Variability in cadmium accumulation in quinoa grain: potential role of crop domestication and other factors mediating differences in resilience and uptake

Quinoa ( Chenopodium quinoa ) is a nutritious crop expanding in importance worldwide, though its capacity to accumulate cadmium (Cd) can put consumers at risk. The objective of this study was to identify genotypes that vary in Cd uptake and explore how domestication, saponins, and root-associated microbes could influence these differences. Twelve genotypes representing wild ancestors and modern landraces or cultivars from four distinct ecoregions were grown in a greenhouse trial using potting media amended with Cd. Differences in phenological developmental traits were recorded during growth, and plant biomass, microbial derived amino sugars in roots, and concentrations of Cd and other essential elements in grains were quantified at harvest. Phenological development of Ancestors were more adversely affected by Cd than modern genotypes, and Cd concentrations were higher in those developed later near coastal regions in South America and the United States, suggesting that quinoa become more tolerant over domestication and selection. Concentrations of several elements were also lower in the Ancestors vs. modern genotypes in response to Cd, indicating that modern genotypes may not downregulate root transporters as an adaptation to Cd stress. Fungal derived amino sugars were negatively correlated with Cd concentrations in the Coastal ecotypes which had the highest uptake, suggesting that the presence of root-associated fungi could help restrict translocation aboveground. Results of this study will provide breeders with new insights into factors that could aid in selecting for quinoa with low Cd-uptake. Early genotypes selected in the Altiplano region may be most useful in these breeding programs.