Australia’s truffle industry may owe part of its success to a surprising underground secret

Imagine ordering a truffle dish in a fancy restaurant, and you might picture pricey gourmet mushrooms from France or Italy. But recent decades have seen an upstart on the truffle scene. Today, one of the world’s largest producers of some of the most prized truffles, known as French black or Périgord truffles (Tuber melanosporum), isn’t in the Northern Hemisphere at all—it’s Australia.

Since truffles were introduced to Australia some 25 years ago, yields have grown so high that the country is now the top T. melanosporum producer outside of Europe, with more than 11 tons harvested from Australian truffle orchards each year.

New findings suggest that the harvests’ success in the Land Down Under can be explained, at least in part, by what the truffles left behind.The results were published April 3 in the journal Applied and Environmental Microbiology.

Black truffles have been cultivated for centuries in Europe, where the species is native. They were first introduced to Australia in the early 1990s, when growers inoculated oaks and other Northern Hemisphere trees with European truffle spores and sold and planted them around Tasmania, Victoria, New South Wales, and Western Australia.

Since then, the country’s truffle industry has expanded to more than 450 farms producing truffle exports worth some $30–40 million each year.

And while truffle orchards in Europe turn out around 44 pounds of truffles per acre, some truffle orchards in Australia have reported yields up to 20 times greater than that.

How black truffles grow and thrive

“Some orchards have these grapefruit-sized truffles,” said Michigan State University mycologist Gregory Bonito, who has been studying truffles for nearly 25 years.

Truffles are mycorrhizal fungi, a type that grows among the roots of certain trees.

The fungi and tree roots form a symbiotic partnership. Threads of fungus envelop and intertwine with roots, helping them extract nutrients like nitrogen and phosphorus in exchange for some of the sugars the trees produce through photosynthesis.

Truffles are the fruiting bodies that form when the fungi reproduce. But they aren’t the only fungi that live symbiotically with plant roots. Truffles share their underground home with numerous other species of mycorrhizal fungi too.

Digging into the underground community

To find out which species are where, a team led by Bonito and Gian Benucci of MSU’s Department of Plant, Soil and Microbial Sciences analyzed microbial diversity in soils from more than 24 truffle orchards across France, Spain, Italy, and Australia.

At each site, they collected spoonfuls of soil under and around truffle-infected trees, and bagged it for future genetic analysis, collecting some 522 samples over two years.

DNA sequencing revealed 4,415 genetically distinct fungi hidden in Australian soils, versus 6,575 in soils from Europe. For mycorrhizal fungi in particular, Australia’s soils were populated by 75% fewer species.

What’s more, T. melanosporum was more abundant in Australia’s soils compared with Europe’s. In the underground community of symbiotic fungi, it had more of a monopoly.

“This dataset allowed us to use robust models that respect the data’s true story,” said Benucci, who performed the data analyses.

Why Australia’s truffles are booming

The results suggest that one reason black truffles have been able to thrive since they were introduced to Australia is because they left their natural enemies and competitors behind, while those in its introduced range are less effective at putting a brake on their growth, said Bonito, a core member of MSU’s Ecology, Evolution and Behavior program.

Black truffles could owe their success in Australia to other factors as well. “Some people say it could be due to climate factors,” Bonito said. “Other people say it’s because of their water, or how they prune, or some secret formula of their management regime.”

“This research suggests there may be some bigger ecological factors working in their favor as well,” Bonito added.

Future research will focus on analyzing microbial diversity in truffle orchards in North America and other Southern Hemisphere countries, to see if the patterns hold up.

“The first country where black truffles were successfully cultivated outside Europe, in the 1980s, was the U.S.,” Bonito said. “Today there are hundreds of U.S. truffle farmers. However, truffle yields are not as high as in Australia,” Bonito said. These findings could help explain why, he added.