Plant growth-promoting bacteria in forestry seedling production: a sustainable biotechnological approach for resilient silviculture

Plant growth-promoting bacteria (PGPB) have emerged as a promising biotechnological tool for enhancing forest seedling production and supporting sustainable silvicultural systems. The objective of this review was to synthesise current knowledge on the mechanisms of action, functional diversity, inoculation strategies, physiological and molecular responses, limitations and future perspectives of PGPB in forestry, with emphasis on their contribution to climate-resilient and sustainable forest production systems. A systematic literature review was conducted using major scientific databases, covering studies from 1947 to 2026, integrating foundational concepts with recent advances in microbial biotechnology. The results indicate that PGPB promote plant growth through multiple complementary mechanisms, including biological nitrogen fixation, phosphate solubilisation, phytohormone production, siderophore synthesis and induction of systemic resistance. These processes enhance nutrient acquisition, improve root architecture, and increase plant tolerance to abiotic and biotic stresses. At the biochemical level, PGPB activate antioxidant defense systems, reducing reactive oxygen species accumulation through enzymes such as superoxide dismutase, catalase and peroxidases. At the molecular level, plant–bacteria interactions modulate gene expression, hormonal signaling pathways and epigenetic regulation, contributing to stress adaptation and potential stress memory formation. In forestry systems, PGPB have demonstrated significant potential to improve seedling quality, rooting efficiency and biomass accumulation in both seed-propagated and clonally propagated species. Advances in inoculation strategies, including seed, root, soil, foliar and endophytic applications, have expanded their applicability. Furthermore, interactions between PGPB and mycorrhizal fungi are increasingly recognised as key components of plant microbiome assembly and ecosystem functioning. Despite these advances, challenges remain regarding strain selection, formulation stability, field performance consistency and large-scale application. Overall, PGPB represent a strategic component in the transition toward biologically based forestry systems, contributing to reduced chemical inputs, improved resource-use efficiency, and enhanced resilience of forest plantations under changing environmental conditions.