French scientists have discovered that the fungus is highly inbred and probably derives from less than 100 ancestors which survived the last Ice Age about 10,000 years ago.
The lack of genetic variation means that the differences in taste and aroma of black truffles, which are found in France, Spain and Italy, are probably due to the various habitats in which they grow rather than inherited traits.
Dr Michel Raymond, a geneticist at the University of Montpellier, said the black truffle has declined significantly this century because of the destruction of the woodlands, where it grows underground in a complicated lifecycle.
At the turn of the century about 1,000 tons of black truffles were collected each year in France. This has now fallen to fewer than 30 tons a year, Dr Raymond says in the current issue of the journal Nature.
The last population bottleneck occurred after the last Ice Age, which had nearly forced the black truffle into extinction. The decline accounts for why present-day truffles are so genetically uniform, Dr Raymond said. ``If there is an attack of disease in truffles this could make them theoretically more vulnerable,'' he said.
Scientists could discover why some truffles are tastier than others by looking at differences in the soil and general environment where they grow, he said. ``Research is needed to identify the environmental variables that affect the black truffle's perfume and taste, which are the objects of intense human interest.''