I have never heard of inoculating mycorrhizal fungi as that is pretty much present everywhere. Legumes however, have symbiotic relationships with nitrogen fixing bacteria. Once present in the soil, new crops will take them up and form root nodules to house them. Getting the correct inoculant for your legume ( each legume species has a specific bacteria species it pairs with ) is a good idea if you haven't done so before and your soil doesn't naturally contain the correct bacteria already.
I have had good results with green soybeans ( edemame ). My first crop had no root nodules, and so I inoculated the second crop and have had good nodulation and better yield since. Pull up a plant and look at the roots and if there are no nodules ( largish knot or ball like structures ) in the roots, then inoculating may help.
Of course, if there is already plenty of nitrogen in the soil ( because you are adding fertilizer ), inoculating probably won't make any difference. I have read studies that say the plants only cultivate the bacteria when they need some more nitrogen than they are getting from the soil.
Note that black/raspberry bushes are not legumes.