P-258 - Identification of markers associated with reaction to clubroot in a canola doubled haploid mapping population.

Clubroot is caused by Plasmodiophora brassicae, an intracellular parasite that has an extraordinary reproductive capacity that, under favorable conditions, could turn infested fields suppressive for canola production. The disease is currently managed with resistant hybrids; however, the ability of this pathogen to overcome genetic resistance highlights the need for the identification of better sources of resistance. The objective of this study was to characterize the resistance present in plant introduction (PI) 432393. For this, a cross was made between this PI and the open pollinated cv. Topas. Microspore culture was used to produce 153 doubled haploid lines from the F₁ of this cross. Phenotypic evaluation of the mapping population was conducted in replicated field and greenhouse trials in 2023 and 2024 using Kuginuki’s 1-3 severity scale. After genomic DNA extraction and purification, samples were genotyped using an 18K Illumina Infinium Array mapped to the Darmor reference genome. Interval mapping and permutation test were conducted using R/qtl to identify quantitative trait loci (QTL) associated with reaction to the disease. Several lines with high levels of resistance were identified. In addition, 18 QTL significantly associated with reaction to clubroot were identified across five chromosomes. A large effect marker, CR_A03, located on chromosome A03, explained 18.5% of the phenotypic variance. Materials and information generated in this study will contribute to the production of improved clubroot resistant canola lines.