Bio control of pathogens by Mr. Ramesh Kumar submitted under Dr. Praveen gehlot department of botany jai Narain Vyas University jodhpur.

1. Seminar topic --: biological control of pathogens
Jai Narain Vyas University jodhpur
Department of botany
SUBMITTED TO -:
DR. PRAVEEN GEHLOT
SUBMITTED BY -:
MR RAMESH KUMAR

2. Topics
1. Introduction
2. History of Biological control
3. Biological control
4. Importance of biological control
5. Mode of actions of biocontrol
6. Biocontrol application methods
7. Limitations of biological control
8. Reference
BIOLOGICAL CONTROL OF PLANT PATHOGENS

3. Introduction
A century ago Harry Scott Smith coined the term ‘biological control ’ in 1919.
Defined as “Biological control of pathogens is "the total or partial destruction of
pathogen population by other organisms", occurs routinely in nature.”.
Biological control depends on the knowledge of biological interaction at the
ecosystem, organisms, cellular, and molecular level .
It’s is more eco-friendly, cost effective, self sustaining and long lasting

4. The term biological control :- as defined by Plant Pathologist;
 the use of microbial antagonists (including bacteria or fungi) to suppress
plant disease pathogens
BIOLOGICAL CONTROL
Inhibition of test organisms by biocontrol organism Sources: google image

5.  Alternative method of disease control
 Can be used in where other methods are not applicable.
 Biocontrol agents are nontoxic to man and the environment.
 Biocontrol agents are self-sustaining-easy adaptation
 Diversify mode of actions.
 Cost effective
 Long term effects
Importance of biological control

6. Mode of actions of biocontrol
1. Direct mechanism: Direct lysis or killing of pathogen by biocontrol agent
 Antibiosis
 Parasitism
2. Indirect mechanism: Exclusion of plant pathogen as a result of the presence, activity
or products of biocontrol agent.
 Competition
 Induced systemic resistance

7. Mode of actions of biocontrol
1. Antibiotic mediated suppression
 Antibiotics are microbial toxins that can, at low concentrations, kill other
microorganisms.
Inhibition of pathogens by biocontrol bacteria.

8. Mode of actions of biocontrol
1. Antibiotic mediated suppression
 Antibiotics are microbial toxins that can, at low concentrations, poison or kill other
microorganisms.
 Volatile antibiotics
• Hydrogen cyanide,
• Aldehydes
• Alcohols
• Ketones
• Sulfides
 Nonvolatile antibiotics:
• Polyketides (diacetylphloroglucinol; DAPG and
mupirocin).
• Heterocyclic nitrogenous compounds.

9. Mode of actions of biocontrol
2. Parasitism
 Direct utilization of pathogens as source nutrients.
 Mycoparasitism refers to association in which a parasitic fungus (hyperparasite) live as a
parasite to another fungus (hypoparasiste).
 Also known as Hyperparasitism, when hyperparasites (biocontrol fungi) utilize
hypoparasites (pathogenic fungi) as source of nutrients.
 Hyperparasites produce parasitizing hyphae to acquire host nutrients.
 May also requires cell wall degrading enzymes.

10. Mode of actions of biocontrol
A B
Source: The Microbial
World.
Example of Mycoparasitism: Pythium oligandrum Vs Fusarium culmorum
A. Single hypha of Pythium
oligandrum stopped the advancement
of Fusarium culmorum hyphae across
an agar plate.
B. At higher magnification F
. culmorum
hyphae are seen disrupted - the contents
are highly vacuolated and coagulated.

11. Mode of actions of biocontrol
3. Competition
 Exclusion of pathogens by biological control
agents via competition for space or
nutrients.
 Production of substances (such as siderophore)
for nutrient (such as iron) acquisition.
 Deprive pathogens of nutrients.
 It’s an indirect mechanism Competition for space and nutrients between Pythium
irregulare pathogen (white restricted growth) and the
Epicoccum purpurascens (reddish wide growth) on
PDAmedium after

12. Mode of actions of biocontrol
4. Induced systemic resistance (ISR):
Also known as systemic acquired resistance (SAR), resistance in plants to
varieties of pathogens induced by the presence or products of biocontrol
agent.
ISR biocontrol agent may be;
 Necrogenic pathogen (applied on leaf).
 Non-pathogenic bacteria (PGPR) (applied to root or seed).
 Metabolites of pathogenic or saprophytic bacteria.

13. Mode of actions of biocontrol
Induced systemic resistance- defense responses
Physical thickening of cell walls by;
 Lignification.
 Deposition of callose.
 Accumulation of antimicrobial low-molecular-weight substances (e.g.,
phytoalexins).
 Synthesis of various proteins (e.g., chitinases, glucanases, peroxidases, and
other pathogenesis related (PR) proteins).

14. Mode of actions of biocontrol
Induced systemic resistance- defense responses
C. Induced systemic
resistance by biocontrol
agent Bacillus
amyloliquefaciens HK34
B. Plant treated with
0.1mM benzothiadiazole
(positive control)
A. Plant treated
with distill
water

15. Biocontrol application methods

16. Biocontrol application methods
1. Seed treatment
2. Dipping
3. Drench
4. Foliar prays
5. Drips
There are five application
methods

17. Biocontrol application methods
1. Seed treatment

18. Biocontrol application methods
2. Seedling dip method

19. Biocontrol application methods
3. Soil drench

20. Biocontrol application methods
4. Foliar spray

21. Biocontrol application methods
5. Irrigation drips

22. Limitations of biological control
1. Expensive/difficult to develop
2. Handling requires training
3. High Selectivity/Host Specificity
4. Variability in effectiveness
5. More susceptible to environmental conditions
6. Slow action
7. Storage Problem

24. • Junaid, J. M., Dar, N.A., Bhat, T.A., Bhat,A. H., & Bhat, M.A. (2013). Commercial biocontrol agents and their
mechanism of action in the management of plant pathogens. International Journal of Modern Plant & Animal
Sciences, 1(2), 39-57.
• Jetiyanon, K., Fowler, W. D., & Kloepper, J. W. (2003). Broad-spectrum protection against several pathogens by
PGPR mixtures under field conditions in Thailand. Plant Disease, 87(11), 1390-1394.
• Lee, B. D., Dutta, S., Ryu, H., Yoo, S. J., Suh, D. S., & Park, K. (2015). Induction of systemic resistance in Panax
ginseng against Phytophthora cactorum by native Bacillus amyloliquefaciens HK34. Journal of ginseng
research, 39(3), 213-220.
• Koutb, M., &Ali, E. H. (2010). Potential of Epicoccum purpurascens Strain 5615AUMC as a biocontrol agent of
Pythium irregulare root rot in three leguminous plants. Mycobiology, 38(4), 286-294.
• Kilic-Ekici, O., & Yuen, G. Y. (2003). Induced resistance as a mechanism of biological control by Lysobacter
enzymogenes strain C3. Phytopathology, 93(9), 1103-1110.
Sources

25. Thanks
Any question?