Tuber Aestivum Research Articles

Food Choice and Fitness of Folsomia candida (Collembola, Isotomidae) Fed on Twelve Species of Truffle

Fungi are a significant food resource for soil fauna, whose grazing behavior can have a significant impact on their development. This relationship is an important aspect in soil functioning, with soil fungi acting as primary agents in decomposition processes. Being one of the most abundant groups among soil fauna, springtails can play a leading role in this context. Despite several previous studies on their epigeous fungal grazing behavior, data regarding the relationship between springtails and truffles are scarce. This study aimed to investigate food preferences of the springtail Folsomia candida for grazing on 12 different species of truffles, 11 belonging to Tuber genus, and 1 to Balsamia genus. We also evaluated how strongly this diet influences survival and reproduction of F. candida. In the first experiment, F. candida were allowed to choose freely between a cereal mixture (choice test) and 12 different species of truffle. In the second experiment, they were fed on the truffles only (no-choice test) for 28 days. 12 truffle species were analyzed for survival and reproduction of F. candida. F. candida’s feeding preference evolved over 72 hours, beginning with a strong preference for the control and finally a general preference for truffles. Moreover, Collembola that fed on some Tuber species had a lower survival rate and fewer juveniles per adult compared to the control. Compared to other species, Tuber aestivum and Tuber melanosporum, which are well-known for their ability to produce brûlés, had a positive impact on collembolan fitness, whereas their palatability was not particularly prominent. Hence there was a relationship between diet and fitness in F. candida, whilst hardly any relationship was observed between fitness and feeding preference.

Orchard Conditions and Fruiting Body Characteristics Drive the Microbiome of the Black Truffle Tuber aestivum.

Truffle fungi are well known for their enticing aromas partially emitted by microbes colonizing truffle fruiting bodies. The identity and diversity of these microbes remain poorly investigated, because few studies have determined truffle-associated bacterial communities while considering only a small number of fruiting bodies. Hence, the factors driving the assembly of truffle microbiomes are yet to be elucidated. Here we investigated the bacterial community structure of more than 50 fruiting bodies of the black truffle Tuber aestivum in one French and one Swiss orchard using 16S rRNA gene amplicon high-throughput sequencing. Bacterial communities from truffles collected in both orchards shared their main dominant taxa: while 60% of fruiting bodies were dominated by α-Proteobacteria, in some cases the β-Proteobacteria or the Sphingobacteriia classes were the most abundant, suggesting that specific factors (i.e., truffle maturation and soil properties) shape differently truffle-associated microbiomes. We further attempted to assess the influence in truffle microbiome variation of factors related to collection season, truffle mating type, degree of maturation, and location within the truffle orchards. These factors had differential effects between the two truffle orchards, with season being the strongest predictor of community variation in the French orchard, and spatial location in the Swiss one. Surprisingly, genotype and fruiting body maturation did not have a significant effect on microbial community composition. In summary, our results show, regardless of the geographical location considered, the existence of heterogeneous bacterial communities within T. aestivum fruiting bodies that are dominated by three bacterial classes. They also indicate that factors shaping microbial communities within truffle fruiting bodies differ across local conditions.

Are bacteria responsible for aroma deterioration upon storage of the black truffle Tuber aestivum: A microbiome and volatilome study

Truffle fungi, luxurious food items with captivating aromas, are highly valued in the culinary world. However, truffles are perishable and their aroma undergoes deep changes upon storage. Additionally, truffle aroma might be partially derived from microbes. Hence, we investigated here the influence of storage on two factors, namely the volatile profile and bacterial community composition in the black truffle Tuber aestivum. The possible linkage among those factors was further explored.Our results demonstrate important changes in the volatile profiles of truffles over nine days of storage at room temperature. In the same time frame, dominant bacterial classes characteristic of fresh truffles (α-Proteobacteria, β-Proteobacteria, and Sphingobacteria classes) were gradually replaced by food spoilage bacteria (γ-Proteobacteria and Bacilli classes). Freshness and spoilage volatile markers (i.e. dimethyl sulfide (DMS), butan-2-one, 2- and, 2- and 3-methylbutan-1-ol, and 2-phenylethan-1-ol) were identified. Lastly, network analysis showed correlations between those markers and specific bacterial classes typical of fresh and spoiled truffles.Overall, our results demonstrate the profound effect of storage on the aroma and bacterial community composition of truffles and highlight how the gradual replacement of the commensal microbiome by spoilage microbes mirrors shifts in aroma profile and the possible loss of fresh truffle flavor.

