Induction of somatic embryos by macrosalt stress from mature zygotic embryos of Panax ginseng

Mature zygotic embryos of ginseng (Panax ginseng C. A. Meyer) were germinated on a Murashige and Skoog medium lacking growth regulators. However, when the zygotic embryos were cultured on MS medium containing increased levels of macrosalts (NH4NO3, KNO3, KH2PO4, MgSO4, or CaCl2) to result is a mild salt stress, growth of zygotic embryos was strongly suppressed and eventually browning occurred. Somatic embryos or embryogenic calli were formed directly from these abnormal stressed zygotic embryos. Cotyledons were the most competent tissue for somatic embryo production. The highest frequency of somatic embryo formation (56.3%) was observed on medium containing 61.8 mM of NH4NO3. The highest frequency of somatic embryo formation by five different macrosalt treatments occurred in the following order: NH4NO3 > KNO3 > KH2PO4 > MgSO4 > CaCl2. Somatic embryos were regenerated into plants with a shoot and root, and the plants survived on soil in the greenhouse.