics (Asexual and Sexual fruiting
bodies).
2) Life cycle, Heterokaryosis and parasexuality.
3) Life cycle and classification with reference to
Saccharomyces, Penicillium, Alternaria and Peizza sp.
14 Hrs

(C):
(Basidiomycota)
 General Characteristics.
 Ecology.
 Life cycle.
 Classification with reference to black stem rust on wheat - a. Puccinia (Physiological specialization)
b. Agaricus (Loose and covered smut – Symptoms only)
c. Biolumenescence, Fairy Rings and mushroom cultivation
(Allied Fungi)
 General characteristics.
 Classification - Status of slime molds.
 Occurrence.
 Types of plasmodia.
 Types of fruiting bodies.
(Oomycota)
 General characteristics.
 Ecology.
 Life cycle.
 Classification with reference to Phytophthora and Albugo sp.

(A) Introduction of Fungi
 A fungus is a eukaryote that digests food externally and absorbs nutrients directly through its cell walls.
 Most fungi reproduce by spores and have a body (thallus) composed of microscopic tubular cells called
hyphae.
 Fungi are heterotrophs and, like animals, obtain their carbon and energy from other organisms.
 Some fungi obtain their nutrients from a living host (plant or animal) and are called biotrophs; others
obtain their nutrients from dead plants or animals and are called saprotrophs (saprophytes, saprobes).
 Some fungi infect a living host, but kill host cells in order to obtain their nutrients; these are
called necrotrophs.

 General Characteristics of Fungi
1) Fungi are the eukaryotic, achlorophyllous, and unicellular or multicellular organisms, which may reproduce by
asexual and sexual spores.
2) All are eukaryotic - Possess membrane-bound nuclei (containing chromosomes) and a range of membrane-bound
cytoplasmic organelles (e.g. mitochondria, vacuoles, endoplasmic reticulum).
3) Most are filamentous - Composed of individual microscopic filaments called hyphae, which exhibit apical growth
and which branch to form a network of hyphae called a mycelium.
4) Some are unicellular - e.g. yeasts.
5) Protoplasm of a hypha or cell is surrounded by a rigid wall - Composed primarily of chitin and glucans, although
the walls of some species contain cellulose.
6) Many reproduce both sexually and asexually - Both sexual and asexual reproduction often result in the
production of spores.
7) Their nuclei are typically haploid and hyphal compartments are often multinucleate – Although the oomycota
and some yeast possess diploid nuclei.

(A) General Characteristics of Fungi
8) All are achlorophyllous - They lack chlorophyll pigments and are incapable of photosynthesis.
9) All are chemoheterotrophic (chemo-organotrophic) - They utilise pre-existing organic sources of carbon in their
environment and the energy from chemical reactions to synthesize the organic compounds they require for
growth and energy.
10) Possess characteristic range of storage compounds - e.g. trehalose, glycogen, sugar alcohols and lipids.
11) May be free-living or may form intimate relationships with other organisms i.e. may be freeliving, parasitic or
mutualistic (symbiotic).

1) Fungi are the eukaryotic, achlorophyllous, and unicellular or multicellular organisms, which may reproduce by asexual
and sexual spores.
2) All are eukaryotic - Possess membrane-bound nuclei (containing chromosomes) and a range of membrane-bound
cytoplasmic organelles (e.g. mitochondria, vacuoles, endoplasmic reticulum).
Yeast Cell

3) Most are filamentous - Composed of individual microscopic filaments called
hyphae, which exhibit apical growth and which branch to form a network of
hyphae called a mycelium.
4) Some are unicellular - e.g. yeasts.
E.g: Yeast Cells (Single Cell) E.g: Penicillium (Septate Hyphae) E.g: Mucormycetes / Zygomycetes
(Aseptate Hyphae)
E.g: Candida (Pseudohyphae)
Types of Hyphae Formation In Fungi

5) Protoplasm of a hypha or cell is surrounded by a rigid wall - Composed primarily of chitin and glucans,
although the walls of some species contain cellulose.

6) Many reproduce both
sexually and asexually -
Both sexual and asexual
reproduction often result
in the production of
spores.

7) Their nuclei are typically
haploid and hyphal
compartments are often
multinucleate – Although the
oomycota and some yeast
possess diploid nuclei.

