A global meta-analysis of Tuber ITS rDNA sequences: species diversity, host associations and long-distance dispersal

Tuber cumberlandense and T. canirevelatum, two new edible Tuber species from eastern North America discovered by truffle-hunting dogs

Ectomycorrhizal fungi in the genus Tuber form hypogeous fruiting bodies called truffles. Many Tuber species are highly prized due to their edible and aromatic ascomata. Historically, there has been attention on cultivating and selling European truffle species, but there is growing interest in cultivating, wild-harvesting, and selling species of truffles endemic to North America. North America has many endemic Tuber species that remain undescribed, including some that have favorable culinary qualities. Here, we describe two such Tuber species from eastern North America. Maximum likelihood and Bayesian phylogenetic analyses of ITS (internal transcribed spacer), tef1 (translation elongation factor 1-alpha), and rpb2 (second largest subunit of RNA polymerase II) sequences were used to place these species within a phylogenetic context. We coupled these data with morphological analyses and volatile analyses based on gas chromatography-mass spectrometry. Tuber cumberlandense, sp. nov. (previously referred to as Tuber sp. 66), is a member of the Rufum clade that has been opportunistically harvested for commercial sale from T. melanosporum orchards across eastern North America. Tuber canirevelatum, sp. nov. belongs in the Macrosporum clade and thus far is only known from eastern Tennessee, USA. Both new species were discovered with the assistance of trained truffle dogs. The volatile profiles of T. canirevelatum and T. cumberlandense were measured in order to characterize aromas based on the chemical compounds produced by these fungi. Ascomata from both species were enriched in acetone, dimethyl sulfide, 1-(methylthio)-1-propene, and 1-(methylthio)propane. In this work, we celebrate and encourage the use of trained truffle-hunting dogs for fungal biodiversity discovery and research.

Application of Quantitative Magnetic Resonance Imaging (QMRI) to Evaluate the Effectiveness of Ultrasonic Atomization of Water in Truffle Preservation

Truffles of the Tuber genus (Pezizales, Ascomycetes) are among the most valuable and expensive foods, but their shelf life is limited to 7-10 days when stored at 4 °C. Alternative preservation methods have been proposed to extend their shelf life, though they may alter certain quality parameters. Recently, a hypogeal display case equipped with an ultrasonic humidity system (HDC) was developed, extending the shelf life to 2-3 weeks, depending on the truffle species. This study assesses the efficacy of HDC in preserving Tuber melanosporum and Tuber borchii ascomata over 16 days, using quantitative magnetic resonance imaging (QMRI) to monitor water content and other parameters. Sixteen T. melanosporum and six T. borchii ascomata were stored at 4 °C in an HDC or a static fridge (SF) as controls. QMRI confirmed that T. borchii has a shorter shelf life than T. melanosporum under all conditions. HDC reduced the rate of shrinkage, water, and mass loss in both species. Additionally, the Apparent Diffusion Coefficient (ADC), longitudinal relaxation time (T1), and transverse relaxation time (T2), which reflect molecular changes, decreased more slowly in HDC than SF. QMRI proves useful for studying water-rich samples and assessing truffle preservation technologies. Further optimization of this method for industrial use is needed.

Three New Truffle Species (Tuber, Tuberaceae, Pezizales, and Ascomycota) from Yunnan, China, and Multigen Phylogenetic Arrangement within the Melanosporum Group

Based on a multi-locus phylogeny of a combined dataset of ITS, LSU, tef1-α, and rpb2 and comprehensive morphological analyses, we describe three new species from the Melanosporum group of genus Tuber and synonymize T. pseudobrumale and T. melanoexcavatum. Phylogenetically, the three newly described species, T. yunnanense, T. melanoumbilicatum and T. microexcavatum, differ significantly in genetic distance from any previously known species. Morphologically, T. yunnanense is distinctly different from its closest phylogenetically related species, T. longispinosum, due to its long shuttle-shape spores (average the ratio of spore length to spore width for all spores (Qm) = 1.74). Tuber melanoumbilicatum differs from the other species in having a cavity and long shuttle-shaped spores (Qm = 1.65). Although T. microexcavatum sampled ascomata have relatively low maturity, they can be distinguished from its closely related species T. pseudobrumale by the ascomata size, surface warts, and spore number per asci; additionally, phylogenetic analysis supports it as a new species. In addition, molecular analysis from 22 newly collected specimens and Genebank data indicate that T. pseudobrumale and T. melanoexcavatum are clustered into a single well-supported clade (Bootstrap (BS) = 100, posterior probabilities (PP) = 1.0); and morphological characteristics do not differ. Therefore, based on the above evidence and publication dates, we conclude that T. melanoexcavatum is a synonym of T. pseudobrumale. By taking into account current knowledge and combining the molecular, multigene phylogenetic clade arrangement and morphological data, we propose that the Melanosporum group should be divided into four subgroups. Diagnostic morphological features and an identification key of all known species in the Melanosporum group are also included. Finally, we also provide some additions to the knowledge of the characterization of T. pseudobrumale, T. variabilisporum, and T. pseudohimalayense included in subgroup 1 of the Melanosporum group.

Three New Species of Tuber Discovered in Alpine Fir Forests in Yunnan, China

Three new species of Tuber, T. albicavum, T. laojunshanense, and T. umbilicicavatum belonging to the Puberulum phylogroup, are described based on specimens collected in alpine Abies forests at 3600-4000 m, Northwest Yunnan, China. T. albicavum is distinguished by its ascomata with a single chamber of 0.5-1.8 cm diameter, with an apical opening of 0.2-0.6 cm in diameter, and light golden-brown alveolate reticulate ascospores up to 30 μm in length; T. laojunshanense is characterized by having ascomata with a slightly tomentose surface, sometimes with a white navel, a relatively thick peridium, up to 280 µm, and yellow-brown spores with alveolate reticulate ornamentation, up to 34 µm in length; T. umbilicicavatum is characterized by smooth ascomata with a distinct white navel, a relatively thin peridium, up to 110 µm, and golden or golden-brown alveolate reticulate ascospores, up to 40 μm in length. The molecular analysis of the internal transcribed spacer region also supports that these three new species differ from previously described Tuber species.

Effects of Black and White Mulch on Mycelial Growth of Tuber Species in Korean Field Environment

Truffles, belonging to the genus Tuber, are ectomycorrhizal (ECM) fungi that form underground ascocarps and primarily establish symbiosis with oaks and hazels. The cultivation of Tuber spp. involves transplanting inoculated seedlings that have formed ectomycorrhiza with Tuber species, with mulching being effective for truffle cultivation. In this study, we investigated the effects of mulching on the mycelial growth of four Tuber species (T. himalayense, T. koreanum, T. melanosporum, and T. borchii) in the Korean natural environment, highlighting the potential for Korea as a truffle cultivation site. We developed and tested species-specific primers for quantifying the soil mycelial biomass of Tuber spp. by qRT-PCR, determined the superior mulch color for mycelial growth, and identified the Tuber species exhibiting the highest growth rate in the Korean field environment. Our results demonstrated that white mulch significantly enhanced mycelial growth in Tuber species than black mulch, likely owing to its ability to maintain low soil temperatures, control weeds, and improve host plant growth. Among the Tuber species, T. himalayense showed the greatest growth potential in the Korean natural environment. Additionally, a significant and positive correlation was observed between the mycelial biomass of Tuber species and the growth of inoculated seedlings, as measured by the total stem length and the number of leaves, thereby indicating the importance of symbiosis between ECM fungi and host plants. This study provides valuable insights into truffle cultivation in Korea and highlights the potential of using white mulch to promote mycelial growth, thereby contributing essential data for understanding the appropriate environmental conditions for Tuber spp. cultivation in Korea. Further study is needed to assess the long-term impact of mulching and to explore the effectiveness of other mulching materials.

