Siam tulip or Patumma (Curcuma alismatifolia) is an economically important flower in
Thailand. Currently, Siam tulip has been crossed to other Curcuma sp. both in subgenus Paracurcuma
and Eucurcuma to create novel and attractive characteristics, especially new bract colors. Therefore,
the study of bract color formation in Patumma and its related species is necessary as supporting
information in breeding program planning. In this study, flavonoid and carotenoid compounds
accumulated in bracts of Patumma and its relatives were identified by HPLC. Our results revealed that
the colors of bract in Patumma and its relatives resulted from the accumulation of both flavonoids and
carotenoids. A pink bract of Patumma contained major unknown anthocyanin pigment, a small amount
of cyanidin-3-O-rutinoside and delphinidin-3-O-rutinoside. Moreover, lutein and b-carotene were also
found in its pink bract. Another pink bract from C. petiolata was also analyzed and found that
delphinidin-3-O-rutinoside was the major anthocyanin pigment in its pink bract. A red bract of C.
aurantiaca accumulated cyanidin-3-O-rutinoside as a major anthocyanin pigment and contained a small
amount of carotenoids like lutein, zeaxanthin, b-cryptoxanthin, b-carotene and a-carotene. An orange
bract of C. roscoeana contained a major unknown anthocyanin pigment and small trace of lutein,
zeaxanthin and b-carotene. Moreover, the expression level of genes involving in flavonoid biosynthesis
pathway which are CHS, CHI and DFR, and in carotenoid biosynthesis pathway which is ZDS was also
studied using real-time PCR. We found the difference in gene expression level of these 4 genes among
various tissue color. The results of gene expression elucidated that the expression of CHS, CHI and
DFR was crucial for plants to synthesize the anthocyanin pigments especially in the tissues
accumulating anthocyanin pigments and displaying the color in pink orange and purple. The expression
of ZDS was also essential for the accumulation of a yellowish carotenoid pigment. Low level of
expression or no expression in one of these genes might result in low level of pigment accumulation or
lead to no accumulation of the pigments. Consequently, plants would display faded color or no color(white) in their tissues. The difference in gene expression level might be because of the regulation of
transcription factor gene, the difference in DNA sequence of promoter regions or in the coding
sequences of the interested genes. Therefore, the study of the mentioned topics in the future might
illustrate the mechanism of color formation in these ornamental curcuma plants more clearly.