Isolates of the snow mold fungus Typhula ishikariensis group III, which is predominant in Finnmark (northern Norway) and Svalbard, are more resistant to freezing stress than group I isolates from the southern part of Norway. Group III isolates showed irregular growth on potato dextrose agar (PDA) plates when subjected to heat stress at 10°C. However, group III isolates showed relatively good growth on PDA at 10°C after freezing treatment. The optimal temperatures for mycelial growth were 5°C on PDA and 10°C in potato dextrose broth (PDB), and group III isolates showed normal mycelial growth at 10°C in PDB. Mycelium of group III isolates cultivated in water poured into PDA plates, and normal hyphal extension was observed only in the liquid media. Hyphal growth became irregular when mycelia had extended above the surface of the liquid media. These results suggested that group III isolates can grow at a sub-lethal temperature after freezing stress and during flooding. Soil freezing and thawing occurs regularly in the Arctic, and physiological characteristics of group III isolates are well adapted to climatic conditions in the Arctic.