8) All are achlorophyllous - They lack chlorophyll pigments and are incapable of photosynthesis.
No Chlorophyll Pigment
Specimen: Trichea decipiens

9) All are chemoheterotrophic (chemo-organotrophic) - They
utilise pre-existing organic sources of carbon in their
environment and the energy from chemical reactions to
synthesize the organic compounds they require for growth
and energy.

10) Possess characteristic range of storage compounds - e.g. trehalose, glycogen, sugar alcohols and lipids
Some Fungi are Edible

11) May be free-living or may form intimate relationships with other organisms i.e. may be freeliving,
parasitic or mutualistic (symbiotic).
These all are example for the
parasitic fungi:
Endothia parasitica, Ceratocystis
ulmi, Puccinia sparganioides,
Puccinia graminis
Examples: molds, mushrooms,
yeast, penicillium, and mucor
Examples: Fungicolous fungi and Lichens.

 Affinities with plants and animals:
Plant get the nutrition from the Mycelium
(N2-fixation and other metabolism).
The animals get benefitted by edible mushroom and other
lipid, protein secretion will heal the body and penetrate them
with chemical action. Even human or mankind also get
benefitted by edible and herbal mushrooms, the usage of
mushroom will get rich protein.

 Affinities with plants and animals:
(Fungi are more similar as plant and animals)
How?
Fungi Animal Plant
Similar structure found in plants than the animals But the both have
cell structure and organelles similar accept the (chlorophyll)
pigmentation Colour.

 Thallus Organization
The body of the fungus is called as 'thallus’.
Eucarpic thallus:
The thallus is differentiated into vegetative part, which absorbs nutrients, and a reproductive part, which forms
reproductive structure. Such thalli are called as eucarpic.
Example: Pythium aphanidermatum. Rhizopus sp, Nectria sp, etc.
Pythium aphanidermatum
Nectria sp
Rhizopus sp

Holocarpic thallus:
The thallus does not show any differentiation on vegetative and reproductive structure. After a phase of vegetative
growth, it gets converted into one or more reproductive structures. Such thalli are called as 'holocarpic’
Examples: yeast, Synchytrium endobioticum
Synchytrium endobioticum
Sachharomyces sp
(Yeast Cells)

Hyphae:
Hyphae is a tubular, transparent filament, usually branched, composed of an outer cell wall and a cavity (lumen) lined or
filled with protoplasm including cytoplasm. Hyphae are divided into compartments or cells by cross walls called septa and
are generally called as septate (with cross wall) or coenocytic (aseptate -without cross wall). Hyphae of most of the fungi
measure 5-10 μm across.
Watch the video Carefully….

Mycelium (pl. Mycelia):
The hyphal mass or network of hyphae constituting
the body (thallus) of the fungus is called as
mycelium. The mycelium of parasitic fungi grows on
the surface of the host and spread between the cells
and it is called intercellular mycelium. The mycelium
of parasitic fungi, which grows on the surface of the
host and penetrates into the host cells and is called
intracellular mycelium. If the mycelium is
intercellular, food is absorbed through the host cell
walls or membrane. If the mycelium penetrates into
the cells, the hyphal walls come into direct contact
with the host protoplasm. Intercellular hyphae of
many fungi, especially of obligate parasites of plants
(fungi causing downy mildews, powdery mildews
and rusts) obtain nutrients through haustoria.
Mycelium Formation
Is There a two types of Mycelia

2. Dikaryotic
mycelium
(binucleate):
Mycelium contains pair of
nuclei (dikaryon), which
denotes the diplophase in the
life cycle of fungi
Figure: Agaricus. A-B. Monokaryotic Mycelia
C. Dikaryotic Mycelia
1. Monokaryotic
mycelium
(uninucleate):
Mycelium contains single
nucleus that usually forms
part of haplophase in the life
cycle of fungi.

Homokaryotic mycelium / Hyphae:
The mycelium contains genetically identical nuclei.
Heterokaryotic mycelium / Hyphae:
The mycelium contains nuclei of different genetic constituents.

