Inflorescence Developmental Stage-Specific High Temperature Effect on Petal Pigmentation in Chrysanthemum

Flower color is one of the most important traits in ornamental plants. Poor coloration of pink flower chrysanthemum during the high temperature season is a serious problem. To determine the effect of high temperature on the pigmentation, inflorescence development was divided into five stages. Plants were exposed to both 20 and 30℃ during various developmental stages of inflorescence. HPLC analysis showed the main anthocyanins of pink flower chrysanthemum(cv. Pelican) were cyanidin 3-O-(6"-O-monomalonyl-ß-glucopyranoside) and cyanidin 3-O-(3",6"-O-dimalonyl-ß-glucopyranoside). The content of the two anthocyanins at 20℃ was much higher than that at 30℃. In the inflorescence exposed to 30℃ during bud break to vertical stage, pigmentation was not enhanced, even though the plants were subjected to 20℃ from the vertical stage to 1-week-old. On the other hand, when the plants were exposed to 30℃ during vertical stage to 1-week-old, pigment content decreased drastically, even though the inflorescence was kept at 20℃ from the bud break to vertical stage. The results indicate that the petal extension to vertical stage is the most temperature sensitive and important for pigmentation. Expression of the anthocyanin biosynthesis-related genes (CmplCHS1, CmplCHS2, CmplCHI, CmplF3H2, CmplC3'H, CmplDFR1, CmplDFR2, and CmplANS) was depressed at 30℃ compared with those at 20℃.