I have no knowledge about how the seed production is done in the USA and I'm wondering whether the microbiome of the commercial corn seeds is worth to study or is not as diverse due to the production process.
There are a lot of commercial seed treatments but these are largely based on fungicides and insecticides. There is interest in utilizing mycorrhizal fungi which will be stimulated through elicitor compounds but this just starting. The vast majority of hybrid maize is seed treatment with synthetic toxic chemistry.