05/01/2023 1

WELCOME…!!

05/01/2023 2

PLANT GROWTH PROMOTING

RHIZOBACTERIA(importance &role in agriculture)

INSTRUCTOR: SPEAKER:Dr. ACHIN KUMAR PRIYANKA KUMARIASST.PROF.SSC B.Sc(Ag) 4 YEAR IAS,RGSC,BHU I.D NO. R-13031

05/01/2023 3

CONTENT:-INTRODUCTIONPGPRSROLE & IMPORTANCE OF PGPR IN AGRICULTUREMECHANISM REACTION OF PGPR DIRECT MECHANISM INDIRECT MECHANISMIMPACT OF PGPR ON RSA & ROOT STRUCTUREPGPR AS BIO-FERTILIZERBIO-CONTROL PROPERTY OF PGPRINFLUENCE OF PGPR ON NUTRIENT UPTAKEABIOTIC STRESS RESISTENCE THROUGH PGPRFUTURE RESEARCH & DEVELOPMENT STRATRGIES FOR SUSTAINABLE TECHNOLOGYCONCLUSION

05/01/2023 4

Plant growth promoting rhizobacteria are the soil bacteria that colonized plant root.

Facilitate the plant growth directly or indirectly.

Decrease the global dependence on hazardous agricultural chemicals.

Stimulate plant growth through mobilizing nutrients in soils.

INTRODUCTION

05/01/2023 5

Characteristic of PGPR : Proficient to colonize the root surface. Survive, multiply and compete with other micro biota. Promote plant growth. Classification based on their functional activities as: Biofertilizers Phytostimulators Rhizoremediators. Biopesticides.

PLANT GROWTH PROMOTING RHIZOBACTERIA

05/01/2023 6

TYPE OF PGPR :

Extracellular (ePGPR) e.g: Agrobacterium, Arthrobacter, Azotobacter, Azospirillum, Bacillus, Burkholderia, Caulobacter, Chromobacterium, Erwinia, Flavobacterium, Micrococcous, Pseudomonas and Serratia.

Intracellular(iPGPR )

e.g :Allorhizobium, Azorhizobium, Bradyrhizobium, Mesorhizobium and Rhizobium of the family Rhizobiaceae.

05/01/2023 7

Plant growth promoting rhizobacteria promote plant growth directly and indirectly.

ROLE AND IMPORTANCE OF PGPRS IN AGRICULTURE

05/01/2023 8

05/01/2023 9

DIRECT MECHANISMSIt facilitate nutrient uptake or increase nutrient availability

NITROGEN FIXATION PGPR fix atmospheric nitrogen and provide it to plants by two

mechanisms.

I. Symbiotic nitrogen fixation : Mutual relationship between microbe and the plant.

II. Non-symbiotic nitrogen fixation: Is carried out by free living diazotrophs.

Biological nitrogen fixing PGPR help in disease management ,growth promoting activity, maintain nitrogen level in agricultural soil.

05/01/2023 10

Phosphorus is the most important key element in the nutrition of plants.

PGPR convert insoluble phosphorus (P) to an accessible form

PHOSPHATE SOLUBILIZATION

• Phosphate solubilization mechanisms employed by PGPR:

(1) Release of complexing or mineral dissolving compounds.

(2)Liberation of extracellular enzymes.

(3) the release of phosphate during substrate degradation.

• PGPR act as inoculums to improve yield and growth.

05/01/2023 11

Movement of phosphorus in soil :-

05/01/2023 12

Potassium is the third major essential macronutrient.

PGPR solubilize potassium rock through production and secretion of organic acids.

Potassium solubilizing PGPR are Acidothiobacillus ferrooxidans, Bacillus edaphicus etc.

  

POTASSIUM SOLUBILIZATION

05/01/2023 13

Siderophores is a iron-chelating compound help in assimilation of iron.

Siderophores have been implicated for both direct and indirect enhancement of plant growth.

 

SIDEROPHORE PRODUCTION 

Impact of microbially secreted siderophores on plant growth

05/01/2023 14

Phytohormones such as auxins, cytokinins, gibberellins and Ethylene affect cell proliferation.

 

PHYTOHORMONE PRODUCTION

INDOLE ACETIC ACID PRODUCTION 

Produced by PGPR.

Help in plant cell division and differentiation.Stimulates seed and tuber germination.Biosynthesis of various metabolites, and resistance to stressful conditions.

Pseudomonas, Rhizobium, Bradyrhizobium, Agrobacterium, Enterobacter and Klebsiella are IAA-producing PGPR. 

