This research investigates how a beneficial soil fungus that forms partnerships with plants maintains genetic diversity within individual fungi. The study reveals that these fungi have a complex and dynamic genetic organization that can change depending on which plant they interact with. This has important implications for agriculture and ecosystem health. Impacts on everyday life: – Better understanding of how beneficial fungi help plants grow could lead to improved crop yields – Insights into plant-fungal partnerships could help develop more sustainable farming practices – Knowledge of fungal genetics could help select better fungal strains for specific crops – Understanding these relationships helps explain how plants and fungi have co-evolved successfully for millions of years – Could lead to reduced need for chemical fertilizers in agriculture