Evaluation of the regeneration potential of twelve cocoa (Theobroma cacao l.) Genotypes through somatic embryogenesis

A limiting factor for cocoa mass production (Theobroma cacao) is lack of procedure for somatic embryogenesis and plantlets regeneration. The response of cocoa to the existing protocols, shows high genotype-to-genotype variation in somatic embryo production rates. Hence, this study aimed at evaluating the regeneration potential of twelve cacao genotypes through somatic embryogenesis on Thidiazuron (TDZ), Benzyl Amino Purine (BAP), Kinetin, and 2,4-Dichlorophenoxyacetic acid (2,4-D) supplemented with Driver and Kuniyaki Walnut (DKW) medium. The floral parts, petal and staminode explants were tested. Callus was initiated from the explants cultured. The calli generated were transferred onto Embryo development medium for embryo production. Data were subjected to Analysis of Variance (ANOVA) SAS 9.4 model and significant means were separated using Duncan’s Multiple Range Test (DMRT) and Least Significant Difference (LSD) at 5% level of probability. Results indicated 0.2 mg/ml TDZ in combination with 1.0 mg/ml of 2,4-D supplemented with DKW medium effectively induced T. cacao somatic embryos. The twelve T. cacao genotypes tested showed different abilities to induce and produce somatic embryos with the induction medium adopted for the study and the response was explant-types dependent. Induction of explants was found to be faster in the staminode tissues compared with the petal tissues. Two types of calli were observed in this study: embryogenic with brown (friable/compact), pinkish, yellowish, and nodular callus features and non-embryogenic with translucent, white, and root features. Over 90% brown callus type was observed for the explants used across the twelve genotypes. Thus, the T. cacao genotypes were highly embryogenic.