RESUMO
The community and Cd-resistance of endophytic fungi from roots of Salix variegata Franch. collected from the water-level-fluctuation zone of Three Gorges Reservoir Region, China, were investigated. A total of 53 strains were isolated and identified to 13 morphotaxa, in which Chromosporium, Fusarium and Gonatobotrys were dominant genera. Among them, 27 isolates were selected to measure their resistance to 0.02 mg ml(-1) Cd(2+) and 11 were growth stimulated (Tolerance index>100%). Of these active isolates, four dark septate endophyte (DSE) isolates (Paraphaeosphaeria sp. SR46, Pyrenochaeta sp. SR35, Rhizopycnis vagum SR37 and R. vagum SR44) were further tested for minimum inhibitory concentrations (MICs) against Cd and SR46 was found to be the most tolerant isolate with MIC of 0.39 mg ml(-1). Additionally, the maximum uptake values of these DSEs ranged from 3.01 to 7.89 mg g(-1), but there was no significant correlation between metal uptake with fungal biomass and metal tolerance. Subsequently, a pot experiment was conducted for investigating the impact of SR46 on corn seedlings in Cd-enriched soil. The results obtained suggested that SR46 reduced the Cd bioaccumulation of plant under low (100 mg kg(-1)) Cd stress and enhanced the Cd translocation from root zone to aerial parts under high (200 mg kg(-1)) Cd stress. Besides, it promoted plant growth without Cd stress. These findings indicated S. variegata harbors an endophytic fungal flora showing a high genetic diversity as well as a high level of metal resistance to Cd that has potential values in cadmium cycling and restoration of plant, soil and water system.
