Overcoming Somatic Embryogenesis Challenges in Cocoa with IM Medium
In vitro recalcitrance is the inability of plant cells, tissues and organs to respond to tissue culture manipulations. In cocoa (Theobroma cacao L.), recalcitrance is a limiting factor in tissue culture for the production of somatic embryos. This study aims to improve the production of somatic embryos by In Vitro culture of improved genotypes deemed recalcitrant to somatic embryogenesis. ‘’Im’’medium was used to induce the production of embryos of four enhanced and recalcitrant somatic embryogenesis genotypes encoded C8, C14, C15 and C16. The plant material consists of explants of petals and staminodes. The best results, which are characterized by levels of cal embryogenesis and the number of somatic embryos of 16% and 07, respectively, were obtained in the C14 genotype. This study showed that it is possible to produce somatic embryos in these improved varieties, thus eliminating the recalcitrance of these genotypes to somatic embryogenesis. The availability of improved material consisting of identical plants will allow the creation of more homogeneous plantations with high yields.
The cocoa tree (Theobroma cacao L.) is a tree that comes from the Amazon basin. This plant with multiple virtues is mainly grown for its beans. They are the main raw material for the chocolate industry (Koné et al., 2021).
Despite its importance, cocoa farming is facing enormous difficulties, which can be explained by the attacks of several pathogenic and parasitic agents, the aging of the orchards, the high cost of inputs, the nonavailability, and the under-use of plant material. improved (Koné et al., 2021).
To overcome these difficulties, several methods have been considered. Conventional techniques for the multiplication of plant material, such as cuttings and grafting, have been proposed. Unfortunately, these vegetative horticultural propagation techniques have several drawbacks that do not allow their easy application (Koné et al., 2021).
To overcome all these difficulties and obtain homogeneous material in abundant quantity, in vitro culture by somatic embryogenesis was considered. It is a method that makes it possible to produce a given genotype in sufficient quantity and in a homogeneous manner.
This method of in vitro propagation has advantages over conventional methods of propagation and largescale production of woody plants while ensuring stability and genetic integrity (Kouassi et al., 2017a; Eliane et al., 2019; Koné et al., 2019). Regenerators, i.e., plants regenerated from somatic embryos, in addition to being genetically identical to each other, behave like seedlings (Jane et al., 2017; Kouassi et al., 2018).
However, this method presents some problems in the cocoa tree because of the recalcitrance of certain genotypes. This recalcitrance is reflected in the variation in the rate of somatic embryos from one genotype to another, often with very low or even zero somatic embryo rates. Overcoming this recalcitrance requires optimizing existing protocols or developing new ones. The works of Koné et al. (2019; 2021) have shown that mineral salts and carbon sources taken individually make it possible to resolve this recalcitrance. The general objective of this study is to test the effect of the Im medium on lifting the recalcitrance of recalcitrant genotypes to allow their production in sufficient quantity and their large-scale distribution.
Source : Use of Im medium to overcome recalcitrance to somatic embryogenesis of improved cocoa genotypes (Theobrama cacao L.)
