Cannabis flower crude extracts as belowground infochemicals shaping the chemotactic responses of parasitic nematodes

The widespread use of synthetic pesticides has raised concerns about their impacts on soil biodiversity and ecosystem functioning, increasing interest in plant-derived compounds as environmentally compatible alternatives. Cannabis sativa L. produces a diverse array of secondary metabolites, including cannabinoids and terpenes, which may act as chemical cues in belowground ecological interactions. This study examined the chemotactic responses of five nematode species - Heterorhabditis bacteriophora (Poinar), Steinernema carpocapsae (Weiser), Steinernema feltiae (Filipjev), Oscheius myriophilus (Poinar), and Phasmarhabditis papillosa (Schneider)- to various concentrations of crude flower extracts of C. sativa. Chemotaxis assays were conducted using an agar-based system, and nematode responses were quantified as overall motility and Chemotaxis Index (CI). Cannabinoid and terpene profiles were determined by HPLC-UV/DAD and GC-MS. Nematode species identity and extract concentration were the primary factors influencing motility and chemotactic behaviour, whereas chemotype extract identity had a minor effect. H. bacteriophora, S. feltiae, and P. papillosa showed positive chemotactic responses (higher CI values) in a species- and concentration-dependent manner, whereas S. carpocapsae and O. myriophilus exhibited mostly neutral responses. Chemotactic behaviour was strongly species-specific and concentration-dependent, with extract identity playing a minor role.