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. 2021 Mar 19;22(6):3154. doi: 10.3390/ijms22063154

Table 1.

Ameliorative effects of plant growth-promoting rhizobacteria (PGPR) on plant growth and physio-biochemical parameters under salinity conditions.

PGPR Treatments GP Hormones PhoPs MDA AEs NEAs Pro Ion Content Sources
B. cepacia SE4,
Promicromonospora SE188, and A. calcoaceticus SE370.
7-day-old tomato seedlings inoculated with PGPR.		 Control [43]
120 mM NaCl +
Uninoculated		 ↓ 17% SFW
↓ 25% SDW		 ↑ 255% ABA,
↑ 194% SA		 ↓ 14% Tchl N/A ↑ 86% CAT
↑ 213% POD
↑ 456% PPO		 ↑ 79% PP N/A In shoot:
↑ 740% Na+
↓ 4% K+
Na+/K+ ratio ~0.28
120 mM NaCl + SE4 ↓ 11% SFW
↓ 8% SDW		 ↑ 10% ABA
↑ 367% SA		 ↓ 0% Tchl ↑ 27% CAT
↑ 163% POD
↑ 333% PPO		 ↑ 45% PP In shoot:
↑ 297% Na+
↑ 17% K+
Na+/K+ ratio ~0.11
120 mM NaCl + SE118 ↓ 13% SFW
↓ 6% SDW		 ↑ 6% ABA
↑ 217% SA		 ↓ 0% Tchl ↑ 23% CAT
↑ 131% POD
↑ 322% PPO		 ↑ 35% PP
120 mM NaCl + SE370 ↓ 10% SFW
↓ 9% SDW		 ↑ 23% ABA,
↑ 261% SA		 ↓ 0% Tchl ↑ 46% CAT
↑ 156% POD
↑ 322% PPO		 ↑ 52% PP

P. putida H-2-3.
21-day-old soybean seedlings inoculated with P. putida. 		Control [41]
120 mM NaCl +
Uninoculated		 ↓ 18% SL
↓ 12% TPFW		 ↑ 33% ABA
↑ 114% SA
↓ 11% JA 		↓ 11% Tchl N/A ↑ 301% SOD ↓ 23%
total PP		 N/A In whole plant: ↑ 86% Na+, ↑ 55% P
0 mM NaCl + P. putida ↑ 17% SL
↑ 8% TPFW		 ↑ 18% ABA
↑ 29% SA
↓ 25% JA		 ↑ 12% Tchl ↑ 2% SOD Unchanged total PP In whole plant: ↓ 17% Na+, ↑ 22% P
120 mM NaCl + P. putida ↓ 9% SL
↓ 0% TPFW		 ↓ 6% ABA
↓ 26% SA
↑ 54% JA 		↓ 7% Tchl ↑ 4% SOD ↑ 4%
total PP		 In whole plant: ↑ 45% Na+, ↑ 30% P

B. pumilus.
14-day-old rice seedlings inoculated with B. pumilus.		 Control [40]
0 mM NaCl + B. pumilus ↑ 22% SFW N/A ↑ 46% Tchl N/A ↑ 22% SOD
↑ 20% POD
↑ 73% CAT		 N/A ↑ 7% In shoot: ↓ 54% Na+,
↑ 57% K+, ↑ 76% Mg2+,
↑ 18% Ca2+, Na+/K+ ratio ~0.27
10 ppm Boron + Uninoculated ↓ 0% SFW ↓ 18% Tchl ↑ 274% SOD
↑ 212% POD
↑ 204% CAT		 ↑ 41% In shoot: ↓ 23% Na+,
↑ 7% K+, ↑ 5% Mg2+,
↑ 0% Ca2+, Na+/K+ ratio ~0.67
10 ppm Boron + Inoculated ↑ 18% SFW ↑ 59% Tchl ↑ 400% SOD
↑ 272% POD
↑ 254% CAT		 ↑ 74% In shoot: ↓ 31% Na+, ↑ 61% K+, ↑ 67% Mg2+, ↑ 18% Ca2+, Na+/K+ ratio ~0.4
150 mM NaCl + Uninoculated ↓ 10% SFW ↓ 9% Tchl ↑ 248% SOD
↑ 168% POD
↑ 204% CAT		 ↑ 56% In shoot: ↑ 458% Na+,
↓ 50% K+, ↓ 38% Mg2+,
↓ 76% Ca2+,
Na+/K+ ratio ~10.4
150 mM NaCl + B. pumilus ↑ 11% SFW ↑ 86% Tchl ↑ 348% SOD
↑ 220% POD
↑ 273% CAT		 ↑ 83% In shoot: ↑ 185% Na+,
↑ 24% Mg2+, ↓ 7% K+,
↓ 18% Ca2+, Na+/K+ ratio ~3
10 ppm Boron + 150 mM NaCl + Uninoculated ↓ 10% SFW ↓ 23% Tchl ↑ 300% SOD
↑ 388% POD
↑ 377% CAT		 ↑ 146% In shoot: ↑ 531% Na+,
↓ 32% K+, ↓ 33% Mg2+,
↓ 27% Ca2+, Na+/K+ ratio ~8.6
10 ppm Boron + 150 mM NaCl + B. pumilus ↑ 3% SFW ↓ 5% Tchl ↑ 322% SOD
↑ 316% POD
↑ 254% CAT		 ↑ 85% In shoot: ↑ 115% Na+,
↓ 11% K+,
↓ 5% Mg2+, ↓ 4% Ca2+, Na+/K+ ratio ~2.2

