CmYAB1 genetic transformation

The CmYAB1 coding sequence was first cloned into a pENTR 1A vector and then introduced into the pMDC43 vector by LR recombination. The pMDC43‐CmYAB1 vector was introduced to the chrysanthemum ‘Jinba’ by Agrobacterium‐mediated genetic transformation as described previously (Wang et al., 2019). After further screening by PCR at the DNA level, the positive transgenic seedlings were grown in a growth chamber for a week under 16 h/8 h and 25 °C/18 °C day/night and were then transferred to greenhouse under standard management. RNA was extracted from ray petals at the SFB stage, and qRT‐PCR was performed to examine the expression level of CmYAB1 with gene‐specific primers. The outermost ray florets were used to measure the distance between petal margins.