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''Tuber oregonense'', commonly known as the Oregon white truffle, is a species of edible
truffle A truffle is the fruiting body of a subterranean ascomycete fungus, predominantly one of the many species of the genus ''Tuber''. In addition to ''Tuber'', many other genera of fungi are classified as truffles including '' Geopora'', '' Pe ...
in the genus ''
Tuber Tubers are a type of enlarged structure used as storage organs for nutrients in some plants. They are used for the plant's perennation (survival of the winter or dry months), to provide energy and nutrients for regrowth during the next growin ...
''. Described as new to science in 2010, the North American species is found on the western coast of the United States, from northern California to southern
British Columbia British Columbia (commonly abbreviated as BC) is the westernmost province of Canada, situated between the Pacific Ocean and the Rocky Mountains. It has a diverse geography, with rugged landscapes that include rocky coastlines, sandy beaches, ...
west of the Cascade Range. A mycorrhizal fungus, it grows in a symbiotic association with Douglas fir. It overlaps in distribution with the closely related '' T. gibbosum'', but they have different growing seasons: ''T. oregonense'' typically appears from October through March, while ''T. gibbosum'' grows from January to June. The
fruit bodies The sporocarp (also known as fruiting body, fruit body or fruitbody) of fungi is a multicellular structure on which spore-producing structures, such as basidia or asci, are borne. The fruitbody is part of the sexual phase of a fungal life cyc ...
of the fungus are roughly spherical to irregular in shape, and resemble small potatoes up to in diameter. Inside the truffle is the
gleba Gleba (, from Latin ''glaeba, glēba'', "lump") is the fleshy spore-bearing inner mass of certain fungi such as the puffball or stinkhorn. The gleba is a solid mass of spores, generated within an enclosed area within the sporocarp. The contin ...
, which is initially white before it becomes a marbled
tan Tan or TAN may refer to: Businesses and organisations * Black and Tans, a nickname for British special constables during the Irish War of Independence. By extension "Tans" can now also colloquially refer to English or British people in general, es ...
color. The large, often thick-walled, and strongly ornamented spores are produced in large spherical asci. The truffle is highly prized for its taste and aroma. Some individuals have claimed success in cultivating the truffles in Christmas tree farms.


Taxonomy and phylogeny

The species was first officially described and named in a 2010 ''
Mycologia ''Mycologia'' is a peer-reviewed scientific journal that publishes papers on all aspects of the fungi, including lichens. It first appeared as a bimonthly journal in January 1909, published by the New York Botanical Garden under the editorship of ...
'' article, although ''T. oregonense'' had been previously used provisionally (as ''Tuber oregonense'' Trappe & Bonito) in American
field guide A field guide is a book designed to help the reader identify wildlife (flora or fauna) or other objects of natural occurrence (e.g. rocks and minerals). It is generally designed to be brought into the "field" or local area where such objects exi ...
s and other popular publications for several years. The
type specimen In biology, a type is a particular specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally attached. In other words, a type is an example that serves to anchor or centralizes th ...
was collected from
Benton County, Oregon Benton County is one of the 36 counties in the U.S. state of Oregon. As of the 2020 census, the population was 95,184. Its county seat is Corvallis. The county was named after Thomas Hart Benton, a U.S. Senator who advocated American contr ...
, on 3 February, 2007 along U.S. Route 20 in Oregon. The specific epithet ''oregonense'' derives from the name
Oregon Oregon () is a state in the Pacific Northwest region of the Western United States. The Columbia River delineates much of Oregon's northern boundary with Washington, while the Snake River delineates much of its eastern boundary with Idaho. T ...
and the
Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...
suffix -''ense'' (relating to), in reference to western Oregon being its central region of abundance. The fungus is commonly known as the Oregon white truffle. Truffle authority James Trappe initially intended to name the species as a
variety Variety may refer to: Arts and entertainment Entertainment formats * Variety (radio) * Variety show, in theater and television Films * ''Variety'' (1925 film), a German silent film directed by Ewald Andre Dupont * ''Variety'' (1935 film), ...
of ''T. gibbosum'' (i.e., as ''Tuber gibbosum'' var. ''oregonense'') before molecular analysis revealed that genetic differences warranted distinction at the species level. ''Tuber oregonense'' is part of the ''gibbosum'' clade of the genus ''
Tuber Tubers are a type of enlarged structure used as storage organs for nutrients in some plants. They are used for the plant's perennation (survival of the winter or dry months), to provide energy and nutrients for regrowth during the next growin ...
'', which contains species that have "peculiar wall thickenings on hyphal tips emerging from the peridial surface at maturity."


