Flower color and pigments in yellow-flowered hybrid progeny raised from the interspecific cross Pelargonium quinquelobatum × white-flowered geraniums

- Normal seeds were obtained only when P. quinquelobatum was used as the seed parent.
- The pigmentation of yellow flowers involved a large amount flavonols.
- The main pigments of yellow flowers were kaempferol or quercetin.
- The quercetin contents were significantly correlated with the yellowness of flowers.
- The yellowness was unaffected by the aluminum content or the pH value in the petals.

The aim of this study was to produce a yellow-flowered geranium (Pelargonium × hortorum Bailey). Interspecific crosses between white-flowered geraniums and Pelargonium quinquelobatum Hochst. ex A. Rich. were performed. Unilateral incompatibility was observed, such that normal seeds were obtained when P. quinquelobatum was used as the seed parent, whereas no seeds were obtained when P. quinquelobatum was used as the pollen parent. The F1 progeny produced sterile pollen; therefore, genome doubling of the F2 progeny was induced by colchicine treatment to ensure fertile pollen; F3 progeny were also produced. The F3 progeny were crossed with tetraploid geraniums to produce BC1 and BC1F2 progeny. The flower color of the hybrid progeny were pale yellow, ranged from green-yellow 1D to yellow 3C, according to the Royal Horticultural Society Color Chart, and became increasingly the value of the colorimetric parameter b* with advancing generations. The pigmentation of the pale yellow flowers involved a large amount of flavonols and a small amount of carotenoids: the main pigments were kaempferol or quercetin. The quercetin contents were significantly correlated with the b* value (r = 0.82, P < 0.001), whereas no correlation was found between the kaempferol or carotenoids contents and the b* value. Furthermore, the b* value was unaffected by the aluminum content or the pH value in the petals.