Environmentally friendly fertilizer: IAA production by <i>Ipomoea carnea</i>-associated rhizobacteria

Abstract Indole acetic acid (IAA) is ne of the types of plant hormones that plays an important role in the growth and development processes of plants and is produced by a variety of microorganisms. Microorganisms capable of producing IAA include plant rhizobacteria, which are often found in the rhizosphere and are known as rhizobia or plant growth-promoting rhizobia (PGPR) due to their ability to stimulate plant growth. One of the plants that potentially has PGPR is Ipomoea carnea. This study aims to obtain bacteria associated with rhizosphere bacteria of kangkung pagar ( Ipomoea carnea ) and characterize rhizosphere bacteria isolates of Ipomoea carnea that can produce IAA hormone. This research was descriptive qualitative and was conducted in May-July 2024 at the Advanced Biology Laboratory and Immunology Laboratory, Faculty of Mathematics and Natural Sciences, University of Mataram. The method used was agar spread technique. Colonies grown on nutrient agar media supplemented with L-tryptophan were then purified and analyzed based on morphological characteristics and cells. The isolates obtained were then tested qualitatively and quantitatively for their ability to produce IAA hormone. As many as 13 isolates of rhizobacteria were obtained, namely R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, R12 and R13. The thirteen isolates were capable of producing IAA hormone with different concentrations of 12.02, 6.08, 5.20, 8.85, 1.67, 2.65, 1.71, 48.45, 16.36, 1.77, 4.16, 1.73, and 10.89, respectively. The results showed that 5 isolates with codes R1, R4, R8, R9 and R13 had the highest IAA concentrations, which had the potential as biological control agents in increasing plant growth.