Table 1.

List of plant growth promotion rhizobacteria.

PGPR	PGPR Mechanisms	Crops	Application Mode	Observation/Findings	Ref.
Azoarcus	Nitrogen fixation	rice	Plants were grown gnotobiotically with a mutant of strain BH72 expressing the b-glucuronidase gene constitutively.	The presence of Azoarcus in the stele, especially in the stelar tissue of culms, suggests that these bacteria might spread systemically in situ, and underline their endophytic life style.	[27]
Azobacter	Cytokinin synthesis	Cucumber	-	-	[28]
Azorhizobium	Nitrogen fixation	Wheat	2 mL of rhizobial culture were added four times to each wheat plant, once during the planting of the seeds, and subsequently three times at one-week intervals.	Five weeks after inoculation with A. caulinodans IRBG314, there were approximately five times more short lateral roots, each up to 3 mm in length, present on inoculated wheat.	[29]
Azospirillum	Nitrogen fixation	sugar cane	-	-	[30,31,32,33]
Azotobacter	Nitrogen fixation	Wheat, barley, oats, rice, sunflowers, maize, line, beetroot, tobacco, tea, coffee and coconuts	-	-	[34]
Bacillus	Auxin synthesis	Potato	Seed-dipping (108 mL−1 cfu)	Both the strains enhanced the auxin content of inoculated plants up to 71.4% and 433%, respectively, as compared to non-inoculated plants.	[35]
Bacillus	Cytokinin synthesis	Cucumber	Seed-dipping 106 cells/mL (106 CFU/mL)	Cucumber seedlings subjected to bacterization had well developed lateral roots.	[36]
Bacillus	Gibberelin synthesis	Pepper	-	-	[37]
Bacillus	Potassium solubilization	pepper, cucumber	Seedling was inoculated with 1 mL of inoculum containing around 108 cells.	The results showed that there was a relatively higher availability of P and K in soils planted with pepper than with cucumber.	[38,39]
Bacillus	Induction of plant stress resistance	Peanuts Maize	Plants were inoculated with 1 mL of a 108 cfu suspension Seed-dipping for 30 min	Increasing salt concentrations, biological N fixation may be competitive, becoming a more economic and sustainable alternative to chemical fertilization. The bacterial inoculants increased the total N, P, and K contents of the shoot and root of maize in calcisol soil from 16% to 85% significantly as compared to the control counterpart.	[40,41]
Bacillus	Antibiotic production	Alfalfa	Seedling was inoculated	Filtrates of cultures suppressed alfalfa disease caused by P. medicaginis and inhibited the growth of the pathogen in an agar plate assay.	[42]
Bacillus	Siderophore production	Maize, pepper	-	-	[43]
Beijerinckia	Nitrogen fixation	Sugar cane	-	-	[30,44]
Burkholderia	Nitrogen fixation	Rice	-	-	[45,46]
Chryseobacterium	Siderophore production	Tomato	Soil drenched	Siderophore production increased as bacterial biomass increased after 16 h of culture	[47]
Frankia	Nitrogen fixation	Alnus	-	-	[48]
Gluconacetobacter	Nitrogen fixation	Sugar cane	Root-dipping of seedlings for 1 h	The endophytic establishment of G. diazotrophicus within stems of sugarcane was confirmed by the scanning electron microscopy.	[49]
Herbaspirillum	Nitrogen fixation	rice	Seed was inoculated	GFP-tagged cells of Herbaspirillum sp. strain B501gfp1 were apparently localized in intercellular spaces of shoot tissues of 7-day-old seedlings of O. officinalis W0012.	[50]
Mycobacterium	Induction of plant stress resistance	Maize	-	-	[40]
Paenibacillus	Indole acetic acid synthesis	Lodgepole pine	-	-	[51]
Paenibacillus	Potassium solubilization	Black pepper	-	-	[52]
Phyllobacterium	Phosphate solubilization	Strawberries	The strawberry seedlings were inoculated with 1 mL of 108 CFU/mL suspensions.	Strain PEPV15 was able to solubilize moderate amounts of phosphate (5mm radius around the colonies).	[53]
Phyllobacterium	Siderophore production	Strawberries	The strawberry seedlings were inoculated with 1 mL of 108 CFU/mL suspensions.	The strain grew on the CAS indicator medium where the colonies were surrounded by a yellow-orange halo (3.5 mm radius around colonies) indicative of the siderophore production.	[53]
Pseudomonas	Chitinase and β-glucanases production	Several crops	-	-	[54]
Pseudomonas	ACC deaminase synthesis	Mung beans, wheat	-	-	[55,56]
Pseudomonas	Induction of plant stress resistance	Cotton, Maize	-	-	[40,57]
Pseudomonas	Antibiotic production	Wheat	-	-	[58]
Pseudomonas	Chitinase and β-glucanases production	Pigeon pea	The method of Weller and Cook (1983) was adopted for seed bacterization	P. fluorescens LPK2 and S. fredii KCC5 showed chitinase activity on chitinase minimal medium. b-1,3-glucanase activity was more pronounced in the fluorescent pseudomonads strains.	[59]
Pseudomonas	Siderophore production	Potato, maize	-	-	[43]
Rhizobia	Nitrogen fixation	Legumes	-	-	[60]
Rhizobia	Induction of plant stress resistance	Peanuts	-	-	[41]
Rhizobia	Hydrogen Cyanide Production	Legumes	-	-	[61]
Rhizobium	Nitrogen fixation	Rice	-	-	[62]
Rhizobium	Indole acetic acid synthesis	Pepper, tomato, lettuce, carrot	Seed Inoculation Seedlings were inoculated with 250 µL plant−1 of a bacterial suspension with a turbidity of 5 in McFarland standards (1.5 × 109 CFUmL−1).	The dry weight of the inoculated seedlings (shoots and roots) was more than twice with respect to the un-inoculated seedlings. Concentrations of N, P, and Ca were significantly higher in inoculated plants, indicating that they had higher potential for nutrient uptake than control plants.	[63,64]
Rhizobium	ACC deaminase synthesis	Pepper, tomato mung beans,	-	-	[55,63]
Rhizobium	Siderophore production	Tomato, pepper, Carrot, lettuce,	Seed Inoculation Seedlings were inoculated with 250 lL plant−1 of a bacterial suspension with a turbidity of 5 in McFarland standards (1.5 × 109 CFU/mL−1).	The colonies of strain TPV08 were surrounded by a yellow-orange halo (3.5 mm radium around colonies) indicative of siderophore production.	[63,64]
Sinorhizobium	Chitinase and β-glucanases production	Pigeon pea	-	-	[59]
Sphingomonas	Gibberelin synthesis	Tomato	-	-	[65]
Streptomyces	Indole acetic acid synthesis	Indian lilac	-	-	[66]
Streptomyces	Siderophore production	Indian lilac	-	-	[66]