Flavonoid is the main pigment responsible for cotton flower color A previous study showed that flavonol and anthocyanin were abundant in cotton flower [36], and the silencing of the flavanone 3-hydroxylase (F3H) gene caused an obvious change in the petal color of one day post anthesis (DPA) flowers in transgenic plants [46]. To determine whether flavonoids are the main pigment in cotton flowers, we additionally compared the petals of wild type G. hirsutum (YZ1) and F3H silence line (f3h) on 0 DPA and the abscission petals on 1 DPA (Figure 5). The color of YZ1 flowers was cream at 0 DPA, which represents the most common color of cotton species, while the flower color of f3h was white (Figure 5A), which indicated that lack of flavonoids caused color loss and the pigment in the cream petals was also mainly composed of flavonoids (Figure 5). This pigment could not be anthocyanin because the OD value of the extract of YZ1 flower on 0 DPA at