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

Various combinations of auxins and cytokinins were tested to achieve advent itious bud induction from hop callus cultures induced on stem or petiole ex plants of 16 genotypes and regenerants were scored to establish the occuren ce of genetic changes. A total of 136 plants from 10 cultivars were regener ated. The most important factors in the regeneration process were a single step callus induction and a shoot regeneration protocol without subculturin g, while the results from various media composition showed that in the pres ence of 0.29 or 1.43 mu M IAA, cytokinins are essential in the induction pr ocess. 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 genoty pes 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 ge netic changes. RAPD profiles did not differ from donor cultivars in 43 rege nerants tested using 22 decamer primers. Flow cytometric analysis showed th at 4 out of 46 regenerants were tetraploid while the others remained diploi d.