Plant Growth-Promoting Bacterium from Non-Agricultural Soil Improves Okra Plant Growth

Abstract

Beneficial soil microorganisms influence nutrient recycling, soil fertility, plant growth, and productivity and reduce chemical fertilizer application. This study aimed to isolate bacteria from non-agricultural soils in the Al-Ahsa region and characterize the bacteria with the best biostimulating characteristics at the physiological, biochemical, and molecular level. DPM17, a bacterial isolate, promotes plant growth through phosphate solubilization, nitrogen fixation, and ammonia production. DPM17 also produces the phytohormones, indole acetic acid (IAA; 4.516 μg mL−1) and gibberellin (1.33 µg mL−1), and ammonia (0.06 µg mL−1). Additionally, DPM17 grows in the presence of up to 10% NaCl, indicating its halophilic nature. DPM17 was identified as Bacillus baekryungensis based on comparative sequence analysis of the 16S rRNA gene, and neighbor-joining phylogenetic analyses indicated that DPM17 was 96.51% identified to Bacillus sp. DPM17 inoculation substantially improved Abelmoschus esculentus (okra) root length, lateral root count, and dry weight from 7.03 to 9.41 (p = 0.03), 3.2 to 7.2, and 6 to 13 mg (p = 0.032), respectively. The results suggest that DPM17 enhances plant growth and can be exploited to develop efficient formulations for sustainable agriculture and food security in Saudi Arabia.