Genetic Variation for Grain Cadmium Concentration in Great Plains Hard Winter Wheat Germplasm.

Pollution-safe cultivars of bread wheat (Triticum aestivum L.) can reduce risk to human health from cadmium consumption.  Cereals are dominant sources of Cd in human diets; therefore grain Cd concentration is regulated by the European Community.  Variation in Cd concentration in durum wheat (Triticum turgidum var. durum) is well documented, but genetic variation in Cd accumulation in hexaploid bread wheat  is less well characterized.  Grain mineral concentration was measured in the 299-genotype hard winter wheat association mapping panel being evaluated through the Triticeae Coordinated Agricultural Project.  The trial was grown in 2012 near Ithaca, NE on the site of a decommissioned munitions factory and missile launch area.  Grain Cd concentration in the trial averaged 0.230 mg kg^-1, above the EU limit of 0.200 mg kg^-1, and Cd concentration of the genotypes ranged from 0.080 to 0.580 mg kg^-1.  Grain Zn and Cd concentrations were not well correlated, indicating independent mechanisms for grain accumulation.  Differences in Cd concentration neither were associated with a concentration effect in low-yielding germplasm nor with kernel size.  Four genotypes, two with below-average Cd concentration and two with above-average Cd concentration, were grown in additional locations across Nebraska in 2012.  Only at Ithaca were grain Cd concentrations above 0.200 mg kg^-1.  Genotype rankings were consistent across environments.  The low-Cd phenotype appears to be heritable and amenable to selection in a high-Cd environment.  Cd concentration was measured in vegetative tissue samples collected at anthesis for six genotypes representing below-average, above-average, and very high grain Cd.  Vegetative Cd concentration was greater in high grain-Cd genotypes than in low grain-Cd genotypes.  Characterization of the hard winter wheat association mapping panel grown at Ithaca, combined with high density SNP marker analyses on the panel, will provide meaningful insights into the underlying genetics of grain Cd accumulation in hard winter wheat.