Mycology

COURSE TEACHER
DR. A.S. KRISHNAMOORTHY
STUDENT
MOHAMMED FAISAL P

INTRODUCTION
Ascomycota are fungi which possess an ascus, containing ascospores,
formed after karyogamy and meiosis.
The ascomycota is the largest phylum of fungi having almost 45 % of
the desribed species.
Now, with the merger of the Deuteromycetes another 20% of the
described species have been assed to this group.
(Taylor,
1995)

Domain – Eukarya
Kingdom – Fungi

Archiascomycetes includes 11 orders of which four orders
are very important

Family Taphrinaceae
Genus Taphrina
Species T. deformans,
T. maculans

Taphrina deformans hyphae growing in intercellular spaces secrete
polysaccharide-degrading enzymes, such as cellulase, causing partial
dissolution of the host cell wall.
This process also results in changes in the plasma membrane.
T. deformans also produces the auxin indole-3-acetic acid from L-
tryptophan via indole-3-pyruvic acid and indole-3-acetaldehyde.
This process is thought to be responsible for the hyperplastic effect
of the infection.
Ascomyces deformans Berk., (1860)Exoascus amygdali Jacz., (1926)
Exoascus deformans (Berk.) Fuckel, (1870)Taphrina amygdali (Jacz.)
Mix, (1936)

Disease cycle of peach leaf curl and plum pocket caused
by Taphrina sp.

• In liquid cultures, especially on media containing tryptophane,
considerable quantities of the auxin-type phytohormone indole
acetic acid (IAA) have been demonstrated.
• A number of different cytokinins are also produced by several
species of Taphrina in culture
(Kern & Naef-Roth, 1975; Tudzynski, 1997)

The classification of the Schizosaccharomycetales has
been the subject of controversial discussions, but the
emerging consensus is that there is only one genus with
three species, S. japonicus, S. octosporus and S. pombe.
(Barnett et al., 2000).
Grow as saprotrophic yeasts which reproduce asexually
by fission, i.e. by division of a vegetative cell into two
daughter cells of equal size.
Schizosaccharomyces is therefore called the fission yeast

Schizosaccharomyces octosporus.
(a) Vegetative cells, showing
transverse division, conjugating
(b) Four- and eight-spored asci.

The life cycle of the homothallic yeast
Schizosaccharomyces octosporus.

The cytoskeleton and the cell cycle in Schizosaccharomyces
pombe

Consist of 8 familes and 75 genera
Characterized by direct development of asci from the zygote, lack
mycelium and absence of ascomata
Pseudomycelium – hyphae consisting of cells formed by budding
8 families are

• About 10-16 species of Saccharomyces are currently
recognized
(Barnett et al., 2000; Kirk et al., 2001)
• S. cerevisiae, which in many ways is the most important
fungus yet discovered.
• About 25 strains of S. cerevisiae exist, and these have
different physiological properties which are relevant to
their biotechnological applications
Saccharomycetaceae

Sketch of a budding yeast cell

The structure of the mating type idiomorphs a (top)
and α (bottom) of Saccharomyces cerevisiae
The two alleles differ only in their central (Y) regions which contain parts of
two genes a1and a2 or a1and a2.
The function of a2 is unknown.In diploid cells,the lack of expression of a1
and the formation of a dimeric α2/a1 protein suppresses the expression of
mating type-specific proteins including hormones and their receptors
(Annual Reviews of Genetics, 32, 1989)

• Alcoholic fermentation mainly by Saccharomyces cerevisiae.
This is the oldest and yet still the most important area of
biotechnology, with about 1011
l of beer and 3X1010
l ofwine
produced worldwide each year
(Oliver, 1991; Kurtzman & Sugiyama, 2001)
• Bread-making. About 1.5 X 106
tons of fresh cells of S.
cerevisiae are produced worldwide per annum for use in the
production of bread dough
Applications of Saccharomyces

• Single-cell protein (SCP). This term describes the conversion
of low-cost substrates into protein- rich biomass of unicellular
organisms.
• Vitamin production. Riboflavin (vitamin B2) is produced
industrially.
• Production of recombinant proteins, e.g. enzymes, or
clinically relevant molecules such as antigens, insulin and
epidermal growth factor.
Expression systems for heterologous proteins, i.e. proteins of interest
whose gene has been linked to the promoter sequence of the producing
organism.

• Single family
• Protomycetaceae comprising of five
genera
• Attack flowering plant and cause
lesions and galls
• Special characeter is formation of
vesicle - synascus

Life cycle of Protomyces macrosporus

Compiled from Alexopoulos et al (1996), Sugiyama (1998) and Landvik
et al (2003)

Filamentous ascomycetes (informally called euascomycetes) are
the most evolved members of phylum Ascomycota
Traditionally segregated based on morphology of ascomata
rDNA sequences has shown the division into classes to be untenable
Study of these class are made know in order of alphabetical
sequence as their evolutionary relationships are not clear.
(Berbee and Taylor, 1999)

Largest order of phyllum Ascomycota, 58 familes and 711
genera and 4774 species.
Ascospores are septate
two important families
•Mycosphaerella is one of the largest genera of ascomycetes,
containing over 2000 described species
(Corlett, 1991)

• Several related Ascochyta-type anamorphs infect legumes,
causing diseases such as blight of chickpea (A. rabiei), foot rot
and blight of peas (A. pinodes), and leaf and pod spot of broad
beans (A. fabae) and peas (A. pisi).
• The pseudothecial state, where present, is now called
Didymella (formerly Mycosphaerella).

