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PGPR & its importance in agriculture

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PGPR & its importance in agriculture

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PGPR & its importance in agriculture

  1. 1. 12/27/2016 1
  2. 2. RAWE (0+4) SPEAKER NEHA TANDON INSTRUCTOR MR. ACHIN KUMAR ASST. PROF SSC IAS,RGSC, BHU 12/27/2016 2
  3. 3. CONTENT 1. INTRODUCTION 2. RHIZOSPHERE AND PLANT GROWTH PROMOTING RHIZOBACTERIA 3. PGPR FORMS 4. PGPR MECHANISMS a. DIRECT b. INDIRECT 5. FUNCTIONS OF PGPR a. BIOCONTROL PROPERTIES b. BIOINOCULANT c. ABIOTIC STRESS RESISTANCE d. CO-INOCULATION 6. HARMFUL ASPECTS OF PGPR 7. FUTURE PROSPECTS 8. CONCLUSION 12/27/2016 3
  4. 4. INTRODUCTION  Indiscriminate use of chemical fertilizers adversely affects soil microorganism, fertility status of soil and environment  So, PGPRs are replacing agrochemicals for the plant growth promotion  Economically, environmentally beneficial for lower production cost and for sustainable agriculture 12/27/2016 4
  5. 5. RHIZOSPHERE AND PLANT GROWTH PROMOTING RHIZOBACTERIA  Term rhizosphere given by Hiltner (1904) and term PGPR given by Kloepper and Schroth (1981)  Rhizosphere is the narrow zone of soil specifically influenced by the root system  Populated by microorganisms and the bacteria called rhizobacteria  Three types: beneficial, deleterious & neutral groups  Beneficial free-living soil bacteria referred to as PGPR  Bacillus and Pseudomonas spp. are predominant among PGPR 12/27/2016 5
  6. 6. PLANT GROWTH PROMOTING RHIZOBACTERIAL FORMS 1. EXTRACELLULAR PGPR (ePGPR)  In rhizosphere, rhizoplane or between cells of root cortex  Includes Agrobacterium, Arthrobacter, Azotobacter, Azospirillum, Bacillus, Caulobacter, Chromobacterium, Erwinia, Flavobacterium, Micrococcous, Pseudomonas and Serratia 2. INTRACELLULAR PGPR (iPGPR)  Inside specialized nodular structures of root cells.  Includes Allorhizobium, Bradyrhizobium , Mesorhizobium and Rhizobium, endophytes and Frankia 12/27/2016 6
  7. 7. PGPR MECHANISMS 1.DIRECT MECHANISM  Providing plant with a compound synthesized by bacterium or facilitating uptake of nutrients from the environment 2. INDIRECT MECHANISM  Reducing or preventing deleterious effects of phytopathogenic organisms by producing antagonistic substances or by inducing resistance 12/27/2016 7
  8. 8. Fig : The possible mode of action used by PGPR towards growth promotion in plants. The flow and location of nitrogen fixation, phosphorus solubilization, and siderophore production are shown (Vacheron, Desbrosses, Bouffaud, Touraine.,2013) MODE OF ACTION OF PGPR 12/27/2016 8
  9. 9. DIRECT MECHANISMS  Two mechanisms:- a. SYMBIOTIC NITROGEN FIXATION  Mutualistic relationship between a microbe and the plant.  Eg. Rhizobium, Bradyrhizobium, Sinorhizobium, Mesorhizobium and Frankia b. NON-SYMBIOTIC NITROGEN FIXATION  By free living diazotrophs  Eg. Azotobacter, Acetobacter, Azospirillum,, Diazotrophicus, Enterobacter, Pseudomonas and cyanobacteria  Provides an integrated approach for disease management and maintains nitrogen level in soil. 1. NITROGEN FIXATION 12/27/2016 9
  10. 10.  The main P solubilization mechanism includes: a. Release of complex or mineral dissolving compounds b. Liberation of extracellular enzymes c. Release of P during substrate degradation  Includes genera Arthrobacter, Bacillus, Beijerinckia, Enterobacter, Erwinia, Flavobacterium, Microbacterium Pseudomonas, Rhizobium, Rhodococcus, and Serratia 2. PHOSPHATE SOLUBILIZATION 12/27/2016 10
  11. 11. MOVEMENT OF PHOSPHORUS IN SOIL Source: Insight Microbiology;volume 1;issue 3, 20112/27/2016 11
