Propagation and associated molecular studies in cacao (Theobroma cacao L.)

Abstract

Cacao (Theobroma cacao L.) cultivation faces several acute problems that reduce its productivity and competitiveness. Production inefficiency of seedlings for replanting remains an issue. Tissue culture is expected to provide pragmatic solutions. Establishment of a reliable, reproducible, and efficient in vitro plant regeneration system is a vital prerequisite for biotechnological application of crop improvement programs. Numerous types of explants and protocols for micropropagation have been studied and used for cacao, and somatic embryogenesis is the main system used to clonally propagate cacao. Although effective somatic embryo production is now possible, the limited frequency of somatic embryos' conversion to ex vitro seedlings still prevents the large-scale clonal propagation of cacao. Most papers in the literature have focused on testing the influence of different types and combinations of plant growth regulators with the aim of improving regeneration and the multiplication stage of some cultivars. Genotype is one of the most influential factors on the in vitro response of cacao. Despite this, no successful universal protocol has yet been developed for multiple genotypes, limiting the usefulness of current protocols to commercial biotechnology labs. This review summarizes current knowledge of how far in vitro plant regeneration systems in cacao have developed. This could help researchers and scientists to improve protocols to a wider range of genotypes as well as collecting, conserving, and breeding cacao to increase productivity.