Preferential expression of somatic embryogenesis in five elite genotypes of Theobroma cacao (L.) associated with explant type and protocols used

Abstract

This study aims to identify the suitable subculturing time, culture media (protocols) and explants type suitable for somatic embryogenesis expression in five elite genotypes of Theobroma cacao L. Thus, petals and staminodes explants extracted from immature flower buds of genotypes (C1, C8, C9, C14, and C16) are first grown in different media (CIM and CDM) to assess the subculturing time. Then, successive transfers in EDM medium at every 4 weeks intervals until 24 weeks. To assess culture media preference, these genotypes were grown in four different protocols (I, II, III, and IV) for callus induction. They were then successively subcultured (four times at 4 weeks intervals) into EDM. About the subculture time, embryo expression is earlier in C1, C9, C14, and C16 genotypes (2nd and 4th weeks) than C8 genotype (12 and 16th weeks). However, C1, C14, and C16 (with staminodes explants) prefer protocol IV, while their petal explants prefer protocol II. Also, C9 staminodes explants prefer protocol III while the C9 and C8 petals explants prefer protocol I. This study has identified suitable explants and protocols for somatic embryo production in the tested genotypes. Moreover, this work has laid out a new strategy to overcome recalcitrance to the somatic embryogenesis of T. cacao genotypes.