Trichoderma sp. PDR1-7 promotes Pinus sylvestris reforestation of lead-contaminated mine tailing sites

• A heavy metal-tolerant, plant growth-promoting fungus was isolated from mine soil.
• Trichoderma sp. PDR1-7 removed heavy metals from mine-tailing soil extract media.
• PDR1-7 reduced plant oxidative stress in heavy metal-contaminated soil.
• PDR1-7 enhanced pine seedling growth and heavy metal accumulation in roots.
• The non-symbiotic fungus can promote afforestation of HM-polluted sites with pine.

Vegetation is critical to stabilize and remediate mine tailing sites, but plant growth is often poor due to toxicity from heavy metal(loid)s (HMs). A non-symbiotic endophytic fungus, Trichoderma sp. PDR1-7, isolated from Pb-contaminated mine tailing soil, exhibited both high tolerance to HMs and desirable plant growth-promoting characteristics. PDR1-7 promoted HM solubilization in mine tailing soil and removed significant amounts of Pb and other HMs from liquid media containing single and multiple metals. Pb removal efficiency increased with initial pH from 4 to 6 and with Pb concentration from 100 to 125 mg L− 1. Inoculating soil with PDR1-7 significantly increased nutrient availability and seedling growth, chlorophyll and protein contents, as well as antioxidative enzyme (superoxide dismutase) activity. A decrease in malondialdehyde indicated less oxidative stress. HM concentrations were much higher in Pinus sylvestris roots when PDR1-7 was present. These observations suggest the utility of Trichoderma sp. PDR1-7 for pine reforestation and phytoremediation of Pb-contaminated mine soil.