Thidiazuron-induced organogenesis and somatic embryogenesis in sugar beet (Beta vulgaris L.)

Improved in vitro tissue culture systems are needed to facilitate the appli cation of recombinant DNA technology to the improvement of sugar beet germp lasm. The effects of N-6-benzyladenine (BA) and thidiazuron (TDZ) pretreatm ent on adventitious shoot and somatic embryogenesis regeneration were evalu ated in a range of sugar beet breeding lines and commercial varieties. Peti ole explants showed higher frequencies of direct adventitious shoot formati on and produced more shoots per explant than leaf lamina explants. TDZ was more effective than BA for the promotion of shoot formation. The optimal TD Z concentrations were 2.3-4.6 muM for the induction of adventitious shoot r egeneration. Direct somatic embryogenesis from intact seedlings could be in duced by either BA or TDZ. TDZ-induced somatic embryogenesis occurred on th e lower surface of cotyledons at concentrations of 0.5-2 muM and was less g enotype-dependent than with BA. A high frequency of callus induction could be obtained from seedlings and leaf explants, but only a few of the calluse s derived from leaf explants could regenerate to plants via indirect somati c embryogenesis. These results demonstrated that TDZ could prove to be a mo re effective cytokinin for in vitro culture of sugar beet than BA. Rapid an d efficient regeneration of plants using TDZ may provide a route for the pr oduction of transgenic sugar beet following Agrobacterium-mediated transfor mation.