Lecture

1. Mycelium (plural mycelia) is the vegetative part of a fungus, consisting of a mass
of branching, thread-like hyphae. Septate refers to fungi that have hyphae with
multiple sectioned compartments by cross walls called septum. Coenocytic hyphae
have no cross-walls and look like one long, filamentous, multinucleated cell.

2. Vegetative Structure
The vegetative structure of the thallus of fungi is either
unicellular (holocarpic) or multicellular (Eucarpic).
A spore of the fungus germinates and produces a germ tube. Germ
tube expands and grows into a thread like structure called hypha.
These hyphae branch and anastomose to form a mesh, called
mycelium. Yeast is unicellular. Mycelium may be colourless or
coloured due to the presence of pigments. The hyphae may have
cross walls or septa called septate mycelium. Mycelium without any
septa is called aseptate or coenocytic (Fig.1 A,B). In some higher
fungi septate mycelium may have barrel-shaped thickenings
(Parenthosomes) covering the pore of a septum and this type of
septum is called dolipore septum(Fig.1 D).
Cell Structure
Fungal cells are bounded by a 3 layered cell wall and the
cytoplasmic membrane or plasmalemma delimits the
cytoplasm. They store their food in the form of glycogen.
Fungi are eukaryotic in the cytoplasm are the vacuoles, oil
globules and cell organelles. Fungi have membrane bound
cell organelles like nucleus, mitochondria, tubular
endoplasmic reticulum, the golgi body and ribosomes.
There are some particles or vesicles formed in between the
cell wall and plasma membrane called lomasomea (Fig. 2)
Ultrastructure of hypha. 1.Cell wall. 2.
Plasma membrane. 3. Lomasome. 4.
Mitochondrion. 5. Vacuole. 6. Nucleus.
7. Endoplasmic reticulum. 8.
Ribosomes
Fungal hyphaa and types of septa. A.
Coenocytic hyphae. B. Septate
hyphae. C. Simple pore septum. D.
Dolipore septum.

3. Taxonomic class
of Fungi
Hypha Type of
Reproduction
Characteristic
spore
Origin of
Spore
Examples of Fungi Pathogenicity
Phycomycetes Asptate Asexually
Sexually
Sporangio-
spore
Zygospore
or
oospore
Sporangio
phore
Fussion of
nuclei
Nuisance fungi
including
general
Absidia,
Muclor, and
Rhizopus
Very rare
Mucormycosis
Ascomycetes Septate Asexually
Sexually
Blastospore
Conidium
Ascospore
Budding
Conidio-
phore
Ascus
Allescheria
Aspergillus
Piedraia
Saccharomyces
(perfect yeast)
Rare
Maduromcosis
Aspergillosis
Black Piedra
Basidiomycetes Septate Sexually Basidio-
spore
Basidium Mushrooms,
smuts and
rusts
Rare
Mushroom
poisoning
Deutero-mycetes
{fungi imperfecti)
Septate Asexually Thallospore
Conidium
Thallus
(hypha)
Conidio-
phore
Most saprophytes
and pathogens
encountered
in medical mycology
(Imperfect mold and
yeast)
Most Mycoses
encountered
in medical
mycology

4. Asexual Reproduction
It is the type of reproduction in which special reproductive structures called spores or
propagates are formed. The fungal spores always result from mitosis and hence are described
as mitospores. Following are the types of spores produced in different groups of fungi:
Zoospores
They are flagellated, motile spores produced inside structures called
zoosporangia. These spores do not have a cell wall. Such spores are
produced in lower fungi such as Achyla and Saprolegnia.
Sporangiospores
These are non-motile spores produced inside structures called sporangia in
fungi such as Rhizopus and Mucor. These spores are dispersed by wind.
typical for Mucor, Rhizopus
Chlamydospores
These are thick walled resting spores which arise directly from
hyphal cells. They store reserve food.
Oidia
These are spore like structures formed by the breaking up of hypha
cells. They do not store reserve food and hence cannot survive under
unfavourable conditions. Such spores are produced in Rhizopus.
Conidia
These are non-motile spores produced singly or in chains at the tip of
the hypha branches that are called conidiophores. Such spores are
produced in fungi like Aspergillus and Penicillium.

