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Researcheres:

Abolfazl Moghadam,Shirin Amirtiemoori

Instructor:

Dr.Rokhbakhsh

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Rhizosphere : the rhizospher is the volume of soil surrounding and under the influence of plant roots, and the rhizoplane is the plant root surfaces and strongly adhering soil particles ( Kennedy,2005)

Rhizobacteria : Rhizobacteria are rhizospher competent bacteria that aggressively colonize plant roots ; they are able to multiply and colonize all the ecological niches found on the root at all stages of plant growth , in the presense of a competing microflora ( Antoun and Kloepper , 2001)

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Neutral bacteria

Pathogenic bacteria

Beneficial bacteria ( PGPR )Suslow, Kloepper, Schroth, Burr, 1979.

Figure 1 Nodules of bacteria soybean root4

PGPR (Plant growth promoting rhizobacteria) A group of bacteria that can actively colonize

plant roots and improve plant grows and yield by direct and indirect mechanisms (Noel et al.,1996)

(B )Legume root with nodules induced by B.japonicum

(A )Soybean plant infected

with Bradyrhizobium japonicim left,

uninfected control plant )right(.

Figure 2 5

Effective Two strain of PGPR icluding B.subtilis GB03 , B.amyloliquefaciens IN937a & the nongrowth-promotin strain E.coli DH5α on growth of A.thaliana.

(MS medium)

DH5α

Refrence ; chhong-min Ryu,mohamed A.Farag,…,2003.,Bacteria volatiles promote growth in Arabidopsis

Figure 3 Figure 4

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These mechanisms Plays a vital role in the management of plant diseases to increase crop productivity via various mechanisms .

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cycle Figure 4 N2 Fixation

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Using growth medium with Tricalcium phosphate (NBRIP). Bacterial mechanisms: phosphatase enzymes or production of

acids

No solubilizationSolubilization of P

Figure 5 Figure 6

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Figure 7 Siderophore10

Figure 8 type of phytohormone produced by PGPR

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Antibiotic encompass a chemically heterogeneous group of organic,low-molecular weight compounds produced by microorganisms at low concentrations that are deleterious to the growth of metabolic activities of other microorganisms (Fravel,1988;Thomashow et al.,1997).

Antibiotics produced by different PGPR have a broad-spectrum activity.

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PGPRDetailes

AcinetobacterGram-negative bacilli

Agrobacterium

Gram-negative bacilli

ArthrobacterGram-positive , rods during exponential growth and cocci in their stationary phase.

AzospirillumGram-negative bacilli

BacillusGram-Positive , rod-shaped

Bradyrhizobium

Gram-negative bacilli

Frankiafilamentous bacteria Gram-Positive,

PseudomonasGram-negative bacilli

RhizobiumGram-negative bacilli

SerratiaGram-negative , rod-shaped

ThiobacillusGram-negative , rod-shaped 13

PGPRAntibioti

cstructureFungusDisease

Reference

P.fluorescens

PhenazinesGaeumannomyces

graminis var.tritici

Strains of P.fluorescens may be involved in the

suppression of G.graminis var. tritici.

Raaijmakers & Weller ,

2000

P.fluorescensPyoluteorinPythium sp.

In pythium contaminated sites, and signficant

increases were observed in plant height,number of heads and grain yield of

winter wheat.

Weller and Cook,1986

P.fluorescens

2,4-Diacetyl phloroglucin

olRhizoctonia

solani

Out of 40 strains, 18 strains showed strong

antifungal activity.

Kumar et al.,2002

Figure 9

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One of the most effective mechanisms that PGPR employ to prevent proliferation of phytopathogens is the systhesis of antibiotic.

some well know PGPR strains are pseudomonas,Bacillus, Azospirillum,Rhizobium,and serratia species.the primary mechanism of biocontrol by PGPR involves the production of antibiotics such as phenazine-1-carboxyclic acid, 2,4-diacetyl phloroglucinol, oomycin, pyoluteorin, pyrrolnitrin, kanosamine, zwittermycin-A, and pantocin.

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AntibioticsPGPRPathogenCropReference

DAPGPseudomonas sp.

Pythium ultimum

sugarShanahan et al.(1992b)

Aerugine P,fluorescens

PhytophthorC.orbiculare

PepperCucumber

Lee et al.(2003)Lee et at.(2003)

Phenazine Pseudomonas sp.

