Fig. 1.
Effect of plant hormones on H. maydis growth in culture medium. Assay plates were inoculated in the middle with a 6-mm (in diameter) culture agar disk cut from the margins of 4-6-day-old H. maydis colonies. H. maydis colonies were grown on potato dextrose agar (PDA) at 28 ± 1 °C in complete darkness. Radial mycelial growth was measured six days after inoculation. Phytohormones were incorporated separately or in a mixture into PDA medium at a high 100 mg/L dosage (a) or at the different concentrations indicated (B, for selected hormones) to evaluate their influence on the colonies’ radial growth. In the synergism testing groups (combination of two different hormones), the final concentration of 100 mg/L was the sum of 50 mg/L of each of the two hormones tested. The following hormones were used: kinetin; auxin (hormone Indole-3-acetic acid, IAA); Gibberellic Acid 3 (GA); the ethylene precursor amino-cyclopropane-1-carboxylic acid (ACC) or 1-aminocyclopropane-1-carboxylic acid (ACPC); abscisic acid (ABA); salicylic acid (SA); and jasmonic acid (JA). Cultures were incubated for 6 (a) or 8 days (b) at 28 ± 1 °C in the dark. Values represent the average of six replicates. Error bars represent standard deviation. Asterisks represent significant (*P = 0.05, ** P = 0.005, *** P < 5*10−4) differences from the control