Cultivating AM Fungi

Though glomeromycotan fungi cannot be grown in pure culture, they can be studied on a petri dish by inoculating the roots of plants such as carrots. These roots (and their associated AM fungi) can be trimmed and transferred many times across petri dishes (or other containers) hosting the correct nutrient medium. This more technical approach to cultivating AM fungi is used by researchers studying the many fine-grain details of the AM symbiosis.

The International Collection of Vesicular Arbuscular Mycorrhizal Fungi (INVAM) has a storied history, based at the West Virginia University, has a collection of 900 isolates of AMF from around the world. On the INVAM website, a detailed protocols are provided for growing AM fungi for research purposes – such as to compare infection rates of a fungus in a plant species, to compare nutrient uptake rates between plant-fungus pairings and different environmental and soil conditions, or to observe how a fungus influences the effects of root pathogens or root-feeding nematodes. The techniques are also used to cultivate a fungus on plant roots to simply perpetuate that culture and to ensure that its vigor and health is maintained.

Practical techniques for propagating AM crop inoculum have also been developed by the Rodale Institute to support land managers wishing to increase the abundance and diversity of AM fungi in their soil. In essence, a source of inoculum (e.g. a commercial AM product or field collected soil) is introduced while transplanting malnourished grass seedlings to large pots filled with low nutrient soil. After months of low fertilization, the fungi will sporulate in the pot, after which point the roots, mycelium, and spores can be collected and stored to use as a planting amendment the following season. This methods thus creates an abundance of local, place-based, and fresh AM inoculum at a fraction of the cost of a commercial product and potentially with greater effectiveness. It is this method that we are using in the Farming with Fungi project.