Plant growth promoting Rhizobacteria(PGPR)

Plant growth promoting Rhizobacteria(PGPR)

1. VIVEKANANDHAARTSANDSCIENCECOLLEGEFORWOMEN
VEERACHIPALAYAM, SANKAGIRI, SALEM, TAMILNADU
SUBJECT:SOIL AND ENVIRONMENTAL MICROBIOLOGY
TOPIC: PLANT GROWTH PROMOTING RHIZOBACTERIA
DEPARTMENT OF MICROBIOLOGY
Subject incharge : Submitted by:
Dr.R.Dineshkumar,Assistant professor , S.Kalaiselvi
Department of Microbiology Department of Microbiology
VIAAS, Sankagiri . VIAAS,Sankagiri

2. Content;
•Introduction
•Characteristics of PGPR
•Classification of PGPR
•Mechanism of PGPR,
1. Direct effect
2. Indirect effects,
•Role of PGPR,
•PGPR as biofertilizer,
•Conclusion.

3. INTRODUCTION;
•Biological control of plant pathogen has been the subject of much
research in recent years.
•It can potentially help us to reduce the use of pesticides that are
harmful to the environment.
•The use of PGPR (Plant Growth Promoting Rhizobacteria) such as
siderophore producing bacteria represents a potentially attractive
alternative disease management approach, since they have the
capacity to increase the yield and protect crop simultaneously.
•Few organisms like Pseudomonas patida, P. fluorescence has
been widely used as bio-control agent.

5. Characteristics of PGPR;
1.Able to colonize the root .
2.Survive and multiply in microhabitats associated with the root surface,
in competition with other microbiota.
3.Promote plant growth Or/and,
4.Promote plant protection activities.
CLASSIFICATION OF PGPR:
1.Extracellular plant growth promoting Rhizobacteria
2.Intracellular plant growth promoting Rhizobacteria

6. Extracellular PGPRs;
•The extracellular PGPR may exist in the rhizosphere, on the rhizoplane
or in the spaces between the cells of root cortex. The bacterial genera
such as Agrobacterium, Azotobacter, Azospirillum, Bacillus,
Caulobacter, Chromo bacterium. Erwinia. Micrococcus, etc…
Intracellular PGPRs;
•While intercellular PGPR locates generally inside the specialized
nodular structures of root cells. The iPGPR belongs to the family of
Rhizobiaceae includes Allorhizobium, Bradyrhizobium, Frankia,
Mesorhizobium etc.

7. MECHANISM OF PGPR;

8. DIRECT EFFECT;
siderophore and ammonia production:
1. Siderophore is a greek word means Iron carrier.
2. They are small high affinity Iron chellating compounds secreted by
bacteria and fungi.
3. Kloeppar et al. (1980) were the first to demonstrate the importance
of siderophore.
4. Plants are able to take up the labeled iron by a large number of
plant growth promoting Rhizobacteria including Azadirachta,
Azotobacter, Bacillus, etc…

9. Potassium solubilizing:
1.More than 90% of potassium in the soil exists in the form of
insoluble rocks and silicate minerals.
2.Plant growth promoting Rhizobacteria are able to solubilize
potassium rock through production and secretion of organic acids.
3.Potassium solubilizing plant growth promoting Rhizobacteria
such Acidothiobacillus Burkholderia, and Pseudomonas has been
reported to release potassium in accessible form from potassium
bearing minerals in soils.
4.Thus, application of potassium solubilizing plant growth
promoting Rhizobacteria as biofertilizer for agriculture improve and
support ecofriendly crop production.

10. Phosphatesolubilization
1. Phosphorus is the major essential plant nutrient.
2.Most of the soil phosphorus is in unavailable form, which is converted
to readily available form by different soil microorganisms.
3.PGPR posses the ability to solubilize the inorganic phosphate and can
mineralize organic phosphatic compounds.
4.Bacillus megaterium & Pseudomonas fluorescens are two of the PGPR
bacteria decomposing organic phosphates, increase crop yield.

12. Nitrogen fixation;
•The atmospheric N, is converted into plant-utilizable forms
by biological nitrogen fixation (BNF) which changes nitrogen
to ammonia by nitrogen fixing microorganisms using a
complex enzyme system known as nitrogenase.
•Nitrogenase complex enzyme carries nitrogen fixation which
is two-component metalloenzyme consisting of
Dinitrogenase reductase and Dinitrogenase.
NITROGENFIXINGORGANISMS
1. Symbiotic N, fixating bacteria –(e.g. Rhizobacteria, Frankia).
2. Non-symbiotic (free living, associative and endophytes)
nitrogen fixing forms such as cyanobacteria, Azotobacter etc.

13. INDIRECT EFFECT:
Lyticenzymes
Plant growth promoting rhizobacterial strains can produce certain
enzymes such as chitinases, dehydrogenase, lipases, proteases etc.
Antibiotic production:-
The production of antibiotics is considered to be one of the most
powerful and studied biocontrol mechanisms of plant growth promoting
Rhizobacteria against Phytopathogens.
Ex :Tropalone, phenazine.

14. Induced systemic resistance (ISR)
1.Induced systemic resistance involves jasmonate and ethylene
signaling within the plant and these hormones stimulate the host
plant’s defense responses against a variety of plant pathogens.
2. ISR may be defined as a physiological state of enhanced
defensive capacity elicited in response to specific environmental
stimuli and consequently the plant’s innate defenses are
potentiated against subsequent biotic challenges.

15. Exo polysaccharides production or biofilm
formation:-
•Effective colonization of plant roots by EPS-producing microbes
helps to hold the free phosphorous from the insoluble one in soils
and circulating essential nutrient to the plant for proper growth
and development and protecting it from the attack of foreign
pathogens.
•Other innumerable functions performed by EPS producing
microbes constitute shielding from desiccation, protection
against stress, attachment to surfaces plant invasion, and plant
defense response in plant-microbe interactions.

16. Role of PGPR:
1.Abiotic stress tolerance in plants;
2. The production of volatile organic compounds; The production of
protection enzyme such as chitinase, glucanase, and ACC-
deaminase for the prevention of plant diseases.
3.Nutrient availability for easy uptake by plant;
4.Plant growth regulators;

17. PGPR AS BIOFERTILIZER:
•Biofertilizer are microbial formulations
constituted of indigenous plant growth-
promoting Rhizobacteria (PGPR) that
directly or indirectly promote plant
growth through the solubilization of soil
nutrients, and the production of plant
growth-stimulating hormones and iron-
sequestering metabolites called
siderophores.

19. CONCLUSION;
1.PGPR has dual role as plant growth promotion and as bio agent.
2.They control the plant pathogen in direct as well as indirect way.
3.PGPR is available in nature but their screening is not easy.
4.It is included in IDM strategy for controlling several plant
pathogens.