Effects of reciprocal grafting on cadmium accumulation in post-grafting generations of two ecotypes of Solanum photeinocarpum

Farmland and mining ecotypes of the potential cadmium (Cd)-hyperaccumulator Solanum photeinocarpum were collected to study the effects of reciprocal grafting on the growth of, and Cd accumulation in, the post-grafting generations. The post generations of the following plant materials were evaluated in a pot experiment: the un-grafted farmland ecotype, grafted plants with the farmland ecotype as the scion or the rootstock, the un-grafted mining ecotype, and grafted plants with the mining ecotype as the scion or the rootstock. The results showed that reciprocal grafting increased the biomass, the activities of superoxide dismutase, peroxidase, and catalase, and the soluble protein content in the post-grafting generations of both ecotypes S. photeinocarpum. Reciprocal grafting also increased the Cd content in, and amount of Cd extracted by, the post-grafting generations of both ecotypes S. photeinocarpum as a result of lower soil pH and higher soil available Cd concentrations. Additionally, grafting affected the DNA methylation levels by inducing hypermethylation or demethylation in the post-grafting generation. Therefore, reciprocal grafting can enhance the Cd accumulation (phytoremediation) capacity of post-grafting generations of both ecotypes S. photeinocarpum by affecting DNA methylation levels.