Studies of somaclonal variation in hop (Humulus lupulus L.)

Various combinations of auxins and cytokinins were tested to achieve adventitious bud induction from hop callus cultures induced on stem or petiole explants of 16 genotypes and regenerants were scored to establish the occurence of genetic changes. A total of 136 plants from 10 cultivars were regenerated. The most important factors in the regeneration process were a single step callus induction and a shoot regeneration protocol without subculturing, while the results from various media composition showed that in the presence of 0.29 or 1.43 mu M IAA, cytokinins are essential in the induction process. For a specific genotype 5.69 mu M zeatin riboside, 9.12 mu M zeatin or 23.20 mu M kinetin was optimal. Regeneration ability varied among genotypes from 0 to 37.5% and was highest in the genotype 200/69. The regenerants obtained were tested with RAPD analysis and flow cytometry for possible genetic changes. RAPD profiles did not differ from donor cultivars in 43 regenerants tested using 22 decamer primers. Flow cytometric analysis showed that 4 out of 46 regenerants were tetraploid while the others remained diploid.