PGPR

1. INSTITUTE OF AGRICULTURAL SCIENCES
BANARAS HINDUUNIVERSITY
RURALAGRICULTURAL WORK
EXPERIECE PROGRAMME
B.Sc.(Ag.),Part-IVth,Semester-Ist
2016-2017

2. PGPR : IMPORTANCE AND ROLE IN
AGRICULTUREA0
COURSE CODE-
SSC-411,(0+4)
Presented by- Guided by-
Shail Kumari Achin Kumar
R-13041
Presentation
on

3. CONTENTS
1.Introduction
2.What is PGPR
3.Classification of PGPR
4.Mechanism of action of PGPR
5.Role of PGPR in agriculture
6.Importance of PGPR in agriculture
7.Commercialization of PGPR
8.Future research and development strategies
9.Conclusion

4. 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 yield and protect crop
simultaneously.
 Few organisms like Psuedomonas Putida,P. fluorescence has been widely used as
bio- control agent.

5. WHAT IS PGPR?
PGPR term was coined for the first time by Kloepper and Schroth(1981) to
describe this microbial population in the rhizosphere which is beneficial,
colonize the roots of plants and shows plant growth promotion activity.
Concept of rhizosphere was first given by Hiltner(1904) to depict the zone of
soil surrounding the roots where microbial populations are accelerated by root
activities.
Plant Growth Promoting Rhizobacteria (PGPR) are the bacteria that colonize
plant roots and promote plant growth and reduce insect or disease damage.
(Stuart Mcmillan 2007).

6. CLASSIFICATION OF PGPR
1. Extracellular plant growth promoting rhizobacteria (ePGPR)
2. Intracellular plant growth promoting rhizobacteria (iPGPR)
 The ePGPRs 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,Chromobacterium,Erwinia,
Micrococcous, etc.
 While iPGPRs 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. Source: Gupta et al. 2015

8. NITROGEN FIXATION
 The atmospheric N2 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.
NITROGEN FIXING ORGANISMS
1. Symbiotic N2 fixating bacteria -(e.g. Rhizobacteria,frankia)
2. Non-symbiotic -(free living, associative and endophytes) nitrogen fixing
forms such as - cyanobacteria ,Azotobacter etc.

9. NODULATION PROCESS
a. Rhizobial attachment with root cells.
b. Excretion of nod factors by rhizobia causes root hair curling.
c. Rhizobia penetrate root hair and form an infection thread through which
they penetrate the cortical cells and form bacteroid state and thereby
nodules are formed.
Source: sciencedirect.com

10. PHOSPHATE SOLUBILIZATION
 Plants absorb Phosphorus in only two soluble forms, the monobasic
(H2PO4
-) and the diabasic (HPO4
-).
 Phosphate-solubilizing bacteria (PSB) are considered as promising
biofertilizers since they can supply plants with P from sources otherwise
poorly available by various mechanisms .
 Bacterial genera like Azotobacter, Bacillus, Beijerinckia, Erwinia,
Pseudomonas, Rhizobium and Serratia are reported as the most significant
phosphate solubilizing bacteria.

11. Source: Khan et al.(2009)

12. POTASSIUM SOLUBILIZATION
 More than 90% of potassium in the soil exists in the form of insoluble rocks and
silicate minerals .
 Plant growth promoting rhizobacteria are able to solubilize potassium rock through
production and secretion of organic acids .
 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 .
 Thus, application of potassium solubilizing plant growth promoting rhizobacteria as
biofertilizer for agriculture improve and support ecofriendly crop production.

13. SIDEROPHORE PRODUCTION
 Siderophore is a greek word means Iron carrier.
 They are small high affinity Iron chellating compounds secreted by
bacteria and fungi.
 Kloeppar et al.(1980) were the first to demonstrate the importance of
siderophore.
 Plants are able to take up the labeled iron by a large number of plant
growth promoting rhizobacteria including Azadirachta, Azotobacter,
Bacillus, etc

14. FORMATION OF SIDEROPHORES

15. PHYTOHORMONE PRODUCTION
Plant growth promoting rhizobacteria produce phytohormones such as auxins,
cytokinins, gibberellins and Ethylene can affect cell proliferation in the root
architecture.
1. Indole acetic acid (IAA)
It is the most common natural auxin found in plants and its positive effect on
root growth. Up to 80% of rhizobacteria can synthesize indole acetic acid (IAA).
Indole acetic acid affects plant cell division, extension, and differentiation.

16. 2. Cytokinins and gibberellins
Several PGPR such as Azotobacter sp.,Rhizobium sp. Etc can producce
cytokinins and gibberellins.
3. Ethylene
The high concentration of ethylene induces defoliation and other cellular
processes that may lead to reduced crop performance .
The enzyme 1-aminocyclopropane-1 carboxylic acid (ACC) is a pre-
requisite for ethylene production, catalyzed by ACC oxidase.

