Somatic embryos formation in five <i>Theobroma cacao</i> L. cultivars grown in Venezuela

Abstract

One of the main problems of cocoa (Theobroma cacao L.) is the observed variability in plantation from seeds that affecting the yield and quality of grain. This has led to considered asexual propagation (cuttings and grafts) as a way to maintain uniformity of materials. However, these methods have not been effective due to vegetative plant dimorphism. Somatic embryogenesis appears to be the most appropriate way to obtain cocoa plants, but, the somatic embryos formation has not been possible in many cultivars. The aim of this work was to form somatic embryos in five cacao cultivars with two types of initial explant (petals and staminodes) using different subculture times (14, 28 and 42 days). The use of callus formation index (IC) allowed to evaluate the process of callus induction and development; as well as variability in the response depending on the cultivar and the type of explant. The best response on the total number of somatic embryos occurred in staminodes `SCA-6' (58 embryos) when it were subcultured every 28 days. Higher embryogenic frequency (46.6%) was observed after 14 days of subculture on the petals with a total of 47 embryos, showing a strong influence on the response of the cultivar and the type of explant. The embryogenic frequency and the number of somatic embryos decreased as subculture time was increased. Key words: cocoa, index of callus formation, petals somatic embryogenesis, staminodes, subculture time