Adventitious shoot regeneration in cultures of Humulus lupulus L. (hop) cvs. Brewers Gold and Nugget

A very efficient protocol for plant regeneration from two commercial Humulu s lupulus L. (hop) cultivars, Brewers Gold and Nugget has been established, acid the morphogenetic potential of explants cultured on Adams modified me dium supplemented with several concentrations of cytokinins and auxins stud ied. Zeatin at 4.56 mu m produced direct caulogenesis and caulogenic calli in both cultivars. Subculture of these calli on Adams modified medium suppl emented with benzylaminopurine (4.4 mu m) and indolebutyric acid (0.49 mu m ) promoted shoot regeneration which gradually increased up to the third sub culture. Regeneration rates of 60 and 29% were achieved for Nugget and Brew ers Gold, respectively. By selection of callus lines, it has been possible to maintain caulogenic potential for 14 months. Regenerated plants were suc cessfully transferred to field conditions.