Determination of fungal IAA production
M. cinnamomi was grown in 25 mL of potato dextrose broth (PDB; CONDA®, Madrid, Spain), pH 6.0 supplemented with 2 mg mL−1 of l-tryptophan in 100 mL Erlenmeyer flask. Five mycelial plugs (5 mm in diameter) from the periphery of a colony growing on PDA in an incubator (25 ± 2 °C) for 2 week were transferred to PDB. Incubation was performed on a reciprocal shaker, at 150 rpm in the dark at 25 ± 2 °C. After 2 week of incubation, the cultures were centrifuged at 11,000 rpm for 15 min to harvest the supernatant. For IAA production screening, a colorimetric assay was used (Tsavkelova et al., 2007). Two milliliters of Salkowski’s reagent (1 mL of 0.5 M FeCl3 in 50 mL of 35% HClO4) was mixed with 1 mL of the supernatant and incubated in the dark for 30 min. A pink to red color was considered positive for IAA production.