Improvement of propagation frequency with two-step direct somatic embryogenesis from carrot hypocotyls

Mass production of the regenerated plantlets from carrot hypocotyls via two-step direct somatic embryogenesis (DSE) was investigated. Somatic embryos were induced in the induction culture with medium containing 2,4-dichlorophenocxyacetic acid (2,4-D) prior to the development culture in this method. The optimum condition for the regeneration efficiency was found to be 2 weeks of induction culture using hypocotyls shorter than 3 cm. The distribution profile of the regeneration efficiency corresponded to that of the normal distribution. The distribution range was observed to depend on the length of the hypocotyls. Calcium addition increased the regeneration efficiency but did not affect the distribution range. We also found that this procedure was applicable to the mass production of regenerated plants using a bioreactor.