Truffles hide underground and rely on hungry animals to spread their spores
A truffle cannot use wind or rain to scatter its spores, because it fruits below the soil. Instead, when ripe, it releases a smell that draws squirrels, voles, deer and people. Its thick-walled spores survive the trip through an animal's gut, much as seeds survive inside fruit.
True truffles are the underground fruiting bodies of Tuber fungi, though more than a hundred other genera are also called truffles. They live as partners of tree roots such as oak, hazel, beech and pine, trading nutrients for sugars; many have lost the enzymes needed to break down plant matter and cannot survive without a host. Some trees depend on them in return, and truffle fungi help oak woodlands establish. The word likely comes via Vulgar Latin from tuber, a lump or swelling.
The underground habit evolved again and again. Within one fungal order it arose independently at least fifteen times, and it appeared separately among mushroom-forming groups as well, probably favoured in dry environments. Most lineages descend from ordinary above-ground mushrooms whose stalks shrank and whose caps closed over the spore tissue. The oldest fossils of this root-partner lifestyle come from Eocene chert in the Okanagan Highlands about 50 million years old, though molecular clocks suggest it began around 130 million years ago.
Italians call them diamonds of the earth, and prices can reach thousands of dollars per pound. The white truffle, Tuber magnatum, comes mainly from Piedmont around Alba and Asti, with much of Italy's supply also from Molise. The black Périgord truffle, whose genome was published in 2010, is harvested in late autumn and winter. Pigs were the traditional hunters, but dogs are now preferred.
Other regions have their own. Oregon harvests black and white species and holds a truffle festival. In the southern United States, pecan farmers once threw away the truffles they dug up; these now sell for about 160 dollars a pound. North America's flying squirrels eat truffles as a main food, finding them by smell and remembering productive spots.
Source: Truffle
