why cannot mycorrhiza be at eutrophic soil and why it cannot be present at oligotrophic soil as it is also rich in nutrients.

Hai Varun,
Fungi is an special type of living organisms,
They prefer marshy environment and utilize dead and decaying material as food.
In eutrophic soil upper layers receive more sunlight and less mineral and decaying nutrients are present.
Oligotrophic soil ( in between layers) have the above mentioned requiremets in good quantities.
Thus the fungi preferthe oligotrophic soil for their survival that eutrophic soil.
The roots often decay and absorb water becomemore marshy,also secrete lots of chemical secretions to attract bacterial and fungal biota for symbiotic process.
All the baoev properties favout the oligotrophic presencer
More is the aeration more is their spreading in the soil.
Hope the doubt is clarified