Description, identification, and growth of Tuber borchii Vittad. mycorrhized Pinus sylvestris L. seedlings on different lime contents

Tuber borchii forms ectomycorrhiza with oaks, hazel, and pines, including Pinus sylvestris. However, its ectomycorrhiza morphotype with P. sylvestris was not comprehensively described so far, and molecular analyses are missing despite a high danger of misidentification of T. borchii ectomycorrhiza with other closely related and less valuable truffle species. We described for the first time the morphology and anatomy of T. borchii-P. sylvestris ectomycorrhiza using differential interference contrast technique and semi-thin sections in combination with molecular confirmation of identity. Color of ectomycorrhiza is reddish to dark brown, and morphotypes are unevenly but densely covered by warts-bearing pin-like cystidia. All layers of the hyphal mantle are pseudoparenchymatous with outer mantle layer formed of epidermoid cells. T. borchii ectomycorrhiza was identified by a molecular comparison with fruitbodies used for inoculation and its respective ectomycorrhizae. T. borchii has a wide ecological amplitude. To get a better insight in mycorrhization requirements, we investigated growth of P. sylvestris and its ectomycorrhiza infection rate with T. borchii in substrate with different lime content. The mycorrhization of P. sylvestris with T. borchii in the mycorrhization substrate and cultivation in greenhouse conditions was successful, with colonization of P. sylvestris varying between 36.5 and 48.1%. There was no significant correlation of mycorrhization to applied lime contents, and consequently to pH in substrate, while the increased levels of lime improved growth of the P. sylvestris seedlings.

Attraction of entomopathogenic nematodes to black truffle and its volatile organic compounds: A new approach for truffle beetle biocontrol

The European truffle beetle, Leiodes cinnamomeus, is the most important pest in black truffle (Tuber melanosporum) plantations. Entomopathogenic nematodes (EPNs) are a promising biological control agents against L. cinnamomeus. EPNs may employ multiple sensory cues while seeking for hosts, such as volatile organic compounds (VOCs) and CO2 gradients. We report for the first time the attraction of EPNs to truffle fruitbodies, and identified some VOCs potentially playing a key role in this interaction. We conducted olfactometer assays to investigate the attraction behavior of Steinernema feltiae and Steinernema carpocapsae towards both T. melanosporum fruitbodies and larvae of L. cinnamomeus. Subsequently, a chemotaxis assay using agar plates was performed to determine which of the 14 of the main VOCs emitted by the fruitbodies attracted S. feltiae at low (0.1 %) and high (mg/100 g truffle) concentrations. Both EPN species were attracted to mature fruitbodies of T. melanosporum, which may enhance the likelihood of encountering L. cinnamomeus during field applications. L. cinnamomeus larvae in the presence of truffles did not significantly affect the behavior of EPNs 24 h after application, underscoring the importance of the chemical compounds emitted by truffles themselves. Chemotaxis assays showed that four long-chain alcohol compounds emitted by T. melanosporum fruitbodies attracted S. feltiae, especially at low concentration, providing a first hint in the chemical ecology of a little-studied ecological system of great economical value. Further studies should be conducted to gain a finer understanding of the tritrophic interactions between T. melanosporum, EPNs, and L. cinnamomeus, as this knowledge may have practical implications for the efficacy of EPNs in the biological control of this pest.

Effects of Storage in an Active and Spontaneous Controlled O2/CO2 Atmosphere on Volatile Flavor Components and the Microbiome of Truffles

This study explored the potential to improve the storage quality and prolong the shelf life of truffles by storing them in a modified atmosphere fresh-keeping box with sealed gas components of Active Modified Atmosphere Packaging (AMAP, 40% O2 + 60% CO2) at 4 °C. During the storage period, a total of 63 volatile components in 10 categories were detected, with aldehydes being the most abundant and the relative content of ethers being the highest. The relative odor activity value and principal component analysis revealed that isovaleraldehyde, 1-octen-3-ol, 1-octen-3-one, and dimethyl sulfide were the characteristic flavor components of fresh truffles. However, 3-methylthiopropionaldehyde and (E, E)-2,4-nonadienal were the components that caused the deterioration of truffle flavor and could potentially serve as markers of truffle decay characteristics. 16S rDNA high-throughput sequencing showed that Leuconostoc and Lactococcus were dominant in the truffle samples stored for 14 days, but the abundance of putrefactive pathogenic bacteria showed an increasing trend in the truffle samples stored for 28 days. During the whole storage period, the common fungi detected in the different treatment groups were Candida and Aspergillus. The relative abundance of the former decreased, while the relative abundance of the latter decreased initially and then increased. The correlation between volatile components and the microbial flora was further analyzed, which indicated that Lactococcus and Lactobacillus had the same contributions to the same flavor, while Pseudomonas and Glutamicibacter had the opposite contributions to the same flavor. The results provide a reference for the storage and preservation of truffles.

European Tuber melanosporum plantations: adaptation status in Hungary, mycorrhizal level, and first ascocarp detection in two truffle orchards

Tuber melanosporum is one of the most economically important truffle species. Besides harvesting from its natural habitats, this truffle can also be extensively grown through artificial cultivation. However, the natural habitat of T. melanosporum has drastically declined, and the demand for the truffle in society is rapidly increasing. Therefore, enhancing production in truffle orchards by seeking new places for the establishment and regularly monitoring its adaptability might be an effective method for ensuring the sustainable productivity of the species. As a truffle science, recent information is important to further success in the growth of this truffle species. This study reports mycorrhization level and ascocarp production in two truffle plantations in Hungary. The estimated mycorrhization levels of the host plants were 43.36% in Biatorbágy and 42.93% in Jászszentandrás plantations. In March 2020, the 6-year-old and 18-year-old T. melanosporum plantations yielded around 100 g and 980 g of ascocarps, respectively. In general, adaptation of mycorrhizal seedlings in Hungary may become more effective as present management practices improve.

Natural occurrence of entomopathogenic nematodes (Steinernema and Heterorhabditis) and Pristionchus nematodes in black truffle soils from Spain

The European truffle beetle Leiodes cinnamomeus is the most important pest in black truffle (Tuber melanosporum) plantations. Current control methods against it are inefficient, so entomopathogenic nematodes (EPNs) could play an important role in their population regulation due to their efficacy against many soil-dwelling insect pests. A survey of EPNs and Pristionchus nematodes was conducted in truffle soils of Spain, considering environmental and physical-chemical soil factors. A total of 164 soil samples were collected from forests, productive plantations and null-low productive plantations, representing three distinct black truffle-growing habitat types. EPNs were isolated from seven soil samples (4.3%); four nematodes were identified as Steinernema feltiae and three as Heterorhabditis bacteriophora. Both species were sampled in three types of soil texture (loam, sandy loam or sandy clay loam), characterized by alkaline pH (7.5 to 8.5) and high organic matter (2.1-11.04%). The presence of these EPNs was influenced by habitat type and organic matter content. Pristionchus nematodes were isolated from truffle soil, around truffle fruit bodies and under the elytra of L. cinnamomeus, with Pristionchus maupasi being the most commonly identified species. No significant associations were found between environmental and soil factors and the occurrence of Pristionchus nematodes. These nematodes were found in alkaline soils (pH 7.75 to 8.7), across all seven sampled soil textures, with variable organic matter content (0.73%-5.92%). The ecological trends and the presence of Pristionchus may affect the occurrence of EPNs and their prospective use as biological control agents against L. cinnamomeus in black truffle plantations.

Accidental cultivation of the European truffle Tuber brumale in North American truffle orchards

Tuber brumale is a European edible truffle species that is often viewed as a contaminant in truffle orchards, as it visually resembles more valuable black truffles such as T. melanosporum, but differs in aroma and flavor and sells for a much lower price. Although T. brumale is not native to or intentionally cultivated in North America, it was reported to have been accidently introduced into British Columbia in 2014 and North Carolina in 2020. However, in winter of 2021, various truffle orchards in eastern North America produced truffles that differed from the anticipated harvest of T. melanosporum. Molecular analysis of these specimens confirmed T. brumale truffle fruiting bodies from ten orchards distributed across six eastern USA states. Phylogenetic analysis of nuclear ribosomal ITS and 28S DNA sequences indicated that all samples belong to the T. brumale A1 haplogroup, the genetic subgroup of T. brumale that is more common in western Europe. This pattern of widespread fruiting of T. brumale in North American truffle orchards is likely the result of T. brumale being introduced in the initial inoculation of trees used as hosts in T. melanosporum truffle cultivation. We review other examples of introduced non-target truffle species and strategies for limiting their impact on truffle cultivation.

