In vitro selection of root-associated fungi for use in ecological engineering and ecosystem restoration of iron ore waste rocks in Arctic and alpine tundra of Northern Quebec, Canada

Mining activities typically involve the removal of plants, soil nutrients, and root-associated microorganisms, which in turn limits natural revegetation and soil restoration. Ecological restoration of mining-impacted sites using beneficial microorganisms, such as mycorrhizal fungi, is considered necessary and useful for the growth and survival of their host plants, but also for their tolerance to poor and contaminated environments, such as mine tailings. Here, nine fungal symbionts associated with plant roots from the Schefferville mine site in northern Quebec were tested for tolerance to overburden, waste rock and pure iron treatments. The production of ergosterol and the exudation of low-molecular-mass organic acids (citrate, malate, succinate, acetate) were measured by high-performance liquid chromatography during an in vitro experiment in liquid medium. These two types of metabolites are indicative of fungal growth and their amount varied in response to iron treatments. The study revealed that the cultivable root-associated fungi did not all respond in the same way to the abiotic stress applied. The results showed that the ericoid fungus Rhizoscyphus ericae exhibited the best growth in the presence of iron treatments. The dark septate endophyte Phialocephala fortinii ranked second in growth, but it produced the highest amount of organic acids. Cadophora finlandica and Hyaloscypha bicolor also showed good tolerance to iron treatments. These fungal isolates with the best growth and highest organic acid production are considered to be the most tolerant species to mine tailings and could potentially improve the survival, growth, and resistance of plant seedlings for mine reclamation in the Boreal Shield.