Threefold difference in cadmium accumulation among Solanum nigrum L. ecotypes at fruit maturity in Northeast China

Solanum nigrum L. has strong potential for the remediation of Cd contaminated soils, however, there is a lacuna of information about the ecotypic variations of S. nigrum towards Cd extraction at fruit maturity when grown under identical soils. The present experiment aimed to determine the Cd remediation potential of 11 S. nigrum ecotypes from diverse geographical regions of Northeast China using pot experiments under Cd concentration of 1.4 mg kg^-1 in soil. The results showed that most (1 out of 11) S. nigrum ecotypes exhibited the fundamental characteristics of Cd hyperaccumulators, but there were threefold differences in their Cd accumulation. Two ecotypes of Tieling (LND) and Changchun (JLC) showed the highest Cd accumulation capacity (> 34 μg plant^-1) in shoots. The Tongliao (NMGA) ecotype showed the lowest Cd accumulation capacity (just 8.1 μg plant^-1). In comparison, shoot Cd accumulation capacities in the LND and JLC ecotypes increased by 333.4% and 323.0%, respectively. Average daily Cd accumulation capacities of LND and JLC were consistently higher than those of other ecotypes, indicating their potentials for Cd extraction. Their enrichment factors (EFs) and translocation factors (TFs) were higher the mean of the S. nigrum ecotypes. The LND and JLC ecotypes had significantly higher SOD activity, chlorophyll a and b, and carotenoid, which may partly contribute to their high Cd accumulation. Soil pH and extractable soil Cd concentration were not associated with Cd accumulation in S. nigrum ecotypes. These findings underscore the need for broader screening efforts to identify S. nigrum ecotypes with high Cd accumulation for direct application in phytoremediation or for the development of improved hyperaccumulator genotypes through genetic approaches.