Salinity is one of the most damaging abiotic stresses due to climate change impacts that affect the growth and yield of crops, especially in lowland rice fields and coastal areas. This research aimed to isolate potential halotolerant plant growth-promoting rhizobacteria from different rhizo-microbiome and use them as effective bioinoculants to improve rice growth under salinity stress conditions. Bioassay using rice seedlings was performed in a randomized block design consisting of 16 treatments (control and 15 bacterial isolates) with three replications. Results revealed that isolates S₃, S₅, and S₆ gave higher shoot height, root length, and plant dry weight compared with control (without isolates). Based on molecular characteristics, isolates S₃ and S₅ were identified as Pseudomonas stutzeri and Klebsiella pneumonia. These isolates were able to promote rice growth under salinity stress conditions as halotolerant plant growth-promoting rhizobacteria. These three potent isolates were found to produce indole-3-acetic acid and nitrogenase.

Salinity stress has become the major devastating constraint for rice growth. Halotolerant rhizobacterial nitrogen fixer (HRNF) was investigated for increasing the nitrogenase activity (NA), organic acid (OA), gibberellic acid (GA), and indole 3-acetic acid (IAA) productions, seedling growth, and rice yield. Six N fixers were isolated using Ashby’s (Ab₁, Ab₂, and Ab₃) and Okon’s media (Az₁, Az₂, and Az₃). Furthermore, bioassay was carried out using rice seedling grown on nitrogen-free medium. The Ab₃ and Az₂ isolates were selected and biomolecularly identified as Pseudomonas stutzeri and Klebsiella pneumoniae, respectively. These selected bacteria were used as active ingredients for Halotolerant rhizobacterial inoculant (HRI) dosage trials (0, 500, 1,000, and 1,500 g ha⁻¹) on simple pot experiments. The Az group isolates had 3–5 times higher ability in fixing N and producing OA, GA, and IAA than the Ab group isolates. Furthermore, N-uptake, number of panicles, filled grain, and the rice yield of HRI treated pots were significantly increased. Application of 1,000–1,500 g HRI ha⁻¹ had resulted in a significant increase in the yield of rice grain (26.10–28.27 g plant⁻¹ or 15.4–25.09%) which was higher than the control. This result concludes that HRI could contribute in enhancing the ability of rice to adapt and grow under saline stress.

Phosphate Solubilizing Bacteria (PSB) plays a significant role to improve phosphate availability, in order to support the growth of maize in acid soil. The experiment aimed to investigate the capability of PSB isolates in solubilizing phosphate and their compatibility with maize seedlings which were conducted in the soil biology laboratory and greenhouse at Department of Soil Science, Faculty of Agriculture, Universitas Padjadjaran. In vitro test using three isolates of PSB was done to understand the synergystic character by using streak method with natrium agar medium. Subsequently, those three isolates were used for bioassay. The bioassay experiment set up as randomized factorial design, consisted of 16 treatments (control, single and consortia of three PSB isolates in two concentrations) and provided by 3 replications. The solubilized phosphate, P uptake and plant dry weight was measured at 14 days after planting. The results revealed that three PSB isolates were synergistic and did not antagonistic to each other. The isolates either in single or consortia application were able to solubilize phosphate up to 23,23 ppm and increase P uptake up to 42%. The consortia of PSB isolates has the highest capability of increasing the growth of maize seedlings.