Abstract
Orychophragmus violaceus is an ornamental plant belonging to the Brassicaceae family, known for its profusion of white to light purple, pink, and purple flowers that bloom in early spring. However, there is a lack of reports regarding the localization of the genes responsible for flower color. The aim of this research was to locate the key genes controlling flower color variation in O. violaceus, providing loci for its genetic improvement of flower color. In this study, we constructed an F(2) mapping population using the purebred white flower mutant line OvW-1 and the purebred purple flower line OvP-37, obtained candidate regions of the Ovwf locus using BSA-seq, and then used extreme recessive white-flowered plants for fine-mapping and combined with RNA-seq to predict key genes controlling the white-flowered trait. Genetic analysis indicated that the Ovwf trait is governed by a single recessive locus, designated as without cytoplasmic inheritance. Subsequently, BSA-seq and fine-mapping of the Ovwf locus within a 1.37 Mb interval. Gene annotation revealed that this interval encompasses 76 genes, of which only two genes-OV03G032130 and OV03G032280-are potentially implicated in anthocyanin biosynthesis. Further RNA-seq analysis suggested that only OvANS (OV03G032130) was differentially expressed, which may be a critical gene influencing the white flower locus Ovwf. This is the first report of fine-mapping of the flower color locus in O. violaceus. These findings contribute valuable insights into the mechanisms underlying flower color variation in O. violaceus and present a promising target for the breeding of colorful varieties.