Effect of Adaptation to High Concentrations of Cadmium on Soil Phytoremediation Potential of the Middle European Ecotype of a Cosmopolitan Cadmium Hyperaccumulator Solanum nigrum L.

The Cd hyperaccumulator Solanum nigrum L. exhibits a cosmopolitan character and proven high and differentiated efficiency. This suggests the possibility of optimizing its Cd phytoremediation capacity and applicability through searching among remote ecotypes/genotypes. However, the extensive studies on this hyperaccumulator have been limited to Far East (Asian) regions. Pioneer pot experiments on the Middle European ecotype of S. nigrum within a concentration range of 0–50 mg kg−1 Cd in soil revealed its Cd phytoremediation capacity to be comparable to Asian ecotypes but with a fundamentally different Cd tolerance threshold. While biomass of the Asian ecotypes declined sharply at Csoil ≈ 10 mg kg−1 Cd, in the Middle European ecotype, a gradual mild biomass decrease occurred within the whole Csoil ≈ 0–50 mg kg−1 Cd range with no toxic symptoms. Its adapted A50 variety was obtained from the seeds of first-generation plants grown in soil with Csoil ≈ 50 mg kg−1 Cd. In this variety, Cd tolerance, accumulation performance, and all physiological parameters (chlorophyll, carotenoids, RuBisCO, and first- and second-line defense anti-oxidant activity) were significantly enhanced, while cell damage by ROS was considerably lesser. This makes the Middle European ecotype and its adapted variety A50 particularly useful to sustainable decontamination of heavily polluted “hot spots” in degraded post-industrial areas.