Enhancing agriculture recovery of Phaseolus vulgaris L. and Cucurbita pepo L. with Olea europaea L. plant growth promoting rhizobacteria

Context. The rhizosphere is an environment created by interactions between root exudates and microorganisms. Interactions are beneficial due to certain components having a plant growth promoting rhizobacteria (PGPR) effect. Aims. This study consists of the isolation, screening of PGPR from the rhizosphere of Olea europaea L. of a Mediterranean climatic region in Algeria and the study of their effects on growth of two agronomic vegetables Phaseolus vulgaris L. and Cucurbita pepo L. Methods. Based on their ability to produce the PGPR molecules indole-3-acetic acid (IAA), phosphatase and siderophores, three rhizobacteria (S25, S75, and S79) were chosen for in vivo tests and capacity to produce the cell wall degrading enzymes chitinase, lipase, protease, glucanase, cellulase, and and phospholipase. They were also examined using scanning electron microscopy (SEM) and analysed using matrix-assisted laser desorption/ionisation time of flight mass spectrometry (MALDI-TOF MS) for identification. Key results. Bacterial strains identified as Bacillus cereus and Bacillus thuringiensis were able to enhance significantly germination of the two vegetables at P < 0.001. Vegetative parameters of C. pepo were significantly affected by the bacterial inoculation. We noted increases in stem length (P < 0.05), number of flowers (P < 0.01), and root length (P < 0.001). Conclusion. The bacterial isolates of this study provide biological options in treatments originating from alternate hosts. Implications. They provide hope for companion/intercrop planting schemes, leading to optimisation of agricultural yields in agroecological blends.