Multinucleate:
The fungal cell contains more than 2 nuclei.
Septa
Transverse septa occur in the thallus of all filamentous fungi to
cut off reproductive cells from the rest of the hypha, to
separate off the damaged parts or to divide the hypha into
regular or irregular compartments or cells. There are two
general types of septa in fungi viz., primary and adventitious.
The primary septa are formed in association with nuclear
division and are laid down between daughter nuclei. The
adventitious septa are formed independently of nuclear
division and are especially associated with changes in the
concentration of the protoplasm as it moves from one part of
the hypha to another.
Types:
 Septate Hyphae
 Coenocytic Hyphae (Aseptate).

Specialized Somatic Structures
Rhizoid:
A rhizoid (Gr. rhiza = root + oeides = like) is a short,
root-like filamentous outgrowth of the thallus
generally formed in tufts at the base of small
unicellular thalli or small porophores. Rhizoid
serves as anchoring or attachment organ to the
substratum and also as an organ of absorption of
nutrients from substratum. Rhizoids are short,
delicate filaments that contain protoplasm but no
nuclei.

 Cell wall composition
 The cell wall is often observed to have a laminar structure in transmission electron micrographs, with an electron-
transparent inner layer and an electron dense outer layer.
 The inner layer is largely composed of a cross-linked chitin–glucan matrix, the outer layer being richer in mannosylated
proteins.
 Where melanin is present, this usually forms a discrete electron-dense layer towards the inner cell wall, or occasionally
is observed in a granular form.
 The polysaccharide components of the wall constitute the majority of the wall by mass, with b1,3-glucan being the
most abundant (70–80%) in the Magnaporthe oryzae mycelium wall.

 The polysaccharide-rich wall, that is “chitin” which envelopes the fungal cell, is pivotal to the maintenance of
cellular integrity and for the protection of the cell from external aggressors. Such as, environmental fluxes and
during host infection.
 This review considers the commonalities in the composition of the wall across the fungal kingdom, addresses how
little is known about the assembly of the polysaccharide matrix, and considers changes in the wall of plant-
pathogenic fungi during on and in planta growth, following the elucidation of infection structures requiring cell
wall alterations.
 It highlights what is known about the phytopathogenic fungal wall and what needs to be discovered.
 The lifestyle of phytopathogenic fungi places unique demands upon the cell wall, which set these fungi apart from
those with exclusively saprotrophic lifestyles, and from opportunistic human pathogens.
 Cell wall composition

 Fungi Nutrition
What are the nutrition factor for the fungi survival ?
 Like plants, Fungi do not require Carbon dioxide and light as a source of Carbon for their food.
 The Fungi get attached to the organic matter and absorb Carbohydrates.
 It absorbs and metabolizes various soluble Carbohydrates like Glucose, Fructose, Xylose, and Sucrose.
 Also, Fungi have the ability to absorb and process insoluble carbohydrates like cellulose, hemicellulose, and starches along
with complex hydrocarbons such as lignin.
 Many Fungi even absorb Proteins as a source of carbon and nitrogen.
 Fungi will produce digestive enzymes to polymers extracellular, this helps to utilize insoluble carbohydrates and Proteins.
 Using the biological catalysts, an enzyme secreted on the surface of the Fungi starts to secure its food.
 The digestive enzyme helps to break down the food and the root-like substance present of the Fungi called hyphal walls
absorbs the food.
 Food in the form of liquid can only enter into hyphae, the entire mycelial surface of Fungus has the capability to absorb
water and minerals entered through hyphae.
 This is how Fungi obtain their food. For example, The surface of the rotten fruits became soft.
 This is because of fungal enzymes. Many parasitic Fungi have some specialized features like absorptive organs. This is
known as haustoria.

Fungi are broadly classified into three types, based on how Fungi obtain their food.
Types of Nutrition in Fungi
 Saprotrophic Fungi - Fungi obtain food from dead and decayed materials.
 Parasitic Fungi - Get feed from living Organisms and destroy them
 Symbiotic Fungi - Grow in a living Organism and get mutually benefited.
 Fungi Nutrition

Saprotrophic Fungi
 Like bacteria, saprotrophic Fungi have a huge responsibility to decompose the organic matter in the earth. The
saprotrophic Fungi takes responsible for decaying and decomposing the foodstuffs.
 Many saprotrophs have the ability to de-structure and destroy giant structures like timber using the digestive enzyme
mycelia.
 The tropical region’s humidity and temperature support the growth of Fungi. The nutritional availability takes
responsibility to determine the growth of saprotrophs.
 Fungi Nutrition