New insights into black truffle biology: discovery of the potential connecting structure between a Tuber aestivum ascocarp and its host root

According to isotopic labeling experiments, most of the carbon used by truffle (Tuber sp.) fruiting bodies to develop underground is provided by host trees, suggesting that trees and truffles are physically connected. However, such physical link between trees and truffle fruiting bodies has never been observed. We discovered fruiting bodies of Tuber aestivum adhering to the walls of a belowground quarry and we took advantage of this unique situation to analyze the physical structure that supported these fruiting bodies in the open air. Observation of transversal sections of the attachment structure indicated that it was organized in ducts made of gleba-like tissue and connected to a network of hyphae traveling across soil particles. Only one mating type was detected by PCR in the gleba and in the attachment structure, suggesting that these two organs are from maternal origin, leaving open the question of the location of the opposite paternal mating type.

Elemental analysis of summer truffles Tuber aestivum from Germany

In an attempt to characterize inorganic constituents in Tuber aestivum, the summer truffle, samples from four different German states were collected by the “hypogea research group” for analytical investigations. Forty three elements in truffles, peridium and gleba were determined by three independent analytical techniques, PGAA, INAA and ICP-MS. PCA analysis of a set of data revealed a clear distinction of the different sampling sites. Results are discussed in view of the functional role of mycorrhizal fungi towards their host trees and the homeostatic control properties of the fungi.

A search for naturally grown Burgundy truffles (Tuber aestivum) on hazelnut plantations in Germany: Results of a survey

To overcome the increasing strain on agricultural crop production in Central Europe, new management practices are in demand that allow for sustainable farming systems while providing the farmers with a reliable income. One option is the establishment of hazelnut plantations (Corylus avellana) to produce and sell hazelnuts. A possibility to further increase benefits from hazelnut plantations might be offered by harvesting summer truffles (or Burgundy truffles, Tuber aestivum), a species that frequently forms mycorrhizae with hazelnut trees in the wild. Consequently, a first systematic survey was undertaken to assess the potential presence of naturally grown T. aestivum on 14 existing hazelnut plantations in Germany using trained truffle dogs. Naturally grown Burgundy truffles were not found on the visited plantations. The dogs unearthed eight other species of hypogeous fungi. Hazelnut farmers should not be too optimistic that naturally grown T. aestivum will provide them with a noteworthy additional income from their plantations.

Ribosomal DNA polymorphisms reveal genetic structure and a phylogeographic pattern in the Burgundy truffle Tuber aestivum Vittad.

ABSTRACTEctomycorrhizal ascomycetes belonging to the genus Tuber produce edible fruiting bodies known as truffles. Tuber aestivum, in particular, is a fungus appreciated worldwide and has a natural distribution throughout Europe. Most of the molecular studies conducted on this species have been focused on the question as to whether or not T. aestivum and the morphologically similar T. uncinatum are conspecific. Conversely, only a handful of studies have assessed the level and distribution of genetic diversity and occurrence of phylogeographic patterns in this species. Here, we analyzed the genetic diversity of T. aestivum over a wide geographic range, performing an extensive sampling of specimens from Turkey, which is novel, to the best of our knowledge. We compared the internal transcribed spacer (ITS) profiles of 45 samples collected in different Turkish areas with those of 144 samples from all over Europe. We identified 63 haplotypes, 32 of which were exclusively present in Turkey. The majority of these haplotyes were also population specific. Haplotype network analysis and statistical tests highlighted the presence of a genetic structure and phylogeographic pattern, with three spatially distinct genetic clusters (northeastern Europe, southern Europe, and Turkey), with Turkey representing a diversity hotspot. Based on these results, we hypothesize the presence of glacial refugia for T. aestivum in Turkey, whereas European populations likely experienced a population bottleneck. The possible occurrence of cryptic species among Turkish T. aestivum samples also emerged. Our results are of practical relevance for the marketing of T. aestivum truffles and mycorrhizal seedlings and the preservation of the biodiversity of this species.

The diversity of macromycetes in the territory of Batočina (Serbia)

The purpose of this paper was discovering the diversity of macromycetes in the territory of Batočina (Serbia). Field studies, which lasted more than a year, revealed the presence of 200 species of macromycetes. The identified species belong to phyla Basidiomycota (191 species) and Ascomycota (9 species). The biggest number of registered species (100 species) was from the order Agaricales. Among the identified species was one strictly protected - Phallus hadriani and seven protected species: Amanita caesarea, Marasmius oreades, Cantharellus cibarius, Craterellus cornucopiaodes, Tuber aestivum, Russula cyanoxantha and R. virescens; also, several rare and endangered species of Serbia. This paper is a contribution to the knowledge of the diversity of macromycetes not only in the territory of Batočina, but in Serbia, in general.