C. gleum SUK.
Wheat plantlets inoculated with C. gleum. 		0 mM NaCl + Uninoculated [99]
100 mM NaCl + Uninoculated ↓ 41% SL
↓ 46% RL
↓ 16% TPFW		 N/A ↓ 36% Tchl N/A N/A ↑ 80% FLA ↑ 31% In shoot: ↑ 128% Na+,
↓ 30% K+, Na+/K+ ratio ~0.12
0 mM NaCl + SUK + FLI ↓ 13% SL
↓ 14% RL
↓ 0% TPFW		 ↑ 18% Tchl ↑ 96% FLA ↑ 48% N/A
100 mM NaCl + SUK + FLI ↓ 9% SL
↓ 9% RL
↑ 19% TPFW		 ↑ 5% Tchl ↑ 147% FLA ↑ 63% In shoot: ↑ 61% Na+,
↓ 19% K+, Na+/K+ ratio ~0.08
0 mM NaCl + SUK ↓ 16% SL
↓36% RL
↓13% TPFW		 ↓ 11% Tchl ↑ 57% FLA ↑ 25% N/A
100 mM NaCl + SUK ↓ 19% SL,
↓ 9% RL, ↓ 6% TPFW		 ↓ 23% Tchl ↑ 84% FLA ↑ 47% In shoot: ↑ 67% Na+,
↓ 19% K+, Na+/K+ ratio 0.08
B. aquimaris DY-3.
Three-day-old maize seedlings inoculated with DY-3		 Control [42]
1% (w/v) NaCl +
Uninoculated		 ↓ 34% TPDW N/A ↓ 13% Tchl ↑ 39% ↑ 21% SOD
↑ 16% POD ↑18% CAT
↑ 23% APX		 ↑ 22% PHE ↑ 36% N/A
0% NaCl +
DY-3		 ↑ 12% TPDW ↑ 5% Tchl ↓ 8% ↑ 13% SOD
↑ 9% CAT
↑ 9% APX
↓ 12% POD		 ↑ 11% PHE ↑ 24%
1% (w/v) NaCl + DY-3 ↓ 13% TPDW ↓ 9% Tchl ↑ 26% ↑ 53% SOD
↑ 42% CAT
↑ 65% APX
↓ 2% POD		 ↑ 67% PHE ↑ 77%
Klebsiella IG3.
Oat seedlings inoculated with IG3		 Control [44]
100 mM NaCl +
Uninoculated		 ↓ 22% SL
↓ 31% SFW
↓ 29% RFW
↓ 18% RL		 ↓ 6% IAA ↓ 22% Tchl In shoot:
↑ 135%
In root:
↑ 231% 		↑ 353% SOD
↑ 540% POD		 N/A ↑ 230% N/A
0 mM NaCl + IG3 ↑ 3% SL
↑ 3% SFW
↑ 1% RFW
↑ 13% RL		 ↑ 41% IAA ↑ 4% Tchl In shoot: ↑ 3%
In root: ↑ 18%		 ↑ 0% SOD
↑ 2% POD		 ↑ 42%
100 mM NaCl + IG3 ↓ 10% SL,
↓ 18% SFW
↓ 16% RFW
↓ 2% RL		 ↑ 67% IAA ↓ 13% Tchl In shoot:
↑ 27%
In root: ↑ 45% 		↑ 96% SOD
↑ 286% POD		 ↑ 155%

