Undergraduate students' slide presentation of Plant pathogenesis caused by fungi for SHEQ3329 Agricultural Microbiology under Dr. Khanom Simarani (2014/2015).

1. PLANT
PATHOGEN
FU
NGI Apple cedar rustBy Hikmal, Ain, Sabrina,
Fatihah

2. • Disease cycle similar to virus and bacteria
• Can not only penetrate host via wounds or natural
opening, they can also actively penetrate via
production of appresoria – allows direct penetration
through mechanical and enzymatic activity
PATHOGENIC FUNGI
Appresoria – swollen tips of hyphae

3. FUNGALLIKE
ORAGANISMS (FLO)
TRUE FUNGI
IMPERFECT FUNGI
With walls containing chitin,
and with many other cellular
and biochemical features
With fungal lifestyle but with
cellulose walls and with cellular
and biochemical features
resembling those of plants
With fungal-like structures, but
grow as wall-less protoplasmic
stages
Acrasids, Myxomycetes,
Plasmodiophorids
Zygomycota, Ascomycota,
Basidiomycota
Oomycota

4. • Extremely destructive
fungal disease of
potatoes – attack both
tubers and foliage at any
stage
• a serious pathogen on
tomatoes in cool, wet
climates
OOMYCOTA
Late blight/Potato
blight
Phytophora
infestans
•Appearance of dark necrotic
lesions within 3 to 5 days of initial
infection on leaves
•Dark, water-soaked lesion on
petioles and stems
•Lesion axpand when P. infestans
colonizes internal plant tissues
•On mature lesions, P. infestans
produce sporangia – underside of
the leaves/surfaces of stem
•As disease progress, the entire
plant becomes blight and decay
SYMPTOM
S

5. Disease cycle
Blight infection on leaf petiole
Infected green fruit

6. • Disease that affects both annual and
perennial crop species in the legume
family
• Aphanomyces – root-infecting
oomycetous fungi, present in wet and
poorly drained soils
Aphanomyces Root
Rot (ARR)
Aphanomyces
euteiches
a) Infected root b) Healthy root
Yellowing due to Aphanomyces
SYMPTOM
S
•infected root tissue appears gray and water-
soaked, becoming soft and honey-brown or
blackish-brown in appearance
•roots are reduced in volume and function
•Primary symptoms of roots and stems will
eventually lead to secondary symptoms of
chlorosis, necrosis, and wilting of the foliage

7. DISEASE
CYCLE

8. Diseased caused by
Plasmodiophoromycetes
Three genus of Plasmodiophoromycetes that known to cause following
diseases:
◦ Plasmodiophora: causing clubroot of crucifiers
◦ Polymyxa : causing a root disease of cereals and grasses
◦ Spongospora: causing the powdery scab of potato
The most common disease : Clubroot of crucifiers

9. Clubroot of Crucifers
The clubroot disease of cruciferous plants such as cabbage and
cauliflower is widely distributed all over the world
◦ Cruciferous plants: or also term as cruciferous vegetables are vegetables of
the family Brassicaceae, are widely cultivated such as cauliflower, cabbage,
broccoli, brussels sprouts and similar green leaf vegetables. This group of
vegetables was originally named for the four-equal sized petals in its flower.
They are also known as cole crops.
Fields once infested with the clubroot pathogen remain so indefinitely
and become unfit for cultivation of crucifers

10. Symptoms
Infected plants at first have pale green to yellowish leaves
Wilting in the middle of hot sunny days
Young plants may be killed by the diseases
Older plants may remain alive but become stunted
The roots of infected plants: appear on the roots as spindle-like,
spherical, knobby or club-shaped swelling
The swelling may be few and isolated or they may coalesce and cover
the entire root system

11. Source: http://www.cals.ncsu.edu/course/pp728/
Plasmodiophora/Plasmodiophora.html
Source:http://www.omafra.gov.on.ca/IPM/english/brassicas/dis
eases-and-disorders/clubroot.html
Figure 1:Clubroot on infected roots
Figure 2: Clubroot on Brussels sprout

12. The pathogen:
Plasmodiophora brassicae
Obligate parasites
Can survive in the soil as resting spores for many years
Plasmodium-shaped body
The plasmodium gives rise to zoosporangia or to resting spore which on
germination produce zoospores
The plasmodium lives off the host cells it invades but does not kill these
cells for a long time
The pathogens spread from plant to plant by means of zoospores, by
anything that moves soil or water containing spores-soil borne fungus

13. Development of Disease

14. Control actions
Avoid growing cruciferous crops in fields known to be infested with the
clubroot pathogen
Plant the cruciferous vegetables in well-drained fields that have a pH
slightly above neutral (pH 7.2) or in fields in which hydrated lime has
been added to raise the soil pH
Treat the soil with chloropicrin, methyl bromide or metam sodium
approximately 2 weeks before planting

15. -Contain fungi called zygomycetes
-Live in soil or on decaying plant
- The hyphae of zygomycetes are
coenocytic
- Asexual spores develop in
sporangia at the tip of aeriel hyphae
- Sexual reproduction produce
tough, thick-walled zygotes called
zygospores
- An example of zygomycetes is black bread
mold (Rhizopus stolonifer)
- Grow on the surface of moist, carbohydrate-
rich food
- Reproduce asexually but in unfavourable
condition, sexual reproduction occur
Zygomycota
Structure of sporangium

16. Disease (Rhizopus)
• Rice disease ( seedling blight)
-fungus secreted a toxin that kills rice seedling
-toxin rhizoxin and rhizonan most commonly
associated with this disease
-lead to rapid browning and shriveling of plant
tissues
ex : Rhizopus microsporus

