Association mapping combined with whole genome sequencing data reveals candidate causal variants for sclerotinia stem rot resistance in Brassica napus .

Canola () yield can be significantly reduced by the disease sclerotinia stem rot (SSR), which is caused by , a necrotrophic fungal pathogen with an unusually large host range. Breeding cultivars that are physiologically resistant to SSR is desirable to enhance crop productivity. However, the development of resistant varieties has proved challenging due to the highly polygenic nature of resistance. Here, we identified regions of the genome associated with SSR resistance using data from a previous study by association mapping. We then validated their contribution to resistance in a follow-up screen. This follow-up screen also confirmed high levels of SSR resistance in several genotypes from the previous study. Using publicly available whole genome sequencing data for a panel of 83 genotypes, we identified non-synonymous polymorphisms linked to the SSR resistance loci. A qPCR analysis showed that two of the genes containing these polymorphisms were transcriptionally responsive to infection. In addition, we provide evidence that homologues of three of the candidate genes contribute to resistance in the model Brassicaceae species . The identification of resistant germplasm and candidate genomic loci associated with resistance are important findings that may be exploited by breeders to improve the genetic resistance of canola varieties.