Tuber wenchuanense, a holarctic truffle with a wide range of host plants and description of its ectomycorrhiza with spruce

Tuber wenchuanense ascomata (Ascomycota, Pezizales), a species originally described from Sichuan (China), were found in the Tatra Mountains in southern Poland. The purpose of this work was to (i) report and assess the first case of the holarctic natural distribution of a Tuber species, (ii) amend the original description of the species, (iii) summarize data on its host plants and (iv) describe its ectomycorrhiza. Specimens of Tuber wenchuanense from the Tatra Mountains were studied morphologically and molecularly. The ectomycorrhiza of this truffle with Picea abies was described for the first time. The distribution of T. wenchuanense, which is reconstructed based on sequences deposited in the publicly available nucleotide sequence databases, makes it the first holarctic Tuber species and the one with the northernmost habitat. In fact, its habitat is confined mainly to mountain coniferous forests and alpine and arctic tundra; although, according to known observations, the fruiting bodies of T. wenchuanense can be produced only under conifers. Based on the sequences of the internal transcribed spacer, this species appears to have low genetic variability over the entire distribution range. The phylogenetic tree showed that some of the unidentified phylotypes from the Rufum clade found by other researchers belong to T. wenchuanense. The ecological implications of these findings are discussed.

Comparative study of characteristic compounds of three species of truffle

The Panxi area in Sichuan Province is the main area for the production of truffles in China, and several species of truffle are known to exist in this region. Nevertheless, it is unclear what the differences in chemical composition between the truffles are. Using an ultra-high-performance liquid chromatography quadrupole/orbitrap high-resolution mass spectrometry coupled with Compound Discoverer 3.0, we identified chemical components in three mainly known truffles from the Panxi region. Further analysis of chemical composition differences was conducted using principal component analysis, and orthogonal partial least squares discriminant analysis. Note that, 78.9% of the variance was uncovered by the principal component analysis model. As a result of the orthogonal partial least squares discriminant analysis model, the three species of truffles (Tuber pesudohimalayense, Tuber indicum, and Tuber sinense) from Panxi were better discriminated, with R² X, R² Y, and Q² being 0.821, 0.993, and 0.947, respectively. In this study, 87 components were identified. T. pesudohimalayense contained significantly higher levels of nine different compounds than the other two species. Hence, it was possible to identify similarities and differences between three species of truffles from Panxi in terms of chemical composition. This can be used as a basis for quality control.

Fungal Planet description sheets: 1436-1477

Novel species of fungi described in this study include those from various countries as follows: Argentina, Colletotrichum araujiae on leaves, stems and fruits of Araujia hortorum. Australia, Agaricus pateritonsus on soil, Curvularia fraserae on dying leaf of Bothriochloa insculpta, Curvularia millisiae from yellowing leaf tips of Cyperus aromaticus, Marasmius brunneolorobustus on well-rotted wood, Nigrospora cooperae from necrotic leaf of Heteropogon contortus, Penicillium tealii from the body of a dead spider, Pseudocercospora robertsiorum from leaf spots of Senna tora, Talaromyces atkinsoniae from gills of Marasmius crinis-equi and Zasmidium pearceae from leaf spots of Smilaxglyciphylla. Brazil, Preussia bezerrensis from air. Chile, Paraconiothyrium kelleni from the rhizosphere of Fragaria chiloensis subsp. chiloensis f. chiloensis. Finland, Inocybe udicola on soil in mixed forest with Betula pendula, Populus tremula, Picea abies and Alnus incana. France, Myrmecridium normannianum on dead culm of unidentified Poaceae. Germany, Vexillomyces fraxinicola from symptomless stem wood of Fraxinus excelsior. India, Diaporthe limoniae on infected fruit of Limonia acidissima, Didymella naikii on leaves of Cajanus cajan, and Fulvifomes mangroviensis on basal trunk of Aegiceras corniculatum. Indonesia, Penicillium ezekielii from Zea mays kernels. Namibia, Neocamarosporium calicoremae and Neocladosporium calicoremae on stems of Calicorema capitata, and Pleiochaeta adenolobi on symptomatic leaves of Adenolobus pechuelii. Netherlands, Chalara pteridii on stems of Pteridium aquilinum, Neomackenziella juncicola (incl. Neomackenziella gen. nov.) and Sporidesmiella junci from dead culms of Juncus effusus. Pakistan, Inocybe longistipitata on soil in a Quercus forest. Poland, Phytophthora viadrina from rhizosphere soil of Quercus robur, and Septoria krystynae on leaf spots of Viscum album. Portugal (Azores), Acrogenospora stellata on dead wood or bark. South Africa, Phyllactinia greyiae on leaves of Greyia sutherlandii and Punctelia anae on bark of Vachellia karroo. Spain, Anteaglonium lusitanicum on decaying wood of Prunus lusitanica subsp. lusitanica, Hawksworthiomyces riparius from fluvial sediments, Lophiostoma carabassense endophytic in roots of Limbarda crithmoides, and Tuber mohedanoi from calcareus soils. Spain (Canary Islands), Mycena laurisilvae on stumps and woody debris. Sweden, Elaphomyces geminus from soil under Quercus robur. Thailand, Lactifluus chiangraiensis on soil under Pinus merkusii, Lactifluus nakhonphanomensis and Xerocomus sisongkhramensis on soil under Dipterocarpus trees. Ukraine, Valsonectria robiniae on dead twigs of Robinia hispida. USA, Spiralomyces americanus (incl. Spiralomyces gen. nov.) from office air. Morphological and culture characteristics are supported by DNA barcodes. Citation: Tan YP, Bishop-Hurley SL, Shivas RG, et al. 2022. Fungal Planet description sheets: 1436-1477. Persoonia 49: 261-350. https://doi.org/10.3767/persoonia.2022.49.08.

Application of Metabolomics in Fungal Research

Metabolomics is an essential method to study the dynamic changes of metabolic networks and products using modern analytical techniques, as well as reveal the life phenomena and their inherent laws. Currently, more and more attention has been paid to the development of metabolic histochemistry in the fungus field. This paper reviews the application of metabolomics in fungal research from five aspects: identification, response to stress, metabolite discovery, metabolism engineering, and fungal interactions with plants.

Role and potentialities of bacteria associated with Tuber magnatum: A mini-review

Among the hypogeous ectomycorrhizal fungi, the white truffle Tuber magnatum Picco is the species of greatest interest, both from an ecological and economic point of view. The increasing market demand of the precious white truffle along with the fall in its natural production led to a growing interest in cultivation techniques and encouraged truffle growers and researchers to deeper investigate factors that could affect and improve T. magnatum productivity. In this context, microbial communities play a central role. Indeed, in the last few years, the hypothesis of a potential link between microbial community composition and truffle orchard productivity is arousing a greater attention. Moreover, since the value of the prized T. magnatum can vary in relation to its provenience, the need to define a reliable tracking system is also emerging and bacteria appear to be a promising tool. Accordingly, the present mini-review summarises the knowledge currently available on T. magnatum microbial communities, focusing on the role of truffle-associated bacteria and highlighting similarities and differences between samples of different origin, to address the following issues: (i) Is there a correlation between microbial taxa and truffle ground productivity? (ii) Can bacteria actually be used as markers of T. magnatum geographic origin? The identification of microorganisms able to promote T. magnatum formation may represent an important advance in the field of truffle farming. Similarly, the detection of bacterial taxa that can be used as markers of T. magnatum origin could have a considerable impact on truffle industry and trade, even at local scale.

