ARS | Publication request: Targeted mapping of Cdu1, a major locus regulating grain cadmium concentration in durum wheat (Triticum turgidum L. var durum)

Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 19, 2010
Publication Date: June 18, 2010
Citation: Wiebe, K., Pozniak, C.J., Harris, N., Faris, J.D., Clarke, J.M., Knox, R.E., Taylor, G. 2010. Targeted mapping of Cdu1, a major locus regulating grain cadmium concentration in durum wheat (Triticum turgidum L. var durum). Theoretical and Applied Genetics. 121:1047-1058.

Interpretive Summary: Some durum wheat cultivars have the genetic propensity to accumulate cadmium (Cd) in the grain. A major gene controlling grain Cd concentration designated as Cdu1 has been reported on durum chromosome 5B. The objectives of this study were to saturate the chromosomal region harboring Cdu1 with molecular markers and to investigate evolutionary relatedness of this wheat chromosomal region with regions of the rice and Brachypodium genomes. The precise physical and genetic chromosomal location of Cdu1 was determined, and new molecular markers were developed that co-segregated with Cdu1. Also, physical segments of rice chromosome 3 and of Brachypodium chromosome 1 that are evolutionarily conserved with the Cdu1 chromosomal region were identified. The molecular markers and the conserved regions of the rice and Brachypodium genomes described here represent tools that will assist in the isolation of Cdu1 and can be used to select for low Cd accumulation in durum wheat breeding programs targeting this trait. The isolation of Cdu1 will further our knowledge of Cd accumulation in cereals as well as metal accumulation in general.

Technical Abstract: Some durum wheat (Triticum turgidum L. var durum) cultivars have the genetic propensity to accumulate cadmium (Cd) in the grain. A major gene controlling grain Cd concentration designated as Cdu1 has been reported on 5B, but the genetic factor(s) conferring the low Cd phenotype are currently unknown. The objectives of this study were to saturate the chromosomal region harboring Cdu1 with newly developed PCR-based markers and to investigate the colinearity of this wheat chromosomal region with rice (Oryza sativa L.) and Brachypodium distachyon genomes. Genetic mapping of grain Cd concentration in two environments coupled with chromosome localization in aneuploid stocks indicated that the Cdu1 gene(s) associated with variation in Cd concentration resides in wheat bin 5BL9 between fraction breakpoints 0.76 and 0.79. Genetic mapping and QTL analysis of grain Cd concentration performed in 155 doubled haploid lines from the cross Kofa (high Cd) by W9262-260D3 (low Cd) revealed two expressed sequence tag markers (ESMs) and one sequence tagged site (STS) marker that co-segregated with Cdu1 and explained >80% of the phenotypic variation in grain Cd concentration. A second, minor QTL for grain Cd concentration was also identified on 5B, 67 cM distal to Cdu1. The Cdu1 interval spans 286 Kbp of rice chromosome 3 and 282 Kbp of Brachypodium chromosome 1. The markers and rice and Brachypodium colinearity described here represent tools that will assist in the positional cloning of Cdu1 and can be used to select for low Cd accumulation in durum wheat breeding programs targeting this trait. The isolation of Cdu1 will further our knowledge of Cd accumulation in cereals as well as metal accumulation in general.