MUSHROOM DIVERSITY IN SHAKI DISTRICT OF AZERBAIJAN

Mushroom diversity in Shaki district of Azerbaijan was studied during 2013-2018. Totally 346 specimens were collected and identified based on the morphologically main diagnostic features. Phenotypic characters, as well as microscopic features (size, shape, color of spores) were considered. In total 111 taxa (106 species, three forms and two variations) belonging to 67 genera, 32 families and 11 orders of Ascomycota and Basidiomycta were identified in view of the latest taxonomic and nomenclature changes. Two taxa Morchella esculenta var. rotunda and Suillus luteus f. albus represent new records for Azerbaijan. Ecological groups of mushrooms were reflected. Amanita fulva, A. pantherina, A. vaginata, Apioperdon pyriforme, Boletus edulis, B. reticulatus, Bovista plumbea, Caloboletus radicans, Cantharellus cibarius, C. subalbidus, Chlorophyllum rhacodes, Coprinopsis atramentaria, Hymenopellis radicata, Hypholoma fasciculare, Lactarius piperatus, Leccinum scabrum, Lepiota cristata, Lycoperdon umbrinum, Morchella esculenta, Mycena crocata, M. pura, Russula foetens, R. rosacea, Sarcoscypha coccinea, Suillus granulatus, S. luteus, Suillellus luridus and Tricholoma ustale were frequently found in the district. The rare species found in the studied area were Butyriboletus regius, Cortinarius triumphans, Clavariadelphus pistillaris, Crepidotus cesatii, Lactarius deliciosus, Morchella crassipes, Otidea onotica, Suillellus queletii and Tuber aestivum. Species variation was observed to increase along the elevation gradient, starting from the low mountain zone. Abundance of species decreases in the middle-upper mountain zone. Species distribution patterns along the elevation gradients are affected by mountain range peculiarities and climate warming. Numerous species have been recorded in more than one altitude. Use possibility of fungi is also elucidated.

Identification of Soils Factors Influence in the Distributions of Tuber aestivum in Transylvanian Subcarpathian Hill, Romania

Truffles are one of the most hunted varieties of mushrooms in Europe due to their high price and their increasingly frequent use in the kitchen. As demonstrated by several studies, soil conditions are among the main factors that influence the spread and development of the black truffle species. The purpose of this study was to identify the soil factors which directly and indirectly influence the distribution of black truffles (Tuber aestivum Vittad.) in Romania and to identify the areas from the Subcarpathian Hills of Transylvania which are highly favourable to their existence and growth, using G.I.S. spatial analysis and databases which include soil characteristics (soil type, texture, gleization, stagno-gleization) and territorial localisation through GPS points indicating the samples of Tuber aestivum. By implementing the statistical model of spatial analysis (BSA – Bivariate Statistical Analysis) for each characteristic, a series of areas were classified into three classes of favourability (low, medium, high) for the growth of Tuber aestivum. The results were validated indirectly by comparing the overlapping of the areas from the high favourability class with the areas covered with tree species from the Quercus genus and directly, through field research (on the surfaces with maximum favourability), done by specialised truffle seekers. The results were validated with a very high confidence rate for both methods (method 1 - overlapping of approximatively 93%, method 2 - Tuber aestivum was identified on 12 out of 15 test surfaces from the high favourability class).

Soil Properties Conducive to the Formation of Tuber aestivum Vitt. Fruiting Bodies

Soil Properties Conducive to the Formation of Tuber aestivum Vitt. Fruiting Bodies

Soil Properties Conducive to the Formation of Tuber aestivum Vitt. Fruiting Bodies

Soil Properties Conducive to the Formation of Tuber aestivum Vitt. Fruiting Bodies

Pezizomycetes genomes reveal the molecular basis of ectomycorrhizal truffle lifestyle

Tuberaceae is one of the most diverse lineages of symbiotic truffle-forming fungi. To understand the molecular underpinning of the ectomycorrhizal truffle lifestyle, we compared the genomes of Piedmont white truffle (Tuber magnatum), Périgord black truffle (Tuber melanosporum), Burgundy truffle (Tuber aestivum), pig truffle (Choiromyces venosus) and desert truffle (Terfezia boudieri) to saprotrophic Pezizomycetes. Reconstructed gene duplication/loss histories along a time-calibrated phylogeny of Ascomycetes revealed that Tuberaceae-specific traits may be related to a higher gene diversification rate. Genomic features in Tuber species appear to be very similar, with high transposon content, few genes coding lignocellulose-degrading enzymes, a substantial set of lineage-specific fruiting-body-upregulated genes and high expression of genes involved in volatile organic compound metabolism. Developmental and metabolic pathways expressed in ectomycorrhizae and fruiting bodies of T. magnatum and T. melanosporum are unexpectedly very similar, owing to the fact that they diverged ~100 Ma. Volatile organic compounds from pungent truffle odours are not the products of Tuber-specific gene innovations, but rely on the differential expression of an existing gene repertoire. These genomic resources will help to address fundamental questions in the evolution of the truffle lifestyle and the ecology of fungi that have been praised as food delicacies for centuries.