Effect of Temperature, pH, and Media on the Mycelial Growth of Tuber koreanum

Members of the genus Tuber are ectomycorrhizal fungi; this genus includes more than 180 species worldwide. In the present study, the optimal pH, temperature, and medium suitable for the mycelial growth of the Korean truffle, Tuber koreanum, were determined. Mycelium of T. koreanum, isolated from fruiting bodies collected in Korea, was used to investigate the effects of these environmental factors. The results showed that malt extract agar and potato dextrose agar were the most suitable for the mycelial growth of T. koreanum when cultured at a pH of 6.0 at 25 °C for 30 days.

Characterization of the Volatilome of Tuber canaliculatum Harvested in Quebec, Canada

The first detailed characterization of volatile compounds from Tuber canaliculatum, a truffle newly grown in Quebec, Canada, was performed with headspace solid phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC/MS). A total of 30 compounds were identified, making up more than 98% of the volatile extract. The volatilome of T. canaliculatum is dominated by (E)-1-methylthio-1-propene, (Z)-1-methylthio-1-propene, dimethyl disulfide, and 1-octen-3-ol. It also includes six compounds identified for the first time in truffles, namely, 4-hydroxy-4-methyl-2-pentanone, pentyl propanoate, (Z)-1-methyl-2-(prop-1-en-1-yl)disulfide, (E)-1-methyl-2-(prop-1-en-1-yl)disulfide, (Z)-1-methyl-3-(prop-1-en-1-yl)trisulfide, and (E)-1-methyl-3-(prop-1-en-1-yl)trisulfide. With the growing interest in gastronomy in truffles in North America, it is becoming important to gather knowledge for identification purposes and to delineate the key volatile compounds responsible for the aroma of North American truffles, especially the newly harvested T. canaliculatum.

Ectomycorrhizal synthesis between two Tuber species and six tree species: are different host-fungus combinations having dissimilar impacts on host plant growth?

Truffle cultivation has drawn more and more attention for its high economic and ecological values in the world. To select symbionts suitable for cultivation purposes, we conducted greenhouse-based mycorrhization trials of two Tuber species (T. formosanum and T. pseudohimalayense) with five broad-leaved tree species (Corylus yunnanensis, Quercus aliena var. acutiserrata, Q. acutissima, Q. robur, Q. variabilis) and one conifer species (Pinus armandii). Axenically germinated seedlings of all tree species were either inoculated, or not, with spore suspensions of these two truffles in the greenhouse. Eight months after inoculation, T. formosanum or T. pseudohimalayense ectomycorrhizae were successfully formed on these six tree species, as evidenced by both morphological and molecular analyses. All selected trees showed good receptivity to mycorrhization by both fungi, with average colonization rates visually estimated at 40-50%. Plant growth, photosynthesis, and nutrient uptake were assessed 2 years after inoculation and were mainly affected by host species. Mycorrhization by both fungi significantly improved P uptake of the hosts, and the interaction between truffle species and host plant species had significant effects on leaf water and leaf K concentrations. In addition, a significantly negative correlation between leaf Ca and leaf C concentration was found across all the seedlings. In addition, mycorrhization had slightly increased plant stem and canopy, but had no significant effects on plant photosynthesis. Overall, these results suggest that the effects of these two Tuber ECMF on plant growth and nutrient acquisition depend on the identity of the host species. Moreover, all selected plant species could be symbiotic partners with either T. pseudohimalayense or T. formosanum for field cultivation purposes.

Tuber eburneum and Tuber mujicii: New pine-associated Tuber species from eastern North America

The ectomycorrhizal truffle genus Tuber is widespread and diverse. Recent sampling of ascomata, ectomycorrhizal root tips, and environmental sequences has resulted in the identification of many Tuber species that cannot be assigned to described species and require formal description. Using morphological and molecular phylogenetic analysis, we describe two North American Tuber species associated with pines (Pinus spp.). Tuber eburneum, sp. nov., is an early-diverging taxon in the Melanosporum clade that differs substantially from all other taxa in that clade due to its light-colored peridium and gleba, lack of peridial warts, and peridial hairs that are ornamented with small, irregular protrusions. Tuber mujicii, sp. nov., is a whitish truffle species in the Puberulum clade. Although T. mujicii is morphologically similar to many related taxa, it can be distinguished by a combination of characters, including peridium color, spore size, number of ascospores per ascus, and number of reticulations across the spore surface.

Mycorrhization of Quercus spp. with Tuber huidongense and T. himalayense Collected in Korea

Fungi of the genus Tuber are ectomycorrhizal fungi that form a symbiotic relationship mainly with oak and hazel trees. Tuber spp. exhibit a highly selective host plant preference; thus, for cultivation purposes it is important to select an appropriate host plant for successful mycorrhization. In addition, as mycorrhizal characteristics differ according to Tuber spp., it is necessary to understand the differences in mycorrhizae according to the fungal species. Tuber huidongense and Tuber himalayense were recently discovered in Korea; therefore, we used spore suspensions from these two species to inoculate two species of oak trees, Quercus acutissima and Quercus dentata, to compare colonization rates and morphologies of the mycorrhizae. The colonization rates demonstrated that the different Tuber spp. favored different host plant species. In addition, unique morphological and anatomical characteristics were observed for T. huidongense and T. himalayense depending on the host species. These findings can lead to new economically important agricultural activities related to truffle cultivation in Korea.

The curse of the uncultured fungus

The international DNA sequence databases abound in fungal sequences not annotated beyond the kingdom level, typically bearing names such as “uncultured fungus”. These sequences beget low-resolution mycological results and invite further deposition of similarly poorly annotated entries. What do these sequences represent? This study uses a 767,918-sequence corpus of public full-length fungal ITS sequences to estimate what proportion of the 95,055 “uncultured fungus” sequences that represent truly unidentifiable fungal taxa – and what proportion of them that would have been straightforward to annotate to some more meaningful taxonomic level at the time of sequence deposition. Our results suggest that more than 70% of these sequences would have been trivial to identify to at least the order/family level at the time of sequence deposition, hinting that factors other than poor availability of relevant reference sequences explain the low-resolution names. We speculate that researchers’ perceived lack of time and lack of insight into the ramifications of this problem are the main explanations for the low-resolution names. We were surprised to find that more than a fifth of these sequences seem to have been deposited by mycologists rather than researchers unfamiliar with the consequences of poorly annotated fungal sequences in molecular repositories. The proportion of these needlessly poorly annotated sequences does not decline over time, suggesting that this problem must not be left unchecked.

Species diversity, phylogeny, endemism and geography of the truffle genus Tuber in China based on morphological and molecular data

