Effect of Quercetin on Mycorrhizal Synthesis between Tuberborchii and Arbutusunedo L. In Vitro Plants

Arbutus unedo L. is a Mediterranean species used for fruit production; it is tolerant to drought and shows regeneration ability following forest fires. Mycorrhizal plants with Tuber borchii add resilience and value. This study aims to test the effect of quercetin on mycorrhizal synthesis between T. borchii and A. unedo. Two genotypes selected for fruit production and hydric stress tolerance, were micropropagated for mycorrhizal synthesis, accomplished during ex vitro rooting in perlite, using lyophilized spores of T. borchii suspended in culture media with different quercetin levels (0–10 µM). Six months after inoculation, plants were transferred to pots and maintained in nursery. Ten and 12 months after inoculation, roots were morphological examined and molecularly characterized using ITS1-5.8SITS2 rDNA region and specific primers. Results showed that mycorrhizae establishment was dependent on studied factors (genotype, quercetin level, and culture medium) and their interaction (genotype X culture medium). Quercetin levels up to 2.0 µM favored mycorrhizae establishment and plant growth, although levels superior to 4 µM showed a toxic effect. Quercetin showed to be an efficient factor on inducing mycorrhiza thriving independent of the genotype. Morphological observations and molecular analysis confirmed the permanence of the fungus association 10 and 12 months after inoculation.

Synthesis and ultrastructural observation of arbutoid mycorrhizae of black truffles (Tuber melanosporum and T. aestivum)

Arbutus unedo (the strawberry tree) is a Mediterranean shrub which forms arbutoid mycorrhizae with a variety of Asco- and Basidiomycetes. After the discovery of the mycorrhizal symbiosis between A. unedo and Tuber borchii, in this study, arbutoid mycorrhizae were synthetized in greenhouse with Tuber aestivum and Tuber melanosporum. Six months after inoculation, both species colonized the roots of all inoculated A. unedo seedlings, but mature mycorrhizae were only observed after 12 months. Ultrastructure analysis of Tuber arbutoid mycorrhizae was described for the first time, showing, as observed in typical endosymbiosis, a rearrangement of host cells and the creation of an interface compartment with both truffle species. Immunolabelling experiments suggested that pectins are not present in the interface matrix surrounding the intracellular hyphae. Thus, the ability to establish symbiosis with A. unedo seems to be a common feature in the genus Tuber, opening up the possibility to use this plant for mycorrhization with valuable truffles. This could represent an important economic opportunity in Mediterranean areas by combining the production of truffles, edible fruits and valued honey.

Food Authentication: Truffle (Tuber spp.) Species Differentiation by FT-NIR and Chemometrics

Truffles are certainly the most expensive mushrooms; the price depends primarily on the species and secondly on the origin. Because of the price differences for the truffle species, food fraud is likely to occur, and the visual differentiation is difficult within the group of white and within the group of black truffles. Thus, the aim of this study was to develop a reliable method for the authentication of five commercially relevant truffle species via Fourier transform near-infrared (FT-NIR) spectroscopy as an easy to handle approach combined with chemometrics. NIR-data from 75 freeze-dried fruiting bodies were recorded. Various spectra pre-processing techniques and classification methods were compared and validated using nested cross-validation. For the white truffle species, the most expensive Tuber magnatum could be differentiated with an accuracy of 100% from Tuber borchii. Regarding the black truffle species, the relatively expensive Tuber melanosporum could be distinguished from Tuber aestivum and the Chinese truffles with an accuracy of 99%. Since the most expensive Italian Tuber magnatum is highly prone to fraud, the origin was investigated and Italian T. magnatum truffles could be differentiated from non-Italian T. magnatum truffles by 83%. Our results demonstrate the potential of FT-NIR spectroscopy for the authentication of truffle species.

Draft Genome Sequence of Tuber borchii Vittad., a Whitish Edible Truffle

ABSTRACT The ascomycete Tuber borchii (Pezizomycetes) is a whitish edible truffle that establishes ectomycorrhizal symbiosis with trees and shrubs. This fungus is ubiquitous in Europe and is also cultivated outside Europe. Here, we present the draft genome sequence of T. borchii strain Tbo3840 (97.18 Mb in 969 scaffolds, with 12,346 predicted protein-coding genes).