17. ACC DEAMINASE ACTIVITY
Source: Kang et al.2010

18. INDIRECT MECHANISM
ANTIBIOTICS
 The production of antibiotics is considered to be one of the most powerful and
studied biocontrol mechanisms of plant growth promoting rhizobacteria against
phytopathogens.
 A variety of antibiotics have been identified, including compounds such as
phenazine, tropolone.
 Some rhizobacteria are also capable of producing volatile compound known as
hydrogen cyanide (HCN) for bio-control of black root rot of tobacco.
LYTIC ENZYMES
Plant growth promoting rhizobacterial strains can produce certain enzymes
such as chitinases, lipases, phosphatases, proteases etc. Exhibit hyperparasitic
activity, attacking pathogens by excreting cell wall hydrolases.

19. INDUCED SYSTEMIC RESISTANT (ISR)
 It 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.
 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 .
 Many individual bacterial components induce induced systemic resistance such as
lipopolysaccharides (LPS), siderophores, and volatiles compounds like, acetoin
etc.

20.  Production of exo polysaccharides is generally important in biofilm
formation.
 Effective colonization of plant roots by EPS producing microbes helps to
hold the free phosphorous from the insoluble one in soils and circulates
essential nutrient to the plant for proper growth and development and
protecting it from the attack of foreign pathogens.
 Some plant growth promoting rhizobacterial producing exo polysaccharides
can also bind cations, including Na+ suggesting a role in mitigation of
salinity stress by reducing the content of Na+ available for plant uptake
EXO POLYSACCHARIDE PRODUCTION

21. ROLE OF PGPR IN AGRICULTURE
PHYTOSTIMULATORS
They are the phytohormones which stimulate the growth of plants in absence of
pathogens. Best example is hormone auxin. Some volatile substances like Acetoin
and 2,3-butanediol are also responsible for significant improvements in plant
growth.
ABIOTIC STRESS TOLERANCE
Abiotic stresses are due to content of heavy metal in soil drought,nutrient
deficiency,salinity,drought etc.
PGPR Improves the leaf water stress of plants under salinity and drought
conditions.
Heavy metal detoxifying potential.

22. BIOFERTILIZERS
Biofertilizers are defined as preparations containing living cells or latent cells of
efficient strains of microorganisms that help uptake of nutrients by their
interactions in the rhizosphere when applied through seed or soil
Sufficient densities of PGPR in biofertilizer provide a beneficial role in creating a
proper rhizosphere for plant growth and converting nutritionally important
elements through biological process.
BIOPESTICIDE
Plant growth promoting rhizobacterial strains produces certain enzymes such as
chitinases, dehydrogenase, lipases, proteases etc. Exhibit hyperparasitic activity,
attacking pathogens by excreting cell wall hydrolases.

23. IMPORTANCE OF PGPR IN AGRICULTURE
 Increased health and productivity of different plant species by the application of
plant growth promoting rhizobacteria under both normal and stressed
conditions.
 The plant-beneficial rhizobacteria may decrease the global dependence on
hazardous agricultural chemicals which destabilize the agro-ecosystems.
 The rhizobacteria are the dominant deriving forces in recycling the soil nutrients
and consequently, they are crucial for soil fertility.
 Novel traits like heavy metal detoxifying potentials, pesticide
degradation/tolerance .
 Salinity tolerance and biological control of phytopathogens and insects.

24. COMMERCIALIZATION OF PGPR
 The success and commercialization of plant growth promoting rhizobacterial
strains depend on the linkages between the scientific organizations and
industries.
 Different stages in the process of commercialization include isolation of
antagonist strains, screening, fermentation methods, mass production,
formulation viability, toxicology, industrial linkages, quality control and field
efficacy.
 Selection of PGPB strains that function optimally under specific
environmental conditions (e.g., those that work well in warm and sandy soils
versus organisms better adapted to cool and wet environments).

25. FUTURE RESEARCH AND DEVELOPMENT
STRATEGIES
 Future research in rhizosphere biology will rely on the development of
molecular and biotechnological approaches to increase our knowledge
of rhizosphere biology and to achieve an integrated management of soil
microbial populations.
 Fresh alternatives should be explored for the use of bioinoculants for
other high value crops such as vegetables, fruits, and flowers.
 The application of multi strain bacterial consortium over single
inoculation could be an effective approach for reducing the harmful
impact of stress on plant growth.

26. CONCLUSION
1. PGPR have a multiple of activities directed towards plant growth and
controlling pollutants, and pesticides.
2. Their productive efficiency can be enhanced by improving soil
conditions.
3. In future they might replace chemical fertilizers and pesticides which
have many bad effects on agriculture.
4. we might be able to find more competent rhizobacterial strains which
may work under several conditions.