Indole-3-acetic acid production by endophytic consortia from red ginger lily (Alpinia purpurata (Vieill.) K. Schum) and its application in plant growth promotion.

Abstract

Indole-3-acetic acid (IAA) is a widely studied plant hormone, produced by plants and microorganisms like bacteria and fungi, which regulates plant growth and development. The current study was conducted to investigate the IAA production by endophytes isolated from Alpinia purpurata (Vieill.) K. Schum (red ginger lily), a medicinally and ornamentally important rhizomatous plant whose endophytic microbiome remains largely unexplored, particularly with respect to phytohormone production. This study assembled an effective IAA producing consortium, confirming IAA production by LC MS and evaluated its plant growth promotion potential by seed-germination assays, hydroponics, tissue culture, and field trials. A total of fifty morphologically distinct bacteria were obtained, whose IAA production ranged from 17.75 ± 0.02 to 257.35 ± 0.77 µg/mL. Three strains, Agrobacterium radiobacter, Pseudomonas psychrophila, and Lysinibacillus macroides, were used to form a microbial consortium that produced more IAA (320.77 ± 02 µg/mL) than the individual isolates. IAA was confirmed to be present in the sample at 0.442 µg/mL with a typical retention period by LC MS analysis. When compared to untreated controls, plant growth assessments showed improved rhizome yield (70.8%), shoot development (41.7%), leaf characteristics (45.6%), and seed germination (50%). This is the first study to report on IAA production by endophytic bacteria derived from Alpinia purpurata, resulting in the formation of a functionally compatible microbial consortium that produces biologically active IAA, validated by LC-MS/MS, and shown to promote germination and plant growth in tissue culture, hydroponic, and field environments.

Supplementary information: The online version contains supplementary material available at 10.1007/s12298-026-01745-z.