Exploration of Plant Growth-promoting Traits of Diazotroph Isolates Obtained from Rhizospheric Soil

Rhizospheric diazotrophs play a pivotal role in sustainable agriculture by enhancing nutrient availability and promoting plant growth. The present study was conducted to explore native plant growth-promoting diazotrophic bacteria from the rhizosphere of different plants. 3 isolates (Hb1R 1, WhR 2, and GrR 1) were selected out of 24 as promising based on plant growth-promoting traits such as phosphate (P), potassium (K), and zinc (Zn) solubilization, as well as production of indole acetic acid (IAA) and ammonia (NH3). All three isolates exhibited quantitative P solubilization and NH3 production, ranging from 13.55 ± 1.20 to 300.3 ± 7.78 µg/ml and 1.074 ± 0.15 to 9.584 ± 0.165 mM/ml, respectively. Indole acetic acid (IAA) production of 85.6 ± 0.33 to 156.75 ± 1.62 µg/ml after 96 hours of incubation was demonstrated only by GrR 1. Maximum N fixation of 2.15 ± 0.22 mg/ml was exhibited by Hb1R 1, followed by GrR 1 (1.85 ± 0.1 mg N/ml) and WhR 2 (1.03 ± 0.09 mg N/ml). 16S rRNA gene sequencing identified isolates Hb1R 1, WhR 2, and GrR 1 as Enterobacter cloacae subsp. dissolvens strain Hb1R1, Enterobacter cloacae strain GrR1, and Enterobacter cloacae strain WhR2, respectively. These isolates show promise as bioinoculants for sustainable agriculture, warranting further studies on field application and adaptability to enhance crop productivity.