An arbuscule is a finely branched fungal structure formed inside a root cortical cell. The plant maintains a membrane around it, creating a specialized interface for exchange. Arbuscules are microscopic and dynamic; they develop and are replaced as the association continues. They are not small roots or structures you can reliably identify with the naked eye.
Keep the context.
Biological compatibility, successful colonisation and a measurable plant response are different questions. The growing conditions matter, and general research is not a promise of a particular result with MegaMyco.
References
Read the biology at its source. These references describe general science and study-specific findings.