5. Arthroconidia or arthrospores
hyphal cell fragmentation or
splitting
Conidiospores
-spores are produced by pinching
off process at the tip or side of a
hyphae
- typical for Aspergillus,
Penicillium
Blastospores
spore development from
vegetative mother cell by budding

6. Ascospores
An ascospore is a spore contained in an ascus or that was produced inside an ascus. This kind of spore is
specific to fungi classified as ascomycetes (Ascomycota).
Typically, a single ascus will contain eight ascospores. The eight spores are produced by a combination of a
meiotic division followed by a mitotic division. The meiosis division turns the original diploid zygote nucleus into
four haploid ones. That is, the single original cell from which the whole process begins contains two complete
sets of chromosomes. In preparation for meiosis, all the DNA of both sets is duplicated, to make a total of four
sets. The nucleus that contains the four sets divides in two stages, separating into four new nuclei – each of
which has one complete set of chromosomes. Following this process, each of the four new nuclei duplicates its
DNA and undergoes a division by mitosis. As a result, the ascus will contain four pairs of spores.
The Fungi Saccharomyces produces ascospores when grown on V-8 medium, acetate ascospor agar, or
Gorodkowa medium. These ascospores are globose and located in asci. Each ascus contains one to four
ascospores. The asci do not rupture at maturity. Ascospores are stained with Kinyoun stain and ascospore
stain. When stained with Gram stain, ascospores are gram-negative while vegetative cells are gram-positive.

7. A basidiospore is a reproductive spore produced by Basidiomycete fungi.
Basidiospores typically each contain one haploid nucleus that is the product of
meiosis, and they are produced by specialized fungal cells called basidia. In gills
under a cap of one common species in the phylum of Basidiomycota, there exist
millions of basidia. Mature state of basidia has the base usually topped with four
basidiospores in which contains one from the two haploid nucleus obtained from the
process of meiosis. Due to the facts mentioned above, a single mushroom has the
ability to release a billion spores. Most basidiospores are forcibly discharged, and
are thus considered ballistospores.
Basidiomycetes form sexual spores externally from a structure called a basidium.
Four basidiospores develop on appendages from each basidium. These spores
serve as the main air dispersal units for the fungi. The spores are released during
periods of high humidity and generally have a night-time or pre-dawn peak
concentration in the atmosphere.
When basidiospores encounter a favorable substrate, they may germinate, typically
by forming hyphae. These hyphae grow outward from the original spore, forming an
expanding circle of mycelium. The circular shape of a fungal colony explains the
formation of fairy rings, and also the circular lesions of skin-infecting fungi that
cause ringworm. Some basidiospores germinate repetitively by forming small
spores instead of hyphae.
These are generally characterized by an attachment peg (called a hilar appendage)
on its surface. This is where the spore was attached to the basidium. The hilar
appendage is quite prominent in some basidiospore, but less evident in others. An
apical germ pore may also be present. Many basidiospores have an asymmetric
shape due to their development on the basidium. These are typically single-celled
(without septa), and typically range from spherical to oval to oblong, to ellipsoid or
cylindrical. The surface of the spore can be fairly smooth, or it can be ornamented.
Basidiospores are the result of sexual reproduction and formed on a structure called
the basidium. Basidiospores belong to the members of the Phylum Basidiomycota,
which includes mushrooms, shelf fungi, rusts, and smuts.

8. Teliospore
It is sometimes called teleutospore is the
thick-walled resting spore of some fungi
(rusts and smuts), from which the basidium
arises.
They develop in telia (sing. telium, or
teliosoruses).
The telial host is the primary host in
heteroecious rusts. The aecial host is the
alternate host (look for pycnidia and aecia).
These terms apply when two hosts are
required by heteroecious rust fungus to
complete their life cycle.
Teliospores are usually dark-coloured , and
consist of two dikaryote cells. As the spores
germinate, the nuclei undergo karyogamy
and thereafter meiosis, giving rise to four-
celled basidia with haploid basidiospores.
They also have a thick-capped telia as
compared to urediniospores.

9. sporangiospores
*spores develop inside a sac-like sporangium at a
hyphal tip.
* in lower fungi, the sporangiospores are frequently
flagellated which are referred to as zoospores.
Example:
typical for Mucor, Rhizopus
A chlamydospore
These are the thick-walled big resting spores of several kinds
of fungi. It is the life-stage which survives in unfavourable
conditions, such as dry or hot seasons.
Chlamydospores are usually dark-coloured, spherical, and
have a smooth (non-ornamented) surface. They are
multicellular, the cells being connected by pores in septae
between cells.
Chlamydospores are a result of asexual (thus being actually
conidia called chlamydoconidia) or sexual
reproduction(rare). Teliospores are special kind of
chlamydospores of rusts and smuts.

