Biotic and abiotic stress management

1. VIJAY JOSHI
Master’s Seminar
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2. GLOBAL PROBLEM
Population growth of Humans!!
CURRENT POPULATION
OF THE WORLD
7 billion
I
N
C
R
E
A
S
I
N
G
10 billion
To feed this
huge population
we need
MORE FOOD 2

3. So how do we get MORE FOOD to feed increasing population??
Increasing agricultural land
Greater use of chemicals
Safe & Efficient Pesticides
More Farm Mechanization
Greater use of Transgenic Crops
Expanded use of PGPR
Limited resource
Against Eco-Friendly Approach
Against Eco-Friendly Approach
Expensive
Restricted due to ethical
concerns
YES ! 3

4. WHAT IS
PLANT GROWTH PROMOTING RHIZOBACTERIA (PGPR) ?
ROOTS
LAND
RHIZOSPHERE
Rhizo Bacteria
Symbiotically supports
plant growth
Used to prepare
fertilizer
BIO-FERTILIZER
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5. WHY PLANT NEEDS PGPR ?
Promotes plant
growth
Decreases
inhibitory biotic
and abiotic stress
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6. HISTORY
• The term PGPR was first used by Joseph W. Kloepper in the
1978.
• Beijerinck (1988) isolated the first rhizobia from nodules
• Hellriegel and Wilfarth demonstrated the ability of bacteria,
residing in ‘swellings’ on root tissue to convert atmospheric N2
into plant useable form.
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7. Plant growth promoting rhizobacteria (PGPR) are bacteria that
colonise the plant root and act as an additional source of hormones, and
growth factors that are helpful to improve plant growth and yield”
(Kloepper and Schroth, 1978)
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What Is PGPR?

8. CHARACTERISTICS OF PGPR
Able to colonize the root
Survive and multiply in microhabitats
associated with root surface in competition with
other microbiota
Promote plant growth
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9. Enhance
Nutrient uptake
Root colonization
Affects over all plant
growth
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10. Reduces
Fertilizer requirement
Stress condition
Damage caused by
pathogens
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11. 11Goswami et al., 2016

12. ACC Deaminase- PGPR Tool
• Lowers level of stress ethylene
• Cleaves ACC to Ammonia and α- ketobutyric
acid to establish sink for ACC
(Glick et al., 1998)
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13. 13
Glick et al., 1998

14. Direct
Biological N Fixation
Phosphate Solubilization
Phytohormone Production
Siderophore production
Indirect
Siderophore Production
Defence Enzymes
Antibiotic Production
Modulation of Plant Stress
Markers
Induced Systemic Resistance
Rhizosphere Competition
PGPR Mechanics
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15. Root-legume associated symbiont (Rhizobium).
Free living N fixers (Azospirillum, Azotobacter,
Burkholderia, Herbaspirillum, Bacillus, and
Paenibacillus).
• 20 & 30 kg N per ha per year
• nif gene cluster.
BIOLOGICAL NITROGEN FIXATION
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16. • Plants are only able to absorb mono- and dibasic phosphate.
• Bacillus megaterium, B. circulans, B. coagulans, B. subtilis, P.
polymyxa, B. sircalmous, and Pseudomonas striata.
• Primary mechanism of phosphate solubilization is based on
organic acid secretion by microbes because of sugar metabolism.
• Organic acids released by the micro-organisms act as good
chelators of divalent Ca2+ cations accompanying the release of
phosphates from insoluble phosphatic compounds.
PHOSPHATE
SOLUBILIZATION ref……
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Patel et al., 2015

