Rhizospheric Bacteria From Artocarpus heterophyllus Exhibit Antimicrobial Traits and Antagonistic Activity Against Pantoea stewartii subsp. stewartii, Causal Agent of Jackfruit Bronzing Disease

The Jackfruit bronzing disease represents a significant phytosanitary constraint affecting Artocarpus heterophyllus production. In this context, the exploration of plant-associated microorganisms as a source of potential biological control agents aligns with sustainable agricultural strategies. This study is aimed at isolating, characterizing, and evaluating the in vitro antagonistic interactions, and antimicrobial potential of indigenous rhizospheric and endophytic bacteria with the potential to be developed as biocontrol agents for the control jackfruit bronzing causal agent Pantoea stewartii subsp. stewartii. A total of 138 bacterial isolates were obtained from rhizospheric soils and internal plant tissues, with a predominance of rhizospheric bacteria (78.3%). In vitro antagonism assays revealed that only rhizospheric isolates exhibited inhibitory activity against the phytopathogen, identifying 12 strains with consistent antagonistic capacity. These isolates were further characterized to elucidate the potential mechanisms involved in microbial antagonism. Functional analyses demonstrated that the antagonistic isolates possessed multiple extracellular enzymatic activities, predominantly lipase, followed by amylase and cellulase activities, whereas protease activity was absent. Additionally, selected isolates exhibited biosurfactant production, suggesting their role in pathogen inhibition. Antibiosis was confirmed through the production of diffusible antimicrobial compounds. Furthermore, molecular screening revealed the presence of nonribosomal peptide synthetase (NRPS) gene fragments in several strains, supporting their genetic potential to synthesize bioactive secondary metabolites. Phylogenetic identification based on 16S rDNA gene sequencing assigned the isolates to bacterial taxa known for their ecological versatility and functional attributes. Overall, this study provides evidence that rhizospheric bacteria associated with jackfruit harbor significant antagonistic and antimicrobial capabilities against jackfruit bronzing causal agent. These findings contribute to the understanding of microbial interactions and functional traits associated with plant microbiota. This study provides the first assessment of microorganisms associated with jackfruit.