ISSN 1021-4437, Russian Journal of Plant Physiology, 2010, Vol. 57, No. 2, pp. 283–289. © Pleiades Publishing, Ltd., 2010. Original Russian Text © Y.J. Kim, M.K. Kim, J.S. Shim, R.K. Pulla, D.C. Yang, 2010, published in Fiziologiya Rastenii, 2010, Vol. 57, No.2, pp. 297–303. 283 INTRODUCTION Korean ginseng (Panax ginseng C. A. Meyer) is a native herb of Korea and is cultivated for its highly val- ued root used for medicinal purposes. This perennial herbaceous plant grows very slowly under natural con- dition and has a long production cycle because seeds are usually produced only after three-year cultivation and must be stratified for an additional 12–18 months before germination. For commercial purpose, ginseng should be harvested after being cultivated for 4–6 years. The yield of the ginseng roots is also very low due to various diseases and its peculiar life style [1]. Tissue culture of Korean ginseng is well studied in the case of callus culture [2], protoplast culture [3], shoot organogenesis [4], somatic embryogenesis [4– 7], and Agrobacterium-mediated genetic transforma- tion [8, 9]. Plant regeneration of ginseng is still consid- ered to be recalcitrant because of the difficulty in obtaining plants with a well-developed root system. Direct somatic embryogenesis from cotyledon explants of Korean ginseng is most studied. Cotyledon explants of Korean ginseng can produce somatic embryos directly on growth regulator-free medium, devel- oping either multiple- or single-state forms [4–7, 9]. The multiple and fused somatic embryos gave only multi- ple shoots, whereas single somatic embryos regenerate into plants with well-developed roots and shoots on hormone-free medium [6]. Choi and Soh [10] reported that plasmolysing pretreatment of P. ginseng cotyledon explants could enhance single embryo for- mation regardless of cotyledon maturity by disrupting plasmodesmal connections between cells. A lot of individual ginseng lines were selected in Korean fields in 1968 to develop new ginseng varieties of good quality and high yield. Among them, several promising lines were selected and pure lines were sep- arated by Korea Ginseng and Tobacco Research Insti- tute [11, 12]. One of them was registered as a new cv. Yun-Poong, the other one as cv. Chun-Poong. Kwon et al. [12] reported that cv. Yun-Poong showed high yield of root production, good root quality, and many seeds per plant and has high contents of the total gin- senoside per dry weight in main roots. Although cv. Chun-Poong has low root weight, the length of tap root is high and the root shape is good; therefore, a high grade of fresh ginseng roots and red ginseng roots can be obtained from cv. Chun-Poong [13, 14]. The objective of this study was to optimize somatic embryogenesis of these two new Korean ginseng culti- vars. We analyzed the effect of zygotic embryo matu- rity, the effect of plasmolysing pretreatment with sucrose and mannitol, the effect of continuous sucrose treatment, and the effect of 2,4-D on somatic embryo- genesis. RESEARCH PAPERS Somatic Embryogenesis of Two New Panax ginseng Cultivars, Yun-Poong and Chun-Poong Y. J. Kim a , M. K. Kim b , J. S. Shim a , R. K. Pulla a , and D. C. Yang a a Korean Ginseng Center for Most Valuable Products and Ginseng Genetic Resource Bank, Kyung Hee University, Suwon 449-701, Korea; fax: +82-31-202-2687; e-mail: deokchunyang@yahoo.co.kr b Department of Bio and Environmental Technology, Division of Environmental and Life Science, College of Natural Science, Seoul Women’s University, Seoul 139–774, Korea Received January 23, 2009 Abstract—Somatic embryogenesis from single cells is important for normal plant regeneration of ginseng. Cotyledon explants from zygotic embryos of two new ginseng cultivars, Chun-Poong and Yun-Poong, pro- duced somatic embryos on Murashige and Skoog (MS) basal medium and MS medium containing growth regulators. The highest frequency of single somatic embryo formation was obtained when cotyledon explants were excised from premature (cultured for 1 day) zygotic embryos (about 6 mm in length) of both cvs. Chun- Poong and Yun-Poong and then cultured on MS medium supplemented with 7% sucrose. The frequency of single somatic embryo formation was strongly enhanced when Chun-Poong cotyledons were subjected to plasmolysis with 0.1–0.5 M sucrose for 24 h and Yun-Poong cotyledons to plasmolysis with 1.0 M sucrose for 24 h and then cultured on MS medium with 2,4-D. Key words: Panax ginseng - somatic embryogenesis - sucrose - plasmolysis - 2,4-D DOI: 10.1134/S1021443710020172 Abbreviations: MS—Murashige and Skoog nutrient medium.