The genus Tuber (Tuberaceae, Pezizales) is an important fungal group of Ascomycota both economically and ecologically. However, the species diversity, phylogenetic relationships, and geographic distribution of Tuber species in China remains poorly understood, primarily because descriptions of many new species relied heavily on morphological features with molecular data either not sought or ignored. The misapplication of European and North American names further added to confusion regarding the taxonomy of Chinese Tuber species. In this study, we examined more than 1000 specimens from China, and performed a comprehensive phylogenetic analysis for Chinese Tuber species using ITS sequences and multilocus sequence data. To infer the phylogeny of Chinese Tuber spp., 11 molecular datasets were assembled, including a concatenated internal transcribed spacers of the nuc rDNA (ITS), nuc rDNA 28S subunit (LSU), translation elongation factor 1-alpha (tef1-α), and RNA polymerase II subunit (rpb2) dataset as well as 10 ITS datasets (totally including 1435 sequences from 828 collections with 597 newly generated sequences, and 168 sequences from the types of 63 species). Our phylogenetic tree based on a concatenated multilocus dataset revealed that all Chinese Tuber species nested in nine phylogenetic clades (phylogroups), including Aestivum, Excavatum, Latisporum, Macrosporum, Maculatum, Melanosporum, Puberulum, Rufum and Turmericum. Of these, five phylogroups (Macrosporum, Maculatum, Melanosporum, Puberulum and Rufum) are shared across the continents of Asia, Europe and North America; two phylogroups (Aestivum and Excavatum) are shared by Europe and Asia; and the phylogroups Turmericum and Latisporum are endemic only to Asia. Phylogenetic trees based on 10 ITS datasets confirmed the presence of at least 82 phylogenetic species in China. Of these, 53 are identified as known species, including three new records for China, and 25 species are identified as new to science. Of the new species, nine are described and illustrated in this paper, and the others remain unnamed due to the paucity or absence of ascomatal materials. Accordingly, the confirmed, excluded and doubtful Tuber species in China are discussed. Tuber species showed high endemism. Of the 82 phylogenetic species found in China, 68 species occur only in China, six species are also found in other regions in Asia, and only eight species (T. anniae, T. excelsum-reticulatum, T. formosanum, T. maculatum, T. wenchuanense, Tuber sp. CHN-3, Tuber sp. CHN-10 and Tuber sp. CHN-11) are shared with other continents. Most Tuber species have a small and limited distribution in China, but a few, such as T. formosanum and T. parvomurphium, are widely distributed across China. Some phylogenetically closely related species, such as T. liaotongense and T. subglobosum, as well as T. xuanhuaense and T. lijiangense, show a pattern of allopatric distribution.

Multilocus Phylogeography of the Tuber mesentericum Complex Unearths Three Highly Divergent Cryptic Species

Tuber mesentericum is an edible European black truffle, apparently easy to recognize, but showing a high degree of genetic variability. In this study, we performed an integrative taxonomic assessment of the T. mesentericum complex, combining a multilocus phylogeographic approach with morphological analyses, and including authentic specimens of Vittadini, and Berkeley and Broome. We performed maximum likelihood phylogenetic analyses, based on single and concatenated gene datasets (ITS rDNA, β-tubulin, elongation factor 1-α), and including all available sequences from previous studies. Phylogenetic analyses consistently recovered three reciprocally monophyletic and well-supported clades: clade I, with a wide range across Europe; clade II, specimens collected mainly in the Iberian, Italian, and Balkan peninsulas; and clade III, specimens collected almost exclusively in central Italy. Genetic distance between clades ranged from 10.4% to 13.1% at the ITS region. We also designed new primer pairs specific for each phylogenetic lineage. Morphology of spores, asci, and peridium were investigated on specimens representing the three lineages. Macro- and micromorphological analyses of ascomata revealed only a few, but not diagnostic, differences between the three phylogenetic lineages, thus, confirming that they are morphologically cryptic. By studying authentic specimens of Vittadini, and Berkeley and Broome, it was possible to identify the three clades as T. mesentericum, Tuber bituminatum, and Tuber suave sp. nov., and to designate an epitype for T. mesentericum s.s. and a lectotype for T. bituminatum. Future investigations on volatile organic compound (VOC) composition are needed to define the aroma repertoires in this species complex.

Eco-archaeological excavation techniques reveal snapshots of subterranean truffle growth

Despite its status as a highly-prized and coveted fungi in gastronomy, many aspects of the subterranean life cycle of the Burgundy truffle (Tuber aestivum) are still unknown, because in situ observations of the formation and maturation of truffle fruitbodies remain difficult. Here, we adopted a suite of archaeological fine-scale excavating techniques to provide unique spatiotemporal snapshots of Burgundy truffle growth at three sites in southern Germany. We also recorded the relative position, fresh weight, maturity level and genotype composition of all excavated fruitbodies. Varying by a factor of thousand, the fresh weight of 73 truffle ranged from 0.1 to 103.2 g, with individual maturity levels likely representing different life cycle stages from completely unripe to fully ripe and even decaying. While only a slightly positive relationship between fruitbody weight and maturity level was found, our results suggest that genetically distinct specimens can exhibit different life cycle stages at the same period of time and under the same environmental conditions. We therefore argue that truffles are likely able to grow, mature and ripe simultaneously between early summer and late winter of the following year. Our case study should encourage further eco-archaeological truffle excavations under different biogeographic settings and at different seasons of the year to gain deeper insights into the fungi's subterranean ecology. The expected cross-disciplinary findings will help truffle hunters and farmers to improve their harvest practices and management strategies.

Report on a New Truffle Species, Tuber koreanum sp. nov., from Korea

The truffle and ectomycorrhizal roots formed by Tuber sp. were collected from the rhizosphere of Quercus aliena in Korea. The morphological characteristics of the ascoma, and molecular phylogenetic analysis using sequences from the internal transcribed spacer (ITS) and large subunit (LSU) of ribosomal DNA, translation elongation factor 1-alpha (TEF), and RNA polymerase second largest subunit (RPB2) regions confirmed the distinct morphology of the truffle. This truffle belongs to a monophyletic clade among the other Tuber species in the phylogeny. This study describes the truffle, Tuber koreanum, as a new species reported from Korea.

Truffle species strongly shape their surrounding soil mycobiota in a Pinus armandii forest

Truffles contribute to crucial soil systems dynamics, being involved in plentiful ecological functions important for ecosystems. Despite this, the interactions between truffles and their surrounding mycobiome remain unknown. Here, we investigate soil mycobiome differences between two truffle species, Tuber indicum (Ti) and Tuber pseudohimalayense (Tp), and their relative influence on surrounding soil mycobiota. Using traditional chemical analysis and ITS Illumina sequencing, we compared soil nutrients and the mycobiota, respectively, in soil, gleba, and peridium of the two truffle species inhabiting the same Pinus armandii forest in southwestern China. Tp soil was more acidic (pH 6.42) and had a higher nutrient content (total C, N content) than Ti soil (pH 6.62). Fungal richness and diversity of fruiting bodies (ascomata) and surrounding soils were significantly higher in Tp than in Ti. Truffle species recruited unique soil mycobiota around their ascomata: in Ti soil, fungal taxa, including Suillus, Alternaria, Phacidium, Mycosphaerella, Halokirschsteiniothelia, and Pseudogymnoascus, were abundant, while in Tp soil species of Melanophyllum, Inocybe, Rhizopogon, Rhacidium, and Lecanicillium showed higher abundances. Three dissimilarity tests, including adonis, anosim, and MRPP, showed that differences in fungal community structure between the two truffle species and their surrounding soils were stronger in Tp than in Ti, and these differences extended to truffle tissues (peridium and gleba). Redundancy analysis (RDA) further demonstrated that correlations between soil fungal taxa and soil properties changed from negative (Tp) to positive (Ti) and shifted from a moisture-driven (Tp) to a total N-driven (Ti) relationship. Overall, our results shed light on the influence that truffles have on their surrounding soil mycobiome. However, further studies are required on a broader range of truffle species in different soil conditions in order to determine causal relationships between truffles and their soil mycobiome.

Heterogeneity of the white truffle Tuber magnatum in a limited geographic area of Central-Southern Italy

Molise region (Central-Southern Italy) is one of the Italian richest areas of truffles and contributes significantly to the national production of the precious Tuber magnatum. Nevertheless, Molise truffle has received little scientific attention. Accordingly, in the present study, two T. magnatum populations collected in two different sites of Molise region were characterised from a morphological, genetic and microbiological point of view. A considerable variability between and within the two analysed groups emerged, suggesting an interesting heterogeneity of Molise white truffle populations. Ascocarps of the two groups significantly differed in size and maturation degree, although no linear correlation between weight and maturity was found. Genetic investigations focused on the Sequence-Characterised Amplified Region SCAR A21-inf. Three haplotypes, randomly distributed within the two truffle groups regardless of their collection sites, were detected. The 16S rRNA gene amplicon high-throughput sequencing provided an overview of the composition of the ascocarp-associated bacterial communities. A predominance of α-Proteobacteria was observed, with Bradyrhizobium among the main genera. However, some truffles showed unusual microbial profiles, with Pedobacter, Polaromonas and other bacterial genera as dominant taxa.

