Quantitative genetic analysis of grain yield in an Australian Brassica napus doubled-haploid population

High yield is a major objective in canola-breeding programs. We analysed the genetic determinants controlling variation in grain yield in a doubled-haploid (DH) breeding population derived from a single BC1F1 plant from the cross Skipton/Ag-Spectrum//Skipton (designated as the SAgS population). DH lines were evaluated for flowering time and yield in two replicated trials and exhibited significant genetic variation for both traits. Yield showed negative correlation with flowering time; lines that flowered earlier had higher yield than late-flowering lines. A genetic linkage map comprising 7716 DArTseq markers was constructed for the SAgS population, and a 'bin' map based on 508 discrete single-position (non-co-segregating) marker loci was used for quantitative trait locus (QTL) analysis. We identified 20 QTLs (LOD =2) associated with variation in flowering time and grain yield. Two QTLs (Qy.wwai-A7/Qdtf.wwai-A7/Qfs.wwai-A7 and Qy.wwai-C3a/Qfs.wwai-C3a) appeared repeatedly across experiments, accounting for 4.9-19% of the genotypic variation in flowering time and yield and were located on chromosomes A07 and C03. We identified 22 putative candidate genes for flowering time as well as grain yield, and all were located in a range of 935bp to 2.97 Mb from markers underlying QTLs. This research provides useful information to be used for breeding high-yielding canola varieties by combining favourable alleles for early flowering and higher grain yield at loci on chromosomes A07, C03 and possibly on A06.