Isolation and Characterization of Endophytic Exiguobacterium acetylicum from Wild Palm Roots grown in Siwa Oasis and Its Application in Enhancing Wheat Growth Under High Salinity Stress | ||
| Alexandria Journal of Agricultural Sciences | ||
| Articles in Press, Corrected Proof, Available Online from 12 September 2025 PDF (770.29 K) | ||
| Document Type: Original Article | ||
| DOI: 10.21608/alexja.2025.418630.1166 | ||
| Authors | ||
| Ahmed Ramadan1; Mohamed El-Halfawy1; Essam Abd ElRahman Koreish1; Nieven Fathi2; Mahrous Kandil* 1 | ||
| 1Soil and Water Dept. Faculty of Agriculture, Alexandria University | ||
| 2Soil Salinity & Alkalinity Laboratory, Ministry of Agriculture, Alexandria University | ||
| Abstract | ||
| Soil salinity severely constrains wheat productivity in arid regions. We isolated an endophytic bacterium from wild date palm (Phoenix dactylifera L.) roots collected at the hypersaline Siwa Oasis (Egypt) and identified it by 16S rRNA sequencing as Exiguobacterium acetylicum. The isolate tolerated up to 15% (w/v) NaCl in vitro and expressed multiple plant growth-promoting (PGP) traits, including growth on ACC as the sole N source (indicative of ACC-deaminase activity), phosphate solubilization, indole-3-acetic acid (IAA) production (≈5 µg mL⁻¹), and ammonification; nitrogen fixation on JNFb⁻ medium was not detected. Colonization of wheat roots and shoots was confirmed by re-isolation and sequence identity (≥98%). In a greenhouse pot experiment (cv. Egypt-2; sand culture), plants were grown under four water salinity levels (ECw 0.7, 4, 8, 12 dS m⁻¹) with or without inoculation. As water salinity increases, inoculation significantly increased wheat biomass and yield components. Under severe salinity (12 dS m⁻¹), inoculated plants showed higher fresh (+42.9%) and dry (+52.1%) biomass, spike weight (+50.7%), and grain weight (+63.5%) relative to non-inoculated controls. Inoculation also maintained higher photosynthetic pigments (chlorophyll a, b, total chlorophyll, carotenoids) and lowered proline accumulation (e.g., −33% at 12 dS m⁻¹), indicating mitigation of osmotic/oxidative stress. Grain nutritional quality improved: at 12 dS m⁻¹, grain N, P, and K increased by 2.06%, 0.36%, and 0.58%, respectively, while Na decreased to 0.50%, increasing grain protein from 7.94% to 12.88%. Overall, these results demonstrated that an endophytic E. acetylicum isolated from a saline desert habitat can enhance wheat growth, yield, ionic balance, and grain protein under saline conditions. This isolate represents a promising bioinoculant for bio-saline agriculture, warranting multi-site field validation. | ||
| Keywords | ||
| Exiguobacterium acetylicum; Endophytic microorganisms; Wild Palm; Siwa Oasis; Salinity Stress and plant growth-promoting (PGP) | ||
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