Improved zinc tolerance in Eucalyptus globulus inoculated with Glomus deserticola and Trametes versicolor or Coriolopsis rigida

The potential of interactions between saprophytic and arbuscular mycorrhizal (AM) fungi to improve Eucalyptus globulus grown in soil contaminated with Zn were investigated. The presence of 100 mg kg −1 Zn decreased the shoot and root dry weight of E. globulus colonized with Glomus deserticola less than in plants not colonized with AM. Zn also decreased the extent of root length colonization by AM and the AM fungus metabolic activity, measured as succinate dehydrogenase (SDH) activity of the fungal mycelium inside the E. globulus root. The saprophytic fungi Trametes versicolor and Coriolopsis rigida increased the shoot dry weight and the tolerance of E. globulus to Zn when these plants were AM-colonized. Both saprophytic fungi increased the percentage of AM root length colonization and elevated G. deserticola SDH activity in the presence of all Zn concentrations applied to the soil. In the presence of 500 and 1000 mg kg−1 Zn, there were higher metal concentrations in roots and shoots of AM than in non-AM plants; furthermore, both saprophytic fungi increased Zn uptake by E. globulus colonized by G. deserticola. The higher root to shoot metal ratio observed in mycorrhizal E. globulus plants indicates that G. deserticola enhanced Zn uptake and accumulation in the root system, playing a filtering/sequestering role in the presence of Zn. However, saprophytic fungi did not increase the root to shoot Zn ratio in mycorrhizal E. globulus plants. The effect of the saprophytic fungi on the tolerance and the accumulation of Zn in E. globulus was mediated by its effect on the colonization and metabolic activity of the AM fungi.