virulence factor

1. GURU NANAK INSTITUTE OF PHARMACEUTICAL SCIENCE AND
TECHNOLOGY
TOPIC : Virulence factors during plant disease development
NAME OF THE STUDENT : ANKIT GHOSH
UNIVERSITY ROLL NUMBER : 31308421036
ACADEMIC SESSION : 2023-24
PAPER NAME : PLANT PATHOLOGY
PAPER CODE : DSEMc 502B
Maulana Abul Kalam Azad University of Technology

2. B. Sc./ SEM 4/2023-24/ / PLANT PATHOLOGY / DSEMc 502B/Presentation_1
Virulence is the ability of a microorganism to invade and cause
injury to the host.
It is the relative capacity of a microorganism to overcome the host
defense mechanism
Virulence is the measurement of the ability to cause a disease in host
It describes the quantitative negative effect on host.
Virulence factors include:
• Poly saccharides
• Type three secretion system.
• enzymes.
• Growth regulators.
• Toxins

3. B. Sc./ SEM 4/2023-24/ / PLANT PATHOLOGY / DSEMc 502B/Presentation_1
Polysaccharides
Many plant pathogens produce large amount of
exopolysaccharides(EPS).
EPS’s are carbohydrate polymers that are secreted by
bacteria and form either a closely attached capsule layer
surrounding the bacterial cell.
The role of the slimy polysaccharides in plant disease
appears to be particularly important in wilt diseases caused
by pathogens that invade the vascular system of the plant.
• Facilitate absorption of water, minerals and nutrients.
• Providing protection against abiotic stresses
• Promoting colonization
• Contributing to the production of disease.
Type III secretion system (T3SS)
T3SS are complex bacterial structures.
Found in Gram negative bacteria.
Pilus like structure called Hrp pili.

4. B. Sc./ SEM 4/2022-23/ / PLANT PATHOLOGY / DSEMc 502B/Presentation_1
Enzymes
Cutinases, cellulases, pectinases and lignases are often
secreted by the pathogenic organism.
Fungi, nematodes and bacteria are all known to produce one
or more of the above enzymes in specific pathogen-host
combinations.
Pathogenic organisms either continually secrete enzymes or
upon contact with the host plant.
• Cutinases degrade the cutin on the cuticle layer presoftening the
tissue for mechanical penetration or as a first step in tissue
degradation.
• Cellulases have been shown to be produced by many pathogenic
fungi, bacteria and nematodes. Cellulolytic enzymes play a role in
softening and disintegration of cell walls.
• Pectin substances constitute the main components of the middle
lamella. Several enzymes degrade pectic substances and are
known as pectinases or pectolytic enzymes.
Microbial toxins
Toxins are metabolites that are produced by invading
microorganisms and act directly on living host protoplast,
seriously damaging or killing the cells of the plant.
Types:
Non-host specific toxin-
• Tabtoxin- is produced by the bacterium Pseudomonas
syringae which causes the wildfire disease of tobacco
• Tentoxin- is produced by the fungus Alternaria alternata
which causes spots and chlorosis in plants by many species.
Host specific toxins-
• Victorin or HV toxin – is produced by the fungus
Cochliobolus Victoriae. This fungus infects the basal portions
of susceptible oat plants and produces a toxin that is carried to
the leaves, causes a leaf blight and destroys the entire plant.
• T-toxin- is produced by race T of Cochliobolus
heterostrophus, the cause of southern corn leaf blight.

5. B. Sc./ SEM 4/2022-23/ / PLANT PATHOLOGY / DSEMc 502B/Presentation_1
Growth regulators
Plant hormones, which are also often referred to as ‘‘plant
growth regulators,’’ are endogenous signaling molecules
important for many aspects of plant growth and development.
Plant pathogens may produce more of the same growth
regulators as those produced by the plant often causing an
imbalance in the hormonal system of the plant and bring about
growth responses incompatible with the healthy development of
the plant.
• Auxins- occurs naturally in plants as indole-3-acetic acid (IAA).
Increased IAA levels occur in many plants infected by fungi,
bacteria, viruses, nematodes and mollicutes, although some
pathogens seem to lower the auxin level of the host e.g. Exobasidium
azalea causing azalea and flower gall.
• Gibberellins- are normal constituents of green plants with a striking
growth promoting effects. The foolish seedling diseases of rice, in
which rice seedlings infected with the fungus Gibberella fujikuroi
grow rapidly and become much taller than healthy plants
CONCLUSION
A plant disease is any physiological or structural
abnormality that is caused by a living organism.
It is a physiological process that affects some or all
plant functions.
Disease is a process or a change that occurs over time.
It does not occur instantly like injury

6. B. Sc./ SEM 4/2022-23/ / PLANT PATHOLOGY / DSEMc 502B/Presentation_1
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1): S2–S18.
• Nazarov PA, Baleev DN, Ivanova MI, Sokolova LM, Karakozova MV (2020-10-
27). "Infectious Plant Diseases: Etiology, Current Status, Problems and Prospects in Plant
Protection". Acta Naturae. 12 (3): 46–
59. doi:10.32607/actanaturae.11026. PMC 7604890. PMID 33173596.
• Martinelli F, Scalenghe R, Davino S, Panno S, Scuderi G, Ruisi P, Villa P, Stroppiana D,
Boschetti M, Goulart LR, Davis CE (January 2015). "Advanced methods of plant disease
detection. A review" (PDF). Agronomy for Sustainable Development. 35 (1): 1–
25. doi:10.1007/s13593-014-0246-1
References