Identification of Quantitative Trait Loci Associated with Resistance to Sclerotinia Stem Rot in Canola Using Genotyping-By-Sequencing.

Sclerotinia stem rot (SSR), caused by Sclerotinia sclerotiorum is considered an economically important disease of canola (Brassica napus). Resistance to SSR is quantitatively inherited. Here we report initial findings of genetic linkage map construction, and identification of QTLs for SSR resistance. Genetic map was constructed for an F₂ mapping population derived from a cross between susceptible parent NEP32, and resistant parent NEP63. The parents are doubled haploids developed from a PI accession and show variability in their response to Sclerotinia Stem Rot. From genotyping-by-sequencing (GBS), >20,000 SNP markers were obtained that were polymorphic between the two parents. A subset of these markers filtered with high stringency for missing data was used for initial map construction. The linkage map has 1313 marker loci covering 7820 cM, with an average marker density of 5.9 cM per marker, which corresponds to 0.62 Mb of the genome. Phenotypic response of the progeny was evaluated following PIT method and quantified as area under disease progress curve (AUDPC). Composite interval mapping was performed to identify three significant QTL associated resistance to SSR. These QTL were detected on chromosomes A1, A3, and C8, and account for 12.9 to 15.3% of phenotypic variation.