Prospective of Indole-3-Acteic Acid (IAA) and Endophytic Microbe Bacillus subtilis Strain SSA4 in Paddy Seedlings Development and Ascorbate-Glutathione (AsA-GSH) Cycle Regulation to Mitigate NaCl Toxicity.

Plant growth promoting endophytes significantly affected plant health. The present study demonstrates effect of endophytic isolate Bacillus subtilis strain SSA4 and exogenous Indole-3-acetic acid (IAA) on paddy seedlings growth parameters, photosynthetic pigments, photosynthesis, leaf gas exchange parameters, respiration, oxidative stress biomarkers and Ascorbate-Glutathione (AsA-GSH) cycle under different NaCl (0-300 mM) stresses. The Bacillus subtilis SSA4 was identified by 16S r-RNA gene sequence analyses and NCBI BLASTn tools. The B. subtilis SSA4 tolerated 1100 mM NaCl and produced IAA (42.15 µg m/L) at 300 mM NaCl stress. The paddy genotype (HUR 917) treated with exogenous IAA (21 µg m/L) and B. subtilis strain SSA4 egg cell based bioformulation was significantly affected seedlings physiology and biochemistry at lower (150 mM) and higher (300 mM) NaCl doses. In conclusion, co-inoculation found as effective green tool to mitigating salinity stress in paddy seedlings.