Differential responses of ectomycorrhizal fungi to heavy metals in vitro

Thirty-nine ectomycorrhizal isolates of Paxillus involutus, Pisolithus tinc torius, Suillus bovinus, S. luteus and S. variegatus were tested on cadmium , copper, nickel and zinc amended media to determine their in vitro toleran ce, measured as inhibition of biomass production. Twenty-one isolates were from heavy metal polluted sites, whereas the others were from non-contamina ted soils. There was a strong interspecific variation in metal tolerance. S . luteus, S. variegatus and P. tinctorius were more tolerant of Cu, Cd and Zn when compared with P. involutus, whereas the reverse was true for Ni. A high intraspecific heterogeneity in metal tolerance was also found. EC50 va lues for isolates originating from polluted sites were not statistically di fferent from EC50 values for isolates originating from non-contaminated sit es. The findings are discussed in relation to the potential benefits of ect omycorrhizal fungi in protecting their host plants from metal contamination .