Fusarium oxysporwn

tomatoChin-A-Woeng et al.(1998)

PCAP.fluorescens

G.g.Var.tritici

WheatThomashow and

Weller(1988)

PyrrolnitrinBurkholderia cepacia

Fusarium sambucinu

m

PotatoBurkhead et al.(1994)

Viscosinam ide

P.Fluorescens

RhizoctoniaSolani

Pythium ultimum

Sugarbeet

Nielsen et al.(1998)

PyoluteorinP.fluorescens

Pythium sppPythium spp

CottonSugarbeet

Howell and Stipanovic(19

80)

Gaeumannomyces graminis Var. tritici16

Primary site of Action pyrrolnitrin is terminal electron transport system.

Refrence : R. K. TRIPATHI AND DAVID GOTTLIEB , July 1969, Mechanism of Action of the Antifungal Antibiotic Pyrrolnitrin

Figure 10 Mechanism of Antibiotic Pyrrolnitrin

Figure 11Structure of pyrrolnitrin

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Refrence: Latifi, A. M., Winson, K., Foglino, M., Bycroft, B. W., Stewart, G. S. A. B., Lazdunski, A. and Williams, P., Multiple homologues of LuxR and LuxI control expression of virulence determinants and secondary metabolites through quorum sensing in Pseudomonas aeruginosa PA01. Mol. Microbiol., 1995, 17, 333–343.

Figure 11 Mechanism of action of Antibiotic Phenazines

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Biofertilizer : living organism which increase the nutrient status of the host plant through their on-going existence in associantion with the plant.( J. Kevin Vessey, 2003)

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Puts acid in the soil Strengthens pestecides(they become stronger and more

resistant to chemicals that should keep them away) It has very little carbon which is a key element in plants Chemical fertilizer also get a lot of water out of the soil

which it contaminated and therfor pollute water It degrades ecosytems It releases a green house gas called nitrous oxide

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Increase soil fertilityProduct increased to 20-30%Stimulate plant growthStimulate soil biological activityProtection against dryness and some

pathogenic factors of soilCoping with NatureReduce costs chemical fertilizers, especially

nitrogen and phosphorus fertilizer.Improve soil structure

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Figure 12 difference effect chemical fertilizer with biofertilizer in plant growth23

Bacterial biofertilizer (Azospirillum ,

…)

Fungi biofertilizer ( Mycorhiza,…)

Algae biofertilizer ( blue-green algae,

….)

Actinomycets (frankia,…)

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Pseudomonas fluorescence bacteria effectively control wilts and root rot diseases of Groundnut, Cotton, Banana, Soybean, Tomato, Pigeon pea etc., It also controls the rice blast and sheath blight of Paddy. This bacterium enters the plant system and act as a systemic biocontrol agent against diseases.

Suitable for: It is suitable for all kinds of Crops. Mode of action: By secreting an enzyme, it has the capability to destroy the cell wall of the

fungal pathogens and annihilate them. It secrets Hydrogen cyanide and antibiotics such as Pycocyanin and

Phenazine, which inhibit the growth of disease causing pathogens. Advantage: It also produces Siderospores which chelate with iron in the soil, and make

it difficult for the pathogens to proliferate. Further, it secretes several plant growth substances, and these

gibberellins like compounds contribute to vigorous crop growth.

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Bacillus subtilis is an antagonistic bacterial Biocontrol agent, which controls many soil and air borne diseases of Paddy, Groundnut, Cotton, Vegetables, Soybean etc., Foliar application of Bacillus subtilis with Pseudomonas fluorescence control leaf diseases of many crops.

Suitable for: Paddy, Millets, Oilseeds, Fruits & Vegetables, Sugarcane, Banana, Coconut, Oil palm, Cotton, Chilly, Lime, Coffee & Tea, Areca nut & Rubber, Flower, Spices, & Contiments, Herbs, Lawns & Ornaments, trees etc.

Mode of action: The bacterium colonizes the developing leaf & root system of the plant and thus

competes with & thereby suppresses plant diseases. Advantage: The Plant Growth Promoting Rhizobacteria (PGPR) having an antagonistic

interaction with various soil borne plant pathogens. It protects plants against seed and root diseases.

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PGPR are indigenouse to soil and plant rhizosphere that improve plant growth and yeild.

one of the important applications of PGPR to use in biological combating with pathogenic agents.

Some of important PGPR Rhizobacteria is Pseudomonas , Bacillus , Rhizobium ,

Azospirilium and … Important Antibiotic produced by PGPR include Pyrrolnitrin , Phenanzine , 2,4-

Diacetyl phloroglucinol , oomycin and… That PGPR have important role in biocontrol of plant pathogens and are used in biofertilizers .

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