A new study from citrus orchards in Iran has uncovered highly potent actinobacterial strains—mainly Streptomyces spp.—capable of suppressing major citrus pathogens while enhancing seedling vigor. The research team isolated 100 rhizospheric and endophytic actinobacteria, screening them for their ability to combat Alternaria alternata and Pseudomonas syringae pv. syringae, two economically important citrus pathogens.
Among these isolates, 25 strains showed strong antifungal activity, with 11 exceeding 80% inhibition of A. alternata. Five isolates also exhibited antibacterial effects, with S4A and S17F demonstrating the highest efficacy. Laboratory assays confirmed that these actinobacteria produced a range of lytic enzymes—including amylase, cellulase, pectinase, and chitinase—each contributing to pathogen suppression.
The study also revealed substantial plant growth-promoting (PGP) traits. All selected isolates produced ammonia, while many also showed capabilities such as nitrogen fixation, phosphate solubilization, siderophore production, ACC-deaminase activity, and IAA synthesis. Notably, isolate S7 significantly enhanced sour orange seed vigor, radicle length, and plumule development.
Chemical profiling of isolate S4A using UHPLC-MS/MS identified pyrrole carboxamide and amicoumacin-related compounds, both known for strong antimicrobial properties. Phylogenetic analysis confirmed that the most effective isolates—S4A, S7, and S17F—were closely related to Streptomyces spp., a genus widely recognized for its bioactive secondary metabolites.
This research highlights the potential of native Iranian Streptomyces strains as powerful biofertilizers and biocontrol agents, offering environmentally friendly alternatives to chemical pesticides and fertilizers. These findings support their potential role in advancing sustainable citrus orchard management.
Reference
Noorizadeh, S., Golmaohamadi, M., Farhangi, M.B. et al. Antibacterial properties and plant growth-promoting effect of actinobacteria obtained from citrus orchards in Iran. J Plant Pathol (2025). https://doi.org/10.1007/s42161-025-02043-5
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