 Fungi Nutrition
 Each Fungus synthesizes the enzyme with different chemical composition. But all Fungi have the same
morphological characteristics in culture media.
 Required carbon is supplied to the Fungi in the form of sugars or starch. Most Fungi absorb the sugar
in the form of fructose, maltose, mannose, fructose, and in some least cases sucrose.
 For a nitrogen source, Fungi compose proteins and produce proteoses, amino acids, and peptones.
 Some Fungi absorb ammonium compounds and nitrates as a nutrient source.
 Also, Fungi have the ability to combine and fix atmospheric nitrogen using suitable compounds.
 To vigorous the growth of Fungi some chemical components like phosphorus, sulfur, magnesium,
potassium, manganese, iron, zinc, copper are essential.
 Also, the least amount of calcium, molybdenum, and gallium are required for species growth.
Saprotrophic Fungi

 Fungi Nutrition
Saprotrophic Fungi
 Fungi require oxygen and hydrogen, which will absorb in the form of water. Also, Fungi require vitamins and
minerals like thiamine and biotin to boost the growth of Fungi and reproduction.
 As Fungi are aerobic Organisms, they require free oxygen for their survival. During its anaerobic condition, it
undergoes a fermentation process.
 Many industries are using saprotrophic Fungi for their fermentation process.
For example: The most known saprotrophic Fungi, which undergo an anaerobic process are Neocallimastix. This
can act upon the plant cell wall components such as Xylem and cellulose. But it cannot act on the animal cell
walls.

 Fungi Nutrition
Parasitic Fungi
 Parasitic Fungi use to live on living Organisms by invading them.
 These types of Fungi start extracting Nutrients from the living cytoplasm.
 This causes disease and death to the host.
 Most pathogenic fungi are parasites of plants, which enter into the body through the natural opening
present in plants like stoma, lenticel in a stem, and broken plants.
 This causes great damage to the crops.
 The spores of a pathogenic Fungus fall on the leaves and stems of plants and increase infection of a
plant.
 The tube grows on the surface of the host and absorbs food for Fungi, this invades the tissues and cell
Parasitic Fungi in plants

 Fungi Nutrition
Parasitic Fungi
Parasitic fungi in insect

 Fungi Nutrition
Parasitic Fungi in Human
Parasitic fungi in
Human
 Many pathogenic Fungi cause disease in human beings and animals.
 The parasitic Fungi generally enter the body through a wound in the epidermis. This may enter through
insects.
 For example, parasitic Fungi Claviceps purpurea causes ergotism in human beings.
 This disease is widely spread among middle-aged people in northern Europe.
 Other fungal diseases that affect humans are ringworm, aspergillosis, coccidioidomycosis,
histoplasmosis, and athlete’s foot.
 People infected by HIV are mainly due to agent acquired immunodeficiency syndrome (AIDS) weakens
the immune system.
 This is mainly due to the parasitic Fungi called Aspergillus fumigatus.

 Fungi Nutrition
Symbiotic Fungi
 The Fungi grows in the other Organism and it does not cause any harmful effects for the living Organism.
Here, both the living Organism and Fungi get mutually benefited.
 The symbiotic Fungi are of two types. They are mycorrhizae and lichen.
 Mycorrhiza shows the mutual relationship between the Fungus and plants.
 This Fungus grows on the root of plants.
 The Fungus avails its food from the soil and takes shelter from the plants. Likewise, plants utilize the
mycelia of Fungi to absorb Nutrients and water.
 Lichen shows the mutual relationship between Fungus and photosynthetic Organisms.
 These Fungi grow in green alga or plants. Here Fungus gets food from photosynthesizers meanwhile
photosynthesizers avail essential Nutrients from Fungi, This method explains the nutrition in Fungi.

Fungi (Mycota)
1. Ascomycota
Dikarya Eomycota
2. Glomeromycota
1. Chytridiomycota
2. Basidiomycota 3. Zygomycota
Fungi classification based on Ruggiero et al. (2015).
In this classification the addition of Phyllum Chytridiomycota and
Glomeromycota has taken for the additional species counter list
basis. The scientist called Ruggiero et al. (2015) done the
monograph of fungal classification based on systematic studies.

