Characterization and application of native Patagonian rhizobacteria to improve clonal performance and growth in Cannabis sativa L

Background The increasing global demand for medicinal Cannabis sativa L. has intensified the need for sustainable agronomic practices capable of supporting high yields and consistent phytochemical profiles. Plant growth-promoting rhizobacteria (PGPR) represent a promising alternative to chemical fertilizers, yet their application in cannabis cultivation remains largely unexplored. In this study, 51 bacterial isolates obtained from Patagonian soils were characterized for key plant growth–promoting (PGP) traits, including nitrogen fixation, phosphate solubilization, siderophore production, indole-3-acetic acid (IAA) synthesis, and amylolytic and proteolytic activities. Then, ten representative strains were selected for in vivo assays to evaluate their ability to increase C. sativa clone survival, root colonization, and plant growth. Clones of 21 days were randomly selected from each treatment for optical and electron microscopic examination of roots. Finally, Seeds of Cannabis sativa were inoculated with four selected plant growth-promoting (PGP) bacterial. Results The isolates exhibited substantial inter- and intraspecies variability in their PGP profiles, as revealed by multivariate analysis. Several strains—including Pantoea agglomerans M4C1, Bacillus sp. AM10, Pseudomonas sp. M4C3’, and Microbacterium sp. M5C1—significantly improved clone establishment and root development. Moreover, compared with no inoculation, inoculation of seeds with selected isolates increased plant height by 12–16%, confirming their biofertilizer potential. Notably, both endophytic and nonendophytic strains effectively promoted plant growth, indicating multiple modes of action. Conclusions Overall, our findings demonstrate that native Patagonian rhizobacteria can increase early propagation and vegetative growth of C. sativa , offering an environmentally sustainable strategy to reduce reliance on synthetic fertilizers. This work provides a foundation for the development of microbial inoculants tailored to cannabis cultivation and highlights the importance of integrating microbial biotechnology into the expanding medicinal cannabis sector.