DIRECT ORGANOGENESIS IN HOP - A PREREQUISITE FOR AN APPLICATION OF A-TUMEFACIENS-MEDIATED TRANSFORMATION

The regeneration ability of primary explants derived from mericlones o f two commercial Bohemian hops was investigated. It was found that the se hops are able to regenerate shoots by direct organogenesis on media containing BAP or zeatin at concentrations 0.5 - 2 mg dm-3. The highe st regeneration of shoots was achieved from either petioles or interno des at frequencies 21 % and 52 % , respectively, on the medium contain ing zeatin (2 mg dm-3), While relatively low amount of regenerated sho ots (1.3 %) was observed for leaf blade explants. On the other hand, m ore efficient rooting occurred on the leaf blades then on other explan ts. A similar pattern of regeneration we observed for HLVd-infected me riclones of clone Osvald 31 even though viroid concentration in in vit ro cultures was about 8-fold higher than in field-grown plants and was 31.1 pg mg-1 of fresh mass in the average. These results suggest that HLVd infection did not impair organogenesis. We found that high 2,4-D concentration pretreatment (11 mg dm-3) did not promote somatic embry ogenesis. Although this treatment suppressed direct organogenesis, the inhibition was not complete and in low frequency the shoot regenerati on was seen. Sensitivity of hop explants to antibiotics commonly used in Agrobacterium-mediated transformation was assayed. It was found tha t kanamycin (100 - 200 mg dm-3) suppressed efficiently callogenesis, r oot formation and shoot proliferation. An estimation of effect of kana mycin (200 mg dm-3) and ticarcillin (500 mg dm-3) on morphogenesis was performed using regeneration medium. The inhibitory effects observed suggest that these conditions could be used in Agrobacterium transform ation/selection system.