The heavy metal Cadmium (Cd) can migrate and accumulate in soil-plant system, and threaten food safety and the health of people. It is thus important to develop pollution control techniques for Cd-contaminated soils and to explore the mechanism affecting cadmium absorption, transportation and accumulation in crops.
Prof. TAI Peidong, a senior researcher from the Soil Pollution Ecology Group of the Institute of Applied Ecology (IAE) of the Chinese Academy of Sciences (CAS), led a series of research investigating the mechanism that regulates long-distance translocation of cadmium from root to shoot by means of grafting.
His research group found that compared to un-grafted controls, grafting led to a prominent reduction of cadmium content (-60%~80%) in the fruits of eggplants (S. melongena) grafted onto Torubamu (Solanum torvum) as a rootstock, without affecting crop yield and quality. The researchers also found that grafting reduced cadmium (Cd) accumulation in soybean (Glycine max). More importantly, the "low Cd traits can be maintained over two generations," the researchers announced.
By performing DNA methylation and high-throughput sequencing analyses, the researchers found that most of the grafting-induced Differentially Expressed Genes were enriched in sulfur-related metabolism pathways (e.g., glutathione, cysteine and methionine metabolism). The researchers further confirmed that sulfhydryl compounds and sulfur-containing compounds involved in the regulation of the translocation and accumulation of cadmium in crops, and that grafting could impact the synthesis and metabolism of these sulfur-related compounds by affecting miRNAs and DNA methylation, and led to low cadmium traits (phenotype) in scions of grafted crops and in their offspring.
The above findings comprehensively explained the mechanisms regulating cadmium transportation and accumulation in crops, indicating that grafting can be used as agronomic measures in heavy metal contaminated farmland to reduce cadmium content in crop products.
The series of studies were funded by the National Natural Science Foundation of China and the National Key R&D Program of the Ministry of Science and Technology. The related results have been published in Plant Soil entitled "Mechanism and stability of low cadmium accumulation in grafted soybeans induced by rootstocks ", in Science of the Total Environment entitled "Maintenance of grafting reducing cadmium accumulation in soybean (Glycine max) is mediated by DNA methylation", in Chemosphere entitled "Grafting with an invasive Xanthium strumarium improves tolerance and phytoremediation of native congener X. sibiricum to cadmium/copper/nickel tailings", in Plant Soil entitled "A reduction in cadmium accumulation and sulphur containing compounds resulting from grafting in eggplants (Solanum melogena) is associated with DNA methylation", and in Journal of Cleaner Production entitled "Grafting as a mitigation strategy to reduce root-to-shoot cadmium translocation in plants of Solanaceae family".
