Proper culture preservation is an integral part of the successful mushroom cultivation. The main objective of culture preservation is to store cultures in viable and stable form for long periods without losing genotypic, phenotypic and physiological traits.
Isolates in culture tubes stored at room temperature had a maximum life of 6–12 months, whereas those kept under refrigeration survived for five years or more. The time gap between sub/culturing varied with species and in general, was in the range of 3–12 months.
The most common and simple method of short-term storage of mushroom culture is storing the culture tubes at room temperature (28–35ºC) for a period of 1–2 months or in refrigerator (5–8ºC) for an average period of 3–4 months. Most tropical basidiomycete isolates grown on PDA or MEA were not viable beyond two months at 4ºC or after six months at 8–10ºC.
Some mushroom varieties are not tolerant cold condition. Example, cultures of Calocybe indica, Volvariella volvacea (commercial edible mushrooms) and some isolates of Ganoderma lucidum (commercial medicinal mushroom) cannot be stored under refrigerated condition. However, some researches revealed that these mushroom cultures could safely be stored at low temperatures on cereal grain (sorghum, millet…) free from contamination for more than one year without any growth and morphological changes.
The probable reason for the better survival of mushroom mycelium on cereal grain may be either because of the protection given by the grain to the soft and tender mycelium, concealed inside the grain and thus could have sustained cooling. Similarly, Singh et al. 2004 reported that mycelium multiplied on wheat grains were genetically more stable as compared to mycelial discs of synthetic media during cryopreservation.
The table below will show up the techniques of mushroom culture preservation and the advantages as well as disadvantages of the techniques
Singh SK, Upadhyay RC, Yadav MC, Tiwari, M. 2004. Development of a novel lyophilization protocol for preservation of mushroom mycelial cultures. Current Science 87, 568–570.
Richard A. Humber. Fungi: Preservation of cultures.