13. Sexual reproduction
It is characterized with the fusion of two haploid cell nuclei to form a diploid zygote.'
Three important phases can be separated during sexual reproduction in fungi:
1. Plasmogamy
- two fungal protoplasts fuse and unite during this initial process
- the resulting cell contains two distinguishable nuclei (Dikaryon)
- the nuclei do not fuse yet at this stage
2. Karyogamy
- in this later stage the two nuclei fuse together to form the diploid zygote
3. Meiosis
- important phase which is accompanied with the recombination of the
genetic material and with the formation of four haploid nuclei;
- the genetic material is rearranged and genetic variability increases to
allow eventually improved adaptation to the environment;
(see Evolution & Natural Selection)
- depending on the fungus, all three phases can happen directly after each other
or with a timely delay;
- in lower fungi, sexual reproduction is initiated with the formation of sex cells or
gametes, which are often build in special structures called gametangia;
- structurally different gametangia which produce male gametes are called
antheridia,
while gametangia producing female gametes are referred to as oogonia;
- if the male and female gametes cannot be differentiated morphologically,
they are referred to as isogametes;
- in lower fungi (= phycomycota), both gametes are motile, while in higher fungi
(= ascomycota, basidiomycota and deuteromycota) only the male gametes are
capable to propel themselves through the liquid environment;

14. Sexual Reproduction
Sexual reproduction is known to occur in all groups of fungi except the Fungi imperfecti or Dueteromycetes. It may
involve fusion of gametes, gametangia or hyphae. The process may involve only fusion of cytoplasm
(plasmogamy) or fusion of nuclei (karyogamy) or production of meiotic spores (meiospores). In most of the lower
fungi plasmogamy is immediately followed by karyogamy and meiosis. In higher fungi karyogamy is often delayed
so that the hyphae remain dikaryotic. This phase of fungal life cycle is called dikaryophase. Such fungi complete
their life cycle in three phases a haplophase, a dikaryophase and a diplophase.
Sexual fusion in fungi is of different types, as follows :
Planogametic Copulation
Here motile gametes called planogametes undergo fusion. When both the gametes are motile and
morphologically similar, the fusion process is called isogamy.
Eg.: Synchytrium When both the gametes are motile but differ in their size, the fusion process is
called anisogamy.
Eg.: Allomyces. When one gamete (male) is smaller and motile and the other (female) gamete is larger and non
motile, the fusion process is called heterogamy.
Gametangial Contact
Here, gamete bearing structures called gametangia come closer to each other and develop a fertilisation tube
through which the male gamete migrates into the female gametangium. Eg. : Phytophthora, Albugo.
Gametangial Copulation
Here, the gametangia fuse with each other, lose their identity and develop into a zygospore. Eg.: Mucor, Rhizopus
Spermatisation
In some fungi like Puccinia, tiny unicellular spore like structures called spermatia are formed. They get transferred
to female gametangia through various agencies.

16. Somatogamy
In examples like Agaricus, fusion occurs between two somatic cells and involves only plasmogamy. This results in the formation
of dikaryotic hyphae. Hence, the process is called dikaryotization.

18. Vegetative Reproduction
It is the type of reproduction which involves the somatic portion of the fungal thallus. It occurs by the following
methods.
Fragmentation
In this process, the mycelium breaks into two or more similar fragments either accidentally or due to some
external force. Each fragment grows into a new mycelium.
Budding
The parent cell produces one or more projections called buds, which later develop necessary structures and
detach to grow into new individuals. Budding is common in unicellular forms like yeast.
Fission
In this process, the parent cell splits into two equal halves, each of which develop into a new individual. Fission
is also common in yeast.
Sclerotia
In some cases, as in Claviceps, the hyphae become interwoven to form a compact mass and get surrounded
by a hard covering or rind. Such structures are called SCLEROTIA. They remain dormant under unfavourable
conditions and germinate into new mycelia on the return of favourable conditions.
Rhizomorphs
In some higher fungi, several hyphae may become interwoven to form rope-like structures called rhizomorphs.
Under favourable conditions, they resume growth to give rise to new mycelia.

