Varietal differences in the absorption and partitioning of cadmium in common wheat (Triticum aestivum L.)

Abstract

Low cadmium (Cd) transfer from the soil to edible parts of crop plants is important to minimize toxicity to humans and animals. We previously showed that Cd accumulation in grains differs substantially among varieties of common wheat (Triticum aestivum L.). In this study, we investigated the factors responsible for these differences by comparing the absorption and partitioning of Cd among wheat varieties with distinct grain Cd concentrations. Three varieties with low grain Cd concentrations (low-Cd/G varieties) and one standard variety were cultivated in a field (under natural conditions) and in pots with Cd application at four growth stages (emergence, jointing, flowering, and grain-filling). The Cd concentration and content in the whole plant and grains were determined at the seedling, flowering, grain-filling, and maturity stages in the field experiment. Cd concentration, content, and partitioning in different plant segments were determined at the maturity stage in the pot experiment. In the field experiment, there were significant differences in Cd partitioning to grains between low-Cd/G varieties and the standard variety. Cd application at different growth stages in the pot experiment indicated the remobilization of Cd from shoots to grains and direct transport of Cd from roots to grains. In the pot experiment, lower Cd absorption was detected in low-Cd/G varieties than in the standard variety and the low-Cd/G varieties exhibited differences in Cd sequestration among plant parts, including the root, leaf, lower stem, first internode, rachis, and/or glume. These results suggest that several factors related to Cd absorption and translocation, such as root traits and xylem and phloem transport, affect the accumulation of Cd in grains in common wheat. Understanding and elucidating the contribution of each of these factors might facilitate the development of common wheat varieties with minimal grain Cd accumulation.