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REPRODUCTION IN FUNGI

CONTENTS
 Introduction
 Asexual Reproduction
 Sexual Reproduction

 Parasexual Reproduction
 Homothallism
 Heterothallism

Reproduction
 Reproduction is the formation of new individuals
with all the characteristics typical of the species
...

 Sexual reproduction involves the union of two
compatible nuclei and generally takes place only
once in a life cycle
...


Asexual Reproduction




Asexual reproduction takes place when a single parent forms progeny
without a nuclear contribution from the second parent
...

In some fungi, fragmentation of parent hyphae into thallospores is a normal
means of propagation
...




 Fission of unicellular thalli:- In this process, the nucleus of a somatic


cell divides by mitosis and the cell contents divide transversely by a septum
into two daughter cells of similar size, shape and contents
...


 Budding of somatic cells:- It is the production of small bud from a
parent cell
...


Production of Asexual spores


Spores may very in shape, size, septation and maybe
unicellular or multicellular ,motile or nonmotile, thick or
thin walled,etc
...




Sporangiospores are formed by the cleavage of cellular
contents of sac like structure called sporangium into
numerous minute uninucleate , fragments
...




Conidiospores are asexual spores
...


Sexual reproduction
 Sexual reproduction involves a cycle of (1)plasmogamy







followed by (2)karyogamy and (3) meiosis
...

This condition is seen in fungi belonging to Mucorales and
Ascomycetes
...

Life cycles of this type are found in many Oomycetes and in
yeast Saccharomyces cerevisiae
...
It is seen in Allomyces
...
e
...
e
...

Antheredial nuclei passes to oogonium
through fertilization tube
...

Spores can resist the adverse
conditions
...


Oospores

Zygospores
 It is result of union of two similar or

identical gametes designated as
positive and negative
...

 The wall consists of two layersexosporium and endosporium
...


Zygospores

 Ascospores
 It is a result of union between female

gamete i
...
ascogonium and male
gamete i
...
antheridium
...


Ascospores

Basidiospores
 These are the sexual spores

produced on club shaped structure
known as basidium on a short stalk
known as sterigmata
...

 They are usually four in number
...


Basidiospores

PARASEXUAL CYCLE
 Process in which plasmogamy, karyogamy and haplodization








takes place but not at specified points in the life cycle
...

The essential events of parasexual cycle are:
HETEROKARYOSIS- Inclusion of genetically different nuclei in
the same cytoplasm is an important step for recombination
and is achieved through heterokaryosis
...

MITOTIC SEGREGATION- Mitotic crossing over is a rare event
occurring at the four strand stage of mitosis
...


HAPLOIDIZATION
 Diploid nuclei give rise to haploid nuclei by gradual loss

of chromosomes during successive mitotic divisions
...

 Aneuploids are unstable, and once the loss of
chromosomes has started, it continues to lose
chromosomes, probably one at a time, until the haploid
condition is restored
...


HOMOTHALLISM AND HETEROTHALLISM
 On the basis of compatibility, fungi can be

homothallic or heterothallic fungi
...

 Heterothallic species are those species which
require mycelia of two different strains to
interact to enable the zygospores to be
formed
...

 PHYSIOLOGICAL HETEROTHALLISM- interacting
thalli, which differ in mating type or incompatibility
factor, irrespective of the presence or absence of
differentiated sex organs or gametes
...


Two allele and multiple allele
heterothallism

 Two allele heterothallism
 Determined by two alleles at one locus
...

 (+) and (-) strains are essential for mating
...


MULTIPLE-ALLELE HETEROTHALLISM
 More than two alleles at the genetic loci

control sexual compatibility
...

 It may be bipolar, tetra polar or octapolar

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