I found a study on

The Effects of Mycorrhizal Fungi Inoculum on Potato Yield

Even though the yield was slightly greater in the non-inoculated bed, the spuds were not choice in appearance. I will personally continue to work with mycorrhizal fungi plant inoculum in the future, focusing on its application in new beds and soils that may be nutrient poor.  I would caution the home gardener that if they are interested in pursuing this avenue of investigation, to purchase inoculum from a reputable source and do your homework first.  Scientific analysis has shown that many of the ‘over the counter’ products that claim to contain live mycelium, do not in fact live up to that promise.

I have seen the beneficial effects of Mycorrhizal Fingi on a number of root crops.
The the study above the yield was not greater but high calorie gardening is all about calories consumed. The treated spuds would have yielded less waste in processing for cooking.