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18. Phytohormone Production
1) IAA Production:
• 80% of the bacterial flora in the rhizosphere
produce IAA.
• IAA released by rhizobacteria mainly affect the root
system by increasing its size & weight, branching
number & surface area in contact with soil.
• These changes lead to Increase in its ability to probe
the soil for nutrient exchange, therefore improving
plant’s nutrition pool and growth capacity
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19. • Most of the PGPRs utilize L-tryptophan which is
secreted in root exudates as a precursor for IAA
production.
• In Azospirillum brasilense, more than 90% of IAA
produced is by L-tryptophan independent
pathway.
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20. 2. Cytokinin Production:
• Pseudomonas, Azospirillum, Bacillus, Proteus,
Klebsiella, Escherichia, Pseudomonas, and
Xanthomonas.
• Most abundant cytokinins are adenine-type, where
N6 position of adenine is substituted with an
isoprenoid, such as in zeatin, or an aromatic side
chain, such as in kinetin.
• Zeatin can be synthesized in two different
pathways: the tRNA pathway and AMP pathway
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21. 3. Gibberellins Production:-
• Seed germination, stem elongation, flowering,
and fruit setting.
• Rhizobium meliloti, Azospirillum sp.,
Acetobacter diazotrophicus, Herbaspirillum
seropedicae and Bacillus sp.
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22. SIDEROPHORE PRODUCTION
• Siderophores are low-molecular weight compounds (<1
kDa) which contain functional groups capable of
binding Fe in reversible way.
• Pseudomonas fluorescens and Pseudomonas
aeruginosa release pyochelin and pyoverdine type of
siderophores.
• Improve Fe nutrition and hinder the growth of
pathogens by limiting the Fe available for the pathogen,
generally fungi, which are unable to absorb the iron–
siderophore complex. (Shen et al.,2013).
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23. DEFENCE ENZYMES
• Cell wall-degrading enzymes such as β-1,3-glucanase,
chitinase, cellulase, lipase and protease secreted by
biocontrol strains of PGPR exert direct inhibitory effect on
hyphal growth of fungal pathogens by degrading their cell
wall.
• Chitinase degrades chitin, an insoluble linear polymer of β-1,
4-N-acetyl-glucoseamine, major component of the fungal
cell wall.
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24. Cont...
• β-1,3-glucanase synthesized by strains of Paenibacillus and
Streptomyces spp. easily degrade cell walls of F. oxysporum.
• Bacillus cepacia synthesizes β-1,3-glucanase, which destroys
the cell walls of R. solani, P. ultimum, and Sclerotium rolfsii.
(Compant et al., 2005)
• The mycelia of the fungal pathogens Rhizoctonia solani and
Fusarium oxysporum co-inoculated with a potent biocontrol
strain Serratia marcescens B2 showed various abnormalities
such as partial swelling in the hyphae and at the tip, hyphal
curling, or bursting of the hyphal tip.
(Someya et al.,2000)
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25. ANTIBIOTIC PRODUCTION
• Pseudomonas fluorescens and Pseudomonas aeruginosa
produces 2,4 Diacetyl Phloroglucinol (DAPG), Phenazine-1-
carboxylic acid (PCA), Phenazine-1-carboxamide (PCN),
Pyoluteorin (Plt), Pyrrolnitrin (Prn), Kanosamine,
Zwittermycin-A, Aerugine, Rhamnolipids, Pseudomonic acid,
Azomycin, antitumor antibiotics FR901463, and Karalicin.
• These antibiotics are known to possess antiviral,
antimicrobial, insect and mammalian antifeedant,
antihelminthic, phytotoxic, antioxidant, cytotoxic, antitumor,
and PGP activities.
(Hammer et al., 1997)

