University of Florida biologists studying fungal evolution and ecology have discovered three new truffle species, including one capable of commanding hundreds of dollars per pound within culinary circles.
The researchers describe their discoveries in a study published in the scientific journal Persoonia . Their work shakes up the Morchellaceae truffle family tree, with key insights related to perhaps the most commercially valuable truffle in North America, the Oregon black truffle. Gourmet chefs, who sometimes grate the odoriferous truffle over dishes or infuse butter with it, have been known to pay as much as $800 per pound for the delicacy.
For decades, the Oregon black truffle has been known scientifically as Leucangium carthusianum. It was originally found in Europe and later found in the Pacific Northwest, from California to British Columbia. However, recent genetic testing and field analysis by researchers from UF's Institute of Food and Agricultural Sciences (UF/IFAS) revealed the North American variety is a distinct species. Scientists are giving this newly recognized species a name honoring the Cascadia region in which it is found: Leucangium cascadiense.
"Our paper confirms what a lot of people had suspected for a long time, which is that the North American truffle species is genetically very distinct from its European relatives," said study co-author Benjamin Lemmond, a former UF student.
Lemmond, now a postdoctoral associate at the University of California at Berkeley, began his research into the truffles as a first-year doctoral student studying under professor Matthew Smith of the UF/IFAS plant pathology department. During the COVID-19 pandemic, Lemmond couldn't access the campus greenhouse where he was conducting an experiment, so Smith secured hundreds of dried truffle specimens from Oregon State University for him to study. The stash included slivers of the Oregon black truffle, a dark-colored, potato-shaped species with tiny, pyramid-shaped warts.
When pandemic restrictions relaxed, Lemmond and Smith conducted genetic testing of the Oregon State specimens and others borrowed from Polish, Greek, Italian, French and Japanese collections.
Their tests indicated Oregon black truffles from North America had at one point diverged from their European counterparts on the Morchellaceae evolutionary tree, according to the study. They also established the existence of another distinct and very rare species, Imaia kuwohiensis, a pale-colored truffle with dark warts, which is native to threatened spruce-fir habitats in the southern Appalachian Mountains. Their name for the truffle comes from the Cherokee word for the Great Smoky Mountains' highest peak, Kuwohi.
Field tests followed. The researchers wanted to understand the origin of Oregon black truffles' energy.
"Understanding the fundamental, basic biology and life cycle of this truffle is really important," Lemmond said. "It's a very valuable commodity, and this knowledge might help us to cultivate the truffle in the future. It also supports long-term conservation and management."
Most gourmet truffles are mycorrhizal, meaning they obtain energy from trees, Lemmond said. It had long been suspected that Oregon black truffles obtain energy through a symbiotic relationship with young Douglas fir trees, but no one had conclusively proven it.
Lemmond traveled to the Pacific Northwest and worked with specially trained sniffer dogs capable of detecting truffles buried as deep as 10 inches beneath soil and leaf litter. With the dogs' help, he unearthed Oregon black truffles nestled among Douglas fir stands. He used fluorescent stain that bonded with the fungal tissue, coloring it green to show where the truffle fungus grew between the cells of the tree root tissue.
"The truffle fungi surround the whole root, but the fungus is healthy, and the plant is healthy," Smith said. "The two trade nutrients back and forth."
DNA sequencing of the roots subsequently proved the truffles rely on the trees as their main source of carbon, according to the study.
As the researchers conducted genome sequencing of the Oregon black truffle, they learned of a peculiar find reported by a citizen scientist on iNaturalist, an online science data network: a Leucangium truffle growing among Eastern hemlock trees in Oneida County, New York.
It was the first time anyone had ever reported a Leucangium species in the United States, east of the Rocky Mountains, Lemmond said.
Lemmond contacted Purdue University, which was preserving the specimen, and requested a sample. The truffle's physical characteristics, including its dense external hairs and lack of warts, distinguished it from other Leucangium species. DNA analysis confirmed significant variation, too. The researchers named the new truffle species Leucangium oneidaense to recognize the county where it was unearthed.
A few years later, just before the researchers submitted their study for publication, someone found a second Leucangium oneidaense specimen growing in Massachusetts, Lemmond said.
"It was great timing, and it suggests to me that there are still a lot of undiscovered truffles out there, waiting to be found," he said.
