Bolete tissue degrades quickly once picked. Enzymes keep working, pigments oxidise and moulds start on the surface within days. How you store a sample decides which analyses it is still good for.
How long can fresh fruiting bodies be kept?
About three days at 2–4 °C, wrapped in paper and not sealed in plastic. After that, softening, browning and microbial growth become visible. If you cannot process the material within that window, decide on arrival whether to freeze, dry or silica-dry it, according to the analyses you plan.
How should tissue be frozen for RNA or metabolomics?
Cut small blocks, a few millimetres thick, from the area you plan to study. Drop them into liquid nitrogen, transfer to pre-chilled tubes and store at −80 °C. Do not freeze whole caps at −20 °C: slow freezing ruptures cells and lets enzymes act during thawing. Avoid repeated freeze-thaw cycles.
For RNA, an RNA-stabilising solution is an alternative if liquid nitrogen is not available on the day. Follow the manufacturer’s tissue-to-volume ratio, which is easy to exceed with dense bolete flesh.
What is the best way to keep tissue for DNA?
Dry a small piece of clean tissue quickly in silica gel, using roughly ten times its volume of gel, in a sealed tube or bag. Once dry, DNA in fungal tissue stays usable for years at room temperature. This is also how voucher tissue is usually preserved alongside herbarium specimens.
How should dried slices be stored?
Sealed, dry, dark and cool. Keep slices in their barrier bag with the silica gel sachet, or in an airtight glass jar with fresh desiccant. A cool cupboard at 15–20 °C is fine. Below about 8–10% moisture, dried fungal tissue is stable for a year or more.
- Check the desiccant. Indicating silica gel changes colour when saturated; replace or regenerate it.
- Keep light out. Pigments fade under daylight over weeks.
- Watch for insects. Dried fungi attract beetles if left in open containers.
How should powder be aliquoted?
Split the powder into single-use vials on the day you open it, working in the driest place available. Fine powder absorbs moisture quickly, and every opening of the main bag adds a little. Label each vial with batch number, date and weight, and store vials with desiccant in a sealed container.
Should I freeze-dry fresh material myself?
If you have a freeze dryer and need dried material with minimal heat exposure, yes. Freeze the tissue first, then lyophilise. The result is closer to fresh tissue chemically than oven-dried slices, at the cost of time. It is a reasonable choice for studies of possibly heat-sensitive constituents.
What should go on every sample label?
At minimum: species, batch number, origin, harvest date, format, how and when it was processed in your lab, and storage temperature. With wild material, the batch number links your result to the certificate of analysis, the retention sample and the harvest record, which is what makes it reproducible.