Alexopoulos and Charles W. Mims in the year 1979 proposed the classification

 The fungi are classified based on the characteristics of the sexual spores and fruiting bodies present
during the sexual stages of their life cycles. Therefore, based on characteristics of their sexual stages
and morphology of their asexual spores and thalli they are classified into different groups.
 The imperfect higher fungi are placed at a special class known as Deuteromycetes. The sexual stage
containing fungi is present mainly in the ascomycetes or basidiomycetes group.
 The given classification of algae is proposed by the eminent American mycologist Alexopoulos in 1979. In this
classification, the fungi and the slime molds are placed within the kingdom mycetae.
Division I – Gymnomycota :
The distinguishable characteristics of these organisms are, they ingest particulate nutrients and also lack cell
walls during the vegetative stage. This division is further divided into two subdivisions such as –
Subdivision 1: Acrasiogymnomycotina
Subdivision 2: Plasmodiogynomycotina
Fungi Classification

Subdivision 1: Acrasiogymnomycotina
The Acrasiogymnomycotina subdivision contains a single class known as Acrasiomycetes.
Class 1. Acrasiomycetes
Acrasiomycetes lack flagellated cells except for one species. In the vegetative stage free-living free living
amoebae aggregate to form a stalked sorocarp bearing spores in a mucilaginous matrix. Some
representative organisms of this class are Dictyostelium discoideum and Polysphondelium violaceum.
Dictyostelium discoideum Polysphondelium violaceum.

Subdivision 2 – Plasmodiogymnomycotina :
It contains two classes such as
Class 1 Protosteliomycetes :
The true slime molds are included within the class Myxomycetes. Some important distinguishing
characteristics of this class are; asexual reproduction by binary fission and sporangiospores formation,
and the sexual phase is absent. Physarum polycephalum is the representative organism of this class.
Physarum polycephalum

Class 2 Myxomycetes.
This class contains three subclasses such as Ceratiomyxomycomycetidae, Mycogasteomycetidae, and
Stemonitomycetidae.
1. Subclass I: Ceratiomyxomycomycetidae: This subclass contains one order known as Ceratiomyxales.
2. Sub Class II: Mycogasteomycetidae: This subclass contains four orders such as
a. Liceales,
b. Echinosteleales,
c. Trichlales and
d. Physarales
3. Sub Class III: Stemonitomycetidae: This subclass contains one order known as Stemonitales.
Stemonitis fusca
Trichia decipiens

Division II - Mastigomycota :
This division contains flagellated lower fungi with absorptive nutrition, unicellular or filamentous, mycelium
coemocytic. Mastigomycota division is consists of two subdivisions such as Haplomastigomycotina and
Diplomastigomycotima.
Subdivision I: Haplomastigomycotina :
This subdivision contains fungi with uni or bi-flagellate zoospores. Haplomastigomycotina contain three
classes such as;
1. Class 1 Chytridiomycetes: Containing fungi can produce zoospores which are furnished with a single
whiplash flagellum at the posterior end.
2. Class 2 Hyphochytridiomycetes: Includes motile cell containing single tinsel flagellum at the anterior
end.
3. Class 3 Plasmodiophoromycetes: These are the parasitic fungi that can produce biflagellate motile
cells containing both the flagella of whiplash-type at the anterior end.

Subdivision II - Diplomastigomycotima :
The distinguishable characteristics of this subdivision are Sexual reproduction ooagamous and
zoospores are biflagellate. It consists of one class;
Class 1 Oomycetes
The Oomycetes class contain four order such as
a. Lagenidiales,
b. Saprolegnailes,
c. Leptomitales &
d. Peronosporales.
Albugo Sp

Division III - Amastigomycota :
The major distinguishable characters of these fungi are absorptive nutrition, lacking flagella, mycelium
aseptate, or septate. This division contains further four subdivisions such as;
 Zygomycotina,
 Ascomycotina,
 Basidiomycotina, and
 Deuteromycotina.
Subdivision I – Zygomycotina :
This subdivision contains two classes such as Zygomycetes and Trichomycetes.
1.Class I Zygomycetes: Consist of six orders.
2.Class II Trichomycetes: consist of five orders.
Trichomycetes
Zygomycetes

