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Mycorrhizal fungi

Hannah Shafer

By Hannah Shafer



Under our feet lies a vast network of mycelium, invisible to the human eye. These aren’t the type of fungi you can harvest and eat, but they are vital in bolstering soil and plant health. Mycorrhizal fungi form symbiotic relationships with approximately 80% of land plants, and encouraging this association benefits many crops.


The largest plant benefit of this symbiosis comes in the form of assistance with nutrient acquisition. At the plant-fungus interface, the plant donates carbohydrates to the fungus, while the fungus provides otherwise unavailable nutrients to the plant. The fungal network acts as an extension of the roots to increase the soil area that the plant can physically reach and also helps break down nutrients that the plants may not usually absorb. This can lead to better crop yields and hardier plants in the face of pest or pathogen threats.


For most crop symbioses, the mycorrhizal fungi involved are called “arbuscular” or “endomycorrhizal,” where the fungus enters plant root cells and fills the cellular space with structures called arbuscules, where the nutrient exchange occurs. About 2% of plants – mostly woody shrubs and trees – form relationships with “ectomycorrhizal” fungi, which do not enter plant cells but instead form a net around the space between cells to facilitate nutrient exchange. Some crops, including brassicas and amaranth family members (e.g., spinach and beets), do not form associations with mycorrhizal fungi, or the associations are not beneficial. Therefore, both crop type and fungus type are important to consider.


Overall, the field of study around mycorrhizal fungi is relatively new. They were first discovered in the late 1880s; the distinction between “endo-” and “ecto-” mycorrhizae came in the 1920s, and the first watershed publication on the symbiosis came in the 1950s. However, it wasn’t until the late 1990s and early 2000s that researchers really started understanding their role in ecosystems and how they function. It is now known that there are many types of mycorrhizal associations beyond “endo-” and “ecto-” and there are thousands of fungal species that bear the title “mycorrhizal.” 


Growers interested in bolstering soil health through beneficial microbes, there are a few ways to encourage mycorrhizal growth. Commercially available powdered or liquid fungal inoculants are available. Inoculated potting soil is growing in popularity, and there are many online recipes for DIY mycorrhizal fungi propagation. Other effective methods for naturally promoting a healthy rhizosphere with mycorrhizal fungi include minimizing tillage and not over-applying fertilizers. These simple steps will improve both plant and soil health in the long term.


Hannah (she/her) is a plant biology graduate student at the University of Vermont. Before starting her graduate studies, she worked on several small farms throughout the Northeast, where she fell in love with plants and growing good food. She is currently an avid gardener and aspiring farmer.



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Photo Credit: Whole Systems Design, VT

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