In vitro selection of ecologically adapted ectomycorrhizal fungi through production of fungal biomass and metabolites for use in reclamation of biotite mine tailings

ABSTRACT

Mineral weathering plays an important role in poor-nutrient environments such as mine spoils and tailings. Ectomycorrhizal (ECM) fungi are able to enhance mineral weathering through different mechanisms, thereby increasing the availability of minerals and nutrients to plants. Six ECM fungi (Cadophora finlandia, Cenococcum geophilum, Hebeloma crustuliniforme, Lactarius aurantiosordidus, Paxillus involutes, and Tricholoma scalpturatum) were tested here for their tolerance to biotite-quartz-rich mine tailings. Either solid- or liquid-medium methods were used for in vitro selection of ECM fungi for their ability to grow on mine tailings. ECM fungi were selected based on their mycelial radial growth and metabolite production (ergosterol and low-molecular-mass organic acids, LMMOAs). We found a strong correlation between fungal ergosterol content and mycelial radial growth using the solid-medium method. However, the liquid-medium method was more appropriate for ergosterol synthesis and permitted direct measurement of organic acid production. We found that LMMOAs were exuded by ECM fungi, which solubilized mine tailings for their own growth and nutrition. Finally, we concluded that the ECM fungi C. finlandia and T. scalpturatum are the species most tolerant to tailings and could potentially improve the survival rate, growth, and health of white spruce seedlings planted on biotite mine spoils and tailings.

KEYWORDS:

• Ergosterol
• low-molecular-mass organic acids (LMMOAs)
• mineral weathering

ACKNOWLEDGMENTS

The authors are grateful to Dr. Jean-Guy Catford for his invaluable advice and to Dr. Alain-René Atangana for his contributions to specific statistical analyses. The authors also thank Mathieu Boudreau, André Gagné, Marie-Ève Beaulieu, Josée Bourassa, and Laurent Fontaine, who aided the authors in various ways to complete this study. The authors are indebted to Drs. William F. J. Parsons (Centre d’étude de la Forêt, Université de Sherbrooke), Line Lapointe (Université Laval), and Suzanne Simard (University of British Columbia) for their careful reviews of an earlier draft, which has helped to improve the manuscript.

Additional information

Funding

The authors thank the Natural Sciences and Engineering Research Council of Canada (NSERC Strategic Grants Program) for their financial support.