22. What is ascus?
An ascus (plural asci; from Greek ἀσκός "skin bag") is the sexual spore-bearing cell produced in
ascomycete fungi. On average, asci normally contain eight ascospores, produced by a meiotic cell
division followed, in most species, by a mitotic cell division. However, asci in some genera or species
can number one (e.g. Monosporascus cannonballus), two, four, or multiples of four. In a few cases, the
ascospores can bud off conidia that may fill the asci (e.g. Tympanis) with hundreds of conidia, or the
ascospores may fragment, e.g. some Cordyceps, also filling the asci with smaller cells. Ascospores are
nonmotile, usually single celled, but not infrequently may be coenocytic (lacking a septum), and in
some cases coenocytic in multiple planes. Mitotic divisions within the developing spores populate each
resulting cell in septate ascospores with nuclei.
In many cases the asci are formed in a regular layer, the hymenium, in a fruiting body which is visible to
the naked eye, here called an ascocarp or ascoma. In other cases, such as single-celled yeasts, no
such structures are found. In rare cases asci of some genera can regularly develop inside older
discharged asci one after another, e.g. Dipodascus.
Asci normally release their spores by bursting at the tip, but they may also digest themselves passively
releasing the ascospores either in a liquid or as a dry powder. Typically, actively discharging asci have
a specially differentiated tip, either a pore or an operculum. In some hymenium forming genera, when
one ascus bursts, it can trigger the bursting of many other asci in the ascocarp resulting in a massive
discharge visible as a cloud of spores – the phenomenon called "puffing". This is an example of positive
feedback. A faint hissing sound can also be heard for species of Peziza and other cup fungi.
Asci, notably those of Neurospora crassa, have been used in laboratories for studying the process of
meiosis, because the four cells produced by meiosis line up in regular order. By modifying a gene
coding for spore color, the biologist can study crossing over and other phenomena.
Asci of most Pezizomycotina develop after the formation of croziers at their base. The croziers help
maintain a brief dikaryon. The compatible nuclei of the dikaryon merge forming a diploid nucleus that
then undergoes meiosis and ultimately internal ascospore formation. Members of the Taphrinomycotina
and Saccharomycotina do not form croziers.

24. Homothallism And Heterothallism
Based on the compatibility in sexual reproduction the fungal hyphae can be
distinguished into two types homothallic and heterothallic. In homothallic
forms, fusion occurs between the genetically similar strains or mating
types. In such forms, meiosis results in the formation of genetically identical
spores. In the heterothallic forms, fusion occurs between the genetically
different mating types or strains. The strains are genetically compatible
and are designated as + strain and strain. In such forms meiosis results in
the formation of both the strains, in equal numbers. Heterothallism is a
device to prevent inbreeding and promote out breeding.

25. What is sclerotia?
A sclerotium (plural sclerotia, from Greek skleros - hard) is a compact mass of hardened fungal mycelium
containing food reserves. One role of sclerotia is to survive environmental extremes. In some higher fungi such as
ergot, it become detached and remain dormant until favorable growth conditions return. It initially were mistaken
for individual organisms and described as separate species until Louis René Tulasne proved in 1853 that sclerotia
are only a stage in the life cycle of some fungi. Further investigation showed that this stage appears in many fungi
belonging to many diverse groups. Sclerotia are important in the understanding of the life cycle and reproduction
of fungi, as a food source, as medicine and in agricultural blight management.
Examples of fungi that form sclerotia are ergot (Claviceps purpurea), Polyporus tuberaster, Psilocybe mexicana,
Sclerotium delphinii and many species in Sclerotiniaceae. The plasmodium of slime molds can form sclerotia in
adverse environmental conditions.
Sclerotia are often composed of a thick, dense shell with thick and dark cells and a core of thin colorless cells.
Sclerotia are rich in hyphae emergency supplies, especially oil. They contain a very small amount of water (5-10%)
and can survive in a dry environment for several years without losing the ability to grow. In most cases, the
sclerotium consists exclusively of fungal hyphae, whereas some may consist partly of fungal hyphae plexus and
partly in between tissues of the substrate (ergot, Sclerotinia). Sclerotia sizes usually range from a few fractions of
a millimeter to a few tens of centimeters. In favorable conditions, sclerotia germinate to form fruiting bodies
(Basidiomycetes) or mycelium with conidia (in imperfect fungi). Sclerotia sizes can range from a fraction of a
millimeter to a few tens of centimeters as, for example Laccocephalum mylittae, which has sclerotia with
diameters up to 30 cm and weighing up to 20 kg.
Sclerotia resemble cleistothecia in both their morphology and the genetic control of their development. This
suggests the two structures may be homologous, sclerotia being vestigial cleistothecia that lost the capacity to
produce ascospores.
In the Middle Ages Claviceps purpurea sclerotia contaminated rye grain used in bread and led to ergot poisoning
by way of which thousands of people were killed and mutilated. Claviceps purpurea sclerotia contain alkaloids
that, when consumed, can cause ergotism which is a disease that causes paranoia and hallucinations, twitches,
spasms, loss of peripheral sensation, edema and loss of affected tissues.[3]
Louis Rene Tulasne discovered the relationship between infected rye plants and ergotism in the 19th century. With
this discovery, more efforts were developed to reduce scerotia from growing on rye and ergotism became rare.
However, in 1879–1881 an outbreak developed in Germany, in 1926–1927 Russia was infected, and in 1977–
1978 Ethiopia was infected. accumulation of reserve substances and pigments.

