title: In vitrogrown thickened taproots, a new type of soil transplanting source inPanax ginseng.
abstract: BACKGROUND
  The low survival rate ofin vitroregeneratedPanax ginsengplantlets after transfer to soil is the main obstacle for their successful micropropagation and molecular breeding. In most cases, young plantlets converted from somatic embryos are transferred to soil.
  
  
  METHODS
  In vitrothickened taproots, which were produced after prolonged culture of ginseng plantlets, were transferred to soil.
  
  
  RESULTS
  Taproot thickening of plantlets occurred near hypocotyl and primary roots. Elevated concentration of sucrose in the medium stimulated the root thickening of plantlets. Senescence of shoots occurred following the prolonged culture of plantlets. Once the leaves of plantlets senesced, the buds on taproots developed a dormant tendency. Gibberellic acid treatment was required for dormancy breaking of the buds. Analysis of endogenous abscisic acid revealed that the content of abscisic acid in taproots with senescent shoots was comparatively higher than that of taproots with green shoots. Thickened taproots were transferred to soil, followed by exposure to gibberellic acid or a cold temperature of 2°C for 4 mo. Cold treatment of roots at 2°C for 4 mo resulted in bud sprouting in 84% of roots. Spraying of 100 mg/L gibberellic acid also induced the bud sprouting in 81% roots.
  
  
  CONCLUSIONS
  Soil transfer of dormant taproots ofP. ginsenghas advantages since they do not require an acclimatization procedure, humidity control of plants, and photoautotrophic growth, and a high soil survival rate was attained.
authors.affiliation: Department of Forest Resources, College of Forest and Environmental Sciences, Kangwon National University, Chuncheon, Korea.
authors.forename: Jong Youn
authors.initials: JY
authors.lastname: Kim
authors.affiliation: Department of Herbal Crop Research, National Institute of Horticultural and Herbal Science, Rural Development Administration, Eumseong, Korea.
authors.forename: Dong Hwi
authors.initials: DH
authors.lastname: Kim
authors.affiliation: Department of Herbal Crop Research, National Institute of Horticultural and Herbal Science, Rural Development Administration, Eumseong, Korea.
authors.forename: Young Chang
authors.initials: YC
authors.lastname: Kim
authors.affiliation: Department of Herbal Crop Research, National Institute of Horticultural and Herbal Science, Rural Development Administration, Eumseong, Korea.
authors.forename: Kee Hong
authors.initials: KH
authors.lastname: Kim
authors.affiliation: Department of Forest Resources, College of Forest and Environmental Sciences, Kangwon National University, Chuncheon, Korea.
authors.forename: Jung Yeon
authors.initials: JY
authors.lastname: Han
authors.affiliation: Department of Forest Resources, College of Forest and Environmental Sciences, Kangwon National University, Chuncheon, Korea.
authors.forename: Yong Eui
authors.initials: YE
authors.lastname: Choi
keywords: Panax ginseng; in vitro taproot thickening; micropropagation; soil transfer