Changes of secondary metabolites during tamarillo somatic embryogenesis

Tamarillo (Solanum betaceum Cav.) is a Solanaceae tree cultivated for its edible fruits. Under specific stimuli, indirect somatic embryogenesis (SE) originates distinct calli: embryogenic (EC) and non-embryogenic (NEC). Both types proliferate, but only EC originates somatic embryos. The presence of secondary metabolites is known to influence induction and embryogenic competence. The objective of this work is to study some of these compounds on SE.

Leaf segments from in vitro established clones were cultivated on solid Murashige and Skoog medium supplemented with sucrose (26 mM) and picloram (20 µM). Phenolic acid influence was tested using caffeic acid (896 and 448 µM), flavonoid were assayed with rutin (197.5 and 98.75µM). Anthranilic acid, an amidobenzoic acid, was also tested (1164.8 and 582.4 µM). Additionally, previously induced EC and NEC lines were grown in liquid medium with the highest concentrations of each compound.

Results showed highest dedifferentiation rates (>90%) in the control and when rutin and caffeic acid were tested, whereas lower concentrations inhibit dedifferentiation. In contrast, the compounds seem to inhibit growth of established calli without affecting protein, phenolic acids and flavonoid levels, measured by spectrophotometric methods. Anthranilic acid completely inhibited both induction and calli growth.

The results seem to present a correlation of some secondary metabolites with dedifferentiation rates during induction and a tendency to inhibit growth of established calli, probably related to metabolic effects. Further studies are underway to further characterize the dose-response relation of these compounds and molecular mechanism underlying this phenotypic effect.