Characterisation of flower colouration in 30 Rhododendron species via anthocyanin and flavonol identification and quantitative traits

Abstract

Floral colour is a key reproductive character, often associated with environmental adaptation, and subject to human intervention. A large number of Rhododendron species differ widely in flower colour, providing a good model for flower colouration. The chromatic features and anthocyanin compositions of 30 species from seven subgenera were systematically analysed. The Royal Horticultural Society Colour Chart and CIE L*a*b* system were employed to describe and investigate flower colours. The UPLC-PDA/ESI-MS system was used to identify and quantify anthocyanins in petal extracts. The flower colours of 30 Rhododendron species were categorised into four groups - red, purplish pink, purple and white. Seven anthocyanins were identified and quantified in petals: delphinidin, cyanidin and malvidin 3-O-arabinoside-5-O-glucosides, cyanidin 3,5-di-O-glucoside, 3-O-galactoside and 3-O-arabinoside, and delphinidin 3-O-glucoside. The red-flowered species mainly contained cyanidin monoglycosides and had much higher total anthocyanin content than purplish pink- and purple-flowered species. Purplish pink- and purple-flowered species had similar anthocyanin types and content. The chromatic differences were significant among groups, except the purplish pink and purple groups. Statistical analysis showed that Cy3Gal and Cy3Arb are characteristic for red-flowered species, and Mv3Arb5G and Dp3Arb5G play important roles in purple colouration; their contents were major components that greatly affected the chromatic parameters. In total, 21 flavonol derivates were identified. However, total flavonol content and co-pigmentation index showed no significant difference or correlation among/with colour groups, suggesting that flavonols might not play a major role in colouration. These results enhance our knowledge of the biochemical basis of flower colouration in Rhododendron species, and provide a foundation for genetic variation studies and aid in breeding cultivars with novel flower colours.

Study on cyanidin metabolism in petals of pink-flowered strawberry based on transcriptome sequencing and metabolite analysis

“…However, the function was limited to flavonols, as a co-pigmentation, to change the petal color from magenta to blue color [34, 35]. Du et al (2018) reported the anthocyanin composition of 30 Rhododendron species and showed that there was no significant difference in co-pigmentation index among color different groups and flavonols might not play a major role in coloration [36]. Our study results showed that the white petal was due to the significant accumulation of flavonols and that the key factor of shades of pink was the accumulation of anthocyanins.…”

Analyses of Pigment Compositions and Anthocyanin Biosynthesis Gene Expression in Hirado Azalea Cultivars

“…'Shiro-ryūkyū' contained only flavonol. Recent research also confirmed that no anthocyanins were detected in white flowers of five wild species, including R. mucronatum (Du et al, 2018). Hirado cultivar groups were divided into four pigment groups: 1) Cy-derivatives only without flavonol, 2) Cy-derivatives and flavonol, 3) Cy-and Dpderivatives and flavonol, and 4) flavonol only.…”

The Importance of Polyphenols as Functional Food in Health

“…Anthocyanins are dominant pigments that give plants the color of red, purple and purple pink. The pigmentation of flowers is determined by the type and amount of anthocyanin in the contents of the flower (7). When lingonberry (Vaccinium vitis-idaea) which is grown in Poland and blueberries (Vaccinium myrtillus L.) are compared in terms of phenolic ingredients they contain, blueberries have shown more antioxidant activity.…”