For the first time, scientists have succeeded in cultivating the highly prized white truffle outside of its natural range
By Roman Goergen
The white truffle is one of the most expensive and desired delicacies. A kilo of the highly aromatic and rare fungi can fetch as much as £9,000 at auction.
Unlike it’s close cousin the black or Périgord truffle (Tuber melanosporum), it isn’t commercially cultivated; it only grows wild in a few valleys in northern Italy and the Balkans. Scientists cracked the secret of cultivating black truffles on a commercial scale more than 50 years ago and today more than 90 per cent of those sold are grown in plantations in the south of France, Italy and now Spain.
Truffles form symbiotic relationships with certain tree species, providing minerals and water in exchange for carbon-based nutrients. Scientists cracked the black truffle cultivation conundrum by developing a method of inoculating trees with its spores. However, despite planting more than 500,000 seedlings inoculated with white truffle (T. magnatum) spores, the technique has consistently failed to bear fruit – until recently.
In July, Claude Murat from France’s National Research Institute for Agriculture, Food and Environment (INRAE) in Nancy revealed that his team had managed to grow 26 white truffles in a secret location in Nouvelle-Aquitaine in western France. This was the third consecutive year that they had managed to grow the elusive truffle.
In 2019, three white truffle ascocarps – the technical name for the precious fruit – were dug up at the orchard, along with a few more the following year. It wasn’t until 2021 that the yield was big and consistent enough for the scientists to believe that they had actually cultivated the white truffle. Last summer, Murat penned an article in the French food magazine Le trufficulteur describing how they harvested a total of 26 T. magnatum with a combined weight of 900 grams under 12 of the 52 inoculated trees. A scientific study, published in the journal Mycorrhiza, explains the significance of the find: ‘These truffles were the first confirmed Tuber magnatum ascocarps in a man-made orchard outside the natural geographic range of the species ever harvested. We conclude that harvested ascocarps originated from strains thriving on planted mycorrhized plants instead of natural inoculation by indigenous strains.’
Alessandra Zambonelli at the University of Bologna in Italy has been investigating why it’s so difficult to cultivate white truffles for more than 40 years. ‘In the past in Italy there was some incidental sporadic production at artificial orchards,’ she says. ‘But the production has always been very poor. Most importantly, these areas were so suitable for Tuber magnatum that we cannot exclude that this production occurred naturally, by coincidence.’
This is what makes the success of the team in Nancy so important, because it happened outside of the range of the truffle, which rules out it being an accident. ‘That means we have now confirmation that planting mycorrhized seedlings is the right method for cultivating Tuber magnatum,’ Zambonelli says. ‘This should rekindle interest in cultivation in Italy as well.’
Truffle cultivation requires a thorough understanding of mycorrhiza – the symbiotic association that many fungi form with the root systems of trees. For white truffles, the association is particularly complex. The term was first coined by German biologist Albert Bernhard Frank in 1885 – using the Greek words ‘myco’ for fungus and ‘rhiza’ for root. Frank observed that truffles don’t occur by themselves in nature but are always near beech, oak, hazel or poplar trees. The botanist eventually figured out that this was because of the partnership in which the fungi supplied the trees with essential minerals and the trees provide the truffles with the nutrients they lacked because they were unable to photosynthesise. Today, science has recorded more than 200,000 species of plant that host mycorrhizal fungi.
In the 1970s, botanists in France refined methods to artificially inoculate tree seedlings with fungi. This opened up possibilities to commercially cultivate most species of truffle. Paul Thomas, a mycologist from the University of Stirling who runs a truffle laboratory on the Scottish island of Bute, explains: ‘We introduce the spores of the truffle to the root system of a potted seedling. Over the course of six, seven months, that germinates or starts to grow, and it forms a covering around the root, which is the actual mycorrhiza – that’s the interface. It’s like a gloved hand covering the roots.’
In the potting soil there’s plenty of mycelium, the root-like structure of the fungus itself, consisting of a mass of branching, thread-like hyphae. After another nine to 12 months, the seedling can be transferred from the pot to the orchard. At the orchard itself, everything needs to be done to create perfect conditions for the fruiting bodies, the ascocarps, to form: the correct range of temperatures, the right amount of moisture from rainfall or controlled irrigation, and suitable soil conditions in terms of acidity, humidity and mineral content.
‘We tried a few times with white truffles but we never got far,’ Thomas explains. Even though mycorrhiza sporadically occurred during their attempts, it disappeared quickly.
‘Why it is so difficult with Tuber magnatum is the million-dollar question,’ he says. ‘Unlike with black truffles, where you have obvious links, for white truffles, quite often in a lot of wild areas where you find the fruiting bodies, you don’t find the mycorrhiza that should come with them. And in other areas, where you find the white truffle mycorrhiza, you don’t find the truffles, which suggests to me that their biology is slightly more complex.’
For the truffle industry, time is of the essence. Most orchards in traditional truffle regions, especially those located in the Mediterranean basin, are battling an ongoing decline caused by climate change and severe droughts. To offset that decline and to keep production at a steady level of output, a large number of new seedlings are being planted, increasing irrigation demands in times of water shortage.
‘Globally, we’re planting about 400,000 truffle trees every single year,’ Thomas says. ‘That’s the kind of scale we’re going to need to offset any decline.’
There’s speculation that changing world temperatures could open up new opportunities for farmers in countries that were previously not suitable for certain crops, but as far as truffles are concerned, Thomas points out that getting started is difficult and requires significant financial stamina. That’s why he doesn’t expect new truffle ventures in locations such as Chile or South Africa to be able to make up for projected losses in Europe over the short or mid-term. ‘People who want to plant truffles need to be comfortable with six years with no income until the first fruiting bodies appear,’ he says. ‘Then you’ve got another few years until you’re at good yields. You’re looking at probably 12 years before you have good production.’
This is precisely why truffle entrepreneurs look to scientific projects for help. They rely on these scholars to tell them how they can cultivate the valuable fungus better, faster and more efficiently. Studies such as the one out of Nancy may decide the fate of the industry. Nonethless, Thomas is optimistic, given the progress of Claude Murat and his colleagues. ‘This is like lighting a match in a cave,’ he says. ‘We’ve seen a little light – we can see it works. And now we’ve got to illuminate the rest of the space.’
