RAPID CLONAL PROPAGATION OF LICORICE, GLYCYRRHIZA GLABRA BY IN VITRO SHOOT CULTURE

摘要

Aims: To develop methods and conditions for rapid and efficient clonal propagation of a selected clonal line (L58) of licorice, Glycyrrhiza glabra, including in vitro shoot culture and nursery pruning. Methods and Results: An efficient pruning regimeof 3-months-old greenhouse-grown plants enhanced auxiliary shoot formation, and significantly increased primary shoot culture (PSC) explant harvest by over 50%. Cloning L58 in vitro from PSC was readily possible within 4-weeks on full strength MS (FMS) medium, however plantlets at 6-weeks were more vigorous based on number of growth parameters. Growth was enhanced with the addition of BA and NAA to the medium (FMS-BA-NAA) and incubating cultures in the dark for one week followed by three weeks in light.Initiating growth in the dark caused considerable elongation in the stem and significantly (p=0.01) increased number of explants (micronodes), which averaged 16.2 cm and 9.0 micronode explants per plantlet. A positive correlation (r=0.75) was found between shoot length and number of micronodes and the number of leaflets favored the initial exposure to light, whereas, shoot length, number of micronodes/plant, root length and the number of main roots favored the dark initiation. Based on these results, from a single explant producing an average of 9.0 nodal micro-sets per plantlet per cycle in a year of 52 weeks and four weeks of subculture intervals, (13 in vitro four weeks cycles) the estimated propagation rate would be 9. Significance of the study: Unlike the conventional vegetative propagation method, the described method requires no use of economically valuable part of the plant such as rhizomes, stolons or other cuttings, and is rapid as it requires no long waiting for explants to develop, compared to conventional planting parts that take years until are ready. This multiplication rate should fill in the need for rapid, easy and less technical method to speed up the number of clonal plants for commercial utilization of the roots, runners and rhizomes. The described methods should improve root yield and glycyrrhizin production as sugar substitute for special dietary need in food, beverage, confectionery and pharmaceutical industries.