The ability of endophytic bacterial isolates to produce IAA
was determined qualitatively and on Yeast Extract Mannitol
broth medium (YEM) (Vincet, 1970) amended with tryptophan
(0.1 g/l). This broth medium was inoculated in triplicate
with standard inoculum 350 · 105 CFU/ml. The cultures were
incubated in dark at 30 C for 7 days, and then, the cultures
were centrifuged at 3000 rpm for 30 min. Two ml of the supernatant
was mixed with 2 drops of orthophosphoric acid, 4 ml
of Salkowski’s reagent (50 ml, 35% perchloric acid; 1 ml 0.5 M
FeCl3) was added, and the mixture was allowed to stand for
15 min as described by Gordon and Weber (1951). The intensity
of the produced rose color was measured at 530 nm using
spectrophotometer. For quantitative determination, color was
also developed in standard solution of pure indole-3-acetic
acid for drawing a standard curve (Sarwart et al., 1992).