Development of adventitious shoots from in vitro grown Cydonia oblonga leaves as influenced by different cytokinins and treatment duration

Abstract

The effects of three cytokinins, kinetin 4.5 μM (Kin), 6-benzylaminopurine 4.5 μM (BA) and N-phenyl-N'1,2,3- thiadiazol-5-yl-urea 4.5 μM (TDZ), and the effects of different treatment duration on the regeneration of adventitious shoots from quince (Cydonia oblonga Mill.) leaves were studied. In a first experiment, leaves treated with Kin for 0, 8, 16 and 24 d were transferred to BA or TDZ-containing growth medium. In a second experiment TDZ applied for 0, 4, 8, 12, 16 and 24 d was followed by BA. All treatments included 0.5 μM α -naphthaleneacetic acid (NAA). In the sequence Kin-BA, the production of adventitious shoots decreased and reddish-coloured nodular structures (RNS) of meristematic appearance increased with increasing duration of Kin treatment, while somatic embryo formation was optimal at 8 d. In the Kin-TDZ sequence, shoot production was initially pronounced, but it declined with increasing duration of the Kin treatment, while the number of roots, somatic embryos and RNS increased. TDZ-BA treatments induced marked shoot production, which gradually increased with increasing duration of TDZ treatment. The presence of TDZ and a long treatment duration appeared to be very important factors in inducing caulogenesis. Kin appeared to be effective in shoot induction but not in shoot development; the results of this work demonstrate that RNS were adventitious shoots blocked at an early developmental stage on account of insufficient cytokinin activity. BA was less effective than TDZ in inducing shoot regeneration. Finally, both Kin and BA applied after 2,4-D treatment promoted somatic embryo induction.