B. Papp szerk.: Studia Botanica Hungarica 29. 1998 (Budapest, 1999)

Vasas, Gizella, Bohus, Gábor; Locsmándi, Csaba: Genetic resource collection of macrofungi in Hungary

After the pre-freezing procedure the cryotubes are fastened onto holders. The holders are placed in canisters, which have a handle and sieve-like bottom. The canisters are sunken into liquid nitrogen in a culture-storing container (40 1, GT-40 type). A total of 1,200 tubes (2 ml) can be stored in one GT-40 type container ( 10 canisters, 20 holders per canister, and 6 tubes per holder). Each tube is furnished with a 5-digit-number code. The first two digits stand for the number of the canisters (01-10), the second two digits for the number of the holders (01-20), and the last digit for the position of the tube on the holder (1-6), numbering from downwards to upwards in increasing order. These code numbers are written by alcohol-based (permanent) marker pen. In our experience, this ink is not damaged by the low temperature. The isolates can be stored in liquid nitrogen at ultralow temperature (-196°C) for decades without any damage. It is very important to revive the cultures in every 2-3 years for testing their vitality, virulence, purity and morphological properties. Two tubes per isolates are recommended to be tested. They are warmed up at 35-^10

o

C for some minutes, until the last ice crystals have been melted. The outer surface of the tubes have to be cleaned very carefully by alcohol, and then the agar disks are placed in Petri plates. If the mycelium web falls off the surface of the agar disk by chance, the whole glycerine solution (incl. the mycelium web and fragments) should be poured onto the medium, after having removed the agar disks. T ("C) 30 20 10 0 -10 -20 -30 -40 10 20 30 40 50 60 t (min) Fig. 1. Freezing curve.