Md. Kamaruzzaman ShakilMd. Kamaruzzaman ShakilDepartment of Plant PathologyDepartment of Plant Pathology

Bangladesh Agricultural Bangladesh Agricultural University, MymensinghUniversity, Mymensingh

I.D .No. 11Ag.P.Path. JJ 07 MI.D .No. 11Ag.P.Path. JJ 07 MReg. No. 33141Reg. No. 33141

Ph.- +8801722449614Ph.- +8801722449614

TitleTitle BIO - WARFARE DURING HOST PATHOGEN INTERACTIONS IN

INDIGENOUS CROP PLANTS

IntroductionIntroduction Plant diseases caused by pathogenic organisms result Plant diseases caused by pathogenic organisms result

in significant economic losses every year. Plants in significant economic losses every year. Plants represent a rich source of nutrients for many represent a rich source of nutrients for many organisms including bacteria, fungi, insects, and organisms including bacteria, fungi, insects, and nematodes. nematodes.

The infection processes by these pathogenic organisms The infection processes by these pathogenic organisms share many common features. These include dispersal share many common features. These include dispersal of an infectious particle, host adhesion, recognition, of an infectious particle, host adhesion, recognition, penetration, invasive growth, and lesion development.penetration, invasive growth, and lesion development.

Human depend on plant in every aspects of life. So, Human depend on plant in every aspects of life. So, Understanding how plants defend themselves from Understanding how plants defend themselves from pathogens and herbivores is essential in order to pathogens and herbivores is essential in order to protect our food supply and develop highly disease-protect our food supply and develop highly disease-resistant plant species.resistant plant species.

ObjectivesObjectives

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.

Plant pathogenPlant pathogenA plant pathogen is a disease-causing A plant pathogen is a disease-causing organism which attacks plants and causes organism which attacks plants and causes diseases.diseases.

Types of plant pathogensTypes of plant pathogens

Necrotrophic Necrotrophic pathogenpathogen

Biotrophic pathogenBiotrophic pathogen

HemibiotrophicHemibiotrophic

Major pathogenic organismsMajor pathogenic organismsFungi : Fungi : Fungi are primitive plants, that are lacking in chlorophyll.Fungi are primitive plants, that are lacking in chlorophyll.

Bacteria Bacteria : Bacteria are microscopic, single-celled : Bacteria are microscopic, single-celled prokaryotic organisms, without a defined nucleus. prokaryotic organisms, without a defined nucleus.

Virus:Virus:Plant viruses are pathogens which are composed mainly of Plant viruses are pathogens which are composed mainly of a nucleic acid (genome) normally surrounded by a protein shell a nucleic acid (genome) normally surrounded by a protein shell (coat).(coat).

Nematode: Nematode: Nematodes are small, multicellular Nematodes are small, multicellular wormlike creatures. Many live freely in the soil, but wormlike creatures. Many live freely in the soil, but there are some species which parasitize plant roots.there are some species which parasitize plant roots.

Fig. nematodeFig. nematode

Description of various weapons:Description of various weapons:Haustoria: Haustoria: A specialized absorbing structure of a A specialized absorbing structure of a

parasitic plant, such as the rootlike outgrowth of parasitic plant, such as the rootlike outgrowth of the pathogenic fungi.the pathogenic fungi.

Fig. haustoria

Bio – warfare :Bio – warfare :Biological warfare means war in plant body against Biological warfare means war in plant body against plant pathogenic organisms by using different plant pathogenic organisms by using different defensive mechanismsdefensive mechanisms. .

Description of various weaponsDescription of various weaponsAppressorium: Appressorium: An appressorium is a flattened, An appressorium is a flattened,

hyphal "pressing" organ, from which a minute hyphal "pressing" organ, from which a minute infection peg grows and enters the host.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.

Description of various weaponsDescription of various weaponsStylet: 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.

Mechanism of penetration & host tissue Mechanism of penetration & host tissue disintegrationdisintegration

Mechanism of penetration & host tissue Mechanism of penetration & host tissue disintegrationdisintegration

Fungi:Fungi:

Natural opening – 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.

Mechanism of penetration & host tissue Mechanism of penetration & host tissue disintegrationdisintegration

Direct Penetration: After contact between a germ tube After contact between a germ tube and the plant surface, the direct penetration of plant and the plant surface, the direct penetration of plant cells requires a combination of mechanical force and cells requires a combination of mechanical force and enzymatic softening of the cuticle. enzymatic softening of the cuticle.

Fig. Direct penetrationFig. Direct penetration

Mechanism of penetration & host tissue Mechanism of penetration & host tissue disintegrationdisintegration

They have a special moleculecalled a RECEPTOR

to attach tothe cellular surface.

Mechanism of penetration & host tissue Mechanism of penetration & host tissue disintegrationdisintegration

Virus: Vector is the important factor for viral disease.

After attachment the virusmay enter the cell by a

process called ENDOCYTOSISand then be released into

the cytoplasm.

Mechanism of penetration & host tissue Mechanism of penetration & host tissue disintegrationdisintegration

ABNORMAL CELLSThe cells become round and enlarge

and may eventually die whenthe new viral particles are released

Mechanism of penetration & host tissue Mechanism of penetration & host tissue disintegrationdisintegration

Mechanism of penetration & host tissue Mechanism of penetration & host tissue disintegrationdisintegration

NematodesNematodes

Curr. Opin. Plant Biol. 6:327-333

•

Infective juvenile

• ••

•••

•• • •

•• •• •• •• . .

Adult Female

Egg Mass

Giant cells

Vascular cylinder

• •••••

••• •• • •• •••

•• •

•

Eggs hatch

Life cycle of root-knot nematode(~30 days)

Root tip

Mechanism of penetration & host tissue Mechanism of penetration & host tissue disintegrationdisintegration

2 hr

4 hr

6 hr

24 hr

Proliferation of destruction by Proliferation of destruction by nematodesnematodes

Mechanism of penetration & host tissue Mechanism of penetration & host tissue disintegrationdisintegration

ConclusionConclusion