ISOLATION AND IDENTIFICATION OF IAA (Indole–3-Acetic Acid) - PRODUCING Rhizobacteria FROM ORCHID NATIVE SPECIES

Abstract

In this study, 44 bacterial strains were isolated from the roots of seven native orchid species cultivated in Ho Chi Minh city and Lam Dong province. Among them, 10 strains were identified as indole-3-acetic acid (IAA)-producing bacteria using the colorimetric method with Salkowski reagent. The highest IAA concentration was recorded at 86.21 ± 1.72 mg/L, produced by strain 1306.5. In addition, the experiment evaluating the effect of IAA-producing bacteria on tissue-cultured Dendrobium sp. plantlets showed that all 10 strains significantly promoted root development within 30 days of observation compared to the untreated control. Among them, strain 1306.5 exhibited the most remarkable effectiveness and was identified as belonging to the genus Pseudomonas, showing the closest relationship to Pseudomonas putida based on molecular identification and biochemical characterization. This opens up a promising direction for applying these bacterial strains as bioagents to support sustainable orchid growth and development, contributing to improved cultivation efficiency and the conservation of valuable plant genetic resources.