Determination of Plant Growth-Promoting (PGP) Activities

One-day-old bacterial culture (1.1 × 10⁸CFU) was used for the detection of PGP activities. Phosphate solubilization activity was determined by the modified method of Mehta and Nautiyal (2001). Bacterial culture was grown in NBRIP-BPB medium supplemented with phenol red dye (0.001%) and incubated at 28 ± 2°C for 3–4 days. The change in medium color from red to yellow indicated Pi solubilization.

Siderophore production was estimated on chrome azurol S agar (CAS) medium. BHU-AV3 culture was inoculated on CAS agar plates and incubated at 28 ± 2°C for 72 h. After incubation, the formation of orange halos around bacterial colonies represents a positive result for siderophore production (Schwyn and Neilands, 1987).

Indole-3-acetic acid (IAA) production by BHU-AV3 bacterium was determined as per the method of Gordon and Weber (1951). One-day-old bacterial culture was inoculated in NB medium containing Tryptophan (200 μg/mL) and incubated for 72 h with shaking (120 rpm) at 28 ± 2°C. Thereafter, complete culture was centrifuged and the supernatant collected. A volume of 1 mL of supernatant was mixed with 3 mL of Salkowski’s reagent (1 mL of 0.5 M FeCl₃ in 50 mL of 35% HClO₄) and kept in the dark for 30 min. The development of a pink color represents a positive result for IAA production.