BRASSINOSTEROIDS PREVENT THE CYTOKININ-INDUCED SOMATIC EMBRYOGENESIS OF COFFEE (Coffea canephora)

Plant somatic embryogenesis is a natural process that can be replicated in vitro by adding plant growth regulators. Reports indicate that the application of brassinosteroids increased the number of embryos when added to the cytokinin-induced somatic embryogenesis of Coffea arabica. Because somatic embryogenesis in the related C. canephora species is induced by cytokinins, we investigated whether brassinosteroids can also improve the embryogenic response in C. canephora. The results showed that the addition of 22(S),23(S)-homobrassinolide to C. canephora embryogenic explants prevented the establishment of the process in a dose-dependent manner, repressed the transcription of the SERK1 gene homolog and increased the conductivity and acidification of the culture medium. The opposite effects of brassinosteroids on somatic embryogenesis of C. canephora and C. arabica demonstrate that the function of plant growth regulators during in vitro somatic embryogenesis is not conserved, even within species of the same genus.