Subdivision II – Ascomycotina :
The major distinguishable characters of these fungi are, contain septate mycelium and can produce
ascospores in a sac-like structure known as asci. This subdivision contains only one class such as
Class 1 Ascomycetes: This class contain five subclasses;
1.Subclass I Hemiascomycetidae Contain three orders.
2.Subclass II Plectomycetidae Contain Five orders
3.Subclass III Hymenoascomycetidae Contain Ten orders
4.Subclass IV Laboulbeniomycetidae Contain Two orders
5.Subclass V Lowloascomycetidae Contain five orders
Ascomycota – Eyelash Fungi

Subdivision III – Basidiomycotina :
The major distinguishable characters of these fungi are Septate mycelium, which can produce
basidiospores, and exogenously on various types of basidia. This subdivision contains only one class such
as;
Class 1 Basidiomycetes:
The Basidiomycetes class is consist of three subclasses such as;
1.Subclass I Holobasidiomycetidae
2.Subclass II Phragmobasidiomycetidae
3.Subclass III Teliomycetidae

Subdivision IV - Deuteromycotina :
Commonly called molds, Deuteromycetes are "second-class" fungi carrying no sexual state in their life cycle,
reproduced only by producing spores via mitosis. This state of asexual fungi is called Anamorph. In other words, this
imperfect fungi class falls under artificial fungi, of which there are approximately fifteen thousand species because of
the asexual reproductive mechanism.
Deuteromycetes are also known as Deuteromycota, Deuteromycotina, fungi imperfecti, and mitosporic fungi.
Aspergillus Sp

(B): Chytridiomycota
 Charectaristic features:
 The chief characteristic feature of this class is the production of uniflagellate reproductive cells (zoospores
and planogametes). The single flagellum is of a whiplash type and is inserted posteriorly. The zoospore
with a posteriorly inserted flagellum is called Opisthocont.
 The flagellum is attached to the Blepharoplast within the cell. The motile cells of some species possess a
nuclear cap which consists of RNA. It shields the nucleus at the anterior end of the cell. Majority of the
members occur in water.
 Some are found in the soil. Many are parasitic on higher plants of economic value. The primitive members
of this class are microscopic. The vegetative body in them is an acellular, coenocytic thallus which is
holocarpic.

The flagellum is attached to the Blepharoplast within
the cell.
The zoospore with a posteriorly inserted flagellum is
called Opisthocont

It has no cell wall in the earlier stages (Olpidium). In the more advanced species, the unicellular thallus is
drawn out at one point into fine, branching hairs (Fig. 4.1 B), the so-called rhizoids which aid in anchorage
and intake of nutrients (Rhizophidium).
In slightly more complex members, there is a much branched rhizomycelium (Fig. 4.1 C). They are eucarpic.

 In still more advanced types, a scanty mycelium consisting of a few short filamentous hyphae is in evidence.
 The advanced members have a mycelium consisting of typical hyphae woven into a eucarpic mycelial
meshwork (Monoblepharis).
 The hyphe are coenocytic. Chitin is the chief constituent of the cell of hyphal wall. Besides, there is B
glucan.
 The septa ordinarily remain suppressed during the vegetative phase but appear to delimit reproductive
organs and are solid plates.
 The asexual reproductive organs are the sporangia, each of which produces numerous tiny, uninucelate and
uniflagellate opisthocont zoospores.
 The liberated zoospores swim for a time. Later each retracts its flagellum and undergoes encystment. After a
short period of rest, the encysted spore germinates.
 The sexual reproduction may be isogamous or anisogamous. In some it is typically oogamous
(Monoblepharidales).

 Chytridomycota usually inhabit freshwater ecosystems. In fact, they are dependent on the presence of
water to survive.
 However, Chytridiomycota often dwell within host organisms, which can be plants or animals.
 They live saprophytically and parasitically. Because Chytridiomycota often feed on decaying organisms,
they are important decomposers.
 While this is an important function, Chytridiomycota can also have a negative impact on human produce,
particularly Synchytrium endobioticum, the species that causes potato wart.
 Others, such as Olpidium brassicae (the "Big Vein" virus in lettuce), are parasitic, but actually do little
damage to the host organism as a whole.
 While this is not true of all species, some, such as Rhizophlyctis rosea and Allomyces anomalus have
structures that allow them to survive draughts or excessive heat.
 Ecology of Chytridiomycota:
Synchytrium endobioticum Allomyces anomalus

