Enhancing the ability of rice to adapt and grow under saline stress using selected halotolerant rhizobacterial nitrogen fixer

Abstract 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.