Figures (3)  Tables (2)

    • Figure 1. 

      Evolution of plant-PGPR interactions under climate change.

    • Figure 2. 

      Ecological and plant benefiting services of plant growth promoting bacteria.

    • Figure 3. 

      Plant growth promoting and disease resistance mechanisms of PGPR.

    • PGPR species Host plant Environmental stress Mechanisms of action Ref.
      Pseudomonas fluorescens Rice (Oryza sativa) Drought Induced root elongation, enhanced water retention, increased ABA production [45]
      Bacillus subtilis Maize (Zea mays) Pathogen-induced stress Production of antifungal compounds, induced systemic resistance [46]
      Azospirillum brasilense Wheat (Triticum aestivum) Salinity Improved ion homeostasis, enhanced antioxidant enzyme activity [47]
      Rhizobium sp. Alfalfa (Medicago sativa) Soil degradation, nutrient deficiency Increased nitrogen fixation, enhanced rhizosphere microbial diversity [48]
      Priestia aryabhattai Alfalfa (Medicago sativa) Drought Increased rhizosphere carbon sequestration, improved soil health [48]
      Pseudomonas putida Barley (Hordeum vulgare) Drought Production of exopolysaccharides, root microbiome modulation [49]
      Bacillus amyloliquefaciens Lettuce (Lactuca sativa) Salinity Phosphate solubilization, zinc uptake enhancement [50]
      Paenibacillus polymyxa Sorghum (Sorghum bicolor) Heat stress Modulation of stress-responsive genes, phytohormone regulation [51]
      Bacillus velezensis Tomato
      (Solanum lycopersicum)      		 Heavy metal stress Bioremediation, metal ion sequestration [52]
      Serratia marcescens Barley (Hordeum vulgare) Drought ACC deaminase production, reduced ethylene stress [53]
      Acinetobacter calcoaceticus Sunflower
      (Helianthus annuus)      		 Heavy metal toxicity Cadmium and lead immobilization, production of metal-chelating siderophores [54]
      Enterobacter cloacae Tomato
      (Solanum lycopersicum)      		 Drought Synthesis of osmo-protectants (proline, trehalose), increased antioxidant activity [55]
      Klebsiella variicola Wheat and maize Salinity Regulation of Na+/K+ balance, secretion of growth hormones [56]
      Bradyrhizobium japonicum Soybean (Glycine max) Heat stress Increased nitrogen fixation, stabilization of chlorophyll pigments [57]

      Table 1. 

      PGPR-host plant-stress interactions.

    • Crop PGPR species Nutrient enhanced Mechanism of action Ref.
      Rice (Oryza sativa) Azospirillum brasilense Nitrogen (N) Biological nitrogen fixation (BNF), production of auxins stimulating root growth [98,99]
      Wheat (Triticum aestivum) Pseudomonas fluorescens Phosphorus (P) Phosphate solubilization via organic acid production [100,101]
      Maize (Zea mays) Bacillus subtilis Nitrogen (N), Iron (Fe) Siderophore production for iron chelation, ammonia production for nitrogen supply [103]
      Soybean (Glycine max) Bradyrhizobium japonicum Nitrogen (N) Symbiotic nitrogen fixation in root nodules [102]
      Tomato
      (Solanum lycopersicum)      		 Rhizobium etli Potassium (K), Phosphorus (P) Enhancement of root architecture, potassium and phosphate solubilization [115]
      Barley (Hordeum vulgare) Paenibacillus polymyxa Phosphorus (P), Zinc (Zn) Phosphate solubilization and zinc mobilization [116]
      Peanut (Arachis hypogaea) Rhizobium sp. Nitrogen (N), Phosphorus (P) Rhizosphere colonization promoting nutrient uptake [117]
      Sugarcane
      (Saccharum officinarum)      		 Gluconacetobacter diazotrophicus Nitrogen (N) Endophytic nitrogen fixation and hormone production [104]
      Potato
      (Solanum tuberosum)      		 Azotobacter chroococcum Nitrogen (N), Phosphorus (P) Nitrogen fixation and phosphatase enzyme production [118]
      Lettuce (Lactuca sativa) Bacillus amyloliquefaciens Calcium (Ca), Phosphorus (P) Solubilization of calcium and phosphorus, root growth promotion [50]
      Carrot (Daucus carota) Pseudomonas putida Phosphorus (P), Potassium (K) Mineral solubilization, root elongation stimulation [119]
      Chickpea (Cicer arietinum) Mesorhizobium ciceri Nitrogen (N) Formation of root nodules, nitrogen fixation [120]
      Cotton
      (Gossypium hirsutum)      		 Bacillus megaterium Phosphorus (P), Sulfur (S) Phosphate solubilization and sulfur oxidation improving plant growth [121]
      Sunflower
      (Helianthus annuus)      		 Azotobacter vinelandii Nitrogen (N), Phosphorus (P) Nitrogen fixation and mobilization of phosphorus in the rhizosphere [122]
      Banana (Musa spp.) Pseudomonas aeruginosa Iron (Fe), Zinc (Zn) Siderophore-mediated iron uptake, zinc solubilization [105]
      Apple (Malus domestica) Bacillus thuringiensis Phosphorus (P), Nitrogen (N) Phosphate solubilization, nitrogen fixation [123]
      Strawberry
      (Fragaria × ananassa)      		 Pseudomonas stutzeri Iron (Fe), Calcium (Ca) Iron chelation through siderophore production, calcium mobilization [124]
      Grapes (Vitis vinifera) Bacillus velezensis Magnesium (Mg), Phosphorus (P) Root enhancement, improved magnesium uptake [125]
      Pepper
      (Capsicum annuum)      		 Pseudomonas fluorescens Nitrogen (N), Sulfur (S) Sulfur oxidation, nitrogen fixation, biocontrol properties [126]

      Table 2. 

      PGPR strains, targeted nutrients, and their specific mechanisms of action.