Cacao (Theobroma cacao L.) somatic embryos development under heat stress condition

The study aimed to evaluate the effect of heat stress on the developments of cacao somatic embryos under in vitro condition. Somatic embryos were induced from petal explants of ICCRI 4 cacao clone using DKW medium with the addition of 2.4-D and kinetin. Mature stage of cotyledonary somatic embryos were cultured on a germination medium and incubated at temperatures of 25 (control), 35, 40, 45 and 35 followed by 45 degrees C with sub-cultured on the same medium monthly. The results showed cacao somatic embryos were turned brown and suffered death after 16, 5 and 3 days of incubation at temperatures of 40, 35-45 and 45 degrees C, respectively, while somatic embryos cultured at temperatures of 25 and 35 degrees C could develop to form normal plantlets. The temperature of 40-45 degrees C might be the lethal temperature for cacao somatic embryos. The results of this study gave illustration how heat stress affected cacao embryo development and could be used as a base information for developing an in vitro selection method for heat stress tolerance in cacao.