Agriculture 2022, 12, 873. https://doi.org/10.3390/agriculture12060873 www.mdpi.com/journal/agriculture Article Plant Growth‐Promoting Bacterium from Non‐Agricultural Soil Improves Okra Plant Growth Heba Adel AlAli 1,2 , Ashraf Khalifa 1,2,3, * and Mohammed Almalki 1,2 1 Al Bilad Bank Scholarly Chair for Food Security in Saudi Arabia, the Deanship of Scientific Research, the Vice Presidency for Graduate Studies and Scientific Research, Al‐Ahsa 31982, Saudi Arabia; 219039525@student.kfu.edu.sa (H.A.A.); malmalki@kfu.edu.sa (M.A.) 2 Biological Sciences Department, College of Science, King Faisal University, Al‐Ahsa 31982, Saudi Arabia 3 Botany and Microbiology Department, Faculty of Science, Beni‐Suef University, Beni‐Suef 62521, Egypt * Correspondence: akhalifa@kfu.edu.sa; Tel.: +966‐13‐589‐9540; Fax: +966‐013‐5899556 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 biostim‐ ulating 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 substan‐ tially 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 sustaina‐ ble agriculture and food security in Saudi Arabia. Keywords: Bacillus; Abelmoschus esculentus; biostimulation; non‐agricultural soils 1. Introduction Soil microbiota function in nutrient recycling, such as carbon and nitrogen, enhanc‐ ing soil quality, increasing crop yield, and decreasing the application of chemical fertiliz‐ ers [1]. Plant growth‐promoting bacteria (PGPB) stimulate plant growth via bioactive compound production, iron sequestration, and inorganic phosphate solubilization, among others. PGPB also enhance the rhizoremediation of petroleum hydrocarbons and phenol biodegradation [2,3] and reduce heavy metal uptake by plants [4]. Thus, they can be used for a wide range of industrial and biotechnological applications. Abelmoschus esculentus (okra) is important in the human diet due to its high carbohy‐ drate, fat, protein, mineral, and vitamin content. It is also used in medicine and industry [5]. The low bioavailability of essential nutrients and high salinity of soils negatively affect okra growth and productivity in Saudi Arabia [6]. Increasing okra production via appli‐ cations of synthetic chemical fertilizers has potential hazards to the environment and as‐ sociated organisms. Hence, searching for a safe, eco‐friendly, and efficient strategy to in‐ crease okra production is of high significance. Various microbial groups, including Aeromonas encheleia and Pseudomonas azotofor‐ mans isolated from earthworms, are affiliated with PGPB [7]. The biostimulation proper‐ ties of PGPB isolated from Al‐Ahsa, Saudi Arabia, have been investigated. Bacillus mega‐ terium and Enterobacter cloacae were isolated from Medicago sativa root nodules and roots, Citation: AlAli, H.A.; Khalifa, A.; Almalki, M. Plant Growth‐Promoting Bacterium from Non‐Agricultural Soil Improves Okra Plant Growth. Agriculture 2022, 12, 873. https://doi.org/10.3390/ agriculture12060873 Academic Editors: Eugenio Llorens, Begonya Vicedo, Loredana Scalschi and Carlos Agustí‐Brisac Received: 28 May 2022 Accepted: 16 June 2022 Published: 16 June 2022 Publisher’s Note: MDPI stays neu‐ tral with regard to jurisdictional claims in published maps and institu‐ tional affiliations. Copyright: © 2022 by the authors. Li‐ censee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and con‐ ditions of the Creative Commons At‐ tribution (CC BY) license (https://cre‐ ativecommons.org/licenses/by/4.0/).