Sensitivity of Ericoid Mycorrhizal Fungi and Mycorrhizal <i>Calluna vulgaris</i> to Copper Mine Spoil from Avoca, County Wicklow

Abstract

Ericoid mycorrhizal fungi were isolated from roots of Calluna vulgaris collected from mine spoil at abandoned copper mines at Avoca, County Wicklow, Ireland, and Parys Mountain, Anglesey, Wales. Two isolates were morphologically identical to Hymenoscyphus ericae and formed typical ericoid mycorrhizal associations. Four fungal isolates? the two mine-site isolates and two H. ericae isolates (obtained from uncontaminated sites) were grown in liquid media containing elevated levels of Cu and Zn. All isolates were determined to have a low sensitivity to these metals, with EC50 values (concentration of metal causing 50% reduction in mycelial dry mass) in the range 0.3-0.9mM Cu and 1.2-5.5mM Zn, but there were differences in metal sensitivity between isolates. There was a significant decline in the tolerance of each isolate to increasing concentrations of mine spoil (up to 10% in the agar medium). Mycorrhizal amelioration of heavy-metal toxicity was determined by growing mycorrhizal (M) and non-mycorrhizal (NM) rooted cuttings of C. vulgaris on mine spoil. Rooted cuttings obtained from an uncontaminated site showed no response to mycorrhizal colonisation. However, C. vulgaris obtained from the Avoca site and inoculated with H. ericae performed better than NM plants. The improved growth of these plants was associated with a reduction in Cu within the host's shoot. Inoculation of C. vulgaris with an ericoid mycorrhizal fungus isolated from the Avoca mine site also reduced Cu accumulation within shoots but there was no change in the growth and Zn accumulation of C. vulgaris on mine spoil. Results are discussed in relation to the potential benefit of the ericoid mycorrhizal association to C. vulgaris at metal contaminated sites. Brian R. Gibson, Division of Food Sciences, School of Biosciences,