Fungi as a source of food

Since ancient times, humans have used fungi as food sources ( 1 , 2 ). The edible sexual structures of basidiomycetes and ascomycetes (e.g., truffles), the so-called mushrooms, are produced mostly in wood because many fungi are tree symbionts or decayers of tree tissues. These fruiting bodies represent a rich source of proteins, with low fat content and otherwise nutritionally quite poor. In some soils, they accumulate pollution (heavy metals and radioactivity) and should only be eaten in moderate quantities. Some mushroom species are considered delicacies (e.g., truffles, boletus, morels), but cultivation attempts have been unsuccessful, with a few exceptions (e.g., Morchella rufobrunnea). Only a few saprobic species can be industrially produced, such as Agaricus bisporus ( 3 ), Lentinus edodes (shiitake), and Pleurotus ostreatus, with production having mainly taken place in Asia for thousands of years ( 4 ). Some other fungi, while not really cultured, are inoculated on trees grown in appropriate natural habitats to increase the production of fruiting bodies, such as for shiitake and oyster mushrooms, with, however, sometimes unpredictable success, as is the case for truffles ( 5 )