Aim of study: In recent decades the cultivation of the black truffle Tuber melanosporum has expanded across all the Mediterranean-climate regions, but also to other regions outside the European standard for the species. We aim to describe the current extent of T. melanosporum cultivation.Area of study: Tuber melanosporum plantations in Europe, the Mediterranean basin, Australia, New Zealand, China, America and South Africa.Material and Methods: The socioeconomic impact of T. melanosporum cultivation, the way in which the current situation has been achieved and the knowledge needed for its progress are reviewed.Research highlights: T. melanosporum has been successfully cultivated in several countries outside its natural area, but many practices are still empirical and thus yields cannot be guaranteed. The recent advances in molecular techniques and genome science are helping to overcome some of the difficulties traditionally constraining truffle research. The role of truffles as a transitional element between agricultural and forestry activities makes its cultivation a paradigm of sustainable rural development.Keywords: Tuber melanosporum; Europe; Australia; New Zealand; Chile; USA.

The European black truffle is a mycorrhizal fungus native to Spanish Mediterranean forests. In most Spanish regions it was originally commercially harvested in the second half of the 20th century. Experts agree that wild truffle yields suffered a sharp decline during the 1970s and 1980s. However, official statistics for Spanish harvest are scarce and seemingly conflicting, and little attention has been paid to the regime for the exploitation of truffle-producing forests and its implications on the sustainability of this resource. Trends in harvest from 1969 to 2013 and current harvesting practices were analyzed as a case study, taking into account that Spain is a major truffle producer worldwide, but at the same time truffles have only recently been exploited. The available statistical sources, which include an increasing proportion of cultivated truffles since the mid-1990s, were explored, with estimates from Truffle Harvesters Federation showing higher consistency. Statistical sources were then compared with proxies for wild harvest (rents from truffle leases in public forests) to corroborate time trends in wild harvesting. Results suggest that black truffle production is recovering in recent years thanks to plantations, whereas wild harvest is still declining. The implications of Spanish legal and institutional framework on sustainability of wild truffle use are reviewed. In the current scenario, the decline of wild harvest is likely to continue and eventually make commercial harvesting economically unattractive, thus aggravating sustainability issues. Strengthening of property rights, rationalization of harvesting pressure, forest planning and involvement of public stakeholders are proposed as corrective measures.

The wild production of the highly appreciated fungus Tuber melanosporum is negatively affected by canopy closure in the stand. Habitat improvement has been proposed as a tool to recover the production in close forests, but evaluations based on scientific monitoring are still lacking. This study analyses the short-term effect of a pilot project on improvement of T. melanosporum reproduction habitat. The results support the project hypothesis that the canopy closure was hampering truffle fruiting in the larger brûlés. The silvicultural treatment alone has not triggered a clear positive response in all the truffières, suggesting that complementary actions are necessary to ensure their sustainability. Weather conditions provoke a year-to-year variation in the fruiting and determine the responsiveness of the truffières to the treatment.

The ectomycorrhizal fungus Tuber melanosporum fruits in association with Quercus in natural forests of Spain.Some of these stands are managed to keep an open canopy and meet the habitat requirements of the fungus.However, there are few quantitative studies analysing in these forests the relationship between soil environment and T. melanosporum. Eight forest stands which produce T. melanosporum have been monitored for six years in order to characterise the below-ground ectomycorrhizal community and to assess its temporal dynamics after experimental canopy opening. The brûlé, the ground where T. melanosporum fruits, shows a distinct ectomycorrhizal community, characterised by lower density of active ectomycorrhizal tips, lower morphotype richness per soil volume, higher abundance of T. melanosporum and lower abundance of Cenococcum geophilum than soil closest to the trunk of the host Q. ilex. Opening the canopy has not stimulated an increase in T. melanosporum, suggesting that a shift in the soil environment alone will not trigger the formation of new truffières in the short term. The dry climate of these truffières may be a factor, as T. melanosporum abundance appears to be sensitive to annual weather conditions.