Tolerance of ectomycorrhizal fungus mycelium to low temperature and freezing–thawing

Very little is known about the tolerance of ectomycorrhizal fungi to the freezing and repetitive freezing–thawing in northern coniferous forests. Isolates of Cortinarius multiformis, Russula densifolia, Suillus granulatus, and Lactarius deliciosus were exposed to a series of temperatures between +4 and –40 °C. The relative electrolyte leakage test indicated that the lethal temperature for 50% of samples was between –7.6 and –13.7 °C. Resume growth experiments showed that the 4 species of ectomycorrhizal fungi had a relatively high tolerance to the low temperatures, with L. deliciosus having the highest tolerance and C. multiformis the lowest. The repeated freezing–thawing delayed the growth of mycelium, which decreased with an increase in the number of freeze–thaw cycles.