microbes used in agriculture

1. Abiotic stress management in
crops using microbes
N. Karthikeyan
Scientist
School of Soil Stress Management
ICAR-NIASM,
Baramati-413133

2. Scope of this presentation
The aim of this presentation is to
 Introduce the audience with beneficial microbes
used in agriculture
 Their classification
 Their usage
 About plant growth promoting rhizobacteria
 About pink pigmented facultative methylotrophs
 Mechanisms of microbes in abiotic stress
alleviation

3. BIOFERTILIZERS
 Biofertilizersaredefinedas preparationscontainingliving cells or latent cells
of efficientstrainsof microorganismsthathelp crop plants uptakeof nutrients
by their interactionsin the rhizospherewhen applied throughseed or soil.
 They acceleratecertainmicrobialprocesses in the soil which augmentthe
extent of availabilityof nutrients ina form easily assimilatedby plants.
 Use of biofertilizersisone of the importantcomponents of integratednutrient
management,asthey arecost effective andrenewable sourceof plant
nutrients to supplement the chemicalfertilizersfor sustainableagriculture.

4. Whydoweneed biofertilizers/bioinoculants?
To reduce the cost of cultivation
To increase the efficiency of nutrients in soil
To maintain/improve soil health
To reduce the release of green house gases?!!!!
To promote ecofriendly agriculture
To produce organic agriculturalproducts

5. Whataretheclassificationsofbiofertilizers?
Based on the utility
1. Nitrogen fixers ( Rhizobium, Azotobacter,
Azospirillum)
2. Phosphate solubilizers (Bacillus, Aspergillus)
3. Potassium solubilizers (Frateuria aurentia)
4. Silicate solubilzers (Bacillus muscilaginous)
5. Zinc solubilizers (Bacillus aryabhattai)

6. Based on the type of microorganisms
1. Bacterial biofertilizers (Rhizobium, Bacillus )
2. Fungal biofertilizers (Aspergillus)
3. Cyanobacterial biofertilizers (Anabaena, Nostoc)
4. Actinomycete biofertilizers (Frankia)
Whataretheclassificationsofbiofertilizers?

7. Nitrogen Fixers
Free Living
Symbiotic
Associative
symbiotic/Endophytic
Photosynthetic

8. Free Living Nitrogen Fixer
Azotobacter is a free livingN2 fixer, the cells are not prevent on the
rhizoplane, but are abundant in the rhizosphere region.
It requires more of organic matter and depend on the energy
derivedfrom the degradationof plant residues.
 Beijerinckwas the first to isolate and describe Azotobacter

9. Azotobacter
Benefits
Ability to fix atmospheric upto 20-40 kg N/ha.
Production of growth promoting substances like Indole Acetic Acid
(IAA), gibberellins,and cytokinins
Ability to produce thiamine, riboflavin, pyridoxine,cyanocobalamin,
nicotinic acid,pantothenic acid, etc
Biological control of plant diseasesby suppressing Aspergillus,
Fusarium
Can also solubilize P and K
Recommendedfor
For all non legume crops as main biofertilizer
For all legumes with Rhizobium as PGPR
Rice, wheat, millets, cereals, cotton, vegetables, sunflower, mustard and
flowers.

11. Symbiotic Nitrogen Fixers

12. Symbiotic N fixers
Azorhizobium (Sesbania
rostrata- stem nodulation)
Rhizobium
leguminosarum
Mesorhizobium Bradyrhizobium
Rhizobium sp

13. Benefits of Rhizobium inoculation
Direct contribution of N symbiotically with legumes
Residual nitrogen benefit for the succeeding crop
Yield increase is by 10-35%
Improve soil structure
Produces exopolysaccharides
Produces plant growth hormone

14. Azolla- Anabena symbiosis

15.  Azolla fern is “Live Nitrogen manufacturing
factory”
 It has Anabaena azollae as symbiont which
fixes atmospheric nitrogen
 Faster growth with doubling time of 3-5 days
depending upon the weather
 Able to fix 40-60 kg N/ha
 Dual cropping of Azolla can increase rice
yield besides reducing N requirement by
50%
 It has high protein content (upto 30%)
 Contains essential amino acids as well
as many important vitamins
 Rich in mineral content
 Can be used as feed for fish, poultry,
goats and cows.
 Helps to suppress the weeds

