Assessment of the effects of physiological development of cocoa (Theobroma cacao l.) explant on somatic embryogenesis

Abstract

Cocoa trees have shown a high degree of segregation for many traits when propagated by seeds. Somatic embryogenesis is an efficient in vitro propagation method which allows the production of several embryos capable of generating plants similar to the initial one from somatic tissues. The use of cocoa floral parts has been reported for regeneration of elite cocoa genotypes. This research is targeted in evaluating the effect of physiological development of the explants (staminode) and its response to two different cytokinase (kinetin and BAP) on embryogenesis. The experiment was laid in factorials with three replications in CRD. Three different physiological ages of the explant were examined: 1 week old (unopened, about 3-4 mm in length),2 weeks old (unopened, about 5-/6 mm in length) and 3 weeks old (unopened; matured flowers). Staminode was studied and explants were initiated for callus induction on Primary Callus Growth medium. The following data were scored for: Explants Induction Percentage, Percentage of callus induced and Percentage of Embryogenic callus. Results showed the interactions among the genotypes, hormones and the physiological age of the explants were significantly different at 0.05% probability level. Explants at 3 and 2 weeks respectively had higher efficiency for embryogenesis while the average performance was observed for explants at a week. Also, BAP recorded higher frequency 80% for embryogenesis compared to kinetin 70% under the present study. Physiological age of explants and the choice of callus development hormone have been found to play significant role in the embryogenesis of cocoa genotypes examined.