Motta-Romero et al. 2021 — Cadmium accumulation in hard winter wheat grains across 80 years of breeding, with fungicide treatment effects
This study evaluated the effects of fungicide application on grain yield, micronutrients, and cadmium (Cd) concentration in 20 hard winter wheat genotypes representing 80 years of US Great Plains breeding history (cultivar registration years 1870-2013). Field experiments were conducted at the University of Nebraska Eastern Nebraska Research and Extension Center (ENREC) near Mead, NE, known for elevated soil Cd concentrations (DTPA-extractable 0.16-0.26 mg/kg), across two growing seasons (2017 and 2018). Metals were measured by ICP-MS. The key finding for food safety is that grain Cd significantly increased over the 80-year breeding period at an annualized rate of 0.4 µg/kg/year in the absence of fungicide treatment (p<0.01), while essential micronutrients Fe and Zn declined. This suggests that modern hard winter wheat cultivars bred for yield may inadvertently accumulate more dietary Cd than older varieties. Fungicide application modified some of these trends.
Key numbers
n=20 wheat genotypes (18 elite + 2 landraces); registration years 1874-2013. Growing seasons: 2017 and 2018. Location: ENREC, Mead, Nebraska (elevated soil Cd site: 0.16-0.26 mg/kg DTPA-extractable). Method: ICP-MS on whole wheat kernels (wet ashing + HNO3/H2O2 digestion). Grain Cd trend: significant increase at 0.4 µg/kg/year over the 80-year breeding period in untreated plots (p<0.01). Fe trend: significant decrease (-35.0 to -44.0 µg/kg/year). Zn trend: significant decrease (-57.0 to -68.0 µg/kg/year). Fungicide application interacted with these trends. Maximum regulatory limit for Cd in wheat grain: 0.1-0.2 mg/kg in multiple jurisdictions.
Methods (brief)
Split-plot field design with fungicide treatment (Caramba fungicide at booting stage) as whole-plot factor and genotype as split-plot factor, 3 replications per season. Grain mineral analysis by ICP-MS (Agilent 7500cx, helium mode). Regression of yield, GPC, mineral elements, and Cd against cultivar registration year (as continuous variable) to estimate genetic trend. Partial correlation analysis to account for dilution effect of increasing yield. Limitation: single location with elevated soil Cd; findings may overestimate national trend but are directionally informative.
Implications
Certification: US hard winter wheat Cd content has increased over recent breeding history; modern cultivars carry higher Cd risk than landraces or older varieties, especially at high-soil-Cd sites. Courses: Documents trade-off between yield-focused breeding and nutritional/contaminant quality in wheat; relevant to supply chain sourcing decisions. App: Wheat variety and growing location (soil Cd level) are key modifiers of grain Cd concentration; modern semi-dwarf wheats may carry higher Cd than heritage or older varieties. Microbiome: Dietary Cd from wheat is a significant exposure pathway; increasing per-capita Cd intake from wheat has implications for gut microbiome.