Description

The
fruit bodies The sporocarp (also known as fruiting body, fruit body or fruitbody) of fungi is a multicellular structure on which spore-producing structures, such as basidia or asci, are borne. The fruitbody is part of the sexual phase of a fungal life cyc ...
of ''T. oregonense'' are hypogeous (growing in the ground), typically broad, although specimens up to have been recorded. Smaller specimens are spherical or nearly so, and have random furrows; larger specimens are more irregular in shape, lobed and deeply furrowed. Young fruit bodies have a white
peridium The peridium is the protective layer that encloses a mass of spores in fungi. This outer covering is a distinctive feature of gasteroid fungi. Description Depending on the species, the peridium may vary from being paper-thin to thick and rubbe ...
, as the truffle matures it develops red to reddish-brown or orangish-brown patches; with age it becomes orange-brown to reddish-brown overall and often develops cracks on the surface. The peridium is 0.2–0.4 mm thick, and the surface texture ranges from relatively smooth to covered with tiny "hairs" that are more dense in the furrows, and more scattered on the exposed lobes. The
gleba Gleba (, from Latin ''glaeba, glēba'', "lump") is the fleshy spore-bearing inner mass of certain fungi such as the puffball or stinkhorn. The gleba is a solid mass of spores, generated within an enclosed area within the sporocarp. The contin ...
is solid; in youth the fertile tissue is whitish and marbled with mostly narrow, white, hypha-stuffed veins that emerge throughout the peridium to its surface. In maturity, the fertile tissue is light brown to brown from the color of the spores, but the marbling veins remain white. The odor and flavor of the flesh are mild in youth, but soon become strong, pungent and complex, or "truffly". left, A two-spored ascus; the ellipsoid spores have a honeycomb-like surface network ornamented with numerous spikes. The spores are ellipsoid to somewhat spindle-shaped with narrowed ends, and light brownish in color. The size of the spores varies depending upon the type of asci in which they develop: in one-spored asci they measure 42.5–62.5 by 17.5–30 µm; in two-spored asci they are 32.5–50 by 15–25 µm; in three-spored asci they are 27.5–45 by 15–25 µm; in four-spored asci they are 25–38.5 by 13–28 µm; in five-spored asci 28–34 by 22–25 µm (all sizes excluding surface ornamentation). The spore walls are 2–3 µm thick and are covered with a honeycomb-like (
alveolate The alveolates (meaning "pitted like a honeycomb") are a group of protists, considered a major clade and superphylum within Eukarya. They are currently grouped with the stramenopiles and Rhizaria among the protists with tubulocristate mitochon ...
) network. The cavities of the honeycomb typically have five or six sides, and the corners form spines that are 5–7 µm tall by 0.5 µm thick. A "microreticulum" appears in some spores when the light microscope
objective Objective may refer to: * Objective (optics), an element in a camera or microscope * ''The Objective'', a 2008 science fiction horror film * Objective pronoun, a personal pronoun that is used as a grammatical object * Objective Productions, a Brit ...
is focused on the optical cross section but not on the spore wall surface, or on scanning electron microscopy micrographs of the surface. Young asci range in shape from spherical to broadly ellipsoid to ovoid (egg-shaped) or pyriform (pear-shaped); sometimes the base of the ascus is narrowed like a stipe, and measures up to 15 by 7 µm. Mature asci are spherical to broadly ellipsoid or misshapen from the pressure of crowded spores within. They are hyaline (translucent), thin-walled, 60–85 by 65–75 µm, 1–4-(occasionally 5)-spored, and astipitate (without a stipe) at maturity. The peridiopellis (the cuticle of the peridium) is 200–300 µm thick plus or minus 80 µm of tightly interwoven hyphae that are 3–5 (sometimes up to 10) µm broad. The cells are short and have nearly hyaline walls that measure 0.5–1 µm thick; the interior veins emerge through the peridium the cells and often form a localized tissue of rounded cells up to 12 µm broad. The degree to which the surface is covered with fine "hairs" is variable; these hairs are made of tangled hyphae and emergent thin-walled hyphal tips 2–5 µm in diameter, some even and smooth, some with
granulated Granulation is the process of forming grains or granules from a powdery or solid substance, producing a granular material. It is applied in several technological processes in the chemical and pharmaceutical industries. Typically, granulation invo ...
surfaces and some with moniliform walls (resembling a string of beads) that are irregularly thickened by hyaline bands that are 0.5–2 µm wide. The subpellis (the tissue layer immediately under the pellis) is abruptly differentiated from the pellis, 150–220 µm thick, and comprises interwoven, nearly hyaline, thin-walled hyphae 2–10 µm wide with scattered cells up to 15 µm wide. The gleba is made of hyaline, thin-walled, interwoven hyphae that are 2–7 µm broad with scattered cells that are inflated up to 15 µm.