17. Life cycle of rice disease fungi
- starts its infection cycle when a three-
celled conidium lands on the rice leaf
surface
- The spore attaches to the hydrophobic
cuticle and germinates
- producing a narrow germ tube
- flattens and hooks at its tip before
differentiating into an appressorium
- single-celled appressorium matures
and the three-celled conidium
collapses and dies in a programmed
process that requires autophagy.
- The appressorium becomes melanized
and develops substantial turgor
- This translates into physical force and a
narrow penetration at the base
- puncturing the cuticle and allowing
entry into the rice epidermis

18. • Rhizopus soft rot
- Disease of the fleshy root in storage
- Happening during packing and shipping
-The disease causes a watery soft rot of the
internal portion of the storage root
-Gray whiskery mould with dusty black spores
may grow on the fruit surface
ex : Rhizopus stolonifer

19. Symptoms of rhizopus soft rot
Dime-sized lesions are
cinnamon or
chocolate-colored
A water-soaked lesion
starts to develop a few
hours after the root
has been wounded
The lesion becomes
covered by a web-like
outgrowth
small cracks and
wrinkled appearance
emits a pleasant
fermented odour that
attracts fruit flies

20. Disease cycle of rhizopus soft rot
The fungus survives unfavorable environmental conditions as
dark colored zygospores in the remnants of rotted fruit
Fruit in the early stages of ripening require injury from
factors such as insects, hail or cracking. Infections occur
through wounds
After the fungus enters the tissues, it penetrates rapidly and
causes a soft wet decay of the entire root in a very few days
The decayed tissues become dry and both ends of the root
remain sound
A combination of wet soil and low temperature at harvest
time causes it susceptible to soft rot

21. Plant Diseases
Caused by
Basidiomycetes
CORN SMUT DISEASE BY
USTILAGO MAYDIS

22. Corn smut disease
Occurs wherever corn is grown- prevalent in warm and moderately dry
areas
Damages plants and reduce yields by forming galls:
◦ Tassels
◦ Ears
◦ Stalks
◦ Leaves
Figure 1: Anatomy of corn

23. Symptoms
Minute galls form on the leaves and stems on young corn. The seedling may remain stunted or
may be killed
Galls formed on young, actively growing tissue of axillary buds, individual flowers of the ear and
tassel, leaves and stalk
Infected areas are permeated by the fungus mycelium-stimulates the host cells to divide and
enlarge-forming galls
Galls-first covered with a greenish white membrane
Matured galls- reach size (1-15cm diameter), their interior darkens and turns into a mass of
powdery, dark, olive-brown spores
The silver gray membranes then ruptures and exposes millions of teliospores-released into air
Galls on leaves: relatively small (1-2cm), hard, dry and do not rupture

24. Corn smut on tassel
Smut galls on an ear of sweet corn
Galls on sweetcorn

25. The Pathogens: Ustilago
maydis
Fungus produces dikaryotic mycelium-the cells transformed into black,
spherical or ellipsoidal teliospores
Teliospores germinates by producing a four-celled basidium
(promycelium) from each cell of which a basidiospore (sporidium)
develops
Figure 2: Ustilago maydis diploid teliospores

26. Development of disease

27. Disease caused by Fungi:
Ascomycete
•Venturia inequalis
•Magnaporthe grisea
•Claviceps purpurea
•Dibotryon morbosum

28. Ascomycete
(Sac fungi)
• Reproduce sexually and
asexually
• Sexual rep: produce large
numbers of asci (in ascocarp)
• Asexual rep: through vegetative
reproductive spores, the
conidiaspores.
• Depending on the species they
may be dispersed by wind or
water, or by animals.
• Heterotrophic organisms that
require organic compounds as
energy sources
• secrete powerful digestive
enzymes that break down
organic substances into smaller
molecule

29. Apple scab
Fungi: Venturia inequalis
Symptoms: Dull black or grey-brown
lesions on the surface of tree
leaves, buds or fruits. Infected
leaves become yellow, then drop
Env. Cond: lack of sunlight, bad
sanitation and management
Effect: Rarely kills its host, but can
significantly reduce fruit yields and
fruit quality
Agents: water (rain)
Treatment: fungicide, good
management and sanitation
Powdery mildew
Fungi: Sphaerotheca fuliginea
Symtoms: Powdery splotches of
white or gray on leaves
Env. Cond: Grows well in
environments with
high humidity and moderate
temperatures
Effect :Photosynthesis is impaired.
Infected leaves often fall
prematurely
Agents: wind, insects, water
splashing
Treatment: fungicide (potassium
bicarbonate), thinning and
pruning, milk

30. Ergot
Fungi: Claviceps purpurea
Symtoms: ergot that replaces the
grain of the rye is a dark,
purplish sclerotium
Env. Cond: Continuous moist
conditions, wet, cloudy and cool
weather extends the period of
flowering and increases the
window of infection for spores to
enter the florets
Effect : convulsive and gangrenous
ergotism.
Agents: insects, wind
Treatment: fungicides, burning,
insect control, row spacing
Black knot
Fungi: Dibotryon morbosum
Symtoms: Rough, black areas that
encircle and kill the infested
parts. Only on the wood parts of
trees, primarily on twigs and
branches but can spread to larger
limbs and even the trunk
Env. Cond: moderate temperatures
Effect : Destructive diseases of the
plum and cherry trees
Agents: insects
Treatment: pruning infected parts
and spraying buds with
a fungicide

31. Life cycle
Apple scab Powdery mildew

32. Ergot Black knot

33. THANK YOU
Question?