Characterization of Drought‐Tolerant Bacterial Strain From Semiarid Soil of Kenya for Plant Growth Promotion and Drought Stress Amelioration

Abstract

Worldwide, drought significantly impacts crop output and agricultural productivity. To mitigate this, eco‐efficient methods to enhance plant growth under drought stress are essential. This study isolated 30 morphologically distinct bacterial strains from the maize rhizosphere in drought‐stressed conditions in Makueni County, Kenya. These strains’ drought tolerance was assessed using three stress treatments of polyethylene glycol (PEG 6000) at 0, −0.75, and −1.3 MPa. The two best isolates, MK6 ( Bacillus cereus ) and MK17 ( Bacillus velezensis ), were identified via 16S rRNA gene sequencing, with sequences deposited in the NCBI database (accession numbers PP064566 and PP064918, respectively). Isolates were screened for plant growth promotion (PGP) properties under both stress and no‐stress conditions, including indole acetic acid, gibberellic acid, exopolysaccharide, siderophore, antioxidant enzyme activity, proline, salicylic acid, biofilm, and biosurfactant production. Results under PEG 6000–induced stress showed MK6 produced the highest GA (51.67 µgmL −1 ) and IAA (2.6 µgmL −1 ). MK6 also had the highest EPS production (4320 µgmL −1 ) and siderophore production (68%) at −1.3 MPa. Antioxidant activities, notably catalase, were highest in MK17 (1260 µgmL −1 ). The emulsification index (%EI 24) for MK6 and MK17 was 16.72% and 10.36% under no‐stress conditions and declined during stress. The combinatorial potential of MK6 and MK17 showed significant improvement in maize vigor index, germination rate, seedling length, height, and dry biomass. Therefore, MK6 and MK17 hold great potential for developing biostimulants to ameliorate drought stress in drought‐prone regions of the world and promoting sustainable crop production.