Identification of a Potential IAA-Producing Fungus Isolated from Alpinia Sp. Rhizome in Hutan Sibayak, North Sumatera

Abstract

Medicinal plant from members of Zingiberaceae have been used as traditional remedies by marginal communities. To date, information and potential of these endophytes, especially endophytic fungi is still limited to certain taxa and properties. The present study investigates one of plant growth promoting properties possessed by endophytic fungi, which is the ability to produce extracellular Indole-3-acetic acid (IAA). Rhizome of Alpinia sp. sampled from Hutan Sibayak, North Sumatera was used as source of isolation of endophytic fungi. The endophytic fungal isolates were grown in Czapek-dox broth supplemented with 0.1% (w/v) L-tryptophan for 7 days to induce secretion of extracellular IAA. IAA concentration was measured colorimetrically using Salkowsky's solution by comparing absorbance (A530) of standard pure IAA with culture filtrates from each isolates. The study obtained 5 endophytic fungal isolates from Alpinia sp. rhizome differentiated morphologically. The highest IAA content in culture filtrate (42.911.41 μg.mL-1) was produced by isolate Al04SU followed with Al02SU, Al05SU and Al01SU with IAA concentration of 26.25, 19.55 and 17.26 μg.mL-1, respectively. Molecular identification of isolate Al04 based on ITS-DNA similarity showed that isolate was closely related to Aspergillus flavus and confirmed through phylogenetic tree construction. The presence of IAA-producing endophytic fungi from Alpinia indicates that medicinal plant may harbor bioprospective strains which could be used in crop improvement with further and deeper investigation.