If the fungi are missing from the soil, plants that depend upon the symbiosis, known as "mycotrophs", will be unable to survive.  In between the extreme forms are facultative mycotrophs, which can survive on their own if the soil is rich in plant nutrients, but need to be mycorrhizal in nutrient poor soils.   

Even if your seed mix includes a diversity of species, the diversity that you see on the project will depend on the presence of mycorrhizal fungi in the soil.  Non-mycotrophic species will do fine if the soil has some fertility, and many such plants are in common use for roadside plantings, mine reclamation, and casual attempts at restoration.  The wheat grasses, widely used in the Great Basin, are representative of such plants.   Facultative mycotrophs can survive in soil with some fertility, but must be mycorrhizal in most conditions.  The obligate and facultative mycotrophs are the plants that appear on an inoculated job but do not appear, or perform poorly, on an uninoculated project.