Phosphate supply and arsenate toxicity in ectomycorrhizal fungi

Abstract

Three species of ectomycorrhizal fungi (Hebeloma crustuliniforme, Suillus variegatus and Cenococcum geophilum) were grown in axenic culture amended with range of AsO4(3-) concentration under three different PO4(3-) regimes. The fungi exhibited different growth responses to AsO4(3-) that varied with PO4(3-) concentration. Suillus variegatus showed the greatest sensitivity to AsO4(3-), with growth almost completely inhibited in the presence of AsO4(3-) under the lower two PO4(3-) treatments. Under the highest PO4(3-) treatment however, growth was enhanced and S. variegatus was able to persist at AsO4(3-) concentrations of up to 4 mM. Hebeloma crustuliniforme also showed high sensitivity to AsO4(3-) especially at low PO4(3-) concentration. The two higher PO4(3-) treatments had an ameliorating effect on AsO4(3-) toxicity in H. crustuliniforme. This demonstrates the ability of PO4(3-) to alleviate AsO4(3-) toxicity. The response from S. variegatus and H. crustuliniforme, both basidiomycetes, was in contrast to the ascomycete C. geophilum. This fungus demonstrated tolerance to AsO4(3-) when grown in culture solution and PO4(3-) did not have an ameliorating effect on AsO4(3-) toxicity in C. geophilum.