Similar species

200px, ''T. gibbosum'' is very similar in appearance, but is harvested in a different season. ''Tuber oregonense'' closely resembles ''T. gibbosum'', which grows in the same habitats, but may be distinguished by the structure of its peridium, and differences in spores size and shape. Further, ''T. gibbosum'' grows from January to June.Trappe ''et al.'', (1997). pp. 102–103. Another similar species in ''Elaphomyces granulatus''.


Edibility

''Tuber oregonense'' is a choice
edible An edible item is any item that is safe for humans to eat. "Edible" is differentiated from "eatable" because it does not indicate how an item tastes, only whether it is fit to be eaten. Nonpoisonous items found in nature – such as some mushroo ...
species. Its odor has been described as "truffly", a complex of garlic, spices, cheese, and "indefinable other essences"; the fungus is prized by commercial truffle harvesters and consumers for its intense fragrance.Trappe ''et al''., (1997). pp. 106–107. Because they grow in the topsoil and needles, they are considered to have a more "floral" and "herbal" flavor profile than related European truffles.


Ecology, habitat, and distribution

Like all ''Tuber'' species, ''T. oregonense'' is mycorrhizal. The fungus grows west of the
Cascade Mountains The Cascade Range or Cascades is a major mountain range of western North America, extending from southern British Columbia through Washington and Oregon to Northern California. It includes both non-volcanic mountains, such as the North Cascades, a ...
from the southern
Puget Sound Puget Sound ( ) is a sound of the Pacific Northwest, an inlet of the Pacific Ocean, and part of the Salish Sea. It is located along the northwestern coast of the U.S. state of Washington. It is a complex estuarine system of interconnected ma ...
region of
Washington Washington commonly refers to: * Washington (state), United States * Washington, D.C., the capital of the United States ** A metonym for the federal government of the United States ** Washington metropolitan area, the metropolitan area centered o ...
, south to southwestern Oregon at elevations from near sea level up to in pure stands of ''
Pseudotsuga menziesii The Douglas fir (''Pseudotsuga menziesii'') is an evergreen conifer species in the pine family, Pinaceae. It is native to western North America and is also known as Douglas-fir, Douglas spruce, Oregon pine, and Columbian pine. There are three va ...
'' forests up to 100 years old, or ''
Pseudotsuga ''Pseudotsuga'' is a genus of evergreen coniferous trees in the family Pinaceae (subfamily Laricoideae). Common names for species in the genus include Douglas fir, Douglas-fir, Douglas tree, Oregon pine and Bigcone spruce. '' Pseudotsuga menz ...
'' mixed with ''
Tsuga heterophylla ''Tsuga heterophylla'', the western hemlock or western hemlock-spruce, is a species of hemlock native to the west coast of North America, with its northwestern limit on the Kenai Peninsula, Alaska, and its southeastern limit in northern Sonom ...
'', ''
Picea sitchensis ''Picea sitchensis'', the Sitka spruce, is a large, coniferous, evergreen tree growing to almost tall, with a trunk diameter at breast height that can exceed 5 m (16 ft). It is by far the largest species of spruce and the fifth-larg ...
'', or ''
Alnus Alders are trees comprising the genus ''Alnus'' in the birch family Betulaceae. The genus comprises about 35 species of monoecious trees and shrubs, a few reaching a large size, distributed throughout the north temperate zone with a few sp ...
'' species. The species has been commercially harvested in the Pacific Northwest since the 1980s. and is often found in Christmas tree plantations as young as five years. The Oregon Truffle Festival, held in Eugene yearly since 2006 to coincide with the maturing of the truffle in late January, features activities such as cultivation seminars and truffle hunting excursions. Fruit bodies are produced from September through the middle of March. The fungus is an important component of the diet of
northern flying squirrel The northern flying squirrel (''Glaucomys sabrinus'') is one of three species of the genus '' Glaucomys'', the only flying squirrels found in North America.Walker EP, Paradiso JL. 1975. ''Mammals of the World''. Baltimore: Johns Hopkins Universit ...
s, and comprises the majority of their diet at certain times of the year. Some individuals have claimed to have had success in growing the truffles in Christmas tree farms in Oregon. Techniques reportedly involve inoculating the ground under young Douglas fir trees with a slurry comprising ground-up truffles mixed in water, or the feces of animals fed truffles, but no concrete evidence shows these methods can be used to establish new truffle patches or to improve the productivity of existing patches.


References


Cited texts

* *


External links

*
North American Truffling Society
Side-by-side comparison of ''T. oregonense'' and ''T. gibbosum'' {{Taxonbar, from=Q7850818 Fungi described in 2010 Fungi of North America Oregon culture Truffles (fungi) oregonense