P. yonginensis DCY84.
Root seedlings of ginseng inoculated with P. yonginensis DCY84		 Short period of stress (3 days of 300 mM NaCl exposure) [50]
Control In shoot: Na+/K+ ratio ~13
In root: Na+/K+ ratio ~11
0 mM NaCl + DCY84 ↑ 15% SFW
↑ 5% RFW		 N/A ↑ 3% Chl a
↑ 2% Chl b
↑ 2% Car		 Unchanged ↑ 62% APX
↑ 40% POD
↑ 114% CAT		 N/A ↑ 253% In shoot: Na+/K+ ratio ~15
In root: Na+/K+ ratio ~11
300 mM NaCl + Uninoculated ↓ 13% SFW
↓ 9% RFW		 ↓ 15% Chl a
↓ 13% Chl b
↓ 16% Car		 ↑ 29% ↑ 55% POD
↑ 0% APX
↓ 14% CAT		 ↑ 20% In shoot: Na+/K+ ratio ~6.4
In root: Na+/K+ ratio ~7
300 mM NaCl + DCY84 ↑ 12% SFW
↑ 0% RFW		 ↑ 3% Chl a
↓ 2% Chl b
↓ 9% Car		 ↑ 21% ↑ 54% APX
↑ 80% POD
↑ 114% CAT		 ↑ 233% In shoot: Na+/K+ ratio ~8.2
In root: Na+/K+ ratio ~9.8
Long period of stress (12 days of 300 mM NaCl exposure)
Control In shoot: Na+/K+ ratio ~7.2; In root: Na+/K+ ratio ~9.9
0 mM NaCl + DCY84 ↑ 17% SFW
↑1% RFW		 N/A ↑ 3% Chl a
↑ 2% Chl b
↓ 2% Car		 Unchanged ↑ 45% APX
↑ 100% POD
↑ 143% CAT		 N/A ↑ 300% In shoot: Na+/K+ ratio ~7.8, In root: Na+/K+ ratio ~11
300 mM NaCl + Uninoculated ↓ 18% SFW
↓22% RFW		 ↓ 53% Chl a
↓ 66% Chl b
↓ 57% Car		 ↑ 36% ↓ 31% APX
↓ 33% POD
↓ 71% CAT		 ↑ 13% In shoot: Na+/K+ ratio ~4.4, In root: Na+/K+ ratio ~3.8
300 mM NaCl + DCY84 ↑ 12% SFW
↓ 3% RFW		 ↓ 3% Chl a
↓ 11% Chl b
↓ 7% Car		 ↑ 14% ↑ 90% APX
↑ 317% POD
↑ 343% CAT		 ↑ 287% In shoot: Na+/K+ ratio ~6.5, In root: Na+/K+ ratio ~7.7

