A 24,482-bp Deletion Increases Seed Weight Through Multiple Pathways in Rapeseed (Brassica Napus L.)

Abstract Exploration of the genes controlling seed weight is critical to improve crop yield and understand the mechanisms underlying seed formation in rapeseed (Brassica napus L.). We previously identified the quantitative trait locus (QTL) qSW.C9, for the thousand-seed weight (TSW) trait, in a double haploid population constructed from F1 hybrids between the parental accessions HZ396 and Y106. Here, we confirmed the phenotypic effects associated with qSW.C9 in BC3F2 populations and fine-mapped the candidate causal locus to a 266-kb interval. Sequence and expression analyses revealed that a 24,482-bp deletion in HZ396 containing six predicted genes most likely underlies qSW.C9. Differential gene expression analysis and cytological observations suggested that qSW.C9 affects both cell proliferation and cell expansion through multiple signaling pathways. After genotyping a rapeseed diversity panel to define their haplotype structure, we suggest that the selection of germplasm carrying two specific markers may be effective in improving seed weight in rapeseed. This study provides a solid foundation for the identification of the causal gene of qSW.C9 and offers an attractive target for breeding higher-yielding rapeseed.