Abstract
Flower colour is mainly due to the accumulation of flavonoids, carotenoids and betalains in the petals. Of these pigments, flavonoids are responsible for a wide variety of colours ranging from pale yellow (flavones, flavonols and flavanodiols) to blue-violet (anthocyanins). This character plays a crucial ecological role by attracting and guiding pollinators. Moreover, in the ornamental plants market, colour has been consistently identified as the main feature chosen by consumers when buying flowers. Considering the importance of this character, the aim of this study was to evaluate flower colour in the native Chilean geophyte Alstroemeria pallida, by using three different approaches. Firstly, the phenotype was assessed using both a colour chart and a colourimeter, obtaining CIELab parameters. Secondly, the anthocyanin content of the pigmented tepals was evaluated by high-performance liquid chromatography (HPLC), and finally, the expression of two key flavonoid genes, chalcone synthase (CHS) and anthocyanidin synthase (ANS) was analysed using real-time polymerase chain reaction (PCR). Visual evaluation of A. pallida flower colour identified 5 accessions, ranging from white (Royal Horticultural Society (RHS) N999D) to pink (RHS 68C). Moreover, this visual evaluation of the accessions correlated highly with the CIELab parameters obtained by colourimetry. An anthocyanidin corresponding to a putative 6-hydroxycyanidin was identified, which was least abundant in the white accession (RHS N999D). Although CHS was not expressed differentially between the accessions, the expression of ANS was significantly higher in the accession with pink flowers (RHS 68C). These results suggest a correlation between phenotype, anthocyanin content and ANS expression for determining flower colour of A. pallida, which could be of interest for further studies, especially those related to the breeding of this species with ornamental value.
Highlights
The accumulation of flavonoids, carotenoids and betalains, is the principal determinant of flower colour [1]
Five accessions were distinguished according to tepal colour using the RHS mini colour chart (The Royal Horticultural Society and Flower Council Holland, London, UK), including white (RHS N999D and RHS 155B), light pink (RHS 56C and RHS 65B) and pink (RHS68C) varieties
The pink accession (RHS 68C) possessed a C* value that is significantly higher (22.02) compared to the other accessions, which means that it has the highest flower colour intensity or saturation of the accessions analysed
Summary
The accumulation of flavonoids, carotenoids and betalains, is the principal determinant of flower colour [1]. Flavonoids represent the most important group with more than 8000 structures reported [2] and their accumulation in petals is responsible for a wide variety of colours, ranging from orange, red, magenta, violet and blue (anthocyanins) to colourless or very pale yellow (flavones and flavonols) [3]. Such pigments have been characterised in species such as Dahlia variabilis [4], Rosa × hybrida [5], Matthiola incana [6] and Paeonia lactiflora [7]. Temperature, pH, oxidising and reducing agents can significantly affect the stability of anthocyanins [10], while co-pigments, vacuolar pH and chelation are important factors that alter flower colour produced by anthocyanins [11]
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