Integrating functional genomics and genetic mapping to clone genes responsible for low grain cadmium concentration in durum wheat

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The dominant source of human exposure to environmental cadmium (Cd) in Canada is through Cd-contaminated food. Accumulation of Cd in Canadian durum wheat, which is worth in excess of $1 billion a year, may pose an unacceptable risk in terms of Cd exposure and may threaten exports of durum wheat. Several pairs of durum wheat lines have been established that differ in grain Cd concentration (high vs. low), but that are otherwise genetically similar. We have previously shown that differences in Cd translocation from the roots to the shoot may explain the differing grain-Cd levels for one of these pairs. The mechanism that limits Cd translocation to the shoot has yet to be identified. We propose to combine the power of transcriptome profiling (to identify genes of interest by comparing gene expression levels) with genetic mapping (to determine which genes of interest are genetically linked to this trait) to identify candidate genes that are potentially involved in regulating Cd accumulation in grain. We will use yeast-based assays as well as a plant-based system (virus-induced gene silencing) to complete a functional analysis of the candidate genes in an attempt to identify the mechanism(s) underlying low grain-Cd. We believe that this approach will expedite the identification of a zero-distance marker for low grain-Cd, thus providing a rapid and accurate method to identify low Cd breeding lines. This will enable continued development of durum wheat varieties with Cd concentrations that meet international regulatory standards. Additionally, such a marker could be used to authenticate and trace Canada's durum wheat exports. Identification of the mechanism underlying low grain-Cd in durum wheat could accelerate similar discoveries in other crops. The techniques and expertise developed in this project could also be extended to other important agronomic traits.