A halotolerant plant growth promoting consortium of Bacillus sp. RB3 and Pseudomonas sp. EB3 primes banana, Musa acuminata cv. Berangan, against salinity and Foc-TR4 stresses

A plant-growth promoting bacterial consortium of halotolerant Bacillus sp. and Pseudomonas sp. was evaluated for the ability to prime banana (Musa acuminata cv. Berangan) plants against abiotic (salinity) and biotic (Foc-TR4) stress challenges. PGPB consortium-primed banana plants showed better growth (plant height, root length and root biomass) and improved physiological parameters (relative water content, chlorophyll, and carotenoid contents) in both stressed conditions compared to non-primed banana plants. In addition, primed banana plants showed a reduction in lipid peroxidation and an increase in proline and antioxidant enzymatic activities (superoxide dismutase, catalase, ascorbate peroxidase, peroxidase, and glutathione reductase). In salt-stress conditions (sea salt at 100 mM NaCl equivalent), primed plants showed higher levels of K⁺, Ca²⁺, and Mg²⁺ and lower levels of Cl^- and Na⁺ compared to non-primed salt-stressed plants. Under Foc-TR4 stress, the primed plants showed significant enhancement in the levels of total soluble phenolics, lignin content and defense-related enzyme activities (β-1, 3-glucanase, phenylalanine ammonia lyase, chitinase, polyphenol oxidase, and lipoxygenase). Expression analysis of nine stress-responsive MaWRKY genes (MaWRKY4, MaWRKY23, MaWRKY24, MaWRKY25, MaWRKY28, MaWRKY45, MaWRKY65, MaWRKY89 and MaWRKY145) showed significant upregulation in primed banana plants under salt and Foc-TR4 stresses compared to non-primed plants. These results demonstrate that inoculation with the PGPB consortium improved banana plant growth characteristics and primed WRKY-mediated protection against abiotic and biotic stresses.