 Ecology of Chytridiomycota:
 Anaerobic rumen fungi, such as Orpinomyces joyonii, inhabit
the guts of cattle, sheep, and goats.
 These fungi live in anaerobic conditions and play an imporant
part in the digestive process.
 They help process plant matter while obtaining food.
 They are so effective that they make their hosts some of the
most effective animals at utilizing cellulose.
 In addition, some species of anaerobic rumen fungi are used for
other purposes.
 Xue et. al. (1996) cloned microbial non-starch polysaccharide
hydrolases from Neocallimastix patriciarum.
 They found that the genes within these hydrolases were valuable
for the production of genetically-engineered cereal crops.

 Significance of Chytridiomycota:
 Some of the soil-inhabiting Chytridiomycetes attack the underground as well as aerial parts of the higher
plants and cause diseases which are of great economic significance.
 For example, Synchytrium endobioticum causes black wart disease of potato; Urophlyctis alfalfae causes
crown wart of alfalfa (Medicago); and Physoderma maydis causes brown spot disease of maize (Zea
mays).
 Many chytrids indirectly harm humans and animals. They parasitize and destroy the phytoplanktonic forms
of algae that form an important link in food chain of aquatic ecosystems.
 Various species of Allomyces and Blastocladiella have been found to be valuable research tools in
studying morphogenesis.
 Species of Coelomomyces (C. anophelescia) are endoparasites on mosquito larvae and can be utilized
for the biological control of the mosquito (Anopheles spp.), which is an important vector for the spread of
malaria in human beings.
 Members of Blastocladiales and Monoblepharidales generally appear to function as decomposers of
detritus in the aquatic and soil ecosystems

 Thallus Organisation of Chytridiomycota:
Types of thallus structure in the Chytridiales :
• Monocentric thallus: When the thallus/ chytrids produces single type of reproductive structure then it
is called monocentric thallus.
• Polycentric thallus: When the thallus/ chytrids produces several or
multiple types of reproductive structure then it is called polycentric
thallus.

 Thallus Organisation of Chytridiomycota:
• Holocarpic: When full body or complete body of the thallus converted into one or more reproductive
type of structure then it is called Holocarpic type of thallus.
• Endobiotic thallus: When complete thallus body presents within the host cell then it is called endobiotic
thallus. e.g: synchytrium.
• Epibiotic thallus: The part which is present outside of the host cell then it is called epibiotic thallus.
e.g: Chytriomyces.

 Reproduction in Chytridiomycota:
For most members of this class,sexual reproduction is unknown. Asexual reproduction
occurs through the release of zoospores (presumably) derived through mitosis.
 Single spore – complete body (Asexual).
 Two gametes – complete body (Sexual).
Asexual reproduction :
 By means of single posteriorly directed whiplash(without hair) flagellated zoospores.
 During early development, zoosporangia contain uncleaved (no divisions) protoplasm with many
nuclei.
 The entire protoplast undergoes cleavege into numerous minute, typically uninucleate sections each
of which develop into a posteriorly flagellate zoospores.

During asexual reproduction zoospores may-
• Discharge through papillae-Allomyces.

• Discharge through opercula (operculate)-Nowakowskiella.

• Discharge through pore or tube (inoperculate)-Synchytrium, Olpidium.

During sexual reproduction zoospores may-
• Sexual reproduction is haploid dominant.
• It also depends on the isomorphic alternation of generations.
• The haploid thallus, called the gametothallus, produces female and male gametes.
• These occur in pairs and are terminal and subterminal.
• Male gametes are orange-colored, while female gametes are colorless.
• In addition, female gametes are much larger than male gametes.
• Males are attracted to females when they produce the hormone sirenin, and females are attracted to males when
they produce the hormone parisin.

 Life Cycle in Chytridiomycota:
 Most chytrids have
haploid zoospores and
thalli but some
Blastocladiales show an
alternation of haploid
(gametothallic) and
diploid (sporothallic)
generations.
 Apart from differences in
the reproductive organs,
the morphology of the
two types of thallus is
very similar, a
phenomenon known as
isomorphic alternation
of generations.

Remaining Notes [National Education Policy 2020 Based Syllabus B.Sc (Botany) Notes] are reserved after payment….
Mail ID – prashant.s.k2012@gmail.com

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