Regulation of cannabinoid biosynthetic pathways in Cannabis sativa by arbuscular mycorrhizal fungi: a molecular and phytochemical perspective

Context Arbuscular mycorrhizal fungi (AMF) modulate regulatory pathways and induce the transcription of critical genes involved in plant–microbe interactions. Aims This study investigates the effects of AMF inoculation on Cannabis sativa under varying drought stress levels, focusing on phytochemical and molecular responses. Methods A factorial greenhouse experiment was conducted using Glomus intraradices inoculation and four irrigation regimes (30%, 50%, 70%, and 90% of field capacity (FC)) to evaluate growth, and biochemical and molecular changes. Key results AMF inoculation significantly increased growth parameters, and relative water content (RWC), mitigating the adverse effects of drought stress. Additionally, AMF enhanced total phenolic and flavonoid contents, particularly under moderate drought conditions. The highest total phenolic and flavonoid concentrations were observed in AMF-inoculated plants at 50% and 70% FC respectively. AMF also reduced oxidative stress markers, decreasing hydrogen peroxide content by 13.6% and malondialdehyde contents by 23.4% across compared with non-inoculated plants. Antioxidant enzyme activities, including catalase (CAT), ascorbate peroxidase (APX), guaiacol peroxidase (GPX), and superoxide dismutase (SOD), were significantly enhanced by AMF, contributing to improved stress tolerance. The expression of THCAS was upregulated, particularly in AMF-inoculated plants, whereas CBDAS and OLS expression levels were downregulated, correlating with altered tetrahydrocannabinol (THC) and cannabidiol (CBD) accumulation. AMF inoculation enhanced THC content by up to 11.7% and CBD content by 11.2% compared with non-inoculated plants. Conclusions AMF inoculation enhances drought resilience in cannabis by boosting metabolites, antioxidant defences, and key biosynthetic pathways. Implications AMF inoculation is a promising strategy for improving crop performance, THC, and CBD under water-limited conditions.