Truffle Market Evolution: An Application of the Delphi Method

Background: The objective of this study was to analyze the current situation of the truffle sector in the main producing countries of the Mediterranean area. Additionally, we identified the challenges for the future and the priority actions to develop the truffle sector in the region. Methods: We used a Delphi process approach, and we selected a total of 17 expert panelists in different positions within the supply chain of the target countries (Spain, France, Italy, Croatia, and Greece). Results: The results obtained allowed us to have a complete description of the current truffle supply chain. We confirmed an evolution of the sector due to the cultivation success of several Tuber species. The maturity of the sector has produced shifts in the roles that form the traditional truffle supply chain operators. We confirmed the trend of a decrease of collectors that hunt truffles in the wild and sell to small travelling buyers, whilst truffle hunters that collect for farmers and specialty wholesalers are emerging. However, a trend of truffle price decrease in the last few years has alerted the sector. Conclusions: As production increases due to truffle cultivation, it will be necessary to promote truffle consumption. We identified actions to develop the truffle sector: (a) strengthen the link between truffles, tourism, and gastronomy; (b) increase the effort at European level for the recognition of truffle production, helping to develop truffle culture and marketing; (c) increase the awareness and consumption of truffles among consumers; and (d) develop tourism workshops for truffle farmers.

Effects of Field Fumigation and Inoculation With the Pecan Truffle (Tuber lyonii) on the Fungal Community of Pecan (Carya illinoinensis) Seedlings Over 5 Years

Truffle fungi are esteemed for their aromatic qualities and are among the most widely cultivated edible ectomycorrhizal fungi. Here we document a successful method for establishing Tuber lyonii, the pecan truffle, on pecan (Carya illinoinensis) seedlings in a field setting. We assessed the impacts of soil fumigation and varying concentrations of truffle spore inoculum on the ectomycorrhizal fungal and the complete fungal communities as well as the colonization of T. lyonii on pecan roots at three nurseries in Georgia, United States. To identify fungal communities on pecan seedlings, we performed high-throughput amplicon sequencing of the fungal ITS1 rDNA region. Our 5-year long field experiment demonstrates that fumigation and inoculation together resulted in the highest persistence of T. lyonii on pecan roots. While fungal OTU numbers fluctuated over the years of our experiments, there was no statistical support to demonstrate diversification of communities when Shannon diversity metrics were used. However, we did find that older seedlings were less likely to be dominated by T. lyonii compared to younger ones, suggesting successional changes in the fungal community over time. This suggests that transplanting inoculated seedlings after 2 or 3 years post-inoculation is optimal for future truffle propagation efforts. Our results demonstrate that T. lyonii can be established in situ with methods that are compatible with current pecan nursery industry practices and that fungal communities on pecan seedlings vary depending on the experimental treatments used during planting. While the pecan truffle is not yet widely cultivated, our results provide insights for future large-scale cultivation of this and perhaps other Tuber species.

Co-occurrence of true truffle mycelia in Tuber magnatum fruiting sites

Tuber magnatum (the white truffle) is the most precious species of the genus Tuber which comprises the hypogeous ectomycorrhizal species called "true truffle." Despite its high economic value, the knowledge on its ecology is scant, principally due to the difficulty to find its mycorrhizas in the soil. The possibility to detect its mycelium by DNA extracted from soil has given a new chance for studying this truffle species. In this work, the co-occurrence of other Tuber species with T. magnatum mycelium was investigated by using species-specific primers in several productive areas located in central and northern Italy. Most (82%) of the examined soil samples showed at least one other Tuber species in addition to T. magnatum. The most common was T. maculatum (72% of soil samples) followed by T. borchii, T. rufum, T. brumale, T. dryophilum, T. macrosporum, and T. melanosporum (40%, 37%, 22%, 19%, 12%, and 1% of soil samples, respectively). Tuber aestivum was never detected in T. magnatum productive patches. Analysis of species co-occurrence showed that the pairwise associations between T. dryophilum-T. brumale, T. brumale-T. borchii, and T. borchii-T. dryophilum was significant. The results suggest that Tuber mycelial network in white truffle grounds is much more extensive than the distribution of their ectomycorrhizas and competitive exclusion between different Tuber species seems to take place only for root colonization.

Control of Leiodes cinnamomeus (Coleoptera: Leiodidae) in Cultivated Black Truffle Orchards by Kairomone-Based Mass Trapping

The monoculture situation of truffle cultivation is favoring the appearance of pests that would not be economically important in naturally balanced forest ecosystems. The most prominent of them is the European truffle beetle Leiodes cinnamomeus (Panzer) (Coleoptera: Leiodidae), for which there are no effective control methods capable of reducing its populations. The potential of the mass trapping technique against this beetle, based on adapted pitfall traps and the semiochemical methyl disulfide as an attractant, is explored in the present work. Two trap densities (40 and 80 traps/ha) were tested in 2-yr field trials carried out in the region of Teruel (Spain) with black truffle cultivation tradition. Kairomone dispensers were placed in the field immediately before adult outbreak and remained active there throughout the season. The efficacy of each treatment was measured according to the reduction in beetle populations and the damaged truffles in the center of the treated areas. The results showed that both trapping densities reduced adult populations (mean 57% catch reduction), but 80 traps/ha were needed to significantly lower damage parameters (>40% reduction), percentage of attacked truffles and number of galleries/g truffle. The cost effectiveness of these treatments and possible improvements are discussed.

Soil Metabarcoding Offers a New Tool for the Investigation and Hunting of Truffles in Northern Thailand

Truffles (Tuber spp.) are well-known as edible ectomycorrhizal mushrooms, and some species are one of the most expensive foods in the world. During the fruiting process, truffles produce hypogeous ascocarps; a trained pig or dog is needed to locate the ascocarps under the ground. Truffles in northern Thailand have been recorded in association with Betulaalnoides and Carpinus poilanei. In this study, we investigated the soil mycobiota diversity of soil samples from both of these truffle host plants in native forests using environmental DNA metabarcoding to target the internal transcribed spacer 1 (ITS1) region of the rDNA gene for the purposes of investigation of truffle diversity and locating truffles during the non-fruiting phase. In this study, a total of 38 soil samples were collected from different locations. Of these, truffles had been found at three of these locations. Subsequently, a total of 1341 putative taxonomic units (OTUs) were obtained. The overall fungal community was dominated by phylum-level sequences assigned to Ascomycota (57.63%), Basidiomycota (37.26%), Blastocladiomycota (0.007%), Chytridiomycota (0.21%), Glomeromycota (0.01%), Kickxellomycota (0.01%), Mortierellomycota (2.08%), Mucoromycota (0.24%), Rozellomycota (0.01%), Zoopagomycota (0.003%), and unidentified (2.54%). The results revealed that six OTUs were determined to be representative and belonged to the genus Tuber. OTU162, OTU187, OTU447, and OTU530 belonged to T. thailandicum, T. lannaense, T. bomiense, and T. magnatum, whereas OTU105 and OTU720 were acknowledged as unrecognized Tuber species. From 38 locations, OTUs of truffles were found in 33 locations (including three previously known truffle locations). Thus, 30 collection sites were considered new locations for T. thailandicum, T. bomiense, and other unrecognized Tuber species. Interestingly, at 16 new locations, mature ascocarps of truffles that were undergoing the fruiting phase were located underground. All 16 truffle samples were identified as T. thailandicum based on morphological characteristics and molecular phylogenetic analysis. However, ascocarps of other truffle species were not found at the new OTUs representative locations. The knowledge gained from this study can be used to lead researchers to a better understanding of the occurrence of truffles using soil mycobiota diversity investigation. The outcomes of this study will be particularly beneficial with respect to the search and hunt for truffles without the need for trained animals. In addition, the findings of this study will be useful for the management and conservation of truffle habitats in northern Thailand.

