Development of Cassava (Manihot esculenta Crantz.) somatic embryos during culture with abscisic acid and activated charcoal

Secondary cassava somatic embryos were cultured on a sequence of developmental media containing either activated charcoal or abscisic acid. Medium supplementation with activated charcoal had a positive effect on both differentiation and subsequent germination. However, sustained exposure to activated charcoal supplemented media beyond the seventh day of differentiation did not appear to be beneficial. Somatic embryos were desiccated over a saturated salt solution of K2SO4 for 10 days and allowed to develop into plantlets on a MS medium containing 0.4 μmol/L BAP. Embryo germination was significantly affected by the culture medium used prior to the desiccation treatment, with culture on a medium supplemented with ABA at a level of 0.1 μmol/L prior to desiccation significantly enhancing germination. The number of normal germinants produced as judged by morphological criteria were not however, dependant on ABA supplementation of the culture medium prior to desiccation. Culture on a separate medium for the differentiation of embryos, different to the medium used for the maturation of somatic embryos is indicated.