Molecular identification and optimization of indole acetic acid production by Fusarium oxysporum AUMC 16,438 for biofertilizer application

Indole-3-acetic acid (IAA) is a key phytohormone that regulates essential plant physiological processes and enhances overall growth. This study aimed to produce and optimize IAA synthesis by a fungal isolate obtained from rhizosphere soils in Egypt. Twenty fungal isolates were screened for IAA production, and isolate FSA12 showed the highest yield (23.98 ± 1.98 µg/mL). Molecular identification based on ITS sequencing, supported by morphological characterization, revealed that FSA12 is most likely Fusarium oxysporum AUMC 16,438, and its sequence was deposited in GenBank (accession no. PP990199). Optimization using the OFAT approach indicated that the optimal L-tryptophan concentration, incubation temperature, pH, incubation period, and inoculum size were 0.6%, 30 °C, pH 6, 12 days, and three mycelial discs, respectively. To reduce production cost, several agro-industrial wastes were evaluated as alternative carbon sources; banana peel proved the most effective, likely due to its natural L-tryptophan content. Application of the produced IAA significantly enhanced wheat seed germination compared with the untreated control, demonstrating its potential use as an eco-friendly biofertilizer in sustainable agriculture.