Phytoremediation efficiency of poplar hybrid varieties with diverse genetic backgrounds in soil contaminated by multiple toxic metals (Cd, Hg, Pb, and As)

Abstract

Fifteen poplar varieties were used in a field trial to investigate the phytoremediation efficiency, stress resistance, and wood property of poplar hybrid varieties with diverse genetic backgrounds under the composite pollution of heavy metals. The coefficient of variation and clone repeatability for growth traits and Cd concentration were large. The Cd accumulation of poplar varieties 107 and QHQ reached 1.9 and 1.7 mg, respectively, followed by QHB, Ti, 69, and Pa, in which Cd accumulation reached 1.3 mg. Most of the intra-specific hybrid varieties (69, QH1, SL4, T3, and ZL46) had low Cd concentrations and small biomass, resulting in weak Cd accumulation and low phytoremediation efficiency for Cd-polluted soil. By contrast, the inter-sectional and inter-specific hybrid varieties exhibited better growth performance and accumulated higher concentrations of heavy metals than the intra-specific hybrids. The bioconcentration factor and translocation factor of Hg, As, and Pb were less than 1, indicating that poplars have low phytoremediation efficiency for these heavy metals. The hybrids between section Aigeiros and Tacamahaca (QHQ and QHB) and the inter-specific hybrid 107 within section Aigeiros were more resistant to composite heavy metal stress than the other poplar varieties were partially because of their high levels of free proline that exceeded 93 μg·g −1 FW. According to the correlation analysis of the concentrations of the different heavy metals, the poplar roots absorbed different heavy metals in a cooperative manner, indicating that elite poplar varieties with superior capacity for accumulating diverse heavy metals can be bred feasibly. Compared with the intra-specific hybrid varieties, the inter-sectional (QHQ and QHB) and inter-specific (107) hybrid varieties had higher pollution remediation efficiency, larger biomass, higher cellulose content, and lower lignin content, which is beneficial for pulpwood. Therefore, breeding and extending inter-sectional (QHQ and QHB) and inter-specific hybrid varieties can improve the phytoremediation of composite pollution. • Inter-sectional and inter-specific poplar hybrids have better growth performance than intra-specific hybrid. • Inter-sectional and inter-specific poplar hybrids accumulated high concentration of heavy metals. • Inter-section and inter-specific poplar hybrids have fine wood property with lower lignin content. • Elite varieties with fine wood property and high remediation efficiency can be produced by inter-species hybridization. • Soil pollution can be controlled without the penalty of economic values by planting elite poplar varieties.

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