Respiration rate determinations suggest Heterobasidion parviporum subpopulations have potential to adapt to global warming

Trees are known to have adapted to local climatic conditions, but the adaptation of their pathogenic associates is poorly understood. Heterobasidion parviporum causes root and butt rot in spruce. In this work, the respiration of H. parviporum subpopulations from climatically diverse environments was examined at various temperatures. Isolates were obtained from three areas in Europe (southern Finland, Denmark and northern Italy) and from two locations in Central Siberia (Krasnoyarsk and Irkutsk). Respiration rates were measured in gas tight vials at eight temperatures from 0 to 33°C, using spruce saw dust as the sole substrate. Strains from Siberian locations with cold winters had higher activity at low temperatures (2–15°C) than strains from European locations with mild winters. Respiration rates of Siberian subpopulations increased more than those of European strains when the temperature rose from 0 to 6°C, but the increase was greater with the European subpopulations when the temperature increased further from 6 to 20°C. Only small differences were found among European as well as Siberian subpopulations. Variation in respiration rates between subpopulations was low compared to variation within subpopulations. Using strains isolated 2–18 years ago and thereafter stored at 5°C, we found lower respiration rates at 20°C in older isolates, independent of geographical origin, suggesting phenotypic plasticity of H. parviporum in regard to responses to temperature. Based on these findings, we propose that subpopulations of H. parviporum have the potential to adapt to global warming.