Having evolved underground, truffles lack the distinctive features of mushrooms such as coloured caps, with many looking more like potatoes or clods of soil than mushrooms. Determining the species of a truffle requires examination of macroscopic characteristics (visible to the naked eye) and potentially, using a microscope to look at the truffle’s spores. Even with the information and tools it’s not easy! Researchers opinions on some species, whether they are the same or different, related or not, can be divided.
For most of us, determining the species of a truffle is based on morphological characteristics. These are macroscopic in scale (visible to the naked eye) although a hand lens may help with finer detail.
- Peridium (truffle skin) presence / absence of warts, wart size / shape, thickness, colour etc.
- Gleba (truffle flesh) colour, marbling, presence / absence of chambers, etc.
Additionally, you consider:
- Aroma and potentially, flavour
- The habitat where the truffle was found – the trees it was growing with and basic knowledge of the soils can further assist.
- For some species, a colour reaction to a chemical such as iodine helps identification.
Getting more accurate identification requires a microscope for examination of the spores, a fair amount of technical expertise, and a lot of practice! Their size, shape, colour and ornaments are among the features examined.
More recently, in the laboratory, molecular (DNA) analyses are used to determine species accurately. Companies that produce truffle trees need to get identifications 100% correct, so they routinely use DNA testing.
If you are struggling to determine the species of a truffle you have found, it can be difficult:
- “All species of Tuber show considerable changes in shape, colour and other characters during development. Variation within the species, due partly to differences in environmental factors, is often considerable.” Lilian E. Hawker (1954), British Hypogeous Fungi, Trans. Roy. Soc., London, Sr B, 237: 429-546
- You may get one species growing in amongst another.
- Scientific (Latin) names change – new studies, including genetic ones, may decide that what were previously distinct species are the same. Authors of different studies may not agree on their findings!
- The literature on this topic is quite technical and sometimes conflicting!
- Not all information may be up to date.
- You will find synonyms – scientific names that applied to a species that (now) goes by a different scientific name.
- Common (English) names can confuse!
- Some truffle species have multiple common names. For example, the Périgord truffle (Tuber melansporum) is also known as the black winter truffle or just simply, the black truffle.
- Some common names are used to refer to more than one species! For example, winter truffle is used for T. melansporum and T. brumale.