Regeneration of plants from cell suspension cultures and encapsulated cell suspension cultures of Solanum tuberosum L. cv. Clarissa

Callus cultures of the cultivar Clarissa were initiated from the end pieces of internode explants producing somatic embryos. The chopped somatic embryos and the basis produced soft callus when cultured on solid Murashige and Skoog media containing 1 mg/L 2,4-dichlorophenoxyacetic acid. Cell suspension cultures were established from these calli. They contained small cell clusters and single large vacuolated cells of variable shape. The embryogenic potential was tested on solid media. Four cell lines could be selected which maintained their embryogenic potential over a long period of time. Regenerates transferred to the greenhouse produced plants and tubers not distinguishable from the control plants. The cell lines did not develop somatic embryos when cultured in hormone-free medium. Somatic embryos formed only in those cultures that were inoculated with a low number of cells. Important were a high concentration of zeatin (2.5 mg/L) and a low level of polyphenols. After transfer on hormone-free medium the somatic embryos regenerated in vitro plants. The yield of somatic embryos could be raised considerably when cells had been encapsulated in hollow beads. Capsules were cultivated in liquid media that contained first auxins in high concentration and then cytokinines. After 4 weeks capsules were cut in halves and cultivated further. Embryo formation was not only observed on solid medium but also in shaken cultures in which they developed further into plantlets. The encapsulation system offers simple means to test phytohormone combinations and concentrations. In addition, the medium can be dosed better and inhibiting substances produced by the cells removed more easily when cells are encapsulated. The entrapment of cells in hollow alginate beads allows testing conditions for the mass production of somatic embryos in bioreactors.