Sequence-based genetic mapping of Ds-tagged insertions to characterize malting-related traits in barley

Among various functional genomics tools used to characterize genes in plants, transposon-based mutagenesis approaches offer great potential, especially in barley and wheat, which possess large genomes and in which genetic transformation is not routine. Two Ds transposon flanking sequences (TNPs), TNP-29 (27.4 cM (centiMorgan)) and TNP-79 (70.3 cM), were mapped in the vicinity of a malting quality QTL located on chromosome 4H of barley. Reactivation of the Ds transposon sequence from these TNP lines led to the identification of genes in the malting QTL regions. Several Ds (dissociation) lines were generated by crossing TNP-29 and TNP-79 with an AcTPase (activator) expressing line (25-B), and F2 progenies were subsequently screened for Ds insertions at new locations. To further characterize these Ds mutants, we mapped the new Ds flanking sequences on a barley genetic map and found that 29% of Ds were located in regions associated with the malting QTL located on chromosome 4H and in close proximity to other important malting-associated QTL across the barley chromosome. Using a sequence based approach, a linkage map was generated that confirmed the position of Ds loci in the barley genome map. Locating these Ds loci on the barley map opens avenues to dissect important malting QTL for facilitating identification of candidate malting genes.