Efficient In Vitro Micropropagation and Regeneration of Humulus Lupulus on Low Sugar, Starch-Gelrite Media

Several Czech and foreign hop mericlones were tested in vitro for efficiency of green callus formation and plant regeneration from internodal or nodal explants. Modified MS media gelled either with agar, starch or a mixture of potato starch and Gelrite, supplemented with different concentrations of either glucose or maltose, were investigated. Two mericlones of Czech hop (Osvald 72 no. 5216 and Sládek no. 6908) were studied in more details because of their different regeneration capacities. The HPLC analysis of medium sugar concentrations after the explant cultivation has revealed slow uptake of sugar from the medium. Presence of glucose at concentration of 45 g dm^–3 in agar medium resulted in a decreased number of nodes compared to the control with 30 g dm^–3 of glucose. The use of a mixture of potato starch plus Gelrite instead of routinely used agar and decreasing the medium glucose concentration to 15 g dm^–3 proved to be most efficient for multiplication rate. The use of this medium results in lower cost of micropropagation of healthy hop cultures without exhibition of vitrification.