The effect of ectomycorrhizal fungi forming symbiosis with Pinus pinaster seedlings exposed to cadmium

Cadmium is one of the most toxic heavy metals and its accumulation in the upper layers of forest soils affects plants, microorganisms and their interactions. Adequate strategies for the reforestation of metal contaminated sites are of vital importance. The aim of this work was to evaluate the response of Pinus pinaster seedlings to Cd exposure and to assess the effect of inoculation with two selected ectomycorrhizal fungi, Suillus bovinus and Rhizopogon roseolus on that response. Seedlings were exposed to soil contaminated at 15 and 30mgCdkg−1. Shoot biomass of P. pinaster decreased ca. 36% when exposed to 15mgCdkg−1. Overall, colonization by S. bovinus significantly enhanced shoot development up to 30% in contaminated soil while colonization by R. roseolus produced no significant effect at both Cd concentrations tested and significantly increased the level of Cd in the shoots at both Cd concentrations. Metal accumulation in the shoots and roots of non-inoculated and S. bovinus-inoculated seedlings increased at the higher Cd levels whereas R. roseolus-inoculated seedlings were not sensitive to Cd variation in the soil. The results from our research show that inoculation with ECM fungi has a significant impact on metal uptake and development of P. pinaster seedlings; the differential response induced by the two tested species highlights the importance of selecting the appropriate strains for nursery inoculation, and, as such, this biological tool ought to be considered in reforestation processes of heavy metal contaminated areas by woody species. ► Ectomycorrhizal fungi can aid the reforestation of heavy metal contaminated areas. ► Cd inhibited the growth of non-inoculated 6months-old Pinus pinaster seedlings. ► Inoculation with Suillus bovinus enhanced P. pinaster growth in Cd contaminated soil. ► Mycorrhizal symbiosis influenced the accumulation of Cd in P. pinaster seedlings.