Alleviation of saline stress by the bio-priming of cotton (<i>Gossypium hirsutum</i>) seeds with prominent indigenous bacterial isolates under axenic conditions

Salinity is an edaphic stress that significantly limits agricultural productivity. Nonetheless, plant growth promoting rhizobacteria (PGPR) has the potential to escalate the resilience of plant against biotic and abiotic stresses. Therefore, the present investigation was designed to examine the effect of seed bio-priming with liquid inoculants of Acinetobacter lwoffii strain PAU_31LN, Bacillus thaonhiensis strain PAU_43RN, Klebsiella pneumoniae strain PAU_35TP, Pseudomonas brassicacearum strain PAU_34RN and Pseudomonas fluorescens strain PAU_43TN on the biometric growth parameters of cotton seedlings under different salinity levels (50, 100 and 150 mM). Also, the bacterial strains were observed to maintain a constant viability at 150 mM NaCl. The production of plant growth promoting traits by all the bacterial strains was found to be in desirable quantity at different salt concentrations. However, the maximum production of indole-acetic acid, gibberellic acid, ammonia and phosphate solubilization was recorded by the strain PAU_31LN and PAU_43RN at all the salt conditions. During in-vitro plant growth assay, it was demonstrated that seed bio-priming with B. thaonhiensis improve the seedling length (6.50 cm shoot and 3.60 cm root length), dry shoot and root biomass (0.037 and 0.0023 g respectively), vigor index (765.9), and germination percentage (79%) under 150 mM salt content. Hence, the study encourages that bio-priming of cotton seeds with Bacillus thaonhiensis strain PAU_43RN can mitigate the pernicious effect of high osmolarity to enhance cotton plant growth.