Super-long-day treatment bypasses vernalization and induces flowering directly in Brassica rapa and Raphanus sativus

Abstract

Flowering promotion is an essential technique in plant breeding. In plants of the Brassicaceae family, flowering generally requires a prolonged period of low temperature, known as vernalization, which often represents a rate-limiting step in breeding programs. In this study, we identified a phenomenon termed Long-day Induced Vernalization Exclusion (LIVE), in which flowering is triggered under non-conventional long-duration light conditions without the need for vernalization. In Brassica rapa and Raphanus sativus, this phenomenon was observed across many lines under super-long-day conditions, and its induction became increasingly pronounced as the day length extended. LIVE was also induced under a repeating 11-hour light/1-hour dark cycle, suggesting that uninterrupted long day length is not strictly required for LIVE induction. This study reveals that low-temperature treatment can be bypassed through these long-duration light conditions across multiple lines, offering important insights for accelerating flowering in practical breeding.