Somatic embryogenesis and plant regeneration from leaf explants and cell suspensions of Solanum melongena (eggplant)

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Abstract
High frequencies of somatic embryogenesis evaluated on the basis of average embryo yield per explant were observed on leaf explants of S. melongena (L.) (eggplant) after 21 days of culture on a modified Murashige and Skoog medium. Callus proliferation and embryogenesis occurred in the presence of 1-naphthaleneacetic acid (NAA), whereas only callus induction occurred in the presence of the other auxins. Maximal embryo yields were obtained at 10 mg/l NAA. Although cytokinins inhibited the NAA-induced embryogenic response, they acted synergistically to promote callus growth. The frequency of embyrogenesis on leaf explants was shown to be under the control of the N content of the medium. Both NH4+ and NO3- were essential for embryogenesis and an optimal ratio of 2:1 (NO3-:NH4+) was established. The optimal sucrose concentration of the medium was 0.06 M, and both elevated and reduced sucrose levels inhibited embryogenesis. Seven cultivars showed significant quantitative differences in their capacities to form embryos, although all were embryogenic. Cell suspension cultures were also embryogenic, when grown under conditions which stimulated embryogenesis in leaf explants. Somatic embryos taken from leaf callus or cell suspensions and cultured on hormone-free medium gave rise to plants which set seed when transferred to the greenhouse. Shoot organogenesis was observed on leaf explants which were cultured in the presence of either of 4 cytokinins. Shoots were rooted on hormone-free medium and mature plants were subsequently obtained.