Temperature stress in arbuscular mycorrhizal fungi: a test for adaptation to soil temperature in three isolates of Funneliformis mosseae from different climates

It has become urgent to explore the potential stimulations or constraints that increasing and fluctuating temperatures derived from climate change may impose on the mycorrhizal symbiosis. We conducted a study to compare the soil temperature response curves (6, 12, 18, and 24 degrees C) of three isolates of Funneliformis mosseae from different regions and climates (Finland, Denmark, Spain), to test if the isolates from cold environments were able to grow better at lower temperatures and the isolates from warmer environments grew better at higher temperatures. The results provided clear evidence suggesting no adaptation to soil temperature in these AMF isolates. All isolates showed reduced development and especially very little external mycelium growth at 6 and 12 degrees C regardless of the temperatures they normally experienced in their original habitats and all showed similar increasing development with increasing soil temperature. These results suggest that AMF have a narrow window to develop in cold regions of the world where temperatures below 15 degrees C prevail which ought to be well exploited, especially in agroecosystems where management is aimed at improving crop performance and soil quality. With proper management, if temperatures continue to increase, mycorrhizal development and mycorrhizal benefit might also increase in cold regions.