Influence of mycorrhizal inoculation on growth of micropropagated Populus x canescens lines in metal-contaminated soils

Micropropagated grey poplar (Populus x canescens (Aiton) Sm.) plantlets selected during in vitro culture as tolerant to toxic Cu and Pb ions, as well as control plantlets, were inoculated ex vitro with selected strains of ectomycorrhizal fungi (Hebeloma crustuliniforme, Paxillus involutus) and an arbuscular mycorrhizal fungus (Rhizophagus irregularis BEG 87) or not inoculated, and were grown for 8 weeks in a growth chamber. Successfully acclimatized microplants were transferred to a greenhouse and grown for 16 weeks in unpolluted soil irrigated during the cultivation period with solutions containing high concentrations of Cu or Pb ions or in soil contaminated with Cu and Pb collected 1 km from a copper smelter. Ectomycorrhizal inoculation enhanced the survival rate of plantlets during ex vitro acclimatization. Poplar microplants inoculated with H. crustuliniforme and selected strains of P. involutus accumulated higher concentrations of Cu and Pb when grown in contaminated soils than the uninoculated plants and reduced concentration of the metals in the soils. In conclusion, grey poplar microplants tolerant to heavy metals and inoculated with appropriate ectomycorrhizal fungi can facilitate the adaptation of these plants to metal-polluted soils and may be used for afforestation and phytoremediation of polluted land.