This study was aimed to isolate and identify the PGPR candidates from the paddy rhizospheres grown in saline soils, and to examine their ability in producing IAA, solubilizing phosphates and fixing nitrogen. Cultural media of Ashby, Pikovskaya, and Caceres were performed to isolate the PGPR candidates. The cultures were incubated for 48 hours at room temperatures. Characterization of bacterial isolates was conducted with conventional methods, and the identification referred to the Bergey’s Manual of Determinative Bacteriology. The bacterial isolates capabilities to fix N₂ qualitatively, to produce IAA quantitatively, to solubilize phosphate, and to inhibit fungal pathogens were tested with semisolid nitrogen-free bromthymol blue medium, a Salkowsky method, a Pikovskaya agar medium, and a challenge method, respectively. The results showed that ten of PGPR candidates were found, and three isolates (PSA2, PSA6, PSA10) were identified as members of genus Azospirillum, six isolates (PSA3, PSA4, PSA5, PSA7, PSA8, PSA9) belonged to genus  Azotobacter, and one isolate (PSA1) was member of genus Marinococcus. Population density of the bacteria was 7.4x10⁶, 2.0x10⁶, and 6.0x10⁶ CFU/g soil, respectively. All bacterial isolates were capable of fixing nitrogen, and solubilizing phosphate with phosphate dissolution index values were ranging from 104.57 to 299.58. Bacterial isolates of PSA1, PSA2, PSA3, PSA4, PSA5, PSA6, PAS7, PSA8, and PSA10 were able to grow on NB medium containing 5% NaCl, while isolate PSA9 was tolerant to 3% NaCl. Isolates PSA5, PSA8, and PSA10 were able to produce IAA in a saline medium at amounts of 71.26, 45.38 and 31.56 ppm, respectively. PGPR candidates of PSA1, PSA6, PSA8, and PSA10 isolates demonstrated the ability to inhibit the growth of Fusarium oxysporum with the highest inhibitory percentage value (46.11%) and against Rhizoctonia solani(26.67%).

Oedjijono

Dian Kusumawardani

Dyah Fitri Kusharyati

Pancrasia Maria Hendrati