Virtual Truffle Hunting—A New Method of Burgundy Truffle (Tuber aestivum Vittad.) Site Typing

The aim of this study was to enable searches for truffles (Tuber spp.), particularly the Burgundy truffle (T. aestivum Vittad.), to be carried out in forests based on a method that has been constantly developed since 2007 by the Forest Research Institute. The method is termed “Virtual Truffle Hunting” and it takes 12 parameters into account: bedrock, soil pH, Ca+ and CaCO3 content in soil, C/N ratio, soil structure, altitude of terrain, type of forest site, forest structure, the Burgundy truffle host trees, and the presence of particular species including orchids and insects. A simple “Virtual Truffle Hunting” software has also been developed, which makes the use of the method easy, fast, and effective. This method is to ascertain the truffle potential for all areas in which digital maps are not available. In 2015, the method was tested in 20 sites, representing forests in 5 Polish macroregions. Hunting for hypogeous fungi was conducted from June to October with the help of trained dogs. Thanks to this method, 14 new truffle sites were found. The knowledge of environmental conditions conducive to the Burgundy truffle growth enabled us to form an effective tool in order to identify new sites of truffle presence.

Biochemical and Health Properties of Truffles

Truffles are the most expensive edible mushrooms refer to genus tuber which grows symbiotically in plant roots such as oaks and hazels. Truffles are underground mushrooms also known for their characteristic earthy flavor which is the major reason for their special place in the culinary. Their characteristic intense aroma helps them in reproduction by attracting small animals. Truffles can survive in a wide range of environments such as deep forests as well as deserts. The most expensive varieties of truffles include Tuber melanosporum (Black truffle), Tuber magnatum (White truffle), Tuber aestivum (Burgundy truffle), Tirmania nivea, and Terfezia chlaveryi (Dessert truffles). Truffles vary in their composition and flavor profile from species to species. The major volatile components which are responsible for truffle aroma are aldehydes, ketones, sulfur compounds, alcohols, and esters. Truffles are highly nutritious, rich in antioxidants, and have therapeutic properties such as antimicrobial activity, antiviral activity, antimutagenic activity, anti-inflammatory activity, hepatoprotective activity, etc. The major active components present in truffle are tuberoside, phenolics, anandamide, and ergosterol.

Identification of bacteria and fungi inhabiting fruiting bodies of Burgundy truffle (Tuber aestivum Vittad.)

Tuber species may be regarded as complex microhabitats hosting diverse microorganisms inside their fruiting bodies. Here, we investigated the structure of microbial communities inhabiting the gleba of wild growing (in stands) T. aestivum, using Illumina sequencing and culture-based methods. The two methods used in combination allowed to extract more information on complex microbiota of Tuber aestivum gleba. Analysis of the V3–V4 region of 16S rDNA identified nine phyla of bacteria present in the gleba of T. aestivum ascomata, mostly Proteobacteria from the family Bradyrhizobiaceae. Our results ideally match the earlier data for other Tuber species where the family Bradyrhizobiaceae was the most represented. The ITS1 region of fungal rDNA represented six alien fungal species belonging to three phyla. To complement the metagenomic analysis, cultivable fungi and bacteria were obtained from the gleba of the same T. aestivum fruiting bodies. The identified fungi mostly belong to the phylum Basidiomycota and same to Ascomycota. Analysis of cultivable bacteria revealed that all the specimens were colonized by different strains of Bacillus. Fungal community inhabiting T. aestivum fruiting bodies was never shown before.

Soil temperature and hydric potential influences the monthly variations of soil Tuber aestivum DNA in a highly productive orchard

Tuber aestivum, also known as the summer or Burgundy truffle, is an ectomycorrhizal Ascomycete associated with numerous trees and shrubs. Its life cycle occurs in the soil, and thus soil parameters such as temperature and water availability could influence it. T. aestivum cultivation has started in several countries, but ecological and agronomic requirements for the establishment and management of orchards are largely unknown. The aims of this work were: 1) to design a specific qPCR protocol using genomic data to trace and quantify T. aestivum DNA in the soil; and 2) to assess the monthly soil DNA dynamic according to soil parameters (i.e. soil hydric potential and temperature) in this orchard. The study was conducted in a highly productive T. aestivum orchard (hazels, oaks, pines, lime and hornbeam). The production started five years after the plantation and then increased exponentially to reach a maximum of 320 kg/ha in 2017. The soil hydric potential and temperature partially explained the monthly T. aestivum soil DNA variability. The data presented here offer new insights into T. aestivum ecology and cultivation.

Ectomycorrhizal communities in a Tuber aestivum Vittad. orchard in Poland

Cultivation of the Burgundy truffle, Tuber aestivum Vittad., has become a new agricultural alternative in Poland. For rural economies, the concept of landscaping is often considerably more beneficial than conventional agriculture and promotes reforestation, as well as land-use stability. Considering examples from France, Italy, Hungary and Spain, truffle cultivation stimulates economic and social development of small, rural communities. Because there is no long tradition of truffle orchards in Poland, knowledge regarding the environmental factors regulating the formation of fruiting bodies of T. aestivum is limited. Thus, knowledge concerning ectomycorrhizal communities of T. aestivum host species is crucial to ensuring successful Burgundy truffle production. We investigated the persistence of T. aestivum ectomycorrhizae on roots of hazel (Corylus avellana L.) and oak (Quercus robur L.) and checked the host-species influence on community structure of ectomycorrhizal fungi. The study was conducted in an experimental plantation located in eastern Poland and established in 2008. We demonstrated that the number of fungal taxa was not significantly different between oak and hazel. However, the species composition differed between these two host trees. During the three-year study, we observed that species richness did not increase with the age of the plantation.

Europe, a continent with high potential for the cultivation of the Burgundy truffle (Tuber aestivum/uncinatum)

The Burgundy truffle (<em>Tuber aestivum/uncinatum</em>) grows, in Europe, in the most varied soils from a physical and chemical viewpoint. The only common point is the presence of a minimum level of exchangeable calcium in the soil. The truffle soils in Europe can be classified in two categories: the soils coming directly from the parent rock, and those formed from deposits covering the parent rock. The first group corresponds to most traditional truffle areas , France, Italy and Spain. It is also true for some soils from Ireland to Eastern Europe (Romania, Bulgaria), from Southern Europe (Greece, former Yugoslavia) to Northern Europe (Sweden, Baltic countries). The sedimentary layers that cover most areas are from the secondary and tertiary era. The primary parent rocks are less frequent. The second group means quaternary or recent alluviums covering the parent rock on huge surfaces and at great depth sometimes. They characterize mainly countries Eastern and Northern Europe. By bringing within reason limestone, it is possible to cultivate <em>T. aestivum/uncinatum</em> on sedimentary soils non-calcareous or decalcified or even on soils issued from magmatic rocks (granite) or metamorphic (schists). The possibilities of truffle cultivation in Europe are therefore enormous, the limiting factors not being the soil but the climate.