Genetic and molecular regulation of flowering time in Brassica napus L.

Flowering time is a key agronomic trait that determines the ecological adaptability and seed yield of Brassica napus L. It is regulated synergistically by the characteristics of the allopolyploid genome (AACC), multiple environmental signals (i.e., temperature, and photoperiod) and endogenous hormones. Presently, the chemical basis underlying flowering time regulation in B. napus was barely reported except for hormones. Quantitative Trait Locus (QTL) mapping and Genome-Wide Association Study (GWAS) revealed many flowering time-related genetic loci under multiple environments, including the candidate genes associated with ecotype differentiation of B. napus, such as FLOWERING LOCUS C (FLC), FLOWERING LOCUS T (FT), and CONSTANS (CO). The network regulating flowering time of B. napus in multiple pathways have been reported, including vernalization regulated by epigenetic silencing of FLC, photoperiod pathway regulated by CO-FT module, hormone related pathway (i.e., gibberellin and cytokinin), and miR156-SPL regulated aging. Moreover, these signals in flowering time regulation were integrated at the shoot apical meristem via the floral pathway integrators FT and SOC1. Here, we summarized the chemicals affecting flowering time in plants, the achievements in flowering time-related genetic loci and regulatory mechanisms of B. napus, providing theoretical support for genetic breeding of flowering time in B. napus and other crops.