Cloning of the candidate gene BnCRY2, associated with the early-flowering locus BnaC08cqDTF, identified an A/G single-nucleotide polymorphism (SNP) within the third exon of the corresponding alleles. Based on this SNP, a KASP marker named BN900449 was developed. This marker, along with four additional markers—multiplex PCR markers PB05 and PB06, and KASP markers A015348 and K000272—tightly linked to the early-flowering loci qFT.A02-1 and qFTA10, was used to genotype a natural population of 497 Brassica napus L. accessions. Genotypic analysis revealed that each of the three loci effectively divided the population into two groups with significantly different flowering times. Notably, accessions carrying two of the early-flowering loci flowered, on average, earlier than those carrying only one. Three representative accessions, each harboring a different single-locus allele (BnaC08cqDTF, qFTA10, and qFT.A02-1), were selected for diallel crosses aimed at pyramiding early-flowering alleles. Marker-assisted selection subsequently yielded 41 extremely early-flowering lines, which exhibited flowering times 3-4 days earlier than their respective parents. Among these, 195 lines were identified that combined extreme earliness with double-low seed quality. Multi-location yield trials conducted at five high-altitude sites over two consecutive years showed that the average yield of selected lines exceeded that of Brassica rapa L. cultivar Haoyou 11—the predominant spring-sown variety in high-altitude regions—by 23.07%. This study not only expands the genetic framework for developing extremely early- flowering B. napus spring-type germplasm but also provides elite parental resources for breeding early-maturing, high-yielding, and high-quality rapeseed cultivars.
Wang et al. (2025) studied this question.