Modification of the droplet-vitrification method of cryopreservation to enhance survival rates of adventitious roots of Panax ginseng

Panax ginseng Meyer is an important medicinal plant producing bioactive compounds. A droplet-vitrification method was developed for cryopreserving adventitious root cultures of mountain ginseng, and variations of this procedure were tested to determine their effects on regrowth rates and osmotic stress responses. Root regrowth rates were examined after exposing root segments to two pre-culture treatments, three loading solutions, and two vitrification solutions with different exposure periods. Pre-culturing excised segments of adventitious roots with 0.3 M sucrose produced the highest rate of regrowth after cryopreservation. Loading for 20 min with 17.5% (w/v) sucrose and 17.5% (w/v) glycerol at room temperature increased the regrowth rate of cryopreserved adventitious roots fourfold, compared with non-loaded samples. Treatments involving different vitrification solutions and exposure periods were compared, and the highest rate of regrowth (15%) after cryopreservation was achieved by incubating adventitious roots in modified plant vitrification solution 3 containing 40% (w/v) glycerol and 40% (w/v) sucrose for 10 min at room temperature, suggesting that ginseng adventitious root tips were sensitive to osmotic stress. Further study is necessary to develop optimal vitrification solutions that enhance the survival rate of cryopreserved adventitious roots of mountain ginseng.