By,

Pooja Walke

Five strains of rhizobacteria were isolated from sugarcane (Saccharum officinarum) rhizosphere of Pimpalgaon region on King’s B medium. These strains were designated as SI, SII, SIII, SIV and SV .

SI, SII and SIII strains were identified as species of Bacillus and strains SIV and SV were identified as Pseudomonas fluorescens.

These strains when used as inoculants both individually and as mixture of five strains for seed bacterization resulted in enhanced germination where compared to individual PGPR strain the germination was more in all five strains mixture.

In the experiment of plant growth promotion for wheat, subsequent increase in growth of shoot length was observed, application of mixture of strains resulted with notable increase in growth compared to the individual strain.

These strains as SI, SII, SIII, SIV and SV were capable of causing phosphate solublization. Cell wall degrading enzyme activities such as casein hydrolysis and cellulose degradation. All five strains were positive for casein hydrolysis where SII and SIV strains were positive for cellulase production.

Plant growth promoting rhizobacteria (PGPR) are a group of bacteria that actively

colonize plant roots and increase plant growth and yield . Plant growth promoting

rhizobacteria (PGPR) were first defined by Kloepper and Schroth .

The ability of a PGPR to establish in the rhizosphere is referred to as

rhizocompetence .

The rhizosphere-associated beneficial bacteria consist of the genera like

Pseudomonas , Bacillus, Azospirillum, Enterobacter, Acetobacter, and Azotobater

etc, as well as many unidentified rhizosphere isolates.

PGPR are free-living, soil-borne and belong to heterogeneous group of bacteria.

Direct mechanisms by PGPR, include nitrogen fixation, production of plant

hormones, Phosphate solubilization .

Indirect mechanisms used by PGPR include antibiotic production against

pathogenic bacteria, siderophores production synthesis of cell wall degrading

enzymes etc.

AIM

The aim of this study was to observe activity of

PGPR strains individually and in mixture.

Compared to the use of individual PGPR strains,

mixtures of several strains can result in:

1. Collection of Sample

2. Isolation of PGPR

3. Identification of PGPR

3.1 morphological characteristics 3.2 biochemical characteristics

4. Plant growth promotion experiment

5. Seed Bacterization

6. Plant growth promotion activities by PGPR:

6.1 Phosphate Solubilization

6.2 Cell Wall degrading enzyme activity

6.2.1 Cellulase production test

6.2.2 Casein hydrolysis

Isolation code Gram’s nature Morphology

S I Gram positive Rod

S II Gram positive Rod

S III Gram positive Rod

S IV Gram negative Rod

S V Gram negative Rod

Identification of PGPR

Isolate code Pigmentation Oxidase Test Endospore

staining

Starch

Hydrolysis

S I - + + +

S II - + + +

S III - + + +

S IV + + - -

S V + + - -

Isolate code Germinated seeds Ungerminated

seeds

Percentage (%) of

Germination

S I 3 1 75%

S II 2 2 50%

S III 3 1 75%

S IV - - -

S V 4 0 100%

SI + SII +SIII + SIV

+ SV

4 0 100%

CONTROL 2 2 50%

Isolatate code No. of days/ Length of shoot (cm) AVERAGE

1 2 3 4 5 6 7 8

S I - 0.9 1.9 4.3 7.3 9.7 15.6 17.1

S II - - - - - 2.3 4.9 6.7

S III - - 0.5 1.3 1.9 4.2 6.2 7

S IV - - - - 0.9 0.5 4.2 6.5

S V - - 0.3 0.2 0.7 1.2 1.7 2.2

SI + SII +SIII - 0.6 1.2 4 5.7 9.5 15.9 18.4

SII +SIII + SIV - 0.4 1.6 4.7 6 8.9 12.3 16

SIII + SIV + SV - 0.1 0.2 1.7 4.8 5 9.8 12.3

SI + SII +SIII + SIV + SV - - 0.3 1.7 4.2 10.2 17 18.6

CONTROL - 0.3 0.5 1.0 1.8 2.8 4.2 6.6

Isolatate code Phosphate

Solubilizing

Test

Cellulase

Production

Test

Casein

Hydrolysis

Test

S I + - +

S II + + +

S III + - +

S IV + - +

S V + + +

In this study, we have investigated the effectiveness of PGPR, whether they

could increase seed germination rate as well as growth of seedlings. Most of

the isolates significantly increased, growth of shoots in terms of shoot

length has been observed.

The positive effects of PGPR strains were explained by phosphate

solublizing capacity and biological control of plant pathogen and

deleterious microorganisms through production of cell wall degrading

enzymes such as cellulose and protease

Numerous studies have indicated that PGPR have great potential in

biocontrol and plant growth promotion but most of the studies focus on

plant growth promotion by using single/ individual strains.

To develop further beneficial inoculants for field study, one approach

should consider inoculation assays with a consortium containing a mixture

of soil organism instead of single organisms. Multiple organisms may

enhance the level and consistency of plant growth promotion by a more

stable rhizosphere community and effectiveness over a wide range of

environmental condition.

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