This presentation Slide was presented by me in final evaluation pf the Course.

1. Md. Kamaruzzaman Shakil
Department of Plant Pathology
Bangladesh Agricultural University,
Mymensingh
I.D .No. 11Ag.P.Path. JJ 07 M
Reg. No. 33141
Ph.- +8801722449614

2. Title
BIO - WARFARE DURING HOST
PATHOGEN INTERACTIONS IN
INDIGENOUS CROP PLANTS

3. Introduction
 Plant diseases caused by pathogenic organisms result
in significant economic losses every year. Plants
represent a rich source of nutrients for many
organisms including bacteria, fungi, insects, and
nematodes.
 The infection processes by these pathogenic organisms
share many common features. These include dispersal
of an infectious particle, host adhesion, recognition,
penetration, invasive growth, and lesion development.
 Human depend on plant in every aspects of life. So,
Understanding how plants defend themselves from
pathogens and herbivores is essential in order to
protect our food supply and develop highly disease-
resistant plant species.

4. Objectives
 To know about host-pathogen
interaction.
 To know about various weapons of
fungi, bacteria, viruses and
nematodes.
 To study about bio-warfare and
penetration mechanisms.

5. Plant pathogen
A plant pathogen is a disease-causing
organism which attacks plants and causes
diseases.
Types of plant pathogens
Necrotrophic
pathogen
Biotrophic pathogen
Hemibiotrophic

6. Major pathogenic organisms
Fungi : Fungi are primitive plants, that are lacking in chlorophyll.
Bacteria : Bacteria are microscopic, single-celled
prokaryotic organisms, without a defined nucleus.

7.  Virus:Plant viruses are pathogens which are composed mainly
of a nucleic acid (genome) normally surrounded by a protein shell
(coat).
 Nematode: Nematodes are small, multicellular
wormlike creatures. Many live freely in the soil, but
there are some species which parasitize plant roots.
Fig. nematode

8. Bio – warfare :
Biological warfare means war in plant body against plant
pathogenic organisms by using different defensive
mechanisms .
Description of various weapons:
 Haustoria: A specialized absorbing structure of a
parasitic plant, such as the rootlike outgrowth of the
pathogenic fungi.
Fig. haustoria

9. Description of various weapons
 Appressorium: An appressorium is a flattened, hyphal
"pressing" organ, from which a minute infection peg grows
and enters the host.
 Capsules : The cell capsule is a very large structure of
some prokaryotic cells, such as bacterial cells. It is a well-
organized layer, not easily washed off, and it can be the
cause of various diseases.

10. Description of various weapons
 Stylet: The stylet is the primitive mouth-parts of some
nematodes. The stylet is adapted for the piercing of
cell walls
Fig. Stylet of nematode
 Toxins: In many pathogens, particularly non-obligate
pathogens, toxins cause the majority of damage to
the host.
 Enzymes: Some of the pathogen Produce enzymes that
break down key structural components of plant cells.

11. Mechanism of penetration & host tissue
disintegration

12. Mechanism of penetration & host tissue
disintegration
 Fungi:
Natural opening – Plants have several types of natural
openings utilized by fungi. The most common are stomates.
Fig. Stomata
wound - Damage to a plant surface may result from
animal and insect activities, environmental causes (e.g. hail),
and mechanical injury.

13. Mechanism of penetration & host tissue disintegration
Direct Penetration: After contact between a germ tube and the
plant surface, the direct penetration of plant cells requires a
combination of mechanical force and enzymatic softening of the
cuticle.
Fig. Direct penetration

14. Mechanism of penetration & host tissue
disintegration

15. Mechanism of penetration & host tissue
disintegration
 Virus: Vector is the important factor for viral disease.
They have a special molecule
called a RECEPTOR
to attach to
the cellular surface.

16. Mechanism of penetration & host tissue
disintegration
After attachment the virus
may enter the cell by a
process called ENDOCYTOSIS
and then be released into
the cytoplasm.

17. Mechanism of penetration & host tissue
disintegration
ABNORMAL CELLS
The cells become round and enlarge
and may eventually die when
the new viral particles are released

18. Mechanism of penetration & host tissue
disintegration
Nematodes

19. Mechanism of penetration & host tissue
disintegration
Life cycle of root-knot nematode
(~30 days)
Giant cells
Root tip
Vascular cylinder
• • ••• • •
• •• •• •
• • •• • • .
• • ••• • •• . •
•• • •• •
• • •• •
Adult
Female
Egg Infective
Mass Eggs hatch juvenile
Curr. Opin. Plant Biol. 6:327-333

20. Mechanism of penetration & host tissue
disintegration
Proliferation of destruction by nematodes
2 hr
4 hr
6 hr
24 hr

21. Conclusion