Anthocyanin extraction and measurement
The buds of the mutant GS, the wild line PS, purple broccoli PB at low temperature (Figure 1C, D, E), were taken for this experiment. Total anthocyanin from buds of different broccolis were extracted with 0.1mol/L ethanol hydrochloride solution, and detected by UV/VIS spectrophotometer. The anthocyanidins were obtained after the anthocyanins were hydrolyzed by 37% HCl and boiling. The anthocyanidin content and constituent were determined by HPLC-MS as described by Yinet al ., 2015 and Zhang et al. , 2004.