Tuber iryudaense and T. tomentosum: Two new truffles encased in tomentose mycelium from Japan

We describe two new Japanese truffle species, Tuber iryudaense and Tuber tomentosum, based on molecular and morphological analyses. Both species are clearly distinguishable from other Tuber species by the ocher tomentose mycelium covering the ascoma surfaces. Tuber iryudaense has one-spored asci that each contain a large (68-97 × 51-80 µm), reddish-brown ascospore; these microscopic characters are similar to those of closely related Chinese species, T. calosporum, T. gigantosporum, T. glabrum, T. monosporum, and T. sinomonosporum. Tuber tomentosum forms one to four ascospores per ascus with a reddish-brown color similar to that of ascospores of T. macrosporum and T. canaliculatum, although their spores are much larger than those of T. tomentosum (27‒64 × 26‒55 µm). Molecular phylogenetic analyses based on ribosomal internal transcribed spacer and partial 28S nuc rDNA sequences support that both species are distinct within the Macrosporum group.

Phylogenetic placements and cultural characteristics of Tuber species isolated from ectomycorrhizas

Pure cultures of Tuber were isolated from ectomycorrhizal root tips in Abies sachalinensis plantations in Hokkaido, Japan. Their phylogenetic relationships as well as vegetative hyphal characteristics on culture media were reported. Phylogenetic analysis based on the internal transcribed spacer within ribosomal DNA settled well-supported eight lineages within Puberulum, Latisporum, and Maculatum clades in Tuber. Three and one lineages were grouped with undescribed species of Puberulum clade in Japan and that of the Latisporum group in China, respectively. Two lineages were closely associated to but distinct from an undescribed species of Puberulum clade in Japan. One lineage did not group with any sequences in the International Nucleotide Sequence Database (INSD), proposing a new taxon in the Latisporum group. One lineage was grouped with T. foetidum in Maculatum clade. All strains in each lineage displayed yellowish white, thin, filamentous colonies on Melin-Norkrans agar medium. Various differences in morphological characteristics of hyphae on pure cultures of various strains were noted, but they were frequently uncommon among strains of the same taxa. Isolation from ectomycorrhizal root tips can be among the effective ways to acquire pure cultures of Tuber strains.

Effect of earthworms on mycorrhization, root morphology and biomass of silver fir seedlings inoculated with black summer truffle (Tuber aestivum Vittad.)

Species of the genus Tuber have gained a lot of attention in recent decades due to their aromatic hypogenous fruitbodies, which can bring high prices on the market. The tendency in truffle production is to infect oak, hazel, beech, etc. in greenhouse conditions. We aimed to show whether silver fir (Abies alba Mill.) can be an appropriate host partner for commercial mycorrhization with truffles, and how earthworms in the inoculation substrate would affect the mycorrhization dynamics. Silver fir seedlings inoculated with Tuber. aestivum were analyzed for root system parameters and mycorrhization, how earthworms affect the bare root system, and if mycorrhization parameters change when earthworms are added to the inoculation substrate. Seedlings were analyzed 6 and 12 months after spore inoculation. Mycorrhization with or without earthworms revealed contrasting effects on fine root biomass and morphology of silver fir seedlings. Only a few of the assessed fine root parameters showed statistically significant response, namely higher fine root biomass and fine root tip density in inoculated seedlings without earthworms 6 months after inoculation, lower fine root tip density when earthworms were added, the specific root tip density increased in inoculated seedlings without earthworms 12 months after inoculation, and general negative effect of earthworm on branching density. Silver fir was confirmed as a suitable host partner for commercial mycorrhization with truffles, with 6% and 35% mycorrhization 6 months after inoculation and between 36% and 55% mycorrhization 12 months after inoculation. The effect of earthworms on mycorrhization of silver fir with Tuber aestivum was positive only after 6 months of mycorrhization, while this effect disappeared and turned insignificantly negative after 12 months due to the secondary effect of grazing on ectomycorrhizal root tips.

First report of European truffle ectomycorrhiza in the semi-arid climate of Saudi Arabia

Tuber melanosporum Vittad. (Black or Périgord truffle) is a truffle native to the Mediterranean Southern Europe, popular for its unique flavor, and has great economic importance. The present work focused on assessing the possibility of cultivating T. melanosporum associated with Quercus robur L. in the desert climate of Saudi Arabia. The plantation was initiated in November 2018 by planting 271 oak seedlings in the Al-Qassim desert area and checked for survival and ectomycorrhiza development after 1.5 years of plantation maintenance. Amongst the 271 seedlings planted, 243 plants survived two harsh seasons (2019 and 2020), and the randomly selected and tested seedlings were still mycorrhized with T. melanosporum. The mycorrhization level with T. melanosporum was between 5 and 35% of all fine roots, and the share of contaminant ectomycorrhiza was low. In comparison to other areas where T. melanosporum is successfully cultivated, the Al-Qassim desert area has 10-15 °C higher average summer temperatures and a low total annual precipitation, which necessitates regular irrigation of the plantation. This work opens the avenue for an adapted, yet sustainable cultivation of T. melanosporum-inoculated oak tree in a desert climatic condition and introduces new opportunities of the agro-forest business in Saudi Arabia and GCC region.

A global meta-analysis of ITS rDNA sequences from material belonging to the genus Ganoderma (Basidiomycota, Polyporales) including new data from selected taxa

Ganoderma P. Karst. is a cosmopolitan genus of white-rot fungi which comprises species with highly-prized pharmaceutical properties, valuable biotechnological applications and of significant phytopathological interest. However, the status of the taxonomy within the genus is still highly controversial and ambiguous despite the progress made through molecular approaches. A metadata analysis of 3908 nuclear ribosomal internal transcribed spacer (ITS) rDNA sequences obtained from GenBank/ENA/DDBJ and UNITE was performed by targeting sequences annotated as Ganoderma, but also sequences from environmental samples and from material examined for the first time. Ganoderma taxa segregated into five main lineages (Clades A to E). Clade A corresponds to the core of laccate species and includes G. shanxiense and three major well-supported clusters: Cluster A.1 ('G. lucidum sensu lato') consists of taxa from Eurasia and North America, Cluster A.2 of material with worldwide occurrence including G. resinaceum and Cluster A.3 is composed of species originating from all continents except Europe and comprises G. lingzhi. Clade B includes G. applanatum and allied species with a Holarctic distribution. Clade C comprises taxa from Asia and Africa only. Clade D consists of laccate taxa with tropical/subtropical occurrence, while clade E harbours the highest number of non-laccate species with a cosmopolitan distribution. The 92 Ganoderma-associated names, initially used for sequences labelling, correspond to at least 80 taxa. Amongst them, 21 constitute putatively new phylospecies after our application of criteria relevant to the robustness/support of the terminal clades, intra- and interspecific genetic divergence and available biogeographic data. Moreover, several other groups or individual sequences seem to represent distinct taxonomic entities and merit further investigation. A particularly large number of the public sequences was revealed to be insufficiently and/or incorrectly identified, for example, 87% and 78% of entries labelled as G. australe and G. lucidum, respectively. In general, ITS demonstrated high efficacy in resolving relationships amongst most of the Ganoderma taxa; however, it was not equally useful at elucidating species barriers across the entire genus and such cases are outlined. Furthermore, we draw conclusions on biogeography by evaluating species occurrence on a global scale in conjunction with phylogenetic structure/patterns. The sequence variability assessed in ITS spacers could be further exploited for diagnostic purposes.

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.