16. Associative symbiosis/Endophytic N Fixers

17. Azospirillum
 The first speciesdescribedbyM.W. Beijerinckas Spirillum lipoferum
in 1925
 Dr. Johanna Döbereiner reported the presenceof Azospirillum on
grain plants and coined the term ASSOCIATIVE SYMBIOSIS
 Microaerophilic organism-need very little oxygen
 An excellentnitrogen fixer for grassfamily plants
 Can help other nitrogen fixers to perform better
 Suitable for all crops both upland and low land crops
 Two speciesare used
 Azospirillumbrasilense
 Azospirillumlipoferum

18. Function of
Azospirillum on
plants

19. Co-inoculation of Bradyrhizobium and Azospirillum on soybean
in Brazil

20. Gluconacetobacter diazotrophicus
 An endophytic N2 fixer and form to occur on large numbers in roots,
stem andleaf of sugarcane andother sugar rich crops
 First isolated from sugarcane
 Cavalcanti and Dobereiner(1988)reported this new endophytic N2 fixer
and recently calledas from G. diazotrophicus.
 Can tolerate upto 30% sucrose concentration and pH upto 3.0.
 Optimumsucrose concentration is 10-15%.

21. Gluconacetobacter diazotrophicus
 An extraordinaryendophytic N2 fixing bacterium
 High amount of fixed nitrogen compared to other nitrogen fixers
 Nitrogen fixation is not inhibited by nitrates
 It has multiple growth promoting traits as well as biocontrol abilities
 It is a boon for low resource sugarcane farmers
 Can be appliedto all crops

22. Algal Biofertilizers

23. Algal Biofertilizers
Nostoc,Anabaena,
Calothrix,Tolypothrix,Plectonema,Aphanotleca,
Gleocapsa,Oscillatoria,Cylindrospermum,
Aulosiraand Scytonema

24. Phosphate solubilising Microorganisms
 Though most soils contain appreciableamounts of inorganic P, most of it
being insoluble forms, cannot be utilized by crops unless they are
solubilzied
 Soils also contain organic P that could not be utilized by plants only
when it is mineralized
 Phosphate solubilizing microorganismsnot only able to solubilize
insoluble forms of inorganic P but are also capableto mineralize
organic forms of P
 Improving the availabilityof native soil P makingtheir P availableto
plants.
Phosphate in soil is like a fixed deposit while Nitrogen is a current
account whilst potassium is like a savings account

25. Mechanism of PO4 solubilization
Different mechanismswere suggestedfor the solubilization of
inorganic phosphates
Production of organic acids
Chelating effect
Production of inorganic acids
Hydrogen sulphide production (H2S)
Effect of carbondioxide
Proton extrution
Siderophore production

26. Mechanism of PO4 solubilization

27. Phosphate solubilising Microorganisms
Bacillus (Bahubali)
Bacillus megaterium
Bacillus polymyxa
Bacillus subtilis
Pseudomonas sp
Aspergillus awamori
Aspergillus niger
Penicillium striata

28. Mycorrhiza
A mycorrhiza is a symbiotic association between a green plant and a
fungus. The plant makes organic molecules such as sugars by
photosynthesis and supplies them to the fungus, and the fungus
supplies to the plant water and mineral nutrients, such as phosphorus,
taken from the soil.
Mycorrhizas are commonly divided into
Ectomycorrhizas (Laccarialaccata,Suillus,Rhizopogan, Amanita)
-10% of plant families, mostly woody plants
Endomycorrhizas (Glomus, Rhizophagus,Sclerocystis,Septoglomus)
-Arbuscular mycorrhizas are found in 85% of all plant families, and occur in
many crop species. (Agriculturally most beneficial)

30. Mechanism of action of Arbuscular Mycorrhiza
Thebeneficialeffect on plant growthandyieldsfollowing inoculation withVAMis
attributedto
 Improved mineral nutrition, especiallyP (P, Zn, Cu, K, S, NH4)
 Mobilizationof nutrients through greater soil exploration.
 Protection of host roots againstpathogen infection.
 Improved water relation
 Better tolerance to stress likesalinity,heavy metal pollution
 Protection againsttransplantationshock.