Effect of soil properties and vegetation characteristics in determining the frequency of Burgundy truffle fruiting bodies in Southern Poland

ABSTRACTThe Burgundy truffle (Tuber aestivum Vittad.) has a wide-ranging distribution across Europe, yet its ecology is far from being well understood. For instance, although the literature on the ecophysiology of this species is dominated by the symbiosis with deciduous hosts, the real range of hosts in nature seems to be much wider than the current distribution of T. aestivum. The aim of this study was to determine the relative importance of abiotic (soil) and biotic (vegetation) properties in determining the performance of T. aestivum in this pioneering stage of research on truffles in Poland. Soil parameters influenced the formation of T. aestivum fruiting bodies more strongly than plant composition. The number of fruiting bodies increased with increasing concentration of soil calcium and phosphorus. The number of plant species was the only significant predictor among the investigated vegetation characteristics. The influence of this predictor was positive, as an increasing number of fruiting bodies was found when the number of plant species was higher. The presence of truffle fruiting bodies was significantly correlated with the presence of five plant species, viz.: Brachypodium sylvaticum, Cephalanthera damasonium, Cornus sanguinea, Sanicula europaea and Viola mirabilis.

Determining mycorrhiza rate in some oak species inoculated with Tuber aestivum Vittad. (summer truffle)

Truffle cultivation is important because it has contributions to tourism as well as other sectors and is a significant activity especially in stimulating rural economy. In this article, it is aimed to determine the most suitable oak species for the development of the Tuber aestivum Vittad. (summer truffle) and to provide guidance for the establishment of truffle gardens. Quercus robur L., Q. ilex L., Q. coccifera L were germinated, the seedlings were inoculated with T. aestivum which is an important element of Turkish biological diversity. The mycorrhiza were counted in the roots after the 15-month growth period of the seedlings to which T. aestivum was inoculated. As a result of the counts, it was determined that the rate of the roots with mycorrhiza (PT) was 0.93 in Q. robur L., 0.91 in Q. coccifera L. and 0.90 in Q. ilex L. Contaminated root rate (PC) was 0.28 in Q. robur L., 0.28 in Q. ilex L. and 0.30 in Q. coccifera L. According to the results, Q. robur is the oak species with the highest mycorrhizal development rate.

Crested porcupines (Hystrix cristata): mycophagist spore dispersers of the ectomycorrhizal truffle Tuber aestivum.

Truffles, as hypogeous, ectomycorrhizal fungi, have no means to actively discharge spores into the environment and thus depend on mycophagists for spore dispersal. After consumption of fruiting bodies by animals and passage through the digestive tract, the spores are released in faecal pellets. Recently, in the Abruzzo region (Italy), Hystrix cristata has been spotted inside private truffières, but its role in spore dispersal has never been investigated. Here, we report our research on the occurrence of Tuber aestivum spores in porcupine's faecal contents in a truffière in L'Aquila, Italy, where a H. cristata specimen was photographed. The spores were isolated from faeces by using a suspension of 0.7M ZnSO4. We also verified degradation and disfiguration of the digested spores' reticular ornamentation compared to that of fresh spores from ascomata collected inside the truffière, through measurements performed by scanning electron microscopy. A few truffle spores had germinated within the faeces.

Multi-cropping edible truffles and sweet chestnuts: production of high-quality Castanea sativa seedlings inoculated with Tuber aestivum, its ecotype T. uncinatum, T. brumale, and T. macrosporum.

