Arsenate resistance in the ericoid mycorrhizal fungus Hymenoscyphus ericae

Differential resistance to arsenate (AsO43-) is demonstrated here among populations of the ericoid mycorrhizal fungus Hymenoscyphus ericae isolated from Calluna vulgaris in natural heathland soils and soils contaminated with AsO43-. Isolates (c. 25) of the fungus from each of two As and Cu mine sites, and a natural heathland site, were screened for AsO43- and Cu2+ resistance by growing isolates in media containing a range of AsO43- and Cu2+ concentrations. H. ericae populations from the mine sites demonstrated resistance to AsO43- compared with the heathland population; the mine-site populations producing significant growth at the highest AsO43- concentration (4.67 mol m(-3)), whereas growth of the heathland population was almost completely inhibited. EC50 values for mine-site isolates were estimated to be 5-41-times higher than the heathland population. All isolates produced identical responses to increasing Cu2+ 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 AsO43-. By contrast, Cu2+ resistance appears to be constitutive. (C) New Phytologist (2001) 151: 265-270.