Although Tuber borchii is a commercially valuable truffle, its habitat has been virtually ignored. Here, we examine the ectomycorrhizal fungal communities in natural T. borchii grounds. Ectomycorrhizas under T. borchii ascomata and up to 1 m away were collected and morphologically assigned to pine or oak host plants. They were then morphotyped and molecular typed using internal transcribed spacer regions. Seventy ectomycorrhizal taxa were identified, many of which were rare. Tuber borchii dominated, forming 20% of ectomycorrhizas, with Thelephoraceae, Inocybaceae and Sebacinaceae being the other main species. Species composition was markedly affected by the host plant, although community structure and composition was also influenced by the location from which the soil cores were collected. Tuber dryophilum, an edible truffle, but without commercial value, shared the habitat with T. borchii. Its mycorrhizas were never found together with those of T. borchii. Tuber borchii was present on both oaks and pines, but was more abundant in soil cores where the roots of both hosts were present. It is suggested that the presence of young oaks contributed to the maintenance of T. borchii colonization on pines.

Tuber magnatum produces the world's most expensive truffle. This fungus produces very rare ectomycorrhizas which are difficult or even impossible to detect in the field. A “real-time” PCR assay was recently developed to quantify and to track T. magnatum mycelium in soil. Here, this technique was used to investigate the spatial distribution of T. magnatum extra-radical mycelium in soil productive patches and its dynamic across seasons. This study was carried out in four different natural T. magnatum truffle grounds located in different Italian regions. During the fruiting seasons, the amount of T. magnatum mycelium was significantly higher around the fruiting points and decreased going farther away from them. Moreover, T. magnatum mycelium inside the productive patches underwent seasonal fluctuations. In early spring, the amount of T. magnatum mycelium was significantly higher than in summer. In summer, probably due to the hot and dry season, T. magnatum mycelium significantly decreased, whereas in autumn it increased again and was concentrated at the putative fruiting points. These results give new insights on T. magnatum ecology and are useful to plan the most appropriate sampling strategy for evaluating the management of a truffle ground.

This survey was carried out in a Quercus suber L. stand with many trees affected by the disease "oak decline". Its aim was to obtain information about both the belowground ectomycorrhizal fungal community in a declining Q. suber stand as a whole, and the ectomycorrhizal fungal community of individual tree (EFT) detected in healthy and diseased plants. To this end, we first categorized the trees into four different decline classes (one for healthy plants and three for diseased plants) and then, by using morphological and molecular tools, we identified the ectomycorrhizas isolated from samples collected near the trees with different declining classes. The ectomycorrhizal community as a whole was seen to be composed of numerous ectomycorrhizal fungal species, only some of which appeared to be dominant (Cenococcum geophilum, Lactarius chrysorrheus, and some species of Tomentella genus), while most occurred sporadically. Results show that all root tips observed are mycorrhized and that decline class does not influence the number of ectomycorrhizal root tips found in the EFTs, thus oak decline does not impact the investment in ectomycorrhizal symbiosis. However, some statistical differences can be observed in the values of evenness and taxonomic distinctness in the EFT associated with trees with different states of health. Finally, both the analysis of similarity test and the ordination technique highlight a compositional difference between the EFT associated with trees in different health conditions, but also suggest that other factors may play a role in causing these differences.

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