Direct and Indirect Somatic Embryogenesis in Mango Ginger (Curcuma amada Roxb.)

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Somatic embryogenesis is a developmental restructuring of somatic cells in the embryogenic pathway and forms a basis for the concept of totipotency in plant cells. Understanding the process of transition from vegetative to embryogenic cells and factors involved in the somatic embryogenesis and subsequent plant development represents a challenge for plant tissue culture studies in any selected species. Although several reviews have been published dealing somatic embryogenesis in several plant species, there is no recent information on somatic embryogenesis in mango ginger (Curcuma amada). Two different types of somatic embryogenetic pathways are available in mango ginger. They are indirect somatic embryogenesis (IDSE) and direct somatic embryogenesis (DSE). Indirect somatic embryogenesis occurs in friable embryogenic callus from leaf sheath explants that undergo an extreme proliferation before the development of somatic embryos, whereas in the direct somatic embryogenesis, two-step system of culture was followed. Initially, leaf sheath explants were subjected to a pretreatment under dark condition before they were transferred to the subculture medium for embryo development. Histological and scanning microscopic studies showed that the formation of translucent globular embryogenic cell suspension is an important visible stage during early somatic embryogenesis through indirect method. In the direct pathway, upon pretreatment, epidermal and subepidermal cells of the leaf sheath explants formed globular and elongated structures. The presence of clear protoderm in the globular embryos and procambial structures are crucial visible stages.