Table 2.

In vitro characterizations of promising PGPB.

Mechanisms		Media	Descriptions	References
Direct
Nitrogen fixation		Nitrogen-free (NF) agar	Nitrogen fixation was observed qualitatively by the blue coloration around the colonies	[80]
		Malate (NFM) semisolid medium	Acetylene production was quantified on a gas chromatograph equipped with a Porapak Q column and a H2-flame ionization detector (FID)	[81,82]
Phosphate solubilization		Pikovskaya’s agar	Phosphate solubilization was determined qualitatively by the formation of halo zones around the colonies	[83]
Siderophore production		Chrome azurol S (CAS) agar	Siderophore production was observed qualitatively by the yellow halo coloration around the colonies	[84]
Phytohormones production	IAA	Nutrient broth medium supplemented with L- tryptophan	IAA production was determined using colorimetric methods and quantified on HPLC using ethyl acetate oxidation method	[85,86,87]
	Cytokinins	Burk’s medium	Cytokinin production was determined using colorimetric methods	[88,89]
	Gibberellins	Nutrient broth medium	Gibberellin production was determined using colorimetric methods	[90]
Indirect
ACC deaminase production		Dworkin and Foster’s (DF) salts medium	Colonies growing on the DF agar were taken as ACC deaminase producers and ACC deaminase activity was determined using colorimetric method	[91,92]
HCN production		Nutrient broth supplemented with 4.4 g/L of glycine	HCN production was observed qualitatively by the changes in the filter paper color from yellow to orange-brown	[93,94]
Antibiotics production		Mueller Hinton (MH) medium	Screening of antimicrobial activity was observed using diffusion methods	[95,96]