Genetic Variation for Grain Cadmium in Hard Winter Wheat

Cereals are dominant sources of cadmium in human diets; therefore grain cadmium concentration is regulated by the EU.  Pollution-safe cultivars of bread wheat (Triticum aestivum L.) can reduce risk to human health from cadmium consumption.  Variation in cadmium concentration in durum wheat (Triticum turgidum var. durum) is well documented, but genetic variation in cadmium accumulation in hexaploid bread wheat is less characterized.  Grain mineral concentration was measured in a 299-genotype hard winter wheat association mapping panel grown in 2012 near Ithaca, NE on the site of a decommissioned munitions factory and missile launch area.  Grain cadmium concentration averaged 0.230 mg kg^-1, above the EU limit of 0.200 mg kg^-1, and cadmium concentration of the genotypes ranged from 0.080 to 0.580 mg kg^-1.  Four genotypes, two with below-average and two with above-average cadmium concentration, were grown in additional locations across Nebraska.  Genotype rankings were consistent across environments, but grain cadmium concentrations were lower in other environments.  The low-cadmium phenotype appears to be heritable and amenable to selection in a high-cadmium environment.  Cadmium concentration in vegetative tissue samples collected at anthesis from six genotypes (representing below-average, above-average, and very high grain cadmium) was greater in high grain-cadmium genotypes than in low grain-cadmium genotypes.  Genome-wide association analysis with 92K SNP markers identified one putative highly significant QTL, on chromosome 5A, with an effect of 0.049 mg kg^-1.  GBS-derived SNPs also detected putative QTLs and may provide a foundation for a candidate-gene approach to understanding variation in grain cadmium in hard winter wheat.