Identification of Quantitative Trait Loci Associated with a Low Cadmium Uptake Gene in Durum Wheat (Triticum Turgidum L. Var. Durum)
Abstract
The main objective of durum wheat breeding is to identify lines that are low in Cadmium accumulation by using linkage mapping. 178 recombinant inbred lines (RILs) derived from across between Grenora × Haurani were used to identify QTL for Cadmium (Cd) tolerance. A total of 1,132 polymorphic loci (1,111 SNP and 21SSR loci) were used for linkage map analysis. Among these, 330 (29 percent) markers were successfully integrated into the linkage maps at a LOD score of 3.0. The linkage map had a total genetic distance of 720.2 cM with an average distance of 2.2 cM between adjacent markers distributed on 14 chromosomes. Quantitative trait loci analysis was conducted using composite interval mapping (CIM). A Single putative QTL associated with Cd uptake was detected on Chromosome 5B. This QTL increased Cd uptake by the presence of alleles from Grenora. The additive effect of the Grenora allele was 0.02 mg/kg. The variation in Cd accumulation explained by this QTL (r2) was 54.3 percent.
Association mapping was also used to analyze two durum wheat collections consisting of advanced breeding lines from the North Dakota wheat breeding program to discover markers associated with the amount of Cd accumulated in the grains. For the 2009 collection, one major QTL that explains 3 percent of phenotypic variation was identified on Chromosome 2B at 7.25 cM which could cosegregate with a height locus identified earlier. For the 2010 collection, one QTL that explains 34 percent of phenotypic variation was identified on Chromosome 5B at 165.7cM and one other at 178.3cM that explains 27 percent of phenotypic variation. Because of the complexity of Cd accumulation in wheat grains, the identification of additional QTL will require a better coverage of markers and a larger collection of genotypes. This will help breeding for low Cd using MAS.