A truffle is the fruiting body of a subterranean ascomycete fungus, one of the species of the genus Tuber. More than one hundred other genera of fungi are classified as truffles including Geopora, Peziza, Choiromyces, and Leucangium. These genera belong to the class Pezizomycetes and the Pezizales order. Several truffle-like basidiomycetes are excluded from Pezizales, including Rhizopogon and Glomus. Truffles are ectomycorrhizal fungi, so they are found in close association with tree roots. Spore dispersal is accomplished through fungivores, animals that eat fungi. These fungi have ecological roles in nutrient cycling and drought tolerance. Some truffle species are prized as food. Edible truffles are used in Italian, French and other national hautes cuisines. Truffles are cultivated and harvested from natural environments.
Taxonomy
Species
Black
The black truffle or black Périgord truffle (Tuber melanosporum), the second-most commercially valuable species, is named after the Périgord region in France. Black truffles associate with oaks, hazelnut, cherry, and other deciduous trees and are harvested in late autumn and winter. The genome sequence of the black truffle was published in March 2010.
Summer or burgundy
The black summer truffle (Tuber aestivum) is found across Europe and is prized for its culinary value. Burgundy truffles (designated Tuber uncinatum, but the same species) are harvested in autumn until December and have aromatic flesh of a darker colour. These are associated with various trees and shrubs.
White
Tuber magnatum, the high-value white truffle (Italian: tartufo bianco) is found mainly in the Langhe and Montferrat areas of the Piedmont region in northern Italy, and most famously, in the countryside around the cities of Alba and Asti. A large percentage of Italy's white truffles also come from Molise. Truffles are subterranean, highly prized fungi (Italian: diamonds of the earth) that grow on tree roots, often selling for thousands of dollars per pound due to their rarity and intense, savory umami flavour. They are found underground, usually with oak or hazelnut trees, and were historically hunted using pigs, though dogs are now preferred.
Whitish
The "whitish truffle" (Tuber borchii) is a similar species native to Tuscany, Abruzzo, Romagna, Umbria, the Marche, and Molise. It is reportedly not as aromatic as those from Piedmont, although those from Città di Castello are said to come quite close.
Other Tuber A less common truffle is "garlic truffle" (Tuber macrosporum). In the U.S. Pacific Northwest, several species of truffle are harvested both recreationally and commercially, most notably, Leucangium carthusianum, the Oregon black truffle; Tuber gibbosum, Oregon spring white truffle; and Tuber oregonense, Oregon winter white truffle. Kalapuya brunnea, the Oregon brown truffle, has also been commercially harvested and is of culinary note. The Oregon white truffle is increasingly harvested due to its high quality and also exported to other countries. Oregon celebrates its traditional truffle harvesting with a 'truffle festival', combined with culinary shows and wine tastings. The pecan truffle (Tuber lyonii) syn. texense is found in the Southern United States, usually associated with pecan trees. Chefs who have experimented with them agree "they are very good and have potential as a food commodity". Although pecan farmers used to find them along with pecans and discard them, considering them a nuisance, they now sell for about $160 a pound and have been used in some gourmet restaurants.
Beyond Tuber
The term "truffle" has been applied to several other genera of similar underground fungi. The genera Terfezia and Tirmania of the family Terfeziaceae are known as the "desert truffles" of Africa and the Middle East. Pisolithus tinctorius, which was historically eaten in parts of Germany, is sometimes called "Bohemian truffle". Geopora spp. are important ectomycorrhizal partners of trees in woodlands and forests throughout the world. Pinus edulis, a widespread pine species of the Southwest US, is dependent on Geopora for nutrient and water acquisition in arid environments. Like other truffle fungi, Geopora produces subterranean sporocarps as a means of sexual reproduction. Geopora cooperi, also known as pine truffle or fuzzy truffle, is an edible species of this genus.
Rhizopogon spp. are ectomycorrhizal members of the Basidiomycota and the order Boletales, a group of fungi that typically form mushrooms. Like their ascomycete counterparts, these fungi can create truffle-like fruiting bodies. Rhizopogon spp. are ecologically important in coniferous forests where they associate with various pines, firs, and Douglas fir. In addition to their ecological importance, these fungi hold economic value, as well. Rhizopogon spp. are commonly used to inoculate coniferous seedlings in nurseries and during reforestation. Hysterangium spp. are ectomycorrhizal members of the Basidiomycota and the order Hysterangiales that form sporocarps similar to true truffles. These fungi form mycelial mats of vegetative hyphae that may cover 25–40% of the forest floor in Douglas fir forests, thereby contributing to a significant portion of the biomass present in soils. Like other ectomycorrhizal fungi, Hysterangium spp. play a role in nutrient exchange in the nitrogen cycle by accessing nitrogen unavailable to host plants and acting as nitrogen sinks in forests. Glomus spp. are arbuscular mycorrhizae of the phylum Glomeromycota within the order Glomerales. Members of this genus have low host specificity, associating with a variety of plants including hardwoods, forbs, shrubs, and grasses. These fungi commonly occur throughout the Northern Hemisphere. Members of the genus Elaphomyces are commonly mistaken for truffles.
Phylogeny
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