THE EFFECT OF ABSCISIC ACID IN THE CONVERSION OF COCOA SOMAIC EMBRYOS INTO PLANTLETS

Abstract

The effects of abscisic acid (ABA) (0, 10, 30 and 50 μMl-1) in embryo development (ED) medium on the conversion of primary and secondary somatic embryos of cocoa at different developmental stages (globular, heart and torpedor) were evaluated in order to overcome the low rate of conversion into plantlets. Genotype COCA 3370-5 was more efficient than genotype AMAZ 3-2 in terms of embryogenesis and response to ABA treatments with secondary embryogenesis being superior over primary embryogenesis. Torpedor stage embryos were more efficient than globular and heart stage embryos in converting into plantlets. The most effective treatments for embryo conversion were 0 and 10 µMl-1 ABA at 2 weeks (wk). ABA concentrations at 0 and 10 µMl-1 were more effective in converting primary and secondary somatic embryos into plantlets than the 30 and 50 µMl-1. The effects of ABA treatments on conversion of secondary somatic embryos into plantlets were superior to primary embryos. Time of ABA treatment in ED medium influenced the conversion of the somatic embryos. ABA treatments at 0 and 10 µMl-1 recorded decreasing embryo conversion rates from two to six wk, the other treatments recorded higher conversion rates at four wk followed by two and six wk respectively.