26. Pleurotus tuber-regium, which forms edible sclerotia up to 30 cm wide, has a history
of economic importance in Africa as food and as a medicinal mushroom.
In fungi, there are three stages in the development of sclerotia:
1.Initial aggregation of hyphae;
2.Increase in size due to the growth and branching of hyphae;
Maturation with the formation of an outer coating that isolates the sclerotia from the
surrounding environment, with the progressive dehydration of the hyphae .
Uses of sclerotia
Over billions of years of Earth's history, organisms have acquired the ability to
produce secondary metabolites, that is chemical compounds that afford protection
from pathogens and ultraviolet light damage from the sun. Fungi are no exception,
and due to their exposure to a wide variety of environments, they have developed
the ability to produce a large number of such chemical compounds that are very
valuable in medicine.
In early times, ergot alkaloids have been used for medicinal purposes. For example,
ergot was used as a form of abortion in Europe, but it led to hyper-contraction. In
the 19th century, it was used to aid in the prevention of bleeding in after childbirth
and treatment for migraines and Parkinson's disease.[3]
Acid hydrolysis is used to convert alkaloids, produced by the fungus Claviceps
purpurea, into D-lysergic acid which is the starting material for many pharmaceutical
and illegal drugs. In 1938 Albert Hofmann synthesized one of the strongest known
hallucinogens, lysergic acid diethylamide (LSD), from ergot alkaloid. Despite side
effects of the drug such as paranoia, loss of judgment and flashbacks,
psychotherapists and psychiatrists used it to treat patients with neuroses, sexual
dysfunctions and anxiety. The secret service may have also used it for interrogation
purposes. In 1966 the United State government made LSD illegal. Recently, clinics
have shown an interest in ergoline to treat patients with autism.[3]

27. What is haustoria?
In botany, a haustorium (plural haustoria) is the appendage or portion of
a parasitic fungus (the hyphal tip) or of the root of a parasitic plant (such
as the broomrape family or mistletoe) that penetrates the host's tissue
and draws nutrients from it. Haustoria do not penetrate the host's cell
membranes.
Fungi in all major divisions form haustoria. Haustoria take several forms.
Generally, on penetration, the fungus increases the surface area in
contact with host plasma membrane releasing enzymes that break down
the cell wall, enabling greater potential movement of organic carbon from
host to fungus. Thus, an insect hosting a parasitic fungus such as
Cordyceps may look as though it is being "eaten from the inside out" as
the haustoria expand inside of it.
Haustoria arise from intercellular hyphae, appressoria, or external
hyphae. The hypha narrows as it passes through the wall of the cell and
then expands on invaginating the cell. A thickened, electron-dense collar
of material is deposited around the hypha at the point of invagination.
Further, the host wall becomes highly modified in the invaginated zone.
Inclusions normally present in plasma membrane are absent, and the
outer layer contains more polysaccharide. The wall of both partners is
severely reduced.
Functional exchange takes place within the haustorial complex. The host
supplies organic carbon to the fungus, and the metabolic activity within
the complex is considerably greater than outside. Carbon from the host is
absorbed by the fungus, and immediately transported to the rest of the
thallus. The host plant appears to be functioning according to signals
from the fungus and the complex appears to be under the control of the
invader.
The haustorium may be balloon-, spiral- or glove-shaped.

