Native PGPR enhance propagation and specialized metabolites in the aromatic and medicinal plant Minthostachys verticillata

The sustainable cultivation of Minthostachys verticillata (peperina), a native Argentine aromatic and medicinal plant of high commercial and conservation value, requires innovative strategies to improve propagation and phytochemical productivity while reducing pressure on wild populations. Plant growth-promoting rhizobacteria (PGPR) represent a promising eco-friendly alternative; however, their effects on propagation and specialized metabolites in this species remain poorly understood. In this study, we evaluated the effects of inoculation with the native rhizobacterial strain Stutzerimonas stutzeri SM33 and the model PGPR strain Pseudomonas simiae WCS417r on propagation, glandular trichome development, phytohormone profiles, phenolic accumulation, expression of genes related to essential oil biosynthesis, and essential oil production in M. verticillata . PGPR inoculation significantly modulated rooting capacity and specialized metabolites, although distinct response patterns were observed between strains. Inoculation with SM33 promoted rooting capacity, glandular trichome density, essential oil accumulation, and pulegone content, suggesting a strong influence on productive traits associated with phytochemical metabolism. Both strains altered the levels of several defense-related phytohormones, particularly jasmonates and SA, whereas ABA levels remained unchanged. In addition, bacterial inoculation modulated the expression of genes involved in monoterpene biosynthesis, supporting the role of PGPR as regulators of metabolic and developmental processes in aromatic plants. Overall, these findings demonstrate that native PGPR represent promising biotechnological tools for improving propagation and phytochemical productivity in M. verticillata , contributing to the development of sustainable cultivation strategies for aromatic and medicinal plants.