Application of temporal temperature gradient gel electrophoresis for characterisation of fungal endophyte communities of Salix caprea L. in a heavy metal polluted soil

Fungal endophytes can affect the heavy metal uptake of their host plants and increase the tolerance of their host plants to heavy metal stress. Therefore, in the present study, a wide-range screening of the fungal endophyte communities was conducted to determine the fungal distribution and diversity on S. caprea roots on a metal polluted site. Fungal communities were screened using amplification with the 5.8S-ITS2-28S part of the rDNA operon, with the resulting amplicons analysed by temporal temperature gradient gel electrophoresis (TTGE) and sequencing. This technique is reproducible and shows good coverage of ascomycete and basidiomycete taxa, as 68% and 32% of all of the sequences, respectively. No clear shift in fungal ITS-TTGE profiles from S. caprea roots was seen along the secondary succession stages. Ascomycetes dominated the more polluted plots, while there was a greater diversity of basidiomycetes in the less polluted and control plots, suggesting greater tolerance of ascomycetes in comparison with basidiomycete fungi. The high diversity of DSEs was confirmed at the highly metal-enriched locations, with species belonging to the genera Phialophora, Phialocephala and Leptodontidium. Furthermore, the DSE colonisation of S. caprea roots and the frequency of the sequences showing affinity towards DSE genus Phialophora, showed good correspondence with soil Pb, Cd and plant-available P concentrations, possibly indicating that DSEs improve metal tolerance of willows to high heavy metal contamination.