Isolation and Characterization of an IAA-Producing Aspergillus nigerfrom Avicennia marina

Mangrove ecosystems harbor diverse endophytic fungi that contribute to plant health and stress tolerance. This study focused on the isolation, identification, and indole-3-acetic acid (IAA) production potential of an endophytic fungus from Avicennia marina. Surface-sterilized leaf, root, and branch tissues were cultured on PDA, and a distinct fungal isolate was obtained. Molecular identification using ITS1 and ITS4 primers followed by sequencing and BLAST analysis confirmed 99% similarity to Aspergillus niger. The isolate was cultured in tryptophan-enriched broth to assess its ability to synthesize IAA. Following extraction and colorimetric analysis using Salkowski reagent, the development of a pink color and absorbance at 530 nm confirmed IAA production. The results indicate that A. niger inhabits the internal tissues of A. marina and synthesizes IAA via a tryptophan-dependent pathway. These findings highlight the potential of this endophytic fungus as a plant growth-promoting organism that may support root development, nutrient uptake, and stress resilience. The study provides a basis for future applications of mangrove-derived endophytes in sustainable agriculture and ecological restoration.