Characterization of the varied output from the anthocyanin pathway in Phalaenopsis-type Dendrobium hybrids and its relationship with flower coloration

Floral color is an important Phalaenopsis-type Dendrobium hybrids (Den-Phals) trait in the flower markets. Anthocyanins are key pigments contributing to purple, pink, and violet floral color. However, the impact of anthocyanin composition on flower coloration has not yet been fully elucidated. In this study, the flower color characteristics of 62 Den-Phals were evaluated. Most flowers contained purple, while pure blue, orange, and red floral colors were scarce. In total 35 anthocyanins were identified and two acylated pelargonidin glycosides were tentatively characterized using ultra-performance liquid chromatography (UPLC)-mass spectrum (MS) analysis. Unfortunately, the major anthocyanin components remained unidentified. However, the hydrolysis anthocyanins to their anthocyanidins suggested that the cyanidin was the major component in most hybrids with a relative content over 85 %. Pelargonidin was almost the only pigment in reddish pink flowers. The slightly higher peonidin content was found in purple-violet flowers (up to 6.23 %). The trend indicated that with the increase of total anthocyanidin and cyanidin pigments, the floral color deepened and turned to purple. Flavones or flavonols as co-pigments contributed to brighter and yellower color. From the above results, the varied output from the anthocyanin biosynthetic pathway among Den-Phals was used to identify the rate-limiting steps involved and a strategy for the cultivation of pure red, blue, and violet flowers is proposed. The study provides a basis for screening excellent germplasm and improving floral color in Den-Phals.