Lack of vernalization requirement in Chinese kale was due to the deletion of BoFLC as well as low expression of its paralogs

Non-vernalization in Chinese Kale, a vegetable with bolting stem harvested and consumed, is an import agronomic trait. However, the genetic and molecular mechanisms underlying non-vernalization in Chinese Kale remain unclear. To better understand the genetic control of flowering time in Chinese kale, a Chinese kale (a non-vernalization crop) was crossed with a kale (a vernalization crop). In the F2 population, flowering time was analyzed using Bulked Segregant RNA-seq (BSR-seq)34. We showed that the phenotypic segregation of early and late flowering was controlled by several QTLs. Based on the genetic results, we constructed an F2:3 family in which the phenotypic segregation of early flowering and late flowering was controlled by a single major QTL. This major QTL was then cloned using map-based cloning procedures. The causal mutation was identified and the impact of the causal mutation were studied in detail. This study provides insight in our understanding of vernalization. Our results will facilitate studies on the genetic and molecular mechanisms of flowering time in other important Brassica crops, and the identified polymorphic gene can be used in breeding programs of B. oleracea crops.

芥蓝（Chinese Kale）是一种以抽薹茎为采收食用器官的蔬菜，其非春化特性是一项重要的农艺性状。然而，芥蓝非春化特性背后的遗传与分子机制仍不明确。为了更好地解析芥蓝开花时间的遗传调控机制，我们将一份非春化型芥蓝与一份春化型芥蓝进行杂交。在F₂群体中，我们采用混合分群RNA测序（Bulked Segregant RNA-seq，BSR-seq）34对开花时间进行了分析。研究表明，早花与晚花的表型分离受多个数量性状位点（Quantitative Trait Locus，QTL）调控。基于上述遗传分析结果，我们构建了F₂:₃家系，该家系中早花与晚花的表型分离仅受单个主效数量性状位点调控。随后我们通过图位克隆技术克隆了该主效QTL，鉴定出其因果突变位点，并对该突变的影响进行了详细研究。本研究为我们理解春化调控机制提供了新的视角。我们的研究结果将有助于解析其他重要芸薹属（Brassica）作物开花时间的遗传与分子机制，而鉴定出的多态性基因可应用于B. oleracea作物的育种工作。