Anatomical and biochemical factors determining ray floret color of Zinnia angustifolia, Z. elegans, and their interspecific hybrids.
1989
Boyle T.H. | Stimart D.P.
Anatomical and phytochemical studies of Zinnia angustifolia HBK, Z. elegans Jacq., and their interspecific hybrids were initiated to define factors affecting ray floret color. Clones of Z. angustifolia with ivory, orange, or white ray florets, and Z. elegans lines with orange, pink, red, white, or yellow ray florets were crossed intraspecifically to produce S1 and F1 progeny. Interspecific hybrids were produced by crossing orange- or white-flowered Z. angustifolia clones (as female-female) with Z. elegans lines (as male-male). In both species and interspecific hybrid, pigments were present mainly in the upper epidermis, more dilute in the lower epidermis, and not observed in internal parenchyma. Variation in ray floret color in Z. elegans was primarily due to presence or absence of carotenoids in chromoplasts and anthocyanidins in vacuoles. Quantitative differences in the anthocyanidins pelargonidin and cyanidin were detected among Z. elegans lines; in vivo expression of anthocyanins was influenced by epidermal cell pH. Ray floret color in Z. angustifolia was due to presence or absence of two novel anthocyanidins and ivory-colored flavonoids, with no attributable effect of epidermal cell pH on anthocyanin expression. Carotenoids were not present in ray florets of Z. angustifolia x Z. elegans hybrids, regardless of whether carotenoids were expressed in the Z. elegans parent line. Presence or absence of the two novel anthocyanidins from Z. angustifolia and cyanidin from Z. elegans permitted unique combinations of floral pigments in interspecific hybrids not previously found in either species.
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