Tolerance to and accumulation of cadmium by the mycelium of the fungi Scleroderma citrinum and Pisolithus tinctorius.

The behavior of ectomycorrhizal (ECM) fungi on exposure to cadmium dependent upon isolation remains a poorly understood phenomenon. The in vitro growth, tolerance, and accumulation of Cd were studied in three strains of ECM fungi exposed to six Cd concentrations (0-10 mg L(-1)). The fungi studied were a strain of Scleroderma citrinum Persoon (Sc) isolated from a tailings heap containing 5 mg kg(-1) available Cd, and two strains of Pisolithus tinctorius (Pers.) Coker and Couch from unpolluted sites (Pt1 and Pt2), both common ECM fungi used for remediation. The growth kinetic (36 days) of Sc was not affected by Cd concentration. By contrast, the ED(50) in Pt1 and Pt2 occurred at 4.8 and 6.9 mg L(-1) of Cd, respectively. The biomass of the three fungi exposed to the highest Cd concentration (10 mg L(-1)) was significantly different. Sc presented the highest biomass, while this was strongly reduced for Pt1 and Pt2. The tolerance index for Sc ranged from 78% to 95% at all Cd concentrations tested, while for Pt1 it was 49% and 31%, and for Pt2 it was 62% and 35% at 5 and 10 mg of Cd L(-1), respectively. The mycelium of both Pt strains accumulated more Cd than the Sc mycelium. At the highest Cd concentration, Pt1 and Pt2 accumulated 1.9 and 1.7 times more Cd than Sc. This study suggests that regardless of the differences in tolerance to Cd by the three ECM fungi, they could have biotechnological applications for soil remediation. However, Sc has greater possibilities of being used successfully when high concentrations of Cd prevail in the environment.