  12. 12. P SOLUBILIZATION BY P SOLUBILIZING BACTERIA Source: Insight Microbiology;volume 1;issue 3, 201112/27/2016 12
  13. 13.  K is the third major essential macronutrient  PGPR solubilize K rock through production and secretion of organic acids.  They release K in accessible form from K bearing minerals in soils  Includes genera Acidothiobacillus ferrooxidans, Bacillus edaphicus, Bacillus mucilaginosus, Burkholderia, Paenibacillus sp. and Pseudomonas 3. POTASSIUM SOLUBILIZATION 12/27/2016 13
  14. 14.  Siderophores are low molecular weight iron- chelating compounds which provide a high affinity to coordinate ferric ions.  Kloeppar et al. (1980) were the first to demonstrate the importance of siderophore.  Direct benefit: Take up the labeled iron and chelating scarcely available iron  Indirect benefit: Enhanced chlorophyll level 4. SIDEROPHORE PRODUCTION 12/27/2016 14
  15. 15. IMPACT OF MICROBIALLY SECRETED SIDEROPHORES ON PLANT GROWTH Source: Insight Microbiology;volume 1;issue 3, 2011 12/27/2016 15
  16. 16. a. Indole Acetic Acid (IAA)  Up to 80% of rhizobacteria can synthesize IAA  IAA stimulate cell proliferation, seed germination, resistance to stressful conditions and enhance uptake of minerals and nutrients  Pseudomonas, Rhizobium, Bradyrhizobium, Agrobacterium, Enterobacter and Klebsiella are IAA- producing PGPR 5. PHYTOHORMONE PRODUCTION 12/27/2016 16
  17. 17.  Includes genera Azotobacter sp., Rhizobium sp., Rhodospirillum rubrum, Pseudomonas fluorescens, Bacillus subtilis etc  Some strains of phytopathogens also synthesize cytokinins  PGPR produce lower cytokinin levels compared to phytopathogens  Thus, effect of PGPR on plant growth is stimulatory while that of pathogens is inhibitory. b. Cytokinin and Gibberellins 12/27/2016 17
  18. 18.  Lowering of ethylene production by inoculation of PGPR strains induces:- 1. Improved nodule number 2. Improved nodule dry weight 3. Higher grain yield and straw yield 4. Increased nitrogen  Includes genera: Pseudomonas sp., Achromobacter, Agrobacterium, Azospirillum, Bacillus, Burkholderia, Enterobacter, Ralstonia, Serratia and Rhizobium etc. c. Ethylene 12/27/2016 18
  19. 19. INDIRECT MECHANISMS  One of the most powerful bio control mechanisms  Antibiotics produced:-  By psuedomonads: amphisin, (DAPG), oomycin A, phenazine, tensin,, and cyclic lipopeptides  By Bacillus, Streptomyces and Stenotrophomonas sp: oligomycin A and xanthobaccin  Drawback: some phytopathogens may develop resistance to specific antibiotics due to increased use. 1. ANTIBIOTICS 12/27/2016 19
  20. 20.  PGPRs produce enzymes such as chitinases, dehydrogenase, β-glucanase, lipases, phosphatases, proteases etc. exhibiting hyperparasitic activity  Suppression of pathogenic fungi including Botrytis cinerea, Sclerotium rolfsii, Fusarium oxysporum, Phytophthora sp., Rhizoctonia solani, and Pythium ultimum 2. LYTIC ENZYMES 12/27/2016 20
  21. 21. 3. INDUCED AND SYSTEMIC RESISTANCE 12/27/2016 21
  22. 22.  Functions of EP-producing PGPR:- a. Biofilm formation and root colonization. b. Holding free phosphorous c. Circulating essential nutrient to the plant d. Protecting from foreign pathogens and stress e. Shielding from desiccation f. Plant defense response in plant–microbe interactions 4. EXO POLYSACCHARIDE PRODUCTION 12/27/2016 22
  23. 23. BIOCONTROL PROPERTIES OF PGPRS  Bio control: Process through which a living organism limits the growth or propagation of undesired organisms or pathogens  Mechanism:- a. Competition for nutrients b. Production of antibiotics c. Production of enzymes to degrade cell wall d. Production of siderophores e. Production of metabolites f. Displacing pathogens 12/27/2016 23
