Somatic embryogenesis in Solanum tuberosum from cell suspension cultures: histological analysis and extracellular protein patterns.

An embryogenic cell suspension, continuously grown in Murashige and Skoog (MS) medium with 0.5 mg/L of 2,4-dichlorophenoxyacetic acid, was established from friable callus of Solanum tuberosum internode sections. The cell suspension was predominantly composed of cell masses and free embryogenic cells. When transferred to an auxin-free medium with zeatin, somatic embryos (SEs) developed and converted to complete plants when cultured on solid MS medium without growth regulators. The system produced approximately 600 SEs per 50 mL of medium. In this investigation, accumulation of extracellular proteins (EPs) of different molecular weights were found associated to different phases of the embryogenic process. At the initiation of the cell suspension, cell clusters and free cells present in the culture (phase "A") secreted a 78kDa EP, unique to this phase. In phase "B", which is related to embryonic cell determination process, proteins (7-14kDa) were secreted mainly by embryogenic cells. In phase "C", SEs in different developmental stages secreted protein of 32 kDa, which appeared as a particular feature of the phase. EPs of phase "D", secreted by torpedo and mature embryos, had molecular weights between 20 and 50 kDa. Further studies will be necessary to identify these proteins and link them to previously identified somatic embryogenesis-related proteins. Histological analysis of the potato embryogenesis in liquid media showed unicellular origin of the SE.

Plant regeneration of Anthurium andreanum cv Rubrun

To establish an efficient regeneration system for Anthurium andreanum cv Rubrun, seeds from plant spadixes were germinated on a medium supplemented with 2.2 muM BA. After 2 weeks, 74 percent of the seeds germinated and four weeks later, micro-cuttings from these plantlets were subcultured on a medium containing 4.4 muM BA and 0.05 muM NAA. On average, 3.6 shoots per explant were obtained. Four weeks old in vitro plants from germinated seeds and the plantlets obtained from micro-cuttings, showed callus proliferation at the stem base. These tissues were subcultured on a medium supplemented with 8.9 muM BA and 2.7 muM NAA. After 6 weeks of culture, about 43.8 plantlets per square cm of callus were obtained. Anatomical studies showed the organogenic nature of these calli. Anthurium andreanum plants regenerated by organogenesis were transferred to pots and a rate of 80 percent of plant acclimatization was obtained.