Characterization of two-step direct somatic embryogenesis in carrot

Direct somatic embryogenesis has been used to induce intact regenerated plantlets. We applied two-step direct somatic embryogenesis to the mass propagation of carrots and characterized this method. Morphological observation revealed that somatic embryos were generated from whole segments except for the callus part. Secondarily formed collenchyma-like structures were observed in the segments after the induction culture. The somatic embryos were generated from the collenchyma-like structure. When the longer-grown hypocotyls which had less potential to generate somatic embryos were used, the collenchyma-like structure did not develop. RAPD-PCR investigation showed that the regenerated plantlets had genetic stability. These results indicated that two-step direct somatic embryogenesis was a useful method for the mass propagation of plants without losing the quality of the donor plants.