Bacteriology

3. Advances of bio-control
3
Mechanism involved in
The bio-control
2
Introduction
1
Characteristics of bio-
control agents
4
Biological control of
bacterial diseases
5
Conclusion
6
Outline

4. definition
Biological control is defined as the reduction of
inoculum density or disease producing activities of
a Pathogen or Parasite in its active or dormant Stage
by one or more organisms accomplished naturally
or through manipulation of the environment, host or
by introduction of one or more antagonists.

5. Antibiosis
Antagonist may
secrete metabolites
(antibiotics)
harmful to the
pathogens
Parasitism
The biological
agent (antagonist),
may parasite the
other organism
Competition
• Antagonist
may compete
with the
pathogens for
nutrients or
space
Mechanisms involved in the bio-control
Alain 2017
Lysis
May cause death of
the parasite by
producing enzymes

6. Mechanisms involved in thebio - control
(a) Parasitism
The biocontrol agent parasitizes the
pathogen by coiling around the hyphae
(b) Lysis
the disintegration of a cell by
rupture of the cell wall or
membrane
Bacillus sp. Causes hyphal
lysis of Gaeumannomyces
graminis
(c) Antibiosis
The antibiotic compounds secreted by the bio-
control agent suppresses the growth of the
pathogen.
Eg: Phenazine-1-carboxylic acid produced by P.
fiuorescens plays an important role in suppressing
the take all disease of wheat.
(d) Competition
The bio control bacteria and fungi compete for food and essential
elements with the pathogen there by displacing and suppressing
the growth of pathogen
Fluorescent siderophores (iron chelators) such as pseudobactinis
and pyoverdins produced by P. fiuorescens chelate the iron
available in the sol, thereby depriving the pathogen of its "Fe
fequirements.

7. Advantages of Bio-control
 Biological control is less costly and cheaper than any other methods.
 Bio-control agents give protection throughout the crop period
 They are highly effective against specific plant disease.
 They do not cause toxicity to the plant
 Application of bio-control agent is safer to the environment and to the person who
applies them.
 They multiply easily in sol and leave no residual problem
 Bio-control agent also enhance the root and plant growth by why of encouraging the
beneficial soil microflora
 Agents are easy to handle and reply
 It can be combined with bio-fertilizers
 Easy to manufacture.

8. Characters of ideal bio-control agents
It should not be pathogenic to plant, human, animal and other beneficial
microorganisms.
lt should have broad spectrum of activity in controlling many types of disease and
must be genetically stable.
It should have fast growth and sporulation
It must be cultured under artificial media
The inoculum must be capable of abundant production using conventional method.
It should be amenable for inexpensive mass multiplication and economically
Viable.

9. Characters of ideal bio-control agents
It should have long shelf life
It must be efficacious under different environmental condition
It should be compatible with bio-fertilizers.
It should have least susceptibility to action by seed treating chemical
It should be easily formulated and method of application must be convenient and
compatible with common cultural practices
It should easily establish in the soil

10. BACILLUS SUBTILIS
Bacillus subtilis is a rod shaped, thermophilic gram positive, aerobic bacterium.
Rods may be formed in chains. It is 5-6 mm in length and 2-3 mm in width.
It forms endospores during adverse conditions.

11. PSEUDOMONAS FLUORESCENS
Pseudomonas fluorescens is a gram negative, Rod shaped non-spore forming
bacteria which may be mono or lopotrichous or non – motile.
 It produces greenish, fluorescent and water soluble pigment - Pyoverdin

12. BIOLOGICAL CONTROL OF BACTERIAL
DISEASES
Rice bacterial leaf blight (Xanthomonas oryzae pv. oryzae) –
Pseudomonas flourescens
Phenazine has been known for long time having suppression activity
against X. oryzae pv. oryzae
Pseudomonas fluorescens (strain 2-79) produced phenazine and has
been studied intensively for biocontrol of take-all of wheat caused by
Gaumanomyces graminis var tritici
Pseudomonas putida strain Pf-20 has been developed for
management of tobacco and tomato bacterial wilt.
Pseudomonas cepacia, Pseudomonas glumae, Bacillus sp.,
Streptomyces against – R. solanacearum

13. Bio-control product commercially available
for bacterial plant diseases
Product Produced From Against
BlightBan A506 Pseudomonas fluorescens Erwinia amylovora
Galltrol
Agrobacterium radiobacter
Strain 84
Agrobacterium tumifaciens
Nogall
Agrobacterium radibacter
K1026
Agrobacterium tumifaciens
Conguer Pseudomonas fluorescens
Pseudomonas tolassii
Norbac 84C
Agrobacterium radiobacter
strain K84
Agrobacterium tumifaciens