Flower pigments in yellow denbrobium species and hybrids

Abstract

Carotenoids and chlorophylls in yellow petals of Dendrobium species and hybrids were examined by high-performance liquid chromatography (HPLC). Six carotenoids, neoxanthin, violaxanthin, antheraxanthin, lutein, zeaxanthin, and β-carotene, and chlorophyll a and b were identified. Lutein, zeaxanthin, and 8-carotene were the major pigments responsible for yellow flower color in several dendrobiums. Color was affected by the numbers and concentrations of pigments. The degradation of flavonoids, carotenoids, and chlorophylls in the flowers at different stages of maturity within a raceme was examined for three progenies, K528 (pale yellow), K637 (white-purple), and K650 (bright yellow). The amounts of carotenoids and chlorophylls in crosses K528 and K637 decreased rapidly after blooming, while cross K650 maintained a high carotenoid content in all stages of maturity. Flavonol content in all three crosses did not show any change over time. Carotenoid and chlorophyll changes in growth and development from the bud stage to flower maturity were determined qualitatively and quantitatively in crosses K528 and K637. All 6 carotenoids and 2 chlorophylls in both crosses declined continually from the bud stage to 2-4 weeks after blooming. The inheritance of yellow flower color in Dendrobium appears to be complex, since at least 6 carotenoids and chlorophyll a and b have been shown to co-exist. Degradation of yellow pigments is not uncommon, and polyploidy further complicates the analysis of color inheritance. Since both carotenoid and chlorophyll concentrations in hybrids often fall between those of the parents, it appears that yellow color is mostly quantitatively inherited although interactions with modifying genes can be significant.