One of the world’s most expensive ingredients, the Périgord black truffle (Tuber melanosporum) has been successfully cultivated in Britain.
Researchers from the University of Cambridge and Mycorrhizal Systems Ltd (MSL) have confirmed this is the farthest north that the species has ever been found.
It was grown as part of a programme in Monmouthshire, South Wales, run by MSL in collaboration with local farmers – and the results suggest that truffle cultivation may be possible in many parts of the UK.
After nine years of waiting, the truffle was harvested in March 2017 by a trained dog named Bella. The aromatic fungus was growing within the root system of a Mediterranean oak tree that had been treated to encourage truffle production.
Further microscopic and genetic analysis confirmed it to be a Périgord black truffle, which can be worth up to £1,700 per kilogram.
Prized for their intense flavour and aroma, black truffles are difficult and time-consuming to grow and harvest. They are normally confined to regions with a Mediterranean climate.
However, their usual Mediterranean habitat has been affected by drought due to long-term climate change, according to the university.
Yields are falling but demand around the world is high and the truffle industry is projected to be worth £4.5 billion annually in the next 10-20 years.
Black truffles grow below ground in a symbiotic relationship with the root system of trees in soils with high limestone content. They are found mostly in northern Spain, southern France and northern Italy, where they are sniffed out by trained dogs or pigs.
They can form naturally, however many truffles are cultivated by inoculating oak or hazelnut seedlings with spores and planting them in chalky soils.
But even through careful cultivation, there is no guarantee truffles will grow.
“It’s a risky investment for farmers – even though humans have been eating truffles for centuries, we know remarkably little about how they grow and how they interact with their host trees,” said Ulf Büntgen of Cambridge’s Department of Geography.
“Since the system is underground, we can’t see how truffles are affected by different environmental conditions, or even when the best time to water them is. There’s been no science behind it until now, so progress is slow.”
In partnership with local farmers, Dr Paul Thomas from MSL and the University of Stirling has been cultivating truffles in the UK for the past decade.
In 2015, MSL successfully cultivated a UK native Burgundy truffle, but this is the first time the more valuable black Périgord truffle has been cultivated in such a northern and maritime climate.
Its host tree is a Mediterranean oak that was planted in 2008. Before planting, the tree was inoculated with truffle spores and the surrounding soil was made less acidic by treating it with lime.
“This is one of the best-flavoured truffle species in the world and the potential for industry is huge,” said Thomas. “We planted the trees just to monitor their survival, but we never thought this Mediterranean species could actually grow in the UK – it’s an incredibly exciting development.”
The researchers have attributed the fact that black truffles are able to grow so far outside their native Mediterranean habitat to climate change.
“Different species respond to climate change on different scales and at different rates, and you often get an ecological mismatch,” adds Büntgen.
“For instance, insects can move quickly, while the vegetation they depend on may not. It’s possible that truffles are one of these fast-shifting species.”
This cultivation has shown that the climatic tolerance of truffles is much broader than previously thought, adds Thomas.
“While truffles are a very valuable crop, together with their host trees, they are also a beneficial component for conservation and biodiversity.”
The first harvested truffle, which weighed 16 grams, has been preserved for posterity, but in future, the truffles will be distributed to restaurants in the UK.