05/01/2023 15

PGPR  Azotobacter sp., Rhizobium sp., Bacillus subtilis etc can produce cytokinins or gibberellins both or can produce either cytokinins or gibberellins for plant growth promotion.

It appears that PGPR produce lower cytokinin levels compared to phytopathogens.

INDIRECT MECHANISMS

CYTOKININS AND GIBBERLINS

PGPR is a promising sustainable and environmentally friendly approach to obtain sustainable fertility of the soil and plant growth indirectly. 

05/01/2023 16

Antibiotics production is biocontrol mechanisms of PGPR against phytopathogens.

Increased use antibiotic-PGPR as biocontrol agent develop resistence against antibiotic

LYTIC ENZYMES

ANTIBIOSIS

•PGPR strains produce enzymes such as chitinases, dehydrogenase, β-glucanase, lipases, etc. exhibit hyperparasitic activity.

•Protecting from biotic and abiotic stresses.

05/01/2023 17

It is a physiological state of enhanced defensive capacity elicited in response to specific environmental stimuli and consequently the plant’s innate defenses are potentiated against subsequent biotic challenges.

INDUCED AND SYSTEMIC RESISTANCE

 

05/01/2023 18

Production of exo-polysaccharides is important in biofilm formation and root colonization.

Effective colonization of plant roots by EPS-producing microbes helps to hold the free phosphorous and circulating essential nutrient to the plant.

Functions performed by EPS producing microbes constitute shielding from desiccation ,attachment to surfaces plant invasion, and plant defense response in plant–microbe interactions.

Exopolysaccharide production

05/01/2023 19

Most terrestrial plants develop their root system to explore soil and find nutrients to sustain growth.

In Fabaceae for example, the root tip help in initiating the rhizobial colonization process.

Poaceae, root hairs and lateral roots are colonized by PGPR.

RSA integrates root system topology, the spatial distribution of primary and lateral roots, and the number and length of various types of roots.

Impact of PGPR on root system architecture and root structure

05/01/2023 20

The search for PGPR and investigation of their modes of action are increasing at a rapid pace as efforts are made to exploit them commercially as biofertilizers.

PGPR help in fixing N2, increasing the availability of nutrients, positively influencing root growth and morphology, and promoting other beneficial plant–microbe symbioses.

The combination of these modes of actions in PGPR is also addressed, and widespread utilization of PGPR as biofertilizers.

PGPR as biofertilizer

05/01/2023 21

Bio control is a process through which a living organism limits the growth.

The mechanisms of bio control by rhizobia include, competition for nutrients, production of antibiotics, production of enzymes.

. Rhizobial strains compete for nutrients by displacing the

pathogens.

Rhizobia starve the pathogens of available iron by producing high affinity siderophores.

Biocontrol properties of PGPRS

05/01/2023 22

The combined application of Azospirillum, phosphobacteria and VAM with 75 % of recommended NPK recorded higher yield of potato (14.96 t/ha).

The inoculation of Rhizobium, P. striata significantly increased nitrogen and phosphorus uptake by chickpea over control.

The highest N and P uptake was recorded in Rhizobium + 20 kg N and 60 kg P per ha.

The promotion mechanism by rhizobial strains, is production of IAA ,resulted in the increase of the plant growth.

An increase in absorption of water and nutrients from soil has been observed in tomato when PGPR has been inoculated.

Influence of PGPR on nutrient uptake

05/01/2023 23

Stress tolerant crops with minimized production costs and environmental hazards can be by the use of PGP microbes as stress relievers.

Indigenous and native microbes were effective and competitive.

This includes:I. Extreme of temperatureII. SalinityIII. Soil acidityIV. Heavy metal resistence

Abiotic stress resistance through PGPRS

05/01/2023 24

The need of today’s world is high output yield and enhanced production of the crop as well as fertility of soil to get in an ecofriendly manner.

Future research in rhizosphere biology will rely on the development of molecular and biotechnological approaches to increase our knowledge of rhizosphere biology.

Fresh alternatives should be explored for the use of bioinoculants.

Future research and development strategies for sustainable technology

05/01/2023 25

The application of multi strain bacterial consortium over single inoculation could be an effective approach for reducing the harmful impact of stress on plant growth.

Research on nitrogen fixation and phosphate solubilization by PGPR is progress on but research done on potassium solubilization is little, will not only increase the field of the inoculants but also create confidence among the farmers for their use.

Higher yield and cost effective PGPR products use by agricultural farmer.

05/01/2023 26

CONCLUSIONPGPR are economically and environmentally beneficial for plant growth promotion.

PGPR may have a direct or an indirect mode of action.

PGPR may function as biofertilizer,bioinoculant, and other growth promoting activity .

New concept need to be constantly developed.

05/01/2023 27