28. Mode of Nutrition: Absorption
The mode of nutrition or the matter in which fungi "eat" is called absorption. Among eukaryotes, absorption
is unique to the fungi. Fungi obtain their food by transporting it through their cell walls, but first, how does
a fungus "find" its food since like plants, they are not mobile organisms and cannot seek out their food. The
answer is fungi do not have to find their food. In order to eat, the spores that give rise to fungi must be
dispersed to a location where there is food and after the spore germinates, the mycelium of the fungus
must grow into its food. Another words, usually fungi must live in their food if they are to eat. If the food
is composed of simple molecules such as glucose or sucrose, soluble food can be immediately transported
through their cell walls. However, most food that a fungus might consume is composed of complex, organic
compounds, e.g., cellulose, lignin, pectin, starch, etc., which is insoluble. In order for this food to be utilized
by the fungus, it must be broken down into simpler molecules that can be transported through their cell
walls. Another way in which you can think of this is that the cell wall is like a sieve that will allow only
particles of a certain size to enter. The fungus breaks down the complex material by secreting digestive
enzymes through their cell wall that will digest the complex organic compounds and convert them into
simple molecules that can readily be transported through their cell walls. For example, If a fungus is
growing in wood, digestive enzymes would be secreted from the fungus, into the wood, and break down the
complex compounds of wood, e.g. cellulose and lignin into simpler materials, such as simple sugars, which
then can be transported into the mycelium.
Although this process may seem very different than our own means of obtaining food. It is not that
different. The essential difference between fungi and animal digestive systems is that fungi digest their
food first and then "eat" it, while animals eat their food before digesting it. The basic process of digestion
is otherwise more or less the same. Our digestive system requires that our food is chewed by teeth, go
through the esophagus, stomach, intestine and many associate organs. So there are a lot of things that can
go wrong when we eat our food. The fungal digestive system is much more simplified and one which has been
very successful for them.
It is important to understand here that different kinds of fungi will secrete only a specific number of
different enzymes. This means that they can only "eat" certain materials. For example, a fungus that is
usually found in your stored food, probably will not be able to "eat" wood because it does not have the
enzymes that is needed to break down or "rot" the wood. Some fungi have a very broad range of enzymes.
Species of Penicillium, for example, can be found on a number of different "food"; leather, cloth, paper,
wood, manure, animal carcasses, ink, syrup, paint, glue, hair, literally thousands of products. A summary of
absorption is illustrated in Figure 7, below:

29. Economic importance of Fungi:
Fungi have both positive ad negative roles in our daily life. So they are our friends as
well as foes (enemy).
They are described as below.
Beneficial Roles or Useful Activities.
i) Fungi are used as food. e.g. Mushrooms and Morels.
ii) Fungi are used in laboratory.
a) Baking Yeast (S. cerevisae)
b) Several alcoholic beverages such as wine, whiskey, beer, rum all are prepared
by fermentation activity of sugar solution by wine yeast. (S. ellipsoidens) c) Some
fungi are used in production of enzymes like amylase, pectimase
iii) Some fungi are used in production of several antibiotics and antibiotics and other
useful medicine like penicillin, streptomycin, ergotine and ephedrine respectively.
iv) Several fungi are used in commercial production of different organic products like
citric acid, fumaric, lactic and oxalic acid.
v) Fungi in agriculture:
a) Being saprophytes they decompose the organic matter and enhance the
fertility of the soil.
b) Some fungi develop symbiotic relation with roots of higher plant like Pinus and
help them in absorption of nutrients. Such fungi are known as mycorrhiza.
vi) Some fungi are used to produce hormone like Gibberellin.

30. Harmful Activities:
i) Food spoilage (destruction) caused by fungi like mucor and yeast.
ii) Some yeasts causes huge loss in silk industry to attack silk worms and kill the
same.
iii) Several types of plant diseases caused by (different types of fungi) species of
Nematospra they attack tomatoes, cotton and bean plants.
Similar disease like causal organisms
a. Stem rust of wheat – Pucvinia graministice
b. Early blight of potato – Alternaria solani
c. Late blight of potato – Phytiphtoria infestans
d. White rust of crucifer – Albugo candida
iv) Some fungi (Cryptococcus neoformans) may cause human disease like
meningitis and brain tumor.
- Torula and other yeasts produce small nodules on the skin and lesions in the
viscera and bones of man.
v) Some fungi are concerned with destruction of substances like attacks textile
materials, paper, leather goods, rubber even optical instruments.
vi) Some fungi are not edible mushroom like different species Amanita.

