A lignified-layer bridge controlled by a single recessive gene is associated with high pod-shatter resistance in Brassica napus L.

Pod shattering causes severe yield loss in rapeseed (Brassica napus L.) under modern agricultural practice. Identification of highly shatter-resistant germplasm is desirable for the development of rapeseed cultivars for mechanical harvesting. In the present study, an elite line OR88 with strong shatter resistance and a lignified-layer bridge (LLB) structure was identified. The LLB structure was unique to OR88 and co-segregated with high pod-shatter resistance. The LLB structure is differentiated at stage 12 of gynoecium development without any gynoecium defects. Genetic analysis showed that LLB is controlled by a single recessive gene. By BSA-Seq and map-based cloning, the resistance gene location was delimited to a 0.688 Mb region on chromosome C09. Transcriptome analysis suggested BnTCP8.C09 as the gene responsible for LLB. The expression of BnTCP.C09 was strongly downregulated in OR88, suppressing cell proliferation in the pod valve margin. KASP markers linked to the candidate gene were developed. This pod shatter-resistant line could be used in rapeseed breeding programs by direct transfer of the gene with the assistance of the DNA markers.