*4.2. Quantitative Statistics and Flower Colorimeter Analysis*

Three rocks with *P. limprichtii* populations which contained individuals with all three color variations were selected, the number of each color individuals were counted. In addition, in order to evaluate the flower color objectively, a hand spectrophotometer (CS-280, Hangzhou Color Spectrum Technology Co., Ltd., Hangzhou, China) was used to measure the CIE L\*a\*b\* color components with five technical repetitions using five different parts of the selected petals, in order to evaluate the flower color objectively. The formula C\* = - *a* ∗<sup>2</sup> + *b*∗2), the L\* (lightness) and C\* (chroma) through the petals were measured using the lightness coefficient 'a\*', which indicates greenness to redness as the value increases from negative to positive, and 'b\*', which represents blueness to yellowness. Principle component analysis was performed using the a\* and b\* values as the principle components [32].

#### *4.3. Sampling and RNA Extraction and cDNA Synthesis*

Petals from rose-purple, pink, and white flowers at the full bloom stage were sampled, immediately frozen in liquid nitrogen, and preserved at −80 ◦C before pigment analysis and RNA extraction. RNA was isolated using a Quick RNA isolation Kit (Huayueyang Co., Ltd., Beijing, China), according to the manufacturer's instructions. The concentration and purity of the RNA was measured with a NanoDrop 2000 (Thermo Fisher Scientific Co., Ltd., Waltham, MA, USA) and Agilent 2100 (Agilent Technologies

Co., Ltd., Palo Alto, CA, USA) to verify RNA integrity. A total of nine samples, including three biological replicates, with high concentrations of RNA for each of the three color morphs were selected, then the strand cDNA synthesis was performed using a Revert Aid First Strand cDNA Synthesis Kit (Thermo Fisher, Foster City, CA, USA), according to the manufacturer's instructions, and was stored at −80 ◦C for RT-qPCR assays.
