Halophilic rhizobacteria promote growth, physiology and salinity tolerance in Sesamum indicum L. grown under salt stress

Sridhar D^1*Saleh S Alheswairini²JAYANTHI BARASARATHI³Hesham Ali El Enshasy⁴Lalitha Sundaram¹Sajad Hussain Mir⁵S Nithyapriya⁶Riyazali Sayyed⁷

• ¹Periyar University, Salem, India
• ²Qassim University, Buraidah, Al-Qassim, Saudi Arabia
• ³INTI International University, Nilai, Negeri Sembilan Darul Khusus, Malaysia
• ⁴University of Technology Malaysia, Johor Bahru, Johor Darul Takzim, Malaysia
• ⁵Anhui Agricultural University, Hefei, Anhui Province, China
• ⁶Padmavati College of Arts and Science for Women, Salem, India
• ⁷University of Nizwa, Nizwa, Oman

Salt stress is a growing global concern, adversely affecting plant growth and physiological processes. Plant growth-promoting rhizobacteria (PGPR) mitigate salt stress and enhance plant growth and development. The present study aimed to isolate and characterize salt-tolerant PGPR from salinity-affected soils in Tamil Nadu, India, and evaluate their potential to enhance sesame's growth and stress tolerance (Sesamum indicum L.) under saline conditions. An isolate, designated as PAS1, exhibited several plant growth-promoting traits, including the production of IAA (48.56 µg ml⁻¹), siderophore (89.20 ± 0.65%), phosphate solubilization (7.8 mm zone of clearance), ammonia, and HCN production. PAS1 was subsequently identified as Bacillus flexus. Sesame plants were grown with B. flexus under varying salt stress conditions (0 mM, 100 mM, and 200 mM NaCl). After 45 days of inoculation, sesame plants exhibited significantly higher levels of biochemical parameters than control plants under salt stress, including increased chlorophyll content (4.4 mg g⁻¹), proline (0.0017 mg g⁻¹), soluble sugars (61.34 mg g⁻¹), amino acids (1.10 mg g⁻¹), and proteins (3.31 mg g⁻¹). Furthermore, enhanced antioxidant enzyme activities were observed, specifically for DPPH (60.25%), SOD (231.29 U mg⁻¹ protein), POD (6.21 U mg⁻¹ protein), CAT (3.38 U mg⁻¹ protein), and MDA (23.32 µmol g⁻¹). These results indicate that B. flexus inoculation improved plant performance under saline conditions compared to uninoculated plants. The findings suggest that halo-tolerant PGPR strains, such as B. flexus, hold promise as biofertilizers for enhancing crop productivity in saltaffected soils.