Microbial biofertilizers and biopesticides from vermicompost tea and rhizosphere of organic soilless melon crop: In vitro assessment

Microorganisms offer an environmentally sustainable alternative to synthetic pesticides and fertilizers. This study focuses on the identification and selection of microorganisms from vermicompost tea and the rhizosphere of an organic soilless melon crop, with potential for use as biopesticides and biofertilizers in agriculture. The biofertilizing capabilities of these microorganisms, such as nitrogen fixation, phosphate solubilization, and siderophore production, were evaluated. As part of the biopesticide assessment, their in vitro antagonistic effects against eight bacterial and fungal plant pathogens were tested. Additionally, a predictive study on the production of secondary metabolites of agronomic interest was conducted for the selected strains. The bacteria Acinetobacter beijerinckii B9, Kocuria palustris B23, Pantoea agglomerans B32, Rahnella aquatilis B21, Streptomyces griseorubiginosus B29 and Bacillus licheniformis B15, as well as the fungi Aspergillus fumigatus H4, Aspergillus niger H6 and Aspergillus terreus H2 showed excellent biopesticidal and biofertilizer activities. Among these, the selected fungi and the filamentous bacterium S. griseorubiginosus B29 were particularly notable for producing many secondary metabolites associated with antimicrobial activity and the induction of plant defense mechanisms. These microorganisms represent promising novel biobased solutions to replace environmentally harmful agrochemicals.