ISHS Acta Horticulturae 131: In Vitro Culture, XXI IHC
IN VIVO AND IN VITRO PRODUCTION OF ALKALOIDS IN THEOBROMA CACAO L. |
| Authors: | M. Paiva, J. Janick |
| Abstract:
Theobromine and caffeine, the major alkaloids in seeds of Theobroma cacao, were quantified by liquid chromatography (HPLC). Alkaloid content (in mg/g dry weight) of individual defatted seeds from 35 clones of cacao varied from 13.5 to 45.0, mean 29.8; theobromine from 10.5 to 41.0, mean 25.2; and caffeine from a trace to 23.9, mean 4.6. Four clones (A43, B38, 'Catongo Blanco' and a 'Catongo Blanco' cross) had low caffeine content varying from 0.4–0.6 mg/g. There was an inverse relationship between theobromine and caffeine content (r=-.47). Alkaloid accumulation in asexual embryos cultured in vitro for 90 days in liquid media (10 days in 3% sucrose, 2 days each in 9%, 15%, 21%, and 74 days in 27% sucrose) increased up to 70 days with a maximum of 5.6 mg/g theobromine and 0.9 mg/g caffeine, indicating that the embryo is the site of synthesis of alkaloids and not merely a site of alkaloid accumulation. Increasing sucrose but not glucose concentration elicited the production of lipids, anthocyanins, and alkaloids in immature zygotic or asexual embryos cultured in vitro. The concomitant development of lipids, anthocyanins, and alkaloids suggests that the development of these metabolites involves a common regulatory pathway that is elicited by high concentration of sucrose. Asexual embryos initiated from clones varying in caffeine and anthocyanin production in vivo maintained this difference in vitro. This suggests the feasibility of selecting asexual embryos that are high producers of desirable metabolites such as flavor components and underproducers of undesirable substances such as caffeine for production of cacao cotyledonary products in an in vitro system based on the performance of zygotic embryos in vivo. | |
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