briefs the role of microbes in agriculture

1. Chapter 5
Application of microbes in
agro-biotechnology

2. 5.1. Biofertilizers
The role of microbes in the production of
biofertilizers
 Biofertilizers are products containing active living
cells or latent cells of efficient strains of MOs which
when, applied to seed, plant surface or soil, colonize
the rhizosphere or the interior of the plant and
promote growth by converting nutritionally important
elements (nitrogen, phosphorus) from unavailable to
available form through biological process such as
nitrogen fixation and solubilization of rock
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3. Types of biofertilizers
A) Nitrogen fixers:
(i) Symbiotic nitrogen fixers
 These are organisms that fix atmospheric
nitrogen using their symbionts.
 These are used as nitrogen sources for plants
in the soil.
 Example: Rhizobium, Frankia, etc.
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4. The formation of a root nodule during the
nitrogen fixation.
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5. (ii) Asymbiotic or free living nitrogen fixers
 These are organisms that fix atmospheric
nitrogen in their own.
 Example: Azotobacter, Azospirillum,
Cyanobacteria or blue green algae, etc.
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6. B) Phosphate solubilizing microorganisms:
 Phosphorus is the most important plant growth-
limiting nutrient in soil besides nitrogen.
 Several soil bacteria and fungi, notably species
of Pseudomonas, Bacillus, Penicillium,
Aspergillus etc. secrete organic acids and lower the
pH in their vicinity to bring about dissolution of
bound phosphates in soil.
 They provide phosphorus to the plants.
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7. C) Silicate solubilizing microbes:
 During the metabolism of microbes several organic
acids are produced and these have role in silicate
weathering.
 They promote hydrolysis of organic acids like citric,
oxalic acid, keto acids and hydroxy carbolic acids
with retention in a dissolved state.
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8. D) Mycorrhizae
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9. Mycorhizal association
 Mycorrhiza is a symbiotic association b/n fungi and
plant roots.
 This symbiotic association is found in most natural
and agricultural ecosystems.
 The fungi grow as long threads (hyphae), often
group into masses called mycelia (look like roots).
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10.  The mycorrhizal fungi are beneficial to the plant in
several ways:
 Provides longevity to feeder roots.
 Improves nutrient absorption/uptake such as phosphate and
other micronutrients available in the soil.
 Enhances selective absorption of ions.
 In some cases, increases resistance to plant pathogens or
improve plant health.
 Maintenance of soil structures.
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11.  The plant provides carbon source to the
mycorrhizal fungi.
 The fungi obtain nutrients from the plant and, in
turn, provide nutrients (especially phosphorus)
and water for plant growth.
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12. Method of biofertilizer inoculation
A) Seed Inoculation
 This is the most common practice of applying
biofertilizers.
 In this method, the biofertilizers are mixed with 10 per
cent solution of jaggary.
 The slurry is then poured over the seeds spread on a
cemented floor and mixed properly in a way that a thin
layer is formed around the seeds.
 The treated seeds should be dried in the shade
overnight and then they should be used.
 Generally, 750 gram of biofertilizer is required to treat
the legume seeds for one hectare area.
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13. B) Soil Application
 This method is mostly used for fruit crops, sugarcane, and
other crops where localized application is needed.
 At the time of planting of fruit trees, 20 g of biofertilizer
mixed with compost is to be added in the ring of one sapling.
 Sometime, the biofertilizers are also broadcasted in the soil
but we may require four to ten times more bio fertilizers.
 Before broadcasting,the inoculants should be incubated with
the desired amount of well decomposed granulated FYM for
24 hours.
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14. C) Self Inoculation or Tubez Inoculation
 This method is suitable for application of
Azotobactor. In this method,50 litres of water is
taken in a drum and 4-5 kg of Azotobacter
biofertilizer is added and mixed properly.
 Planting materials required for one acre of land
are dipped in this mixture.
 Similarly, if we are treating the potato, then the
tubers are dipped in the mixture and planting is
done after drying the materials in the shade
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15. ADVANTAGES
 There are many advantages of using the biofertilizers. They
form an important association with other soil microbes and
help in nutrient supply.
 Fixes atmospheric nitrogen.
 Increase availability or uptake of nutrients through
solubilization or increased absorption.
 Stimulate plant growth through hormonal or antibiotics action
or by decomposing organic waste.
 They are cheap, hence, reduced cost of cultivation.
 Improves soil properties and sustaining soil fertilityLead to soil
enrichment.
 Are compatible with long term sustainability.
 Build up soil fertility in the long term.
 They are eco-friendly and pose no damage to the
environment
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16. Disadvantages
 As such there is no harmful impact of biofertilizers
if it is used properly some constraints:
 Specific to the plants.Rhizobiurn spp. culture
doesn't work well in high nitrate tolerant strains of
soybean.
 The acceptability of biofertilizers has been rather
low chiefly because they do not produce quick and
spectacular responses.
 Require skill in production and application.Difficult
to store.
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17. 5.2. Biopesticides
Constitute the pest control agents of biological
origin
►Microbials: bacteria, fungi, viruses, protozoa
►Pheromones/semiochemicals: message-bearing
substances produced by plants and animals
(interfere with mating or disrupt pest insect
behavior)
►Invertebrate Biological Control Agents (macro
organisms): parasitoids, predators and parasites
►Botanical pesticides: Tobacco, neem
►Transgenic crops: BT cotton

