WATER – within the Network of excellence EVOLTREE

Episodes of drought have increased in frequency and duration during the 20th century and climate change scenarios predict that this trend will continue. Climate change has already altered global patterns of forest biodiversity, which may induce fundamental shifts in species interactions. Here we study how soil water regime acts as the determining abiotic factor shaping patterns of biodiversity, in particular the biotic interactions between Scots pine (Pinus sylvestris) and the associated mycorrhizal fungus Cenococcum geophilum. Enhanced drought resistance is considered one of the important functions of the mycorrhizal symbiosis for the host trees and in this respect, the mycorrhizal symbiont C. geophilum is known to be especially important.

We address two main issues: 1. Is there a structuring role of genetic variation within Scots pine on the mycorrhizal community in general and the genetic and functional diversities of the associated mycorrhizal fungus C. geophilum in particular? 2. What is the impact of the site water regime on the mycorrhizal community and the genetic and functional diversities of C. geophilum associated with Scots pine?

We study natural populations in four intensive study sites along a latitudinal cline representing a drought gradient across Europe, and by two field experiments, one with different planted families of Scots pine and one with irrigation in a dry Scots pine forest. We use nuclear microsatellites to assess the genetic diversity of host trees and associated C. geophilum, and pyrosequencing of the ITS region from roots to record the mycorrhizal fungal community. To study functional aspects of the symbiosis and the impact of drought, we use transcriptomic and proteomic approaches to measure gene and protein expression in both host tree and mycorrhizal partner on root tips.