31. Reasons for Enhanced P uptake by AM Fungi
 Physical exploration of soil.
 Higheraffinitytowards P
 Lower threshold concentration
 Rhizospheremodification
 Differencesin anion and cation absorption due to exudation pattern.
 Siderophore production.
 Selectivestimulation of microorganisms in the rhizosphere.
 Increasedhyphal area for absorption (EMH).
 Absorb and transport P beyond the depletion zone around the root.
 P absorption by AM is 1000 times faster than normal hyphae and 3-4 times greater.
Disease resistance
 Resistthe parasiticinvasion andminimisesthe loss.
 Mycorrhizal roots harbour more actinomycetes.
 Mycorrhizal roots have elevatedlevelsof phenols, while offers resistanceto fungal
 hydrolytic enzymes.
 Mycorrhizal infectionstimulatesbiosynthesisofphytoalexins.
Mycorrhiza

32. Potassium solubilizing Microorganisms
 Potassiumsolubilizing bacteria(KSB) cansolubilize K-bearingmineralsand
convert the insoluble Kto soluble formsof K availableto plant uptake
 Many bacteriasuch as Acidothiobacillusferrooxidans,Paenibacillusspp.,
Bacillusmucilaginosus,B.edaphicus,andB.circulanshavecapacityto
solubilize Kminerals (e.g., biotite,feldspar,illite, muscovite, orthoclase, and
mica)
Comparison of K solubilization on the Aleksandrov agarplate (a) andmodified agarmedium plate (b)
after 72 hof incubation (Rajawat et al., 2016)

33. Potassium solubilizing Microorganisms
Mechanisms
 By loweringthe pH;
 Byenhancing chelation of the cationsbound to K;
 Acidolysisof the surroundingareaof microorganism
Commercially
Frateuriaaurentia
is being used as KSB
by many companies.

34. Plant growth Promoting Rhizobacteria(PGPR)

35. How to apply biofertilizers?
Seed treatment:
200 g each of nitrogenous biofertilizerand Phosphotika are suspended
in 300-400 ml of water andmixedthoroughly. Ten kg seedsare treated
with this paste and driedin shade.The treated seedshave to be sown as
soon as possible.
Seedling root dip:
Recommended biofertilizers are mixed10 litres of water in a container
and the roots of seedlingsare dippedfor 20 minutes to 1 hr.
Soil treatment:
4 kg each of the recommended biofertilizers are mixedin 200 kg of
compost andkept overnight. Thismixture is incorporated in the soil at
the time of sowing or planting.

36. Mechanisms of abiotic stress alleviation by
microbes
Phytohormone production
Exopolysaccharides production
Production of ACC deaminase
Production of antioxidants
Improvement in nutrient absorption

37. Phytohormone production

38. Exopolysaccharides(EPS)Production

39. Production of ACC deaminase

40. Overview of abiotic stress management by
microbes

41. Pink Pigmented Facultative Methylotrophs (ppfm)
for abiotic stress management

43. How PPFM alleviate abiotic stress of plants?
 By the productionof
 Auxins
 Cytokinins
 VitaminB12
 Exopolysaccharides
 Osmoprotectants
 Phosphate solubilisation
 Siderophoreproduction
 Nitrogenfixation
 ACC deaminaseactivity
 Inhibitionof plant pathogens

44. 2013

45. Success story using PPFM

47. Conclusions
Microbes provide numerous benefits directly
or indirectly to plants
They help plants in nutrient utilization
They help in protecting plants from both biotic
and abiotic stressess
Microbes help us to maintain the soil health
It is indispensible to use them in organic
agriculture

48. Thank You