26. PGPR Producing Antifungal Metabolites
• PGPR produces a wide range of low molecular weight metabolites with
antifungal activity .
• Some Pseudomonads can synthesize hydrogen cyanide to which these
pseudomonads are themselves resistant, a metabolite that has been
linked to the ability of those strains to inhibit some pathogenic fungi.
• Several different microorganisms including strains of Cladosporium
werneckii, Burkholderia cepacia and Pseudomonas solanacearum are able
to hydrolyze the compound, fusaric acid.
(Toyoda and Utsumi,1991)
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27. PGPR Exhibiting Rhizospheric
Competition
• Competition for nutrients and suitable niches on the root
surface is a somewhat overlooked mechanism by which some
PGPR may protect plants from phytopathogens.
(Kloepper et al., 1988; O’Sullivan and O’Gara, 1992)
• In one study, Stephens et al., (1993) concluded that the major
factor influencing the ability of a pseudomonad isolate to act
as a biocontrol agent against Pythium ultimum on sugar beets
in soil is their ability to metabolize the constituents of seed
exudate in order to produce compounds inhibitory to Pythium
ultimum.
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28. Induced Systemic Resistance
• Non-specific character of induced resistance constitutes an increase in the
level of basal resistance to several pathogens simultaneously, which is of
benefit under natural conditions where multiple pathogens remain
present.
(Thakker, Patel, & Dhandhukia, 2011)
• Rhizobacteria in the plant roots produce signal, which spreads systemically
within the plant and increases the defensive capacity of the distant tissues
from the subsequent infection by the pathogens.
(Thakker, Patel, & Dhandhukia, 2012)
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29. Flooding Stress
• In PGPR expression of ACC deaminase gene is increased
during anaerobic conditions.
• Seeds bacterized with organisms expressing ACC deaminase
e.g. Enterobacter cloacae UW4, E. Cloacae CAL2,
Pseudomonas putida ATCC17399/ pRKACC or P. putida
ATCC17399/ pRK415 showed a substantial tolerance to
flooding stress.
(Grichko and Glick, 2001)
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30. Drought Stress
• Exopolysaccharide which protects
microorganisms from water stress by
enhancing water retention and by regulating
the diffusion of organic carbon sources.
• Pseudomonas spp. PGPR are reported to be
effective in drought stress.
(Shaik et al., 2013)
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31. Salt Stress
• Inadequate irrigation management leads to
secondary salinization that affects 20% of irrigated
land worldwide.
• Achromobacter piechaudii ARV8 containing ACC
deaminase increases the resistance of tomato
seedlings to salt.
• The bacterium reduces the production of ethylene by
the seedlings, hence alleviating the suppression of
growth.
• The bacterium increases the water use efficiency.
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32. Heavy Metal Stress
 Damage occurs due to
• Iron deficiency
• Evolution of active oxygen species.
• Increased ethylene production inhibit root and shoot development, reduce CO2
fixation and limit sugar translocation. (Prasad and Strazalka, 2000)
• The best way to prevent plants from becoming chlorotic in high levels of heavy
metals is to provide them with an associated siderophore -producing PGPR that
could provide a sufficient amount of iron to the plant.
• ACC deaminase containing plant growth-promoting bacteria can significantly
increase the growth of plants in the presence of heavy metals including nickel, lead
and zinc by lowering the level of stress-induced ethylene.
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33. Commercial formulations of different
PGPR Strains
S.N
o.
Biocontrol agents Product Target
organism
Crop Manufacturer
1 Bacillus subtilis strain GB 34 GB 34 Rhizoctonia,
Fusarium
Soyabean Gustafon USA
2 Bacillus subtilis strain GB 03 Kodiac Rhizoctonia,
Fusarium
Wheat,
barley, peas
Growth Product, USA
3 Pseudomonas aureofaciens
strain TX-1
Bio-Jet Pytium, Rhizoctonia
solani
Vegetable
and
ornamental
Ecosoil system
4 Pseudomonas fluorescence
strain A 506
Frost-ban Erwinia amylovora Fruit Plant health
technologies
5 Streptomycin griseoviridis Mycostop Soil borne
pathogens
Ornamental Kemira Agro, Finland
6 Pseudomonas fluorescence Biomonas Erwinia amylovora Apple , Pear Bio-Tech International
Limited , New Delhi
7 Bacillus subtilis Deepa bio
plus-bacillus
Rhizoctonia and
Fusarium
Vegetable Deepa farm Inputs
Private Limited
Thiruvanthapuram ,
Kerela

34. CASE
STUDY
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37. Fig.- Amplification of ACC
deaminase (acdS) gene. (M)
DNA Ladder, (Ps4)
Pseudomonas isolate SorgP4.
Fig.- ACC deaminase activity from
Pseudomonas isolate SorgP4
under non-stress and drought
stress.
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42. FUTURE PROSPECTS
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43. CONCLUSION
CONCLUSION
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