Epiphytic bacteria from Tacinga inamoena (K. Schum.) N.P. Taylor & Stuppy improve plant growth in cucumber seedlings

Under stress conditions, the phyllosphere of host plants harbors microorganisms with potential for the development of agricultural bioinputs. In this study, the potential of Brevibacillus sp. UPT4 and Pantoea sp. SPM1, two epiphytic strains from Tacinga inamoena isolated from the Caatinga biome, was assessed through in vitro assays and a greenhouse experiment. The experiment was conducted in a randomized block design with four treatments (individual strains, bacterial consortium, and control) and five replicates. Biometric parameters (shoot and root length, stem diameter, root volume, and biomass allocation to shoot and root) were measured and analyzed by the Scott-Knott test at a probability level of 5%, as well as Redundancy Analysis (RDA). The strains exhibited auxin production, nitrogen fixation, and tolerance to abiotic stresses, showing significant increases (p < 0.05) in shoot and root parameters (13.58% to 194.86%) compared to the control. RDA indicated that most of the variability observed in the parameters was associated with auxin production and stress tolerance. These findings highlight the potential of epiphytic bacteria isolated from the Caatinga biome as promising tools to address challenges posed by climate change.