Inoculation with a Pb-tolerant strain of Paxillus involutus improves growth and Pb tolerance of Populus × canescens under in vitro conditions

Abstract

Aims: Ectomycorrhizal fungi can improve poplar growth and tolerance to heavy metal stress, and may be useful during the afforestation and phytoremediation of polluted regions with poplar trees. In this study, we determined the effects of the symbiotic interaction between Populus × canescens trees and Paxillus involutus strains different in their tolerance to lead. Methods: In vitro inoculated and non-inoculated plants were treated with 0.75 mM Pb(NO3)2. The root colonization rate of the two fungal strains, as well as their impacts on poplar health and lead accumulation were examined. Results: Based on the colonization level, the roots were classified into one of three categories: non-mycorrhized, changed (ie, fungal cells were present on the root surface, but the Hartig net did not fully develop), and fully mycorrhized. The lead-tolerant P. involutus strain colonized roots better than the non-tolerant strain (ie, changed and fully mycorrhized roots). Moreover, plants inoculated with the tolerant fungal strain grew better than the control plants (217 % increase in dry weight over the controls), and accumulated lead in the roots and stems. Conclusions: Inoculation of P. × canescens trees with a Pb-tolerant strain of P. involutus improves host plant growth and may increase Pb phytostabilization potential.