  24. 24. APPLICATION OF PGPR AS BIOINOCULANT  Bio-fertilizers are defined as “substances that contain living microorganisms that when applied to seed, plant surfaces, or soil, colonize the plant and promote its growth by increasing the nutrient availability”  Mechanism:- a. Increase efficiency of N-fixation b. Ability to solubilize phosphate c. Improve availability of Fe and Zn d. Alter growth of roots and shoots by phytohormones  Eg: strains of Pseudomonas putida & Pseudomonas fluorescens 12/27/2016 24
  25. 25. ABIOTIC STRESS RESISTANCE THROUGH PGPR  High temperatures lead to increased drought intensity; reduction in nodule number; infectious events; delay in nodulation  Heat-tolerant, actively nodulating and N2 fixing Rhizobium strains identified that play a key role in normal growth. 1. EXTREME TEMPERATURES 12/27/2016 25
  26. 26.  Soil acidity affects plant growth and cause crop failures  Some strains of Rhizobium, Azorhizobium and Bradyrhizobium are low pH tolerant.  Tolerance to acidity by rhizobia correlated with the production of extracellular polysaccharide 2. SOIL ACIDITY 12/27/2016 26
  27. 27.  Key pollutants to plants, ecosystem and humans.  Use of recombinant rhizobia plays a major role in phyto-remediation measures.  Microorganisms with high metal-binding capacity through metallothionins for enhancing the tolerance, sequestration of heavy metals widely exploited. 3. HEAVY METAL RESISTANCE 12/27/2016 27
  28. 28. SYNERGISTIC EFFECTS OF RHIZOBIAL CO- INOCULATION  Inconsistency of beneficial results, when single microbe used  Co-inoculation causes synergy by functioning as helper bacteria  Best combination of PGP bacteria, rhizobia and host genotype selected  Examples:- a. Azospirillum: In leguminous crops b. A. lipoferum and R. leguminosarum pv. trifolii : White clovers c. Azotobacter d. Bacillus sp. e. Psuedomonas sp. f. Enterobacter g. Serratia 12/27/2016 28
  29. 29. HARMFUL ASPECTS OF PGPR  Cyanide acts as a growth inhibitor for some plants  High levels of auxin inhibits root growth  Rhizobitoxine produced by Bradyrhizobium elkanii may have a negative effect on nodulation  Rhizobitoxine can also induce foliar chlorosis in soybeans.  A select few bacterial species may inhibit growth. 12/27/2016 29
  30. 30. 12/27/2016 30
  31. 31. FUTURE RESEARCH AND DEVELOPMENT STRATEGIES  Need of today’s world – higher yield and enhanced production in an eco-friendly manner 1. New concepts of rhizo-engineering 2. Research in rhizosphere biology (molecular & biotechnological approaches) 3. Integrated management of soil microbial populations 4. Bioinoculants for high value crops like vegetables, fruits, and flowers 5. Application of multi strain bacterial consortium over single inoculation 6. Addition of ice-nucleating plant growth promoting rhizobacteria 7. Comprehensive research on potassium solubilization 8. Biosafety data required for the registration of PGPR 9. Non-phytotoxic PGPR 10. PGPRs tolerant to adverse environmental condition 11. Cost effective PGPR products 12/27/2016 31
  32. 32. CONCLUSION  PGPRs are economically and environmentally beneficial for plant growth promotion  PGPRs may have a direct or an indirect mode of action  PGPRs may function as biofertilizer, bioinoculant, abiotic stress resistance inducers, co-inoculants and other growth promoting activities  New concepts and development strategies regarding PGPRs need to be constantly developed 12/27/2016 32
  33. 33. THANK YOU 12/27/2016 33

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