Whitish truffles found in Finland: soil characteristics, and identification based on morphological and molecular properties.

The growing demand for truffles has led to a global pursuit for their occurrence in the wild, and studies concerning their cultivation. Although European countries such as Italy, France and Spain have been known for truffle production, truffle hunting is new to Finland. The present study reports for the first time, the findings of Tuber maculatum in Finland on the basis of morphological and molecular analysis. The chemical characteristics of soil samples collected from the truffle sites have also been discussed. The species of the Tuber samples were identified primarily using morphological analysis. Molecular analysis was carried out for the confirmation of the identity of the species. Two phylogenetic trees were constructed based on internal transcribed spacer (ITS) sequences produced in this study and including representative sequences of whitish truffles available in GenBank. The truffles were identified as T. maculatum and T. anniae. This study could be considered as a basis for encouraging research on findings and identification of truffles in Finland.

Draft Genome Sequence of the Ectomycorrhizal Ascomycete Sphaerosporella brunnea.

Sphaerosporella brunnea is a pioneer ectomycorrhizal fungus with facultative saprophytic capacities. Here, we sequenced the genome of S. brunnea strain Sb_GMNB300, which is estimated at 51.6 Mb in size with 872 assembled contigs accounting for 12,597 predicted coding genes. This genome will be useful for comparative studies of Pezizales ectomycorrhizal symbioses.

Mycorrhization of Quercus robur L., Quercus cerris L. and Corylus avellana L. seedlings with Tuber macrosporum Vittad.

Tuber macrosporum Vittad. is not a common truffle species, but with remarkable organoleptic qualities and much economic interest. After the addition of truffle spore slurry, 30 seedlings of Quercus robur L., Quercus cerris L. and Corylus avellana L. were grown inside a greenhouse for 11 months before evaluation of the mycorrhizal level. Two different potting mixes were used: a natural soil-based potting mix for Q. robur, Q. cerris and C. avellana and a peat-based potting mix for Q. robur. Quercus robur planted in soil potting mix was the most receptive towards the truffle spore inoculum, with a level of formation of T. macrosporum ectomycorrhizas (ECMs) of approximately 14 %, ranging from a minimum of ∼4 % to a maximum of ∼44 % in different seedlings. No T. macrosporum ECMs developed on Q. cerris (soil potting mix) or on Q. robur (peat potting mix), whereas a low percentage of ECMs was detected on only three C. avellana (soil potting mix) seedlings. The fungus Sphaerosporella brunnea (Alb. & Schwein.) Svrcek & Kubicka was also detected as a contaminant on almost half the truffle-inoculated seedlings. A new detailed description of the morphological and anatomical characteristics of T. macrosporum ECMs and their DNA-based verification with species-specific markers were also reported.

Mycorrhization of pecan trees (Carya illinoinensis) with commercial truffle species: Tuber aestivum Vittad. and Tuber borchii Vittad.

Pecan (Carya illinoinensis) is an economically important nut tree native to the Mississippi basin and cultivated worldwide. In North America, species of truffles are regularly found fruiting in productive pecan orchards and the truffle genus Tuber appears to be abundant in pecan ectomycorrhizal (EM) communities. As an initial step to determine the feasibility of co-cropping European truffle species with pecan, we evaluated whether mycorrhizae of highly esteemed European truffle species (Tuber aestivum Vittad. T. borchii and T. macrosporum) could be formed on pecan seedlings. Seedlings were inoculated with truffle spores and were grown in a greenhouse for 10 months. Levels of EM colonization were estimated visually and quantified by counting EM tips. Ectomycorrhizae were identified both morphologically and molecularly with species-specific amplification and by sequencing of the ITS region of the nuclear ribosomal DNA (nrDNA). Both T. borchii and T. aestivum spores produced well-formed ectomycorrhizae on pecan seedlings with average root colonization levels of about 62% and 42%, respectively, whereas no ectomycorrhizae of T. macrosporum were formed. The anatomy and morphology of these truffle ectomycorrhizae on pecan was characterized. The co-cropping of T. aestivum and T. borchii may hold promise as an additional stream of revenue to pecan growers, although, further studies are needed to assess whether this symbiosis is maintained after planting in the field and whether truffle production can be supported by this host species.

The AD-type ectomycorrhizas, one of the most common morphotypes present in truffle fields, result from fungi belonging to the Trichophaea woolhopeia species complex.

Belowground ectomycorrhizal communities are often species rich. Characterization of the ectomycorrhizas (ECMs) underneath native truffle areas and/or cultivation sites is particularly relevant to identifying fungal species that might interfere with or promote truffle propagation and fruiting. Fungal identification at the genus/species level can now be achieved by combining detailed morphological and anatomical descriptions with molecular approaches. In a survey of the mycorrhizal biodiversity of Tuber melanosporum orchards and inoculated host plants in nurseries, we repeatedly sampled ECMs with morphological features resembling those of the ECMs widely known as the AD type. Despite the fact that the AD type is regarded as one of the most competitive fungal species towards Tuber spp., its taxonomical rank has yet to be resolved. By analyzing the 28S and internal transcribed spacer (ITS) rDNA regions, here, we show that AD-type ECMs result from host plant colonization by the pyronemataceous species Trichophaea woolhopeia. Further to this, the 28S and ITS phylogenetic trees built from the AD-type ECMs analyzed sustain the hypothesis that T. woolhopeia is a species complex.

Morphological and molecular analyses of ectomycorrhizal diversity in a man-made T. melanosporum plantation: description of novel truffle-like morphotypes.

Below-ground ectomycorrhizal communities are often species-rich, and monitoring their dynamics is important to understand the conditions that promote truffle fructification. Characterization of the different ectomycorrhizas (ECM) at the species level can now be achieved by combining detailed morphological and anatomical descriptions with molecular approaches. Following this strategy, we have characterized ectomycorrhizal biodiversity in an artificial Tuber melanosporum plantation. Although the plantation was unproductive, T. melanosporum mycorrhizas were the most present and two Tuber-like mycorrhizal morphotypes, named ECMm1 and ECMm3, showing distinctive features were found. Internal transcribed spacer (ITS) phylogenetic analysis demonstrated that ECMm3 is related to the Tuber rufum/Tuber ferrugineum species complex, whereas ECMm1 shows the highest ITS similarity with Tuber scruposum and fungi-colonizing Epipactis roots. The results presented here provide more insights into genetic variability, mycorrhizal morphology, and below-ground distribution of fungi associated with artificial truffle plantations.