Family - Venturiaceae
The mycelium in living tissues is located only between the cuticle and
the epidermal cells.
There, it produces short, erect, brownish conidiophores that give rise to
several, one- or two-celled, Spilocaea-type conidia of rather
characteristic shape
Genus Venturia
Species V. inaequalis

Life cycle of Venturia inaequalis

• 13 families and 2000 species
• One important family

• Members of families produce stalked apothecia which grow
from stromata located within the colonized host plant tissue.
• In Sclerotinia the apothecia arise from a seed like sclerotium
which, though formed in host tissue, fall off to lie in the soil.
• The conidial stage is represented by Botrytis.
• Monilinia forms apothecia on mummified and stromatized
fruits; the conidial stage is Monilia
Family - Sclerotiniaceae

GENUS - Sclerotinia Sclerotia of
the fungus
inside a
tomato stem
Sclerotia of
the fungus
inside a
tomato stem
Stem
rot or
white mould
in pepper
Stem
rot or
white mould
in pepper
Stalkrotofcabbage
Stalkrotofcabbage
Carrotwhite
mouldwith
sclerotia
Carrotwhite
mouldwith
sclerotia

• The mycelium produces chains of elliptical Monilia- type
conidia on hyphal branches arranged in tufts (sporodochia).
• The fungus also produces microconidia (spermatia) in chains
on bottle-shaped condiophores.
• The sexual stage, the apothecium, originates from
pseudosclerotia formed in mummified fruit buried partly or
wholly in the soil or debris.
Monilinia fructicola

Symptoms caused by Monilinia on peach

The life cycle of Monilinia fructicola

Black Mildew
Black mildew is widespread in bamboo
stands, especially in humid tropical areas
with closed canopy
Cobweb-like to powdery black patches
appear on the upper surfaces of mature
leaves.
As the infection develops, the upper leaf
surface becomes densely coated with a
black powdery growth of fungal hyphae

Meliola fabri parasitic on Castanopsis fabri and Meliola
hosagoudarii parasitic on Tutcheria microcarpa

• Ceratocystis fimbriata, causing canker
diseases on cacao, coffee, stone fruits

• Includes opperculate discomycetes.
• 17 families and 177 genera
• Families are
Ascobolaceae, Helvellaceae, Morchella, Otideaceae,
Pezizaceae amd Tuberaceae
• Ascobolus is the type genus, having 50 species most of
which forms apothecia on dung of herbivore animals

MORPHOLOGY OF Ascobolus sps
Ascobolus immersus
Ascobolus furfuraceus

• Single family – Phyllachoraceae and 42 genera
• The anamorphs are coelomycetous mitosporic fungi.
• 2 important genera
Order - Phyllachorales
PhyllachoraPhyllachora
GlomerellaGlomerella

• G. cingulata causing many anthracnose diseases and bitter
rot of apples; anthracnose of mango, banana its anamorphic
stage is Colletotrichum gloeosporioides
Genus – Glomerella

• Forms perithecia or clestothecia
• Asci are cylinderical or clavate
• Conidia stage is absent or sometimes spermatial
• Most are saprobes
• 8 families two are important
– Cheatomiaceae
– Sordariaceae

• Beaked or ostiolate perithecia with ornamental hairs
• Asci are spherical or globose
• Anamorphs are absent
• Genus – Cheatomium – cellulose degarding fungi
• 80 species are recorded.
Family - Cheatomiaceae

• Most species of Sordaria are cellulolytic.
• Perithecia are common on the dung of herbivores and
occasionally on other substrata such as seeds and plant
remains, while a few species are reported from soil.
• Sordaria fimicola is especially common on horse dung and
has been widely used in experiments on nutrition, the
physiology of fruiting, spore liberation and genetics.
FAMILY - SORDARIACEAE

a) L.S. Perithecium. (b) Ascus apex. (c) Ascospore showing mucilaginous
epispore.

• There are about 12 species of Neurospora, mostly growing on
soil.
• Neurospora has been widely used in genetic and biochemical
studies
• The development of auxotrophic mutants deficient in successive
steps of arginine biosynthesis led to the proposition of the ‘one-
gene-one-enzyme’ hypothesis by Beadle and Tatum (1941) who
were awarded the Nobel Prize in 1958.
• The loci of over 1000 genes have been mapped
(Perkins et al., 2000)
• complete genome of N. crassa has now been sequenced. It is
haploid and has seven chromosomes.
Genus - Neurospora

Life cycle and mating types in Neurospora

Mycology

Recomendados

Recomendados

Mais conteúdo relacionado

Mais procurados

Mais procurados (20)

Destaque

Destaque (20)

Semelhante a Mycology

Semelhante a Mycology (20)

Mais de Mohammed Faisal Peeran

Mais de Mohammed Faisal Peeran (6)

Último

Último (20)

Mycology