Toga Pangihotan Napitupulu, Anisah Farah Dinah Oktavia, Siti Maysarah, I. Made Sudiana
Endophytic microorganisms of mangrove trees are marked by their inhabitant inside the plants. Some of them produced indole-3-acetic acid (IAA) that advantage the host plants in terms of growth and coping with abiotic stresses. However, their spreading within specific mangrove plant sections that might be related to their beneficial physiological function is barely investigated. Therefore, by using in vitro bioassay, this study attempted to investigate the IAA production ability of endophytic bacteria and fungi within various loci of mangrove trees, namely leaves, propagules, and roots. The bacteria and fungi were isolated from two resilient tropical mangrove trees, Rhizophora apiculata (RA) and R. mucronata (RM). In RA, a total of 18 bacteria and 12 fungi were found. While in RM, 23 bacteria and 11 fungi were isolated. The IAA concentration was measured by colorimetric method toward fermented supernatant of Pikovskaya broth that was supplemented with 0.1 and 0.2 % (w/v) of exogenous L-tryptophan for bacterial and fungal isolates, respectively. The results showed that propagules resided in the highest IAA-producing endophytic bacteria, followed by leaves and roots, although no significant difference between all organs. However, for the endophytic fungi, roots harbored the highest IAA-producing fungi among all organs, followed by propagules and leaves, but without significant differences as well. These patterns were observed similarly for RA as well as RM. In conclusion, this study showed evidence of organ specificity related to the IAA-producing bacteria domination in mangrove trees that was possibly driven by their interkingdom interactions. © 2025 Author(s).
Research Center for Applied Microbiology, Research Organization for Life Sciences and Environment, National Research and Innovation Agency (BRIN) Indonesia, Jl. Raya Jakarta Bogor Km.46, Cibinong, 16911, Indonesia; Department of Soil Science, Agroecotechnology Study Program, Faculty of Agriculture, Brawijaya University, Jl. Veteran No.1, Malang, 65145, Indonesia
