A naturally occurring insertion in the RsFLC2 gene associated with late-bolting trait in radish (Raphanus sativus L.)

Premature flowering reduces the yield and quality of the harvested fleshy taproot in radish. However, there has been little molecular marker research on the radish late-bolting trait. In this study, F-2 and F-2:3 populations derived from a cross of Ninengo (late-bolting) and Maer (early-bolting) were analyzed to map late-bolting genes. Five hundred insertion and deletion (InDel) markers were designed according to the whole-genome resequencing data of the two parents. A genetic map was constructed based on the F-2 population, and a late-bolting gene was detected in a 1.1-cM region between the markers InDel520 and InDel535 on chromosome R02 that explained the highest (76.4%) phenotypic variance. RsFLC2 was identified as a candidate gene in this region. Notably, Ninengo contains a 1627-bp insertion near the 5 end of the first intron of RsFLC2. Allelic variation analyses in the F-2 population further validated that RsFLC2was associated with the late-bolting trait in radish. The expression pattern of RsFLC2 was significantly different between Ninengo and Maer during vernalization. Vernalization suppressed RsFLC2 expression, and the 1627-bp insertion in the first intron weakened gene repression in Ninengo plants, resulting in late-bolting. This study lays a foundation for uncovering the molecular mechanism of late-bolting and marker-assisted selection for breeding late-bolting varieties of radish.