High efficient micropropagation of Panax vietnamensis Ha et Grushv. from immature zygotic embryos

Despite its significant economic benefit as medicinal plant, cultivation of Ngoc Linh ginseng ( Panax vietnamensis Ha et Grushv.) has not been enlarged due to limited source of planting material. Even though considerable research efforts to develop tissue culture systems have been made, micropropagation of Ngoc Linh ginseng is still considered difficult. Here, a micropropagation protocol was established for Ngoc Linh ginseng through somatic embryogenesis from immature zygotic embryos. Direct somatic embryogenesis from immature zygotic embryos was obtained at a rate of 44.33 % on Schenk and Hildebrandt (SH) basal medium with 7 % sucrose. Secondary somatic embryogenesis with proliferation coefficient of 26.71 was induced in liquid-shake culture for 4 week in 1/2 SH medium with 0.1 mg/l kinetin and 0.1 mg/l thidiazuron. The SH medium supplemented with 1 mg/l a-naph-thalenacetic acid, 0.5 mg/l benzyladenine and 5 mg/l gibberellic acid stimulated germination of somatic embryos and early formation of microrhizomes. On two next 10-week cultures on SH medium with 0.5 mg/l a-naphthalenacetic acid, 1 mg/l benzyladenine and 4 % sucrose, micropropagated plantlets were produced with well-developed root system and thickened microrhizome with a dormant bud. The acclimatization of micropropagated plantlets were successfully accomplished with survival rate of 91.67 % when using the soil mixing forest humus with sand in a ratio of 1:2. An efficient protocol developed for Ngoc Linh ginseng micropropagation from immature zygotic embryos comprised five steps, including embryogenesis induction, proliferation of somatic embryos, germination of somatic embryos, development of plantlets, and acclimatization of plantlets.