THE EFFECT OF TDZ AND 2, 4-D CONCENTRATIONS ON THE INDUCTION OF SOMATIC EMBRYO AND EMBRYOGENESIS IN DIFFERENT COCOA GENOTYPES

Abstract

The effect of 2, 4-D and TDZ concentrations on primary embryogenesis seem to be genotype dependent. There were significant differences between the control and the other treatments on somatic embryo production by genotype AMAZ 3-2. Genotype COCA 3370-5 did not show any significant difference among the treatments with 1mg/l 2, 4-D + 1μg/l TDZ, 1mg/l 2,4-D + 10μg/l TDZ and the control treatment. Treatment 2mg/l 2, 4-D + 10μg/l TDZ seem to be better for the production of somatic embryos by genotype COCA 3370-5. Lower concentrations of 2, 4-D + TDZ seem to generate greater proportions of normal somatic embryos as compared with higher 2,4-D + TDZ by genotypes AMAZ 3-2 and COCA3370-5 Somatic embryogenesis using floral tissue explants was used to induce primary somatic embryos from the staminodes of 16 cocoa genotypes. Four genotypes (AMAZ 3-2, AMAZ 10-1, COCA 3370-5 and GU 183H) showed high frequencies of embryogenesis while the remaining genotypes generated little or no embryos. Secondary embryos were induced from the cotyledonary explants of the four genotypes that exhibited efficient primary embryogenesis. Percentage embryogenesis generally increased with culture time. GU 183 which demonstrated the highest primary and secondary embryogenesis recorded the lowest conversion rate of somatic embryo into plantlets.