The present invention relates to a method and a system for the production of arbuscular mycorrhizal fungi (AMF). More specifically, the invention described herein relates to a method and a system for the continuous in vitro culture of arbuscular mycorrhizal fungi, preferably including steps of harvesting and/or passaging. Further, the invention relates to culture conditions suitable for said continuous cultivation method and system. Another aspect of the invention is a sterile inoculum comprising AMF-colonized root material and other propagules, like AMF spores. Yet another aspect of the invention relates to the use of AMF-colonized root material for continuous production of arbuscular mycorrhizal fungi material in liquid culture medium.