Biotechnological potential of Burkholderia and Paraburkholderia spp. from the Caatinga biome: Phosphorus and Potassium solubilization and growth promotion in cucumber (Cucumis sativus L.)

• Rhizobacteria from Caatinga were screened for P and K solubilization • Rhizobacteria showed multiple plant growth-promoting traits • Burkholderia and Paraburkholderia were the dominant bacterial genera • Selected strains enhanced cucumber growth in greenhouse conditions • Two strains, Burkholderia GB20 and Paraburkholderia GB15, showed high potential as bioinputs Soil is one of the richest microbial ecosystems, and the rhizosphere harbors the majority of these microorganisms. In the Caatinga biome, the rhizospheric microbiota contributes to structuring the environment, protecting plants, and promoting their growth. Therefore, the aim of this study was to bioprospect phosphorus (P) and potassium (K) solubilizing rhizobacteria associated with Caatinga plants and evaluate their effect on plant growth promotion. Bacterial screening was performed on selective media designed to evaluate the ability of isolates to solubilize phosphorus and potassium. Positive isolates were tested for exopolysaccharide (EPS) production, indole-3-acetic acid (IAA) synthesis, siderophore production, nitrogen fixation, biofilm formation, and root colonization ability. The 16S rRNA gene region of the isolates was sequenced. Eight isolates with the most promising plant growth-promoting traits in vitro were inoculated into cucumber plants under greenhouse conditions. The following parameters were evaluated: root and shoot length, leaf area, stem diameter, root density, and shoot and root dry mass. In the initial screening, 33 bacterial isolates were obtained: 18 showed the ability to solubilize P and 30 solubilized K. All isolates exhibited at least four plant growth-promoting traits, and BOX-PCR analysis revealed genetic variability among them. The predominant genus was Burkholderia (20 isolates). Among the tested isolates, Burkholderia sp. GB20 and Paraburkholderia sp. GB15 showed the best performance, significantly enhancing all analyzed plant growth parameters, highlighting their potential as plant growth-promoting bioinputs.