Disentangling the factors of contrasting silver and copper accumulation in sporocarps of the ectomycorrhizal fungus Amanita strobiliformis from two sites

Highlights: • Contrasting Ag and Cu accumulation in Amanita strobiliformis from two sites. • Soil mycelium of A. strobiliformis was quantified below sporocarps by qPCR approach • Pb isotopes were used to trace the metal transfer between mushrooms and soil • Topsoil layer of circa 12 cm depth is the major source of the accumulated metals. • A. strobiliformis accumulates Ag from the reducible soil fraction. -- Abstract: Amanita strobiliformis (European Pine Cone Lepidella) is an ectomycorrhizal fungus of the Amanitaceae family known to hyperaccumulate Ag in the sporocarps. Two populations (ecotypes) of A. strobiliformis collected from two urban forest plantations in Prague, Czech Republic, were investigated. The concentrations of Ag, Cu, Cd, and Zn were determined in the mushrooms. The metal mobility and fractionation in the soils was investigated by single extractions and sequential extraction. The soil distribution of A. strobiliformis mycelium was assessed by quantitative polymerase chain reaction (qPCR). The metal uptake from the soil into the mushroom sporocarps was traced by Pb isotopic fingerprinting. The findings suggested that A. strobiliformis (i) accumulates primarily Ag from the topsoil layer (circa 12 cm deep) and (ii) accumulates Ag associated with the "reducible soil fraction". The concentrations of all metals, particularly Ag and Cu, were significantly higher in the A. strobiliformis sporocarps from one of the investigated sites (Klíčov). The elevated concentrations of Ag in the sporocarps from Klíčov can possibly be attributed to the higher Ag content in the topsoil layer found at this site. However, the simultaneously elevated concentrations of Cu in A. strobiliformis from Klíčov cannot be explained by the differences in the geochemical background and should be attributed to biological factors.