<i>BnaFLC.A10</i> , <i>BnaFLC.A2</i> , and <i>BnaFT.A2</i> jointly regulate flowering time in <i>Brassica napus</i>

Allelic variations in BnaFLC.A10, BnaFLC.A2, and BnaFT.A2 have been associated with flowering time regulation in Brassica napus. However, the effects of their interactions remain insufficiently understood. In this study, we investigated the genetic basis underlying flowering time differences between the winter-type Tapidor and the spring-type Westar. Utilizing quantitative trait locus sequencing (QTL-seq) and transcriptome analysis, BnaFLC.A10, BnaFLC.A2, and BnaFT.A2 were identified as candidate genes associated with flowering time variation. Functional evidence from transgenic ectopic expression and CRISPR/Cas9-mediated genome editing supports their involvement in flowering time regulation. Genotypic and phenotypic analysis of 248 individuals from an (Westar×Tapidor) F2 population, along with 226 B. napus accessions, indicated additive effects of BnaFLC.A10 and BnaFLC.A2 in vernalization requirements and potential epistatic interactions with different BnaFT.A2 alleles. These results provide insights into the genetic interactions underlying flowering time variation and may assist in optimizing allele combinations for enhanced adaptation in B. napus breeding.