Persistence of Tuber melanosporum in truffle orchards in North Carolina, USA

A survey was conducted to determine the persistence of mycorrhization by Tuber melanosporum in truffle orchards established with European and American species of oak and common hazel trees in North Carolina. The trees had reportedly been inoculated and colonized by T. melanosporum prior to planting. Root samples were collected from 95 trees among seven orchards in 2015 and roots were analyzed by morphology and quantitative PCR. Samples that tested negative for T. melanosporum or where ectomycorrhizal morphology was not observed were analyzed by sequencing to identify the mycorrhizal fungal symbiont present. The presence of T. melanosporum was detected in all seven orchards. In six orchards, T. melanosporum was detected on all trees, but in only two of fifteen trees in one orchard. Other species of Tuber including T. brennemanii, T. canaliculatum, and T. lyonii, species of Scleroderma, and members of the Pezizales were also detected by sequence analysis. Sporocarps of T. aestivum and T. brumale were found in 2017 and 2018 in separate orchards in North Carolina after the survey was conducted. Overall, results indicate that T. melanosporum has persisted in truffle orchards sampled in North Carolina. Indigenous and contaminating fungal species, including Tuber species, were also detected and present a challenge to the truffle industry in North Carolina.

Tuber iranicum, sp. nov., a truffle species belonging to the Excavatum clade

Truffles in the genus Tuber are hypogeus fungi that have a worldwide distribution. Despite this, knowledge about their diversity in the Middle East is very limited. In recent years, large quantities of truffles have been imported from Iran for being sold in Italy. While analyzing certain commercial batches of T. aestivum from Iran, we found some ascomata that resembled T. excavatum but had macro- and micromorphological features that were distinct from this species. They were subglobose, or depressed to slightly irregular, with a conspicuous basal cavity, grayish brown, brown, or pinkish gray, with a minutely papillose peridium. The gleba was pinkish gray in youth, brown at maturity, marbled with cream branched veins. Ascospores were broadly ellipsoid, with an irregular reticulum and distinctive long crests along the longitudinal axis, up to 9 µm high. Analysis of internal transcribed spacer (ITS) and large subunit (LSU) rDNA sequences showed that these specimens form a monphyletic and well-supported taxon within the Excavatum clade. Morphological and molecular analyses supported the proposal of the new species T. iranicum.

The new truffle genus Babosia and a new species of Stouffera from semiarid grasslands of Hungary

Truffles with distinct morphological and anatomical features were collected during a study of hypogeous fungi of semiarid sandy grasslands of the Great Hungarian Plain in Hungary, representing the westernmost localities of the Eurasian steppe belt. None of the ascomata were collected near ectomycorrhizal plant species, and none were identified as ectomycorrhizal during previous surveys in the collection area. We studied morphoanatomical characteristics of these truffles with light and scanning electron microscopy and investigated their phylogenetic positions based on analyses of different nuclear loci. The truffles were found to represent two novel lineages that grouped with the Marcelleina-Peziza gerardii clade of the Pezizaceae. One formed a distinct lineage, for which we propose a new genus Babosia with a new species Babosia variospora characterized by diverse spore ornamentation varying even within one ascus. The truffles in the other lineage clustered with the rarely collected American truffle Stouffera longii and share with it similar spore ornamentation and habitat features. However, our material differs from S. longii by geographic origin, the quick and strong coloration of the ascomata to dark gray at cut surface or bruised area, varying spore number in asci, and smaller spore size; thus, we describe it as a new species, Stouffera gilkeyae.

Fungal Planet description sheets: 1042-1111

Novel species of fungi described in this study include those from various countries as follows: Antarctica, Cladosporium arenosum from marine sediment sand. Argentina, Kosmimatamyces alatophylus (incl. Kosmimatamyces gen. nov.) from soil. Australia, Aspergillus banksianus, Aspergillus kumbius, Aspergillus luteorubrus, Aspergillus malvicolor and Aspergillus nanangensis from soil, Erysiphe medicaginis from leaves of Medicago polymorpha, Hymenotorrendiella communis on leaf litter of Eucalyptus bicostata, Lactifluus albopicri and Lactifluus austropiperatus on soil, Macalpinomyces collinsiae on Eriachne benthamii, Marasmius vagus on soil, Microdochium dawsoniorum from leaves of Sporobolus natalensis, Neopestalotiopsis nebuloides from leaves of Sporobolus elongatus, Pestalotiopsis etonensis from leaves of Sporobolus jacquemontii, Phytophthora personensis from soil associated with dying Grevillea mccutcheonii.Brazil, Aspergillus oxumiae from soil, Calvatia baixaverdensis on soil, Geastrum calycicoriaceum on leaf litter, Greeneria kielmeyerae on leaf spots of Kielmeyera coriacea. Chile, Phytophthora aysenensis on collar rot and stem of Aristotelia chilensis.Croatia, Mollisia gibbospora on fallen branch of Fagus sylvatica.Czech Republic, Neosetophoma hnaniceana from Buxus sempervirens.Ecuador, Exophiala frigidotolerans from soil. Estonia, Elaphomyces bucholtzii in soil. France, Venturia paralias from leaves of Euphorbia paralias.India, Cortinarius balteatoindicus and Cortinarius ulkhagarhiensis on leaf litter. Indonesia, Hymenotorrendiella indonesiana on Eucalyptus urophylla leaf litter. Italy, Penicillium taurinense from indoor chestnut mill. Malaysia, Hemileucoglossum kelabitense on soil, Satchmopsis pini on dead needles of Pinus tecunumanii.Poland, Lecanicillium praecognitum on insects’ frass. Portugal, Neodevriesia aestuarina from saline water. Republic of Korea, Gongronella namwonensis from freshwater. Russia, Candida pellucida from Exomias pellucidus, Heterocephalacria septentrionalis as endophyte from Cladonia rangiferina, Vishniacozyma phoenicis from dates fruit, Volvariella paludosa from swamp. Slovenia, Mallocybe crassivelata on soil. South Africa, Beltraniella podocarpi, Hamatocanthoscypha podocarpi, Coleophoma podocarpi and Nothoseiridium podocarpi (incl. Nothoseiridium gen. nov.) from leaves of Podocarpus latifolius, Gyrothrix encephalarti from leaves of Encephalartos sp., Paraphyton cutaneum from skin of human patient, Phacidiella alsophilae from leaves of Alsophila capensis, and Satchmopsis metrosideri on leaf litter of Metrosideros excelsa.Spain, Cladophialophora cabanerensis from soil, Cortinarius paezii on soil, Cylindrium magnoliae from leaves of Magnolia grandiflora, Trichophoma cylindrospora (incl. Trichophoma gen. nov.) from plant debris, Tuber alcaracense in calcareus soil, Tuber buendiae in calcareus soil. Thailand, Annulohypoxylon spougei on corticated wood, Poaceascoma filiforme from leaves of unknown Poaceae.UK, Dendrostoma luteum on branch lesions of Castanea sativa, Ypsilina buttingtonensis from heartwood of Quercus sp. Ukraine, Myrmecridium phragmiticola from leaves of Phragmites australis.USA, Absidia pararepens from air, Juncomyces californiensis (incl. Juncomyces gen. nov.) from leaves of Juncus effusus, Montagnula cylindrospora from a human skin sample, Muriphila oklahomaensis (incl. Muriphila gen. nov.) on outside wall of alcohol distillery, Neofabraea eucalyptorum from leaves of Eucalyptus macrandra, Diabolocovidia claustri (incl. Diabolocovidia gen. nov.) from leaves of Serenoa repens, Paecilomyces penicilliformis from air, Pseudopezicula betulae from leaves of leaf spots of Populus tremuloides. Vietnam, Diaporthe durionigena on branches of Durio zibethinus and Roridomyces pseudoirritans on rotten wood. Morphological and culture characteristics are supported by DNA barcodes.

Tuber luomae, a new spiny-spored truffle species from the Pacific Northwest, USA

Tuber luomae, a new truffle species known only from the Pacific Northwest, USA, is distinguished by spiny, non-reticulate spores and a two-layered peridium — the outermost layer (pellis) consists of inflated, globose to subpolygonal cells and the inner (subpellis) of narrow hyphae. ITS sequence analyses show that it has phylogenetic affinity to other Tuber species in the Rufum clade. The only other members of the Rufum clade with a strongly developed peridiopellis of large, inflated cells are the southern European T. malacodermum and T. pustulatum and the northern Mexican T. theleascum. We find it interesting that this peridial structure that is uncommon in the Rufum clade has been found in geographically disjunct species.