Induction of somatic embryogenesis from young, fully expanded leaves of chilli pepper ( Capsicum annuum L.): effect of leaf position, illumination and explant pretreatment with high cytokinin concentrations

Abstract

The effect of the explant position on the donor plant, illumination and explant pretreatment with high cytokinin concentrations on the induction, proliferation and development of somatic embryos from young, fully expanded leaves of chilli pepper ( Capsicum annuum L.) was investigated. Explants were cultured either directly on a solid Murashige and Skoog medium supplemented with 9 μM 2,4-dichlorophenoxyacetic acid + 12.9 μM 6-benzyladenine or incubated for 24 h in a liquid MS medium containing the cytokinin at a tenfold concentration (129 μM) and then transferred to the solid MS medium. Globular embryo proliferation depended on the leaf position on the donor plant: fewer embryos were derived from the third leaf (counting from the base of the shoot) than from the first two leaves. The initial pretreatment of pepper explants with increased 6-benzyladenine concentrations significantly reduced the overall proliferation of somatic embryos without affecting the percentage of globular embryos which further developed into the torpedo-shape stage and germinated. Depending on the leaf position, somatic embryo induction was significantly affected by the initial culture incubation under illumination or in darkness. Heart- and torpedo-shaped embryos could be observed only on callus pieces initially incubated for 3 weeks in darkness.