Arsenate resistance in the ericoid mycorrhizal fungus Hymenoscyphus ericae.

•  Differential resistance to arsenate (AsO ) is demonstrated here among populations of the ericoid mycorrhizal fungus Hymenoscyphus ericae isolated from Calluna vulgaris in natural heathland soils and soils contaminated with AsO . •  Isolates (c. 25) of the fungus from each of two As and Cu mine sites, and a natural heathland site, were screened for AsO and Cu resistance by growing isolates in media containing a range of AsO and Cu concentrations. •  H. ericae populations from the mine sites demonstrated resistance to AsO compared with the heathland population; the mine-site populations producing significant growth at the highest AsO concentration (4.67 mol m ), whereas growth of the heathland population was almost completely inhibited. EC values for mine-site isolates were estimated to be 5-41-times higher than the heathland population. All isolates produced identical responses to increasing Cu concentrations, with no differences observed between mine-site and heathland isolates. •  Populations of H. ericae on the contaminated mine sites have developed adaptive resistance to AsO . By contrast, Cu resistance appears to be constitutive.