To overcome low, genotype dependent regeneration capacity of some commercially important potato cultivars, two alternative treatments of stem primary explants were employed: modification of the hormonal composition of inductive MS medium and insertion of some Agrobacterium oncogenes. A replacement of 6-BAP with zeatin in the inductive MS medium stimulated bud/shoot formation in only two of three tested cultivars with naturally low regeneration capacity. GA 3 did not affect the bud initiation phase (i.e. regeneration capacity of cultivars), it only stimulated shoot development. The insertion of some bacterial oncogenes (in particular genes 4, rolB, C and 5) enhanced bud/shoot formation, especially in the case of low-regenerating cultivars.

SECTION 5 -IN VITRO CULTURES Uptake of 14C-sucrose and 14C-NAA by tissue cultures ofNicotiana tabacum and Brassica oleracea in regenerating and non-regenerating cultures