2.3.1. Colorimetric Determination of Indole-3-Acetic Acid (IAA)

Bacterial endophytes were inoculated in 20 mL of LB broth (contain g L⁻¹: tryptone, 10; yeast extract, 5; NaCl, 10; 1.0 L dis. H₂O, adjusted to pH 7) amended with 5 g L⁻¹ of L-tryptophan (chosen as the best concentration from our previous study) and incubated in orbital shaker (180 rpm) at 30 ± 2 °C for 7 days. Also, fungal discs (10 mm in diameter) covered with hyphae were cultured in 20 mL CD broth containing 5 g L⁻¹ of L-tryptophan and incubated in the same manner at 28 °C for 10 days. At the end of incubation period, five mL of each endophytic culture were collected and centrifuged at 6000 rpm at 4 °C for 30 min. Two mL of Salkowski’s reagent was added to 1.0 mL of each culture supernatant and measured at 530 nm (Jenway 6305 UV spectrophotometer). IAA was quantified with pure IAA standard [28].