2.4.5. Indole acetic acid (IAA) production
It was done as per the protocols of Patten and Glick (1996). The
actinomycetes were grown in starch casein broth supplemented
with L-tryptophan (1 mg ml1) for four days. At the end of the
incubation, the cultures were centrifuged at 10,000 g for 10 min
and the supernatants collected. One ml of this culture filtrate was
allowed to react with 2 ml of Salkowsky reagent (1 ml of 0.5MFeCl3
in 50 ml of 35% HClO4) at 28 2 C for 30 min. At the end of the
incubation, development of pink color indicated the presence of
IAA. Quantification of IAA was done by measuring the absorbance
in a spectrophotometer at 530 nm. A standard curve was plotted to
quantify the IAA (mg ml1) present in the culture filtrate.