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Table 2 Growth-promoting traits of the selected bacterial isolates (NT15, NT19, NT20, and NT 27) in the presence of Cr (VI) at 100, 150, and 200 mg/L. Data are the mean of replicates with SE±. Values with different letters are significantly different (p < 0.05)

From: Improved chromium tolerance of Medicago sativa by plant growth-promoting rhizobacteria (PGPR)

Isolate

[Cr (VI)] (mg/L)

PGP traits

PSI

N2

[IAA] (mg/L)

NH3

HCN

Case

Chase

Pecase

NT15

Control

3.55 ± 0.5a

+

197.63 ± 2.43a

+

+

–

+

–

100

3.04 ± 0.3a

+

164.74 ± 1.44b

+

–

–

–

–

150

2.90 ± 0.3a

+

142.63 ± 1.42c

+

–

–

–

–

200

–

–

47.11 ± 0.17d

+

–

–

–

–

NT19

Control

2.50 ± 0.2a

+

89.21 ± 1.16a

+

–

+

+

+

100

2.00 ± 0.1a

–

71.58 ± 1.17b

+

–

+

–

–

150

1.78 ± 0.0a

–

63.29 ± 0.41c

+

–

+

–

–

200

–

–

31.71 ± 0.11d

+

–

+

–

–

NT20

Control

2.05 ± 0.4a

+

560 ± 5.65a

+

+

+

+

+

100

1.58 ± 0.2a

+

353.50 ± 4.55b

+

–

+

–

+

150

0.71 ± 0.1a

+

247.36 ± 2.51c

+

–

+

–

+

200

–

+

115.44 ± 1.22d

+

–

+

–

–

NT27

Control

2.55 ± 0.3a

+

66.14 ± 1.17a

+

+

+

+

+

100

1.44 ± 0.3ab

+

49.11 ± 1.12b

+

+

+

–

+

150

1.12 ± 0.2b

+

35.26 ± 0.43c

+

–

+

–

+

200

0.95 ± 0.1b

+

19.40 ± 0.03d

+

–

+

–

–

  1. + positive test, – negative test, Chase chitinase, Case: cellulase, Pecase pectinase, PSI phosphate solubilization index