B. megaterium A12 (BMA12).
Ten-day-old tomato seedlings inoculated with BMA12		 Control [45]
200 mM NaCl +
Uninoculated		 ↓ 37% PH
↓ 50% RL
↓ 59% TPFW
↓ 54% TPDW
↓ 35% TLA		 ↓ 32% IAA
↓ 43% GA4
↑ 100% C2H4 ↑ 82% ABA		 ↓ 32% Chl a
↓ 40% Chl b
↓ 41% TChl
↓ 49% Car		 N/A
 ↑ 24% SOD
↑ 27% CAT
↓ 24% APX
↓ 24% POD
↓ 57% PPO		 ↑ 74% GSH
↑ 228% ASC		 N/A N/A
0 mM NaCl + BMA12 ↑ 23% PH
↑ 37% RL
↑ 28% TPFW
↑ 40% TPDW
↑ 25% TLA		 ↑ 53% IAA,
↑ 170% GA4
↓ 16% C2H4
↓ 14% ABA		 ↑ 53% Chl a
↑ 14% Chl b ↑ 41% TChl
↑ 35% Car		 ↑ 86% SOD
↑ 54% CAT
↑ 34% APX
↑ 37% POD
↑ 55% PPO		 ↑ 17% GSH
↑ 5% ASC
2000 mM NaCl + BMA12 ↓ 13% PH
↓ 28% RL
↓ 33% TPFW
↓ 35% TPDW
↓ 21% TLA		 ↑ 0% IAA
↑ 11%C2H4
↑186% ABA,
↑ 86% GA4 		↑ 5% Chl a
↓ 17% Chl b ↓ 4% TChl
↓ 24% Car		 ↑ 213% SOD
↑ 91% CAT
↑ 78% APX
↑ 18% POD
↓ 10% PPO		 ↑ 250% GSH
↑ 100% ASC
Pseudomonas (wild-type UW4 and mutant strains).
Seven-day-old tomato plants inoculated with UW4.		 Control [46]
200 mM NaCl +
Uninoculated		 ↓ 56% RL
↓ 37% SL
↓ 37% TPDW		 N/A ↓ 42% Tchl N/A
200 mM NaCl + WT UW4 ↑ 16% RL
↑ 3% SL
↑ 25% TPDW		 ↑ 31% Tchl
200 mM NaCl + acdS-mutant ↓ 33% RL
↓ 9% SL
↓ 17% TPDW		 ↓ 25% Tchl
200 mM NaCl + treS- mutant ↓ 39% RL
↓ 31% SL
↓ 8% TPDW		 ↓ 13% Tchl
200 mM NaCl + acdS-/treS- double mutant ↓ 58% RL
↓ 37% SL
↓ 35% TPDW		 ↓ 56% Tchl
200 mM NaCl + OxtreS ↑ 45% RL
↑ 3% SL
↑ 54% TPDW		 ↑ 61% Tchl
S. maltophilia BJ01.
Seven-day-old peanut seedlings inoculated with BJ01		 Control [48]
0 mM NaCl +
BJ01		 ↑ 4% SL,
↑ 11% TPFW,
↓ 15% RL		 ↑ 19% Aux ↑ 11% Chla, ↑ 0% Chl b, ↑ 17% Tchl ↓ 26% N/A ↓ 32% N/A
100 mM NaCl + Uninoculated ↑ 9% RL,
↓ 45% TPFW,
↓ 39% SL		 ↑ 16% Aux ↓ 56% Chl a, ↓ 42% Chl b, ↓ 50% Tchl ↑ 47% ↑ 1355%
100 mM NaCl + BJ01 ↓ 26% SL,
↓ 3% RL,
↓ 26% TPFW		 ↑ 29% Aux ↓ 11% Chl a
↓ 34% Chl b ↓ 23% Tchl		 ↑ 16% ↑ 1173%

Note: All calculations in the Table 1 represent the comparisons between the treated plants and the control plants (non-stress conditions and un-inoculation). The up arrowhead (↑) indicates an increase in a tested parameter as compared to the control. The down arrowhead (↓) displays a reduction in a tested parameter relative to the control. Abbreviation in the Table 1: ABA, Abscisic acid; A. calcoaceticus, Acinetobacter calcoaceticus; A. aneurinilyticus, Aneurinibacillus aneurinilyticus; AEs, antioxidant enzymes; APX, Ascorbate peroxidase; ASC, Ascorbate; Aux, Auxin; B. aquimaris, Bacillus aquimaris; B. brevis, Bacillus brevis; B. cepacia, Burkholdera cepacia; B. megaterium, Bacillus megaterium; B. pumilus, Bacillus pumilus; C2H4, ethylene; Car, Carotenoids; CAT, Catalase; C. gleum, Chryseobacterium gleum; Chl, Chlorophyll; E. aerogenes, Enterobacter aerogenes; FLA, Flavonoids; FLI, Feather lysate inoculum; GA4, Gibberellins 4; GSH, Glutathione; GP, Growth parameter; IAA, Indole-3-acetic acid; JA, Jasmonates; MDA, Malondialdehyde; N/A, Not available; NEAs, Non-enzymatic antioxidants; P. fluorescence, Pseudomonas fluorescence; PH, Plant height; PHE, Phenols; PhoPs, Photosynthetic pigments; POD, Peroxidase; PPs, Polyphenols; Pro, Proline; P. putida, Pseudomonas putida; PPO, Polyphenol oxidase; Pro, Proline; P. yonginensis, Paenibacillus yonginensis; RDW, Root dry weight; RFW, Root fresh weight; RL, Root length; SA, Salicylic acid; SDW, Shoot dry weight; SFW, Shoot fresh weight; SL, Shoot length; S. maltophilia, Stenotrophomonas maltophilia; SOD, Superoxide dismutase; Tchl, Total chlorophyll; TLA, Total leaves area per plant; TPDW, Total plant dry weight; TPFW, Total plant fresh weight; TPP, Total polyphenol; X. autotrophicus, Xanthobacter autotrophicus; Y, Yield.