Characterization of bacterial endophytes isolated from <i>Cannabis sativa</i> L. and <i>Chelidonium majus</i> L. for their application as biostimulants and biocontrol agents

Endophytic bacteria contribute to plant growth, stress tolerance, and pathogen resistance. Their effective use in agriculture requires the identification of strains that combine multiple beneficial traits with consistent performance across different field conditions. Accordingly, this study examines <i>Bacillus</i> and <i>Pseudomonas</i> endophytes isolated from <i>Cannabis sativa</i> L. and <i>Chelidonium majus</i> L. for plant growth promotion, abiotic stress tolerance, and biocontrol properties. Plant growth-promotion traits included indole, siderophore, and organic acid production, phosphate and zinc solubilization, and biofilm formation. Results showed that all the tested bacterial isolates produced indoles, with the highest levels recorded in <i>Pseudomonas</i> strain PPW-26, whereas several <i>Pseudomonas</i> strains exhibited strong siderophore production. Strain PPW-26 tested positive for methyl-red, indicating organic acid production, whereas other <i>Pseudomonas</i> strains tested negative. Moderate to high nutrient solubilization profiles were observed across all <i>Pseudomonas</i> strains. <i>Bacillus</i> strains, particularly BS-114, exhibited higher biofilm formation relative to <i>Pseudomonas</i>. Assessment of abiotic stress tolerance included proline accumulation, superoxide dismutase activity, and growth under varying temperature, salinity, and drought conditions. All strains displayed tolerance to the tested stresses, with <i>Bacillus</i> strains showing stronger resilience to high temperature and salinity, accompanied by elevated proline accumulation and superoxide dismutase activity in selected strains. Biocontrol potential was evaluated through biosurfactant production and antifungal activity. <i>Bacillus</i> strains showed high biosurfactant activity and strong inhibition of fungal pathogens. Strain BS-120 exhibited broad-spectrum inhibition against <i>Fusarium oxysporum</i>, <i>Fusarium graminearum</i>, and <i>Rhizoctonia solani</i>-AG3. Analysis of genome sequences identified biosynthetic gene clusters encoding antifungal metabolites, including fengycin and surfactin, consistent with the observed inhibition. Genome-wide similarity analysis and ANI-based clustering revealed the presence of highly similar and genetically distant strains within each genus. For <i>Bacillus</i> spp., ANI values ranged from 87.62% to 98.83%, whereas for <i>Pseudomonas</i> spp. they ranged between 83.91% and 99.99%, confirming the presence of substantial intra-genus diversity. Phylogenetic analysis showed well-supported clades consistent with ANI clustering. Overall, this study demonstrates that endophytic <i>Bacillus</i> and <i>Pseudomonas</i> strains exhibit complementary and strain-dependent traits associated with plant growth promotion, stress tolerance, and pathogen suppression, supporting their further evaluation as potential bioinoculants for sustainable agriculture.