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Background and Aims: Intercropping of truffle-producing trees with aromatic plants is used to improve profitability of truffle orchards during the initial 4–7 years. However, after that period the viability of this system is challenged by the appearance of brûlés, an area around host tree characterised by scarce plant cover where the fungus exhibits allelopathic activity. We aimed to investigate the ecological interactions between these crops and between their associated mycorrhizal fungi in adult truffle plantations. Methods: We simulated two intercropping systems, truffle oak – lavender and truffle oak – rosemary in their adult stage. We analysed and compared aromatic plants and soil samples inside and outside the brûlés during the first year of the aromatic plants in the field. Results: We found a strong negative relation of brûlés with the growth of the aromatic plants, although not a decrease in the arbuscular mycorrhizal colonization of their roots. The essential oil yield and composition of aromatic plants was affected by brûlés. The extraradical truffle mycelium was not significantly affected by the presence of aromatic plants. Conclusions: The growth and yield of aromatic plants was impaired during their first year growing in brûlés, whereas no negative effect of aromatic plants on truffle fruiting potential was found. The study improves our understanding of the mechanisms influencing the viability of the truffle tree – aromatic plant intercropping and the possible technical challenges. [ABSTRACT FROM AUTHOR]

The highly prized black truffle is a fungus mostly harvested in orchards planted with mycorrhizal seedlings. It is an obligatory outcrossing fungus with a single MAT locus containing two alternative mating-type idiomorphs. In the orchards, at the mycorrhizal level, these mating types are frequently spatially segregated. Some studies found that this segregation was pronounced from the nursery stage, whereas others did not find such a marked segregation. Besides, information on the host tree species and nursery conditions used in Spain, one of the main truffle-producing countries, are very scarce. In this study, we investigated the temporal dynamics of mating types in nursery seedlings of Quercus ilex and Quercus faginea, as well as the influence of cultural conditions in the nursery. Our results indicated that at the plant level, there was a trend for one of the mating types to dominate over the other from the first to the second year in the nursery, in both host species and both nursery conditions tested. However, this segregation process was not so sharp as previously reported. Our results support the hypothesis that intraspecific competition results in reduced evenness of mating-type abundance from the nursery stage, although almost all seedlings maintained both mating types and, at the seedling batch scale, the occurrence of both mating types was roughly balanced. [ABSTRACT FROM AUTHOR]

The cultivation of the ectomycorrhizal fungus Tuber melanosporum has considerably spread in recent years throughout the world. During the first years of truffle cultivation, weed control is a key practice to improve the establishment of host trees and the proliferation of the fungus in the soil. Glyphosate is nowadays the most commonly used herbicide in Spanish truffle orchards. We explored the effect of glyphosate on the proliferation of T. melanosporum mycorrhizae, on extraradical mycelium and on the inoculum potential of T. melanosporum spores in greenhouse experiments using Quercus ilex seedlings as host plants. No detrimental effect on the secondary infection of T. melanosporum was found after three sequential glyphosate applications in young seedlings during one vegetative period. Instead, a change in the distribution of fine roots and T. melanosporum mycorrhizae along soil depth was observed. On the other hand, results indicate that high application rates of glyphosate hinder the infectivity of T. melanosporum spore inoculum, without apparent impact on the host performance. Our results suggest that glyphosate has the potential to jeopardise the role of the soil spore bank as inoculum source for the colonisation of new roots, also raising the question of whether glyphosate could hinder the presumed role of spores in sexual mating. [ABSTRACT FROM AUTHOR]