Low Accumulation of Potentially Toxic Elements in Crops: An Integrated Soil–Plant Framework for Food Safety

Contamination of agricultural soils by potentially toxic elements (PTEs) poses a persistent challenge to sustainable crop production and food safety. Because complete remediation of contaminated farmland is often difficult to achieve in the short term, the development and utilization of crop varieties with low PTE accumulation in edible tissues provide a practical strategy for reducing dietary exposure while maintaining agricultural productivity. However, low-accumulation traits arise from coordinated regulation across the soil–plant continuum rather than from a single uptake or detoxification process. This review integrates the major mechanisms governing PTE accumulation in food crops and proposes a regulatory framework encompassing “entry restriction–transport modulation–spatial allocation–cellular immobilization.” We first examine how soil physicochemical properties, nutrient–metal interactions, rhizosphere processes, and root structural traits regulate PTE bioavailability and root entry. We then discuss how transporter networks, metal chelation systems, xylem loading, and phloem redistribution control long-distance transport and delivery to aerial and edible organs. Tissue partitioning, cell wall immobilization, and vacuolar sequestration are further considered as key processes determining the final distribution of PTEs within crops. Importantly, similar low-accumulation phenotypes may arise through different regulatory routes, with the relative importance of individual control points varying among elements, crop genotypes, and environmental conditions. These regulatory routes are further discussed in the context of element specificity, strength of supporting evidence, potential trade-offs with mineral nutrition and crop productivity, field robustness, and food-safety relevance. Representative low-accumulation germplasm and current approaches for molecular breeding and agronomic management are also summarized. Together, these considerations position low PTE accumulation as an integrated crop phenotype resulting from multiple, potentially compensatory regulatory processes rather than simply reduced root uptake. Integrating mechanistic understanding with genotype selection and soil–crop management may facilitate the development of low-accumulation crops that combine reduced contaminant delivery to edible tissues with stable agronomic performance, thereby supporting safer and more sustainable production on contaminated agricultural land.