Understanding the physiological and molecular mechanisms of grain cadmium accumulation conduces to produce low cadmium grain crops: a review

Soil cadmium (Cd), which can occur naturally in the environment or arise from industrial pollution, seriously affects crop quality and threatens human health. Therefore, reducing grain Cd accumulation (GCA) has become an important topic worldwide. To comprehensively assess the research status of GCA, we reviewed the research into physiological and molecular mechanisms of GCA, including the characteristics of Cd uptake, transport, and accumulation from roots to grain; furthermore, literature on GCA-related quantitative trait locus identification and gene functional analysis were reviewed. Based on physiological and molecular mechanisms, two strategies to reduce GCA, namely soil management and genetic improvement, were also critically summarized. It became clear that further research is necessary into the physiological mechanisms of Cd uptake, transportation, and accumulation in grain. It is also important to accelerate the discovery and use of effective functional markers and genes associated with low Cd accumulation and to improve the feasibility and potential value of breeding low Cd grain crops.