Doctoral defence: Sanni Maria Aurora Färkkilä “Methods for studying plant-fungal interactions – reflecting on the old, the new and the upcoming”

On 9 February at 10:15 Sanni Maria Aurora Färkkilä will defend her doctoral thesis “Methods for studying plant-fungal interactions – reflecting on the old, the new and the upcoming” for obtaining the degree of Doctor of Philosophy (in Botany and Mycology).

Supervisors:
Professor Leho Tedersoo, University of Tartu
Associate Professor Raivo Jaaniso, University of Tartu
Associate Professor Uno Mäeorg, University of Tartu

Opponent:
Professor Suzanne Simard, University of British Columbia (Canada)

Summary
Soils are filled with organisms crucial for life. However, their study is hindered by their size and inaccessibility. Plants roots connect to the soil environment and many bacteria, fungi and small animals live in close connection with them. Among these organisms, root symbiotic fungi are particularly important. The "wood-wide-web" concept, popularized in media, suggests that forests are interconnected through fungi that enable talking among trees. However, scientific critique questions their spread and significance.
It has been argued that previously used methods cannot prove that the wood-wide-web exists. Thus, the utilization of a new method, so-called fluorescent nanoparticles, was explored in this thesis. Results from previous studies in different biological and environmental studies were reviewed. Practical experimentation revealed that the application of these particles in the study of complex natural systems like the wood-wide-web is at present very difficult. Many things about the interactions between the particles and fungi and soil are unknown. While carbon-based particles showed some promise in a simple uptake experiment, previous methods are currently more suitable for the study fungal networks.
The thesis also includes an experimental study utilizing more traditional DNA metabarcoding. This study examined how genetic differences between plant individuals affect the diversity and abundance of fungi living in the roots, revealing that individuals have differences in their ability to host root fungi. There were no differences in these abilities between populations from different latitudes. These results could have implications for tree competitiveness, and genetic factors should thus be considered in studies of the wood-wide-web as well. This thesis contributes to the discourse on the wood-wide-web, emphasizing methodological considerations.