Intraspecific and interspecific growth variation of ectomycorrhizal fungi at different temperatures

Abstract

Geographically distinct isolates of the ectomycorrhizal fungi Pisolithus tinctorius, Cenococcum geophilum, Thelephora terrestris, and Suillus granulatus showed definite temperature optima for growth in pure culture. Temperatures promoting the greatest fungal growth varied interspecifically and intraspecifically over the temperature treatments of 16, 21, 27, 32, and 38 °C. Of the four fungal species, Pisolithus tinctorius exhibited the greatest growth at the higher temperature treatments, with growth optima for all isolates occurring between 21 and 32 °C. The maximum temperature for growth of Cenococcum geophilum was 27 °C, with optimal mycelial growth occurring between 16 and 27 °C, depending upon the particular isolate considered. Suillus granulatus showed greatest mycelial growth at 27 °C and below, with temperature optima for the different isolates ranging from 16 to 32 °C. The pure-culture growth of Thelephora terrestris was high relative to the other fungal species examined with growth optima between 21 and 27 °C. The degree of intraspecific variation of mycelial growth in response to temperature was high for all fungal species, indicating the existence of physiologically distinct genotypes. Attempts to relate fungal growth performance to geographic origin of isolate showed a trend for Pisolithus tinctorius. However, no such relationships were apparent for the other species.