HOW PATHOGENS ATTACK PLANTS

Pathogens attack plants through 4 methods : 
1. Mechanical force 
2. Chemical weapon
3. Microbial toxins
4. Growth regulators

A) Mechanical structures

2 special structures to penetrate plant surface :
i. Appressorium
ii. Haustorium

B) Chemical Weapon

5 enzymes responsible for degrading cell wall subtances :
i. Cutinase > cutin
ii. Pectinase > peptide
iii. Cellulase > cellulose
iv. Hemicellulase > hemicellulose
v. Ligninases > lignin

3 additional enzymes to degrade substances in the plant cell :
i. Proteolytic enzymes > proteins
ii. Amylases > starch
iii. Lipases, phospholipase > lipids

C) Microbial toxins

Produced by plant pathogenic microorganism :

a)   Non host specific

b)  Host specific

A)  Non host specific (wide range of host plant)

i) Tabtoxin

- bacterium Pseudomonas syringe

- cause wild fire disease of tobacco

ii) Phaleosotoxin

- bacterium Pseudomonas syringe

- halo blight of bean and other legumes

iii) Tentoxin

- fungus Alternaria alternata 

- chlorosis of plant seedlings

B) Host specific (particular host)
i) Victorin/ HV toxin
- fungus Cochliobolus victoriae
- leaf blights (oat plants)

ii) T-Toxin
- fungus Cochliobolus victoriae
- southern corn leaf blight 

iii) HC-Toxin
- Cochliobolus carbonum
- leaf spot disease

Hormonal imbalance and lead to abnormal plant growths

such as:

i. Stunting

ii. Overgrowths

iii. Excessive root branching

iv. Stem malformation

References :

http://www.davidmoore.org.uk/21st_Century_Guidebook_to_Fungi_PLATINUM/Ch14_12.htm
https://www.slideshare.net/saciidroyal/how-pathogens-attack-plants

Prepared by :
Ibni Alfirajullah Hafiz bin Ibni Alfirdaus