31. Symbiosis
Symbiosis (meaning living together) is a close and often long-term interaction
between two or more different biological species. In 1877, Bennett used the word
symbiosis (which previously had been used of people living together in community)
to describe the mutualistic relationship in lichens. In 1879, by the German
mycologist Heinrich Anton de Bary, defined it as "the living together of unlike
organisms i.e. parasite and host “
The definition of symbiosis is controversial among scientists. Some believe
symbiosis should only refer to persistent mutualisms, while others believe it should
apply to any types of persistent biological interactions (i.e. mutualistic,
commensalistic, or parasitic).
Some symbiotic relationships are obligate, meaning that both symbionts entirely
depend on each other for survival. For example, many lichens consist of fungal and
photosynthetic symbionts that cannot live on their own. Others are acultative,
meaning that they can, but do not have to live with the other organism.
Symbiotic relationships include those associations in which one organism lives on
another (ectosymbiosis, such as mistletoe), or where one partner lives inside the
other (endosymbiosis, such as lactobacilli and other bacteria in humans or
zooxanthelles in corals).
Certain plants establish a symbiotic relationship with bacteria enabling them to
produce nodules that facilitate the conversion of atmospheric nitrogen to ammonia.
Similarly, over 95% higher plant form mycorrhizal association.

32. Mutualism
Mutualism is any relationship between individuals of different species where both individuals enjoy
benefit. In general, only lifelong interactions involving close physical and biochemical contact can properly
be considered symbiotic. Mutualistic relationships may be either obligate for both species, obligate for
one but facultative for the other, or facultative for both. Many biologists restrict the definition of
symbiosis to close mutualist relationships.
A large percentage of herbivores have mutualistic gut fauna that help them digest plant matter, which is
more difficult to digest than animal prey. Most land plants and land ecosystems rely on mutualisms
between the plants, which fix carbon from the air, and mycorrhyzal fungi, which help in extracting
minerals from the ground.
An example of mutual symbiosis is the goby fish, which sometimes lives together with a shrimp. The
shrimp digs and cleans up a burrow in the sand in which both the shrimp and the goby fish live. The
shrimp is almost blind, leaving it vulnerable to predators when above ground. In case of danger the goby
fish touches the shrimp with its tail to warn it. When that happens both the shrimp and goby fish quickly
retreat into the burrow.
One of the most spectacular examples of obligate mutualism is between the siboglinid tube worms and
symbiotic bacteria that live at hydrothermal vents and cold seeps. The worm has no digestive tract and is
wholly reliant on its internal symbionts for nutrition. The bacteria oxidize either hydrogen sulfide or
methane, which the host supplies to them. These worms were discovered in the late 1980s at the
hydrothermal vents near the Galapagos Islands and have since been found at deep-sea hydrothermal
vents and cold seeps in all of the world's oceans.
There are also many types of tropical and sub-tropical ants that have evolved very complex relationships
with certain tree species.

33. Commensalism
Commensalism describes a relationship between two living organisms where one
benefits and the other is not significantly harmed or helped. It is derived from the
English word commensal used of human social interaction. The word derives from
the medieval Latin word, formed from com- and mensa, meaning "sharing a table".
Commensal relationships may involve one organism using another for transportation
(phoresy) or for housing (inquilinism), or it may also involve one organism using
something another created, after its death (metabiosis). Examples of metabiosis are
hermit crabs using gastropod shells to protect their bodies and spiders building their
webs on plants.

34. Parasitism
A parasitic relationship is one in which one member of the association benefits
while the other is harmed. Parasitic symbioses take many forms, from
endoparasites that live within the host's body to ectoparasites that live on its
surface. In addition, parasites may be necrotrophic, which is to say they kill their
host, or biotrophic, meaning they rely on their host's surviving. Biotrophic
parasitism is an extremely successful mode of life. Depending on the definition
used, as many as half of all animals have at least one parasitic phase in their life
cycles, and it is also frequent in plants and fungi. Moreover, almost all free-living
animals are host to one or more parasite taxa. An example of a biotrophic
relationship would be a tick feeding on the blood of its host.

