Table 2. Effect of PGPB on plants under Ni stress.

Plant species	Bacteria	Effect	References
Brassica campestris L.	Kluyvera ascorbata SUD165	Bacterium displayed ACC deaminase activity, and produced siderophores, and decreased the level of stress ethylene induced by the Ni	Burd, Dixon & Glick (1998)
Brassica juncea L.	Bacillus subtilis SJ-101	Bacterium produced IAA and stimulated of Ni-phytoextraction	Zaidi et al. (2006)
Brassica juncea L.	Psychrobacter sp. SRA1, Bacillus cereus SRA10	Bacteria displayed ACC deaminase activity, produced a siderophores and IAA, increased the accumulation of Ni in the root and shoot tissues	Ma, Rajkumar & Freitas (2009)
Brassica juncea L.; Brassica oxyrrhina Coss	Psychrobacter sp. SRA2	Bacterium displayed ACC deaminase activity, produced a siderophores and IAA, increased the fresh and dry biomass of the plants
Brassica juncea L.; Ricinus communis L.	Pseudomonas sp. A3R3, Psychrobacter sp. SRS8	Bacteria improved plant biomass production and decreased heavy metal accumulation	Ma et al. (2015)
Brassica juncea L.; Luffa cylindrical L.; Sorghum halepense L.	Bacillus megaterium SR28C	Bacterium alleviated the detrimental effects of Ni by reducing its uptake and translocation to the plants	Rajkumar, Ma & Freitas (2013)
Vigna unguiculata L.	Streptomyces acidiscabies E13	Bacterium produced hydroxamate siderophores and promoted plant growth under Fe- and Ni- stress	Dimkpa et al. (2008)
Vinca rosea L.	Bacillus megaterium MCR-8	Bacterium alleviated Ni stress, increased the accumulation of total phenols, flavonoids and enzymes SOD, CAT, POD, APX, improved phytoextraction	Khan et al. (2017)
Oryza sativa L.	Enterobacter ludwigii SAK5, Exiguobacterium indicum SA22	Bacteria increased plant growth parameters under Cd and Ni stress, also enhance glutathione, proline, and sugar content	Jan et al. (2019)
Cicer arietinum L.	Pseudomonas aeruginosa SFP1	Bacterium declined the level of stress markers (proline and APX, SOD, CAT, and GR), as well as with Cr (VI) and Ni uptake by plants	Saif & Khan (2018)
Rafanus sativus L.	Bacillus sp. CIK-516	Bacterium produced IAA, and displayed ACC deaminase activity, and increased Ni uptake by radish	Akhtar et al. (2018)
Triticum aestivum	Bacillus subtilis BM2	Bacterium displayed ACC deaminase activity, produced IAA, siderophores, ammonia. Bacterium increased plant growth parameters under Ni stress, decreased Ni content in plants and decrease SOD, GR and CAT activity	Rizvi et al. (2019)

Notes.

ACC deaminase

1-aminocyclopropane-1-carboxylic acid deaminase

IAA

indole-3-acetic acid

SOD

superoxide dismutase

CAT

catalase

POD

peroxidase activity

APX

ascorbate peroxidase

GR

glutathione reductase