Fine-Mapping of OvANS: A Novel Gene Controlling White Flowers in Orychophragmus violaceus

<i>Orychophragmus violaceus</i> 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 <i>O. violaceus</i>, providing loci for its genetic improvement of flower color. In this study, we constructed an F₂ mapping population using the purebred white flower mutant line OvW-1 and the purebred purple flower line OvP-37, obtained candidate regions of the <i>Ovwf</i> 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 <i>Ovwf</i> trait is governed by a single recessive locus, designated as without cytoplasmic inheritance. Subsequently, BSA-seq and fine-mapping of the <i>Ovwf</i> locus within a 1.37 Mb interval. Gene annotation revealed that this interval encompasses 76 genes, of which only two genes-<i>OV03G032130</i> and <i>OV03G032280</i>-are potentially implicated in anthocyanin biosynthesis. Further RNA-seq analysis suggested that only <i>OvANS</i> (<i>OV03G032130</i>) was differentially expressed, which may be a critical gene influencing the white flower locus <i>Ovwf</i>. This is the first report of fine-mapping of the flower color locus in <i>O. violaceus</i>. These findings contribute valuable insights into the mechanisms underlying flower color variation in <i>O. violaceus</i> and present a promising target for the breeding of colorful varieties.