35. Neutralism
Neutralism describes the relationship between two species which interact but do not
affect each other. It describes interactions where the fitness of one species has
absolutely no effect whatsoever on that of the other. True neutralism is extremely
unlikely or even impossible to prove. When dealing with the complex networks of
interactions presented by ecosystems, one cannot assert positively that there is
absolutely no competition between or benefit to either species. Since true neutralism
is rare or nonexistent, its usage is often extended to situations where interactions are
merely insignificant or negligible.

36. Amensalism
Amensalism is the type of relationship that exists where one species is inhibited or
completely obliterated and one is unaffected. This type of symbiosis is relatively
uncommon in rudimentary reference texts, but is omnipresent in the natural world. An
example is a sapling growing under the shadow of a mature tree. The mature tree can begin
to rob the sapling of necessary sunlight and, if the mature tree is very large, it can take up
rainwater and deplete soil nutrients. Throughout the process the mature tree is unaffected.
Indeed, if the sapling dies, the mature tree gains nutrients from the decaying sapling. Note
that these nutrients become available because of the sapling's decomposition, rather than
from the living sapling, which would be a case of parasitism.
In other way, Amensalism is a relationship in which a product of one organism has a
negative effect on another organism. It is specifically a population interaction in which one
organism is harmed, while the other is neither affected nor benefited. Usually this occurs
when one organism exudes a chemical compound as part of its normal metabolism that is
detrimental to another organism. The bread mold penicillium is a common example;
penicillium secrete penicillin, a chemical that kills bacteria. A second example is the black
walnut tree (Juglans nigra), which secrete juglone, a chemical that harms or kills some
species of neighboring plants. This interaction may nevertheless increase the fitness of the
non-harmed organism by removing competition and allowing it greater access to scarce
resources. In this sense the impeded organism can be said to be negatively affected by the
other's very existence, making it a +/- interaction. A third example is when sheep or cattle
make trails by trampling on grass, thereby destroying a food source.

38. Competition
Competition can be defined as an interaction between organisms or species, in which the
fitness of one is lowered by the presence of another. Limited supply of at least one resource
(such as food, water, and territory) used by both usually facilitates this type of interaction,
although the competition may also exist over other 'amenities', such as females for
reproduction (in case of male organisms of the same species). Competition is one of many
interacting biotic and abiotic factors that affect community structure. Competition among
members of the same species is known as intraspecific competition, while competition
between individuals of different species is known as interspecific competition.
Interspecific competition is normally not as fierce as intraspecific competition, unless in
case of a sudden drastic change. However, it is the most conspicuous competition in
grasslands, where, for example, cheetahs and hyenas are often killed by lion prides.
Competition is not always a straightforward, direct interaction either, and can occur in both
a direct and indirect fashion.
Competition between species at the same trophic level of an ecosystem, who have common
predators, increases drastically if the frequency of the common predator in the community
is decreased by a large margin. The magnitude of competition therefore depends on many
factors in the same ecosystem.
According to the competitive exclusion principle, species less suited to compete for
resources should either adapt or die out. According to evolutionary theory, this competition
within and between species for resources plays a critical role in natural selection.

39. predation
Predation describes a biological interaction where a predator (an organism that is
hunting) feeds on its prey (the organism that is attacked). Predators may or may not
kill their prey prior to feeding on them, but the act of predation often results in the
death of its prey and the eventual absorption of the prey's tissue through
consumption. Other categories of consumption are herbivory (eating parts of
plants) and detritivory, the consumption of dead organic material (detritus). All
these consumption categories fall under the rubric of consumer-resource systems. It
can often be difficult to separate various types of feeding behaviors.[1] For example,
some parasitic species prey on a host organism and then lay their eggs on it for
their offspring to feed on it while it continues to live or on its decaying corpse after
it has died. The key characteristic of predation however is the predator's direct
impact on the prey population. On the other hand, detritivores simply eat dead
organic material arising from the decay of dead individuals and have no direct
impact on the "donor" organism(s).
Selective pressures imposed on one another often leads to an evolutionary arms
race between prey and predator, resulting in various antipredator adaptations. Ways
of classifying predation surveyed here include grouping by trophic level or diet, by
specialization, and by the nature of the predator's interaction with prey.