Somatic Embryogenesis from Clonal Leaf Tissues of Cassava

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Abstract
Leaf lobes were isolated from palmate leaves of clonal cassava (Manihot esculenta Crantz) material growing in vitro or in glasshouse conditions and subjected to a two-stage culture procedure involving incubation on Murashige and Skoog (MS2) basal medium supplemented with 2–12 mg l−1 2,4-D for 20 d (Stage I) before transfer to MS2 basal medium supplemented with 0.01 mg l−1 2,4-D and 0.1 mg l−1 6-benzylamino purine (BAP) (Stage II medium). Embryogenetic tissues, foliose structures and somatic embryos developed from leaf lobes at all Stage I 2,4-D concentrations, except on those explants isolated from shoot-tip cultures incubated on MS2 basal medium supplemented with 0.1 mg l−1 NAA and 1.0 mg l−1 BAP. Leaf lobes isolated directly from glasshouse plants showed optimal embryogenetic competence when subjected to a Stage I culture period of 17 d, although foliose structure initiation was optimal with shorter Stage I durations. Leaf lobes of 2–4 mm length and those isolated from phyllotaxic leaf numbers 4 and 5 showed the greatest embryogenetic competence.