Carotenoid Synthesis in Tissue Cultures of Daucus carota L.1

Abstract

Abstract Carotenoid synthesis was studied in tissue cultures derived from different carrot phenotypes of red, dark orange, orange, light orange, yellow and white root colors. Cultures derived from a single genetic source or even from a single root often differed in color. Yellow, pink, orange-red and red cultures were derived from red roots; yellow and orange cultures from dark orange and light orange roots; and yellow cultures from the roots of the other genetic sources. The total carotenoid content in tissue cultures partly reflected that of the parent root, but was generally lower than in the intact root. Cultures derived from white roots were exceptions to this; the carotenoid contents in these cultures sometimes exceeded the contents of the parent roots. Carotenes predominated in cultures and roots of the red and orange sources; xanthophylls were the main components in cultures and roots of the yellow and white sources. Individual cultures from one root differed in quantities of carotenes, but the main carotene was the same as in the root, lycopene for the red sources and B-carotene for the orange sources. The effects of kinetin, 2,4-dichlorophenoxyacetic acid (2,4-D) and gibberellic acid3 (GA3) on growth and pigmentation were tested in 13 selected cultures. Kinetin inhibited and 2,4-D enhanced carotenoid synthesis in several of the cultures. GA had no effect on pigment formation. Kinetin and 2,4-D affected the relative quantities of carotenoid components in one orange-red culture, R 1-1, but little in the orange-red culture R 1-2. Low total carotenoid content was associated with a relatively high xanthophyll content and a low lycopene to B-carotene ratio. Variation in culture pigmentation due to mutations was not confirmed. Plants regenerated from tissue cultures which had been derived from a single root had the same phenotype even though the colors and carotenoid contents of the callus cultures differed widely. If plantlet regeneration is limited only to cells with a diploid chromosome number, aneuploidy, which is very common in callus cultures, may have contributed to the observed pigmentation differences in the cultures.