A MYB Transcription Factor from Brassica juncea Regulates Purple Leaves in Pak Choi (Brassica campestris L. ssp. chinensis)

The purple-leaf phenotype in pak choi is due to the accumulation of anthocyanin. The main regulated genes are unclear. The gene controlling the purple-leaf phenotype was mapped on A03 using BSA-seq, but the candidate interval was not further narrowed with InDel markers. Based on our previous study, we hypothesized that the candidate gene that regulates purple leaves in pak choi may also be the Dark_Pur gene from B. juncea. Using the Dark_Pur-1 marker to identify P1, P2, F1, and F2, it was confirmed that the purple trait in purple-leaf pak choi was controlled by the Dark_Pur gene from B. juncea through distant hybridization. A DNA segment of approximately 514 Kb containing the Dark_Pur gene was reintroduced into pak choi from B. juncea. Meanwhile, a new purple pak choi germplasm line was created with green pak choi × purple B. juncea via distant hybridization, which proved that distant hybridization is an effective method for creating new germplasms. Furthermore, the purple-leaf phenotypes of 20 pak choi varieties were identified, and the purple-leaf traits of all lines were derived from B. juncea via distant hybridization. At present, few studies have focused on the background of the purple trait in pak choi; however, in this study, our results suggest that there is a high probability that the purple trait in pak choi may be completely derived from purple B. juncea via distant hybridization. This study also lays a good foundation for research on the creation of new germplasms through distant hybridization among the Brassica species.