Effects of cytokinin/auxin combinations on organogenesis, shoot regeneration and tropane alkaloid production in Duboisia myoporoides

Leaf explants of Duboisia myoporoides R. Br. were exposed to 65 different cytokinin/auxin combinations and the morphogenetic responses compared. Two different types of calluses were induced depending on the cytokinin/auxin combinations used for callus induction. Non-rooted shoots were regenerated from calluses induced with 7 different cytokinin/auxin combinations, cultured in the regeneration medium and also from the calluses induced with 2 different cytokinin/auxin combinations, cultured in the callus induction medium. Shoot-bud regenerating ability of the calluses, number of leaves formed/shoot, lengths of the leaves and shoots and tropane alkaloid biosynthetic ability of the non-rooted shoots depended on the cytokinin/auxin combinations used at the callus induction stage. Hyoscyamine and scopolamine were detected in the 11-week-old callus induced with BA 10 muM + NAA 1 muM. These alkaloids were also detected in the 6 and 9-week-old non-rooted shoots regenerated from callus induced with BA 10 muM + NAA 1 muM, cultured in regeneration medium and from the callus induced with BA 10 muM + IBA 0.1 muM, cultured in callus induction medium. Shoots were regenerated in liquid medium supplemented with BA 10 muM + IBA 0.1 muM. No tropane alkaloids were detected in the 4-week-old shoot cultured in liquid medium.