-1- ABSTRACT Rice (Oryza sativa L.) has mechanism for morphological, physiological, and bio- chemical self-defense in response to drought conditions. The ability of osmotoler- ant rhizobacteria to develop association with plants suggests that it could be used as an inoculum to support plant growth under drought stress. The purpose of this study is to determine the response of ‘IR64’ and ‘Situ Bagendit’ to the inoculation with osmotolerant rhizobacteria under drought conditions. The experiment had 3 treatment factors: 2 rice cultivars ('IR64' and 'Situ Bagendit'), 3 drought treatments (25%, 50% and 100% field capacity), and 2 types of rhizobacteria treatments (without inoculation and with inoculation using osmotolerant rhizobacteria (Enterobacter flavescens). Plant growth was measured in terms of plant height, number of leaves, number of tillers and panicles, and percentage of filled grain. Physiologi- cal and biochemical parameters, namely chlorophyll, carotenoids, proline, superox- ide dismutase (SOD) peroxidase (POX) and ascorbate peroxidase (APX) were measured. The inoculation of osmotolerant rhizobacteria enhanced ‘IR64’ and ‘Situ Bagendit’ growth (plant height, number of leaves, tillers and panicles) and increased the percentage of grains in ‘IR64’ cultivar. Proline content, SOD, and APX activities were all increased by osmotolerant rhizobacteria inoculation, how- ever, carotenoid content was decreased. Plant growth, physiological and biochemi- cal responses of both cultivar to drought were enhanced by inoculation with os- motolerant rhizobacteria. Copyright: © 2022, J. Tropical Biodiversity Biotechnology (CC BY-SA 4.0) Research Article Growth and Physiological Attributes of Rice by the Inoculation of Osmotolerant Rhizobacteria (Enterobacter flavescens) under Drought Condition Hasna Dyah Kusumardani 1 , Triwibowo Yuwono 2 , Diah Rachmawati 1 * 1) Departement of Tropical Biology, Faculty of Biology, Universitas Gadjah Mada, Jl. Teknika Selatan, Sekip Utara, Yogyakarta, Indonesia, 55281 2) Departement of Agricultural Microbiology, Faculty of Agriculture, Universitas Gadjah Mada, Bulaksumur, Yogyakarta, Indonesia, 55281 * Corresponding author, email: drachmawati@ugm.ac.id Journal of Tropical Biodiversity and Biotechnology Volume 07, Issue 02 (2022): jtbb67359 DOI: 10.22146/jtbb.67359 INTRODUCTION Water availability is crucial in sustaining growth and development of plant. Climate change has reduced the availability of water for agriculture. Drought can affect various cellular, biochemical, and physiological attributes in plant (Bouman & Tuong 2001; Mundree et al. 2004). This stress can cause meta- bolic changes in plant by controlling osmotic pressure and creating free radi- cals as ROS (reactive oxygen species) (Bhattacharjee 2005; Halliwell 2006). Plants develop non-enzymatic or enzymatic oxidative defense system in re- sponse to free radicals (Miller 2008). The non-enzymatic defense system can take the form of antioxidant production, while enzymatically it can take form Keywords: drought stress Enterobacter flavescens ‘IR64’ osmotolerant rhizobacteria ‘Situ Bagendit’ Submitted: 04 July 2021 Accepted: 02 February 2022 Published: 01 June 2022 Editor: Ardaning Nuriliani