European researchers have successfully decoded the genome of the Perigord black truffle.
Scientists say that within its nucleotides reside secrets to the flavour and elusive lifestyle of this fungus, offering clues that could help a truffle industry that is fraught with unpredictable yields and a counterfeit market.
Mycologist Francis Martin, at the French National Institute for Agricultural Research in Nancy, and his colleagues are compiling a database of genetic markers to verify the geographic origins of black truffle populations.
The genome of the black truffle (Tuber melanosporum) includes genes encoding flavour-related sulphur metabolites and enzymes that degrade amino acids.
This shows that its distinctive aroma and flavour is all produced in-house, and not by microbes native to the region in which the truffle grows, as many researchers had thought.
"When we started this work, many thought that truffles could be like cheese or wine, in that the microflora and yeast living on the truffles played a vital role in releasing volatile compounds. But we in fact demonstrated that the volatiles giving rise to the truffle's perfume are encoded in the truffle's genome," Martin said.
Truffle cultivation is notoriously difficult, in part because of its clandestine life cycle as an underground symbiont, in which the fungus trades nutrients with oak-tree roots.
The T. melanosporum genome also reveals that the fungus reproduces sexually more often than researchers thought. Many growers rely on asexual truffle propagation, in which two haploid cells from a single fungus - each with one copy of the genome - fuse to form the diploid fruiting body (the truffle), which has two copies.
Ye, the researchers found two different sets of mating genes in the black truffle, suggesting that two strains of T. melanosporum with opposite mating types combined through sexual reproduction.
Martin advises growers to use both mating types when inoculating oak trees, and to genetically fingerprint the truffles to be sure that they are not from the same family.
The new research has been published online in Nature.