18. Agrochemicals Vs. Biologicals
Factors Agrochemicals Agri-biologicals
Cost effectiveness Cheap but increased spraying
cost
Costlier but reduced number of
applications
Persistence and residual
effect
High Low, mostly Bio-degradable
and self perpetuating
Knockdown effect Immediate Delayed
Handling and Bulkiness Easy but danger and
Hazardous
Bulky : Carrier based
Easy : Liquid formulation
Pest resurgence More Less
Resistance More prone Less prone
Effect on Beneficial flora At times destruction of friendly
pest
Less harmful on beneficial pests
Target specificity Mostly broad spectrum Mostly host specific
Waiting time Very high Almost nil
Nature of control Curative Preventive
Shelf life More Less

19. Microbial insecticides
►Consist of a microorganism as the active ingredient
(e.g., bacterium, fungus, virus or protozoan)
►About 3000 reported to cause diseases in insects
►Viruses isolated from 1000 species of insects
►More than 100 bacteria identified as pathogens
►Over 800 fungal species belonging to 100 genera
recognized
►More than 100 protozoans identified as pathogens

20. A)Virus
►Set of one or more nucleic acid template molecules,
normally encased in a protective coat or coats of
protein or lipoprotein that is able to organize its own
replication only within suitable host cells

21. Baculoviruses
► Rod-shaped, double stranded DNA genomes of 88-153 kbp
► Causes infection by mouth
► Replicate rapidly & causes extensive cell and tissue
destruction in host cell
► Mostly found in nucleus of host cells
► Virions are contained within proteinaceous particles called
occlusion bodies
► Can be mass produced by single cottage industries
► Highly host specific and have been isolated only from
invertebrates
► Primarily pathogens of insects of order Lepidoptera but can
also infect Hymenoptera, Diptera, Coleoptera and
Trichoptera

22. Baculoviruses are safe
►Only found in insects (mainly lepidopteran species)
►Narrow host range, high selectivity
►No production of metabolites or toxins
►Baculoviruses are safe and cause no hazards to human
health

23. Metarhizium anisopliae Beauveria bassiana infection of
Clover Worm
Beauveria bassiana infection of worm within woody substrate
B) Fungi

24. Crystal
Sporulated culture
Bacillus thuringiensis (Bt)
C) Bacteria

25. Insecticidal toxin of Bacillus thuringiensis
 B. thuringiensis is an aerobic spore-forming
bacterium which produces a toxin (Bt toxin or Cry)
that kills certain insects
 The Bt toxin or Cry is produced when the bacteria
sporulates and is present in the parasporal crystal
 They have no toxicity to human & there is no
withholding period on produce sprayed with Bt

26. Botanicals
Allium cepa
Chrysanthemum sp. Annona squamosa Tagetes erecta
Ricinus communis
Ipomoea fistulosa

27. 5.3. Restoration of degraded lands
 Restoration of degraded ecosystems can be slow
and unsuccessful if conditions are unfavorable for
the development of soil biota
 4 main groups of beneficial microorganisms can be
distinguished:
1. plant growth–promoting rhizobacteria (PGPR),
2. nitrogen-fixing bacteria,
3. arbuscular mycorrhizal fungi (AMF) together with
ectomycorrhizal fungi (EMF).
4. cyanobacteria in biological soil crusts (BSCs)

29. Land degradation types and examples of beneficial microorganisms acting
as remediation agents plant growth–promoting rhizobacteria (PGPR);
arbuscular mycorrhizal fungi (AMF); biological soil crusts (BSCs);
polycyclic aromatic hydrocarbons (PAHs)

30. Main types of
land degradation
and main types of
useful bacteria