The plantation and management of sweet chestnut (Castanea sativa Mill.) orchards is a common and traditional land use system in many areas of Europe that offers the advantage of simultaneous production of nuts and timber. During the last decades, sweet chestnut has declined dramatically in many regions because of the profound social changes in rural areas coupled with pathogen attacks. Truffles, the hypogeous ascocarps of the ectomycorrhizal genus Tuber, are currently cultivated using host trees inoculated with these fungi for improving production in truffle orchards. The production of good forestry quality chestnut seedlings inoculated with European truffles in nurseries is essential for multi-cropping plantation establishment, but so far, it has not been implemented in agroforestry practices. Moreover, it is necessary to assess the physiological condition of the seedlings due to the high calcium amendment needed for the growth of Tuber spp. mycelium that can become toxic for the host plants. In this study, seedlings of C. sativa were inoculated with Tuber aestivum and its ecotypes T. uncinatum, T. brumale, and T. macrosporum and were grown in a greenhouse using culture conditions favorable for the production of high-quality plants for forestry purposes. At the end of the assay, levels of root colonization and morphological and physiological parameters of the seedlings were measured. The colonization of C. sativa with T. aestivum, its ecotype T. uncinatum, and T. brumale was successful, and the seedlings showed normal growth. Inoculation protocols with T. macrosporum need to be improved. Tuber species formed well-developed ectomycorrhizae on C. sativa in nursery conditions.

Characterization of the Key Aroma Compounds in White Alba Truffle (Tuber magnatum pico) and Burgundy Truffle (Tuber uncinatum) by Means of the Sensomics Approach.

Aroma extract dilution analysis of distillates prepared by solvent extraction and solvent-assisted flavor evaporation distillation from white Alba truffle (WAT; Tuber magnatum pico) and Burgundy truffle (BT; Tuber uncinatum) revealed 20 odor-active regions in the flavor dilution (FD) factor range of 16-4096 in WAT and 25 in BT. The identification experiments in combination with the FD factors showed clear differences in the overall set of key odorants of both fungi. While 3-(methylthio)propanal (potato-like) followed by 2- and 3-methylbutanal (malty), 2,3-butanedione (buttery), and bis(methylthio)methane (garlic-like) showed the highest FD factors in WAT, 2,3-butanedione, phenylacetic acid (honey-like), and vanillin (vanilla-like) had the highest FD factors in BT. Odor activity values (OAVs, ratio of concentration to odor thresholds), which were calculated on the basis of quantitative data obtained by stable isotope dilution assays, of >1000 for bis(methylthio)methane, 3-methylbutanal, and 3,4-dihydro-2-(H)pyrrol (1-pyrroline) revealed they are key contributors to the aroma of WAT. In BT, 1-pyrroline and 2,3-butanedione showed the highest OAVs of 1530 and 1130, respectively. Aroma recombination experiments successfully mimicked the overall aroma profiles of both fungi when all odorants showing OAVs of >1 were combined. Omission experiments confirmed the amine-like and sperm-like smell of 1-pyrroline, identified for the first time as a key odorant in both truffle species.

Ecological indicators of Tuber aestivum habitats in temperate European beech forests

Abstract Although Tuber aestivum is widely distributed across Europe, little is known about its biology and ecology. We assess the vegetation composition of wild T. aestivum sites and use this information to characterise suitable habitats in Fagus sylvatica , Carpinus betulus and Ostrya carpinifolia (FCO) forests. Plant species composition at 16 naturally colonised T. aestivum sites in southwestern Germany and Switzerland was compared with that of 232 reference sites in Swiss FCO forest communities. The vegetation composition of truffle sites exhibits a high proportion of herb and shrub species that are indicators of a warm and dry climate, alkaline soil, and open tree canopy and thus typically occur in thermophilous FCO communities on calcareous bedrock. We conclude that T. aestivum is associated with a set of key species in addition to known host species. Based on their floristic composition, we identified FCO forest communities with high and low suitability for T. aestivum .

Soil receptivity for ectomycorrhizal fungi: Tuber aestivum is specifically stimulated by calcium carbonate and certain organic compounds, but not mycorrhizospheric bacteria

Mycelium of ectomycorrhizal fungi colonizes soil that is extremely heterogeneous in terms of spatial arrangement as well as chemical and biological properties. Here we addressed which of the soil components would have the greatest influence on hyphal development of an ectomycorrhizal fungus, the summer truffle (Tuber aestivum). We tested a range of inorganic and organic compounds and bacterial strains isolated from truffle mycorrhizosphere, added to truffle grounds in small compartments accessible exclusively to the hyphae and not to host plant roots. Our results showed stimulation of truffle hyphal growth by high dosis of lime powder, whereas leaf litter had no effect. Further, we recorded significant stimulation of the hyphal growth by several organic compounds (gallic acid, cellulose and calcium formate), whereas no significant stimulation was observed by any of the inorganic compounds or bacterial cultures mixed with an inert carrier. None of the amendments, however, sustained the truffle growth rate recorded in unsterile field soil. These results indicate that the development of hyphae of T. aestivum in soil may well require complex and micro-heterogeneous environment, where specific organic compounds and calcium carbonate play particularly important roles.