USE OF GENETIC VARIABILITY IN REDUCING CADMIUM UPTAKE BY PLANTS
C. A. Grant¹, J. M. Clarke², S. Duguid³ and R. Chaney⁴

¹AAFC Brandon Research Centre, Box 1000A, R. R. #3, Brandon, MB Canada R7A 5Y3 [cgrant@agr.gc.ca]
²Semiarid Prairie Agricultural Research Centre, P.O. Box 1030, Swift Current, SK, Canada S9H 3X2 [clarkej@agr.gc.ca]
³AAFC Morden Experimental Farm, Unit 100, 101 Route 100, Morden, MB Canada R6M 1Y5 [sduguid@agr.gc.ca]
⁴US Dept. Agriculture, Agr. Res. Serv., Animal Manure and Byproducts Lab, Bldg. 007, BARC-West, Beltsville, MD 20705-2350 [ChaneyR@BA.ars.usda.gov].

Trace element content of food has a large impact on human health, worldwide. Deficiencies of essential nutrients such as Fe, Zn and Se are widespread, while excess accumulations of potentially toxic trace elements such as Cd may also occur. This is of particular concern in staple crops such as cereals, which make up a large proportion of the diet. The potential risk of Cd to human health is affected not only by the concentration of Cd, but by the concentration of Cd relative to essential trace elements such as Zn and Fe. Natural variation occurs in both the uptake and the distribution of trace elements in crop species and in cultivars within species. Therefore, plant breeding can be an important tool to improve crop quality, both by increasing crop concentrations of desirable trace elements and reducing the concentration and bioavailability of potentially harmful trace elements such as Cd. Selection programs for low Cd concentration of various crops have been established and low Cd cultivars of durum and sunflower have been developed. In durum wheat (Triticum turgidum L. var durum), low Cd concentration is controlled by as single dominant gene. The trait is highly heritable, and incorporation of the low cadmium allele reduces average grain cadmium to levels well below proposed international limits. The allele for low cadmium concentration does not appear to affect major economic traits or the concentrations of other ions, and should not cause problems when incorporated into durum cultivars. In sunflower, low Cd inbred and restorer lines are available and have been used to produce low Cd hybrids. Potential for selection for low Cd cultivars exists in many other crops. Selection for increased availability of essential trace nutrients such as Zn and Fe may be of benefit both in decreasing bioavailability of Cd and enhancing overall nutritional status. However, plant breeding programs must select for a wide range of agronomic and quality characteristics, such as disease resistance, protein content, lodging resistance, maturity and yield. Addition of further traits, such as low Cd, requires increased investment in selection. In addition, increasing levels of Cd in soils and management practices which enhance Cd phytoavailability will increase Cd concentration in both low- and high-Cd cultivars. Production of low Cd crops cultivars can be used as a short-term tool to reduce the risk of movement of Cd into the human diet. In the long-term, accumulation of Cd in soils may still be a concern for sustainability of crop production and quality.