Abstract
Seed biochemical composition critically influences the quality and industrial value of oilseed rape (Brassica napus L.). Understanding the genetic basis of seed oil, protein, and fiber content is essential for breeding improved cultivars. Here we conducted a genome-wide association study (GWAS) on 350 diverse winter oilseed rape lines over three years, using near-infrared reflectance spectroscopy (NIRS) to measure seed traits and SNP genotyping for association mapping. We identified numerous SNP markers significantly associated with seed oil, protein, acid detergent fiber (ADF), and neutral detergent fiber (NDF) content. From 18,566 detected SNPs, 3782 met stringent criteria and were used for association mapping, resulting in 3189 significant associations across three years. The highest number of associations was observed for protein (3480), followed by NDF (3662), ADF (3422), and oil (2046). Individual markers explained up to 35% of phenotypic variation, indicating strong genetic control of these traits. Gene ontology enrichment analyses linked candidate genes to key metabolic and regulatory pathways influencing these traits: protein biosynthesis and post-translational modification, lipid metabolism regulated by phosphorylation, and transcriptional control of cell wall polysaccharide synthesis. These findings provide valuable molecular markers that can be validated for further use in marker-assisted selection, supporting the development of rapeseed cultivars with optimized seed quality for food, feed, and industrial applications.