3.4. Plant growth promoting traits
All isolates, except the two Bacillus species i.e. BC1AW and
BC4SS, were able to scavenge the ferric form of iron from the ferric-
blue dye complex which was shown by a color change in the
medium from blue to orange indicating siderophore production
(Fig. 1).
Analysis of in vitro production of cyanide revealed a positive result
only for PP2SS, which produced HCN on NGA-plate medium
amended with glycine as a precursor of HCN. In the inorganic phosphate
solublization test, all isolates except Bacillus species produced
a clear zone (halo) on Sperber medium, indicating their
capability to solubilize the inorganic phosphate with the highest
solublization index of 5.12 by P. putida PP3WT (Table. 4). The pH
of nutrient broth amended with Ca3-(PO4)2 significantly dropped
to 3.5 by test isolate P. veronii (PV6BA). All isolates produced the
plant growth promoting hormone indole acetic acid however at
different levels, with P. putida PP4AM and P. putida PP1WT being
the highest and lowest producers with values of 5.6 and
2.8 lgm L1, respectively.