A Truffle is the fruiting body (sporocarpum and ascocarpum) of a group of underground (hypogeus) fungi. It belongs to the group of Ascomycetes, order Pezizali, family Tuberaceae, genus Tuber. It is made up of an external covering called peridium (smooth or bumby, light or dark-coloured), and of an internal fleshy part called glebum whose colour may range from white to brown, grey, pink and black. The glebum consists of tightly interwoven veins which define the alveoli containing many big cells (asci), each of which contains the spores. The morphological features of the peridium, gleba, asci and spores, as well as the size and organoleptic characteristics, allow to identify the truffle variety.
All the mushrooms are sub-divided into three big groups according to the way they absorb organic substances, and namely;
- saprotrophics
- parasites
- symbionts
The third group is definitely the most important, since it involves species of mushrooms for culinary use. For example, the “royal mushroom” or “ovulo buono” (Amanita caesarea), the “porcino” (Boletus edulis), and especially the sought-after truffles (Tuber spp) belong to this group.
Truffles must live in symbiosis with trees in order to produce the rare sporocarpum so appreciated by gourmets. The exchange of nutrients between the two parties takes place at the root level, thanks to the so-called mycorrhizae. A mycorrhiza is normally a sheath (mycoclena) made up of 5-6 layers of filaments called hyphae which wrap the apical roots of the tree and get into the first layers of root cells, thus creating the Hartig net. At this point, the tree offers the mushroom carbon hydrates (sugars), besides other substances (probably amino acids and hormones), and gets mainly water and mineral salts in exchange. From this net several hyphae branch off, and the all group is called mycelium. It then spreads into the ground (even several metres deep) in search of nutrients.
When the environment conditions are appropriate, some hyphae interweave and make up the fruiting body, whose spores, while germinating, create a new mycelium which will be able to join young apical roots and form new mycorrhizae.
Classification
