Evaluation of Soluble Sugar Content, Phenolic, and Amino-Acid Profiles of Three Cocoa (Theobroma cacao L.) Genotypes for Embryogenic Development

Abstract

Somatic embryogenesis (SE) in cocoa (Theobroma cacao L.) offers significant potential for mass propagation of elite genotypes, but the metabolic changes needed for successful regeneration are not well understood. This study investigated temporal changes in amino acid, phenolic, and soluble sugar profiles during callus development in three cocoa genotypes (TC-1/G5, TC-8/G12, and T86/2/G1) cultured on hormone-supplemented media. Staminode explants were induced on 1 mg/L 2,4-D and 0.2 mg/L TDZ, then developed on 1 mg/L 2,4-D and 1 mg/L 6-BA. Metabolite analyses were conducted at 4, 6, and 8 weeks of culture. Results revealed highly significant genotype × week interactions for all metabolites (P < 0.01), indicating distinct metabolic strategies among genotypes. Correlation analysis identified three co-regulated metabolic modules, a serine-centered network linking one-carbon metabolism and stress responses, an aspartate-glutamine axis governing nitrogen assimilation, and lysine functioning as a negative feedback regulator. Temporal flux analysis revealed a three-phase metabolic model: metabolic priming (Week 4), quiescence and reset (Week 6), and coordinated pathway reactivation (Week 8). The C/N balance ratio showed genotype-specific patterns, with G5 exhibiting dramatic shifts potentially associated with organogenic transitions. These findings provide mechanistic insights into the effect of genetic factors and physiological developments of the callus on embryogenic capacity of floral explants in T. cacao, showing coordinated pathway reactivation supporting regeneration competence.