Somatic embryo, adventitious root and shoot regeneration in in vitro grown quince leaves as influenced by treatments of different length with growth regulators

The purpose of this work was to acquire more information on the capacity of in vitro grown quince (Cydonia oblonga Mill.) leaves to simultaneously regenerate somatic embryos, adventitious roots and shoots, and to evaluate the variations induced on regeneration response by treatments of different length with growth regulators. After 2 days of liquid treatment with 2,4-dichlorophenoxyacetic acid, the leaves were cultured for 0, 3, 6, 9, 12, 15, 18 and 21 days on gelled growth medium containing the basal components of Murashige and Skoog and kinetin (Kin) 4.5 μM + naphthaleneacetic acid (NAA) 0.5 μM. At the end of each treatment period, the leaves were cultured on a transfer medium in the absence or in the presence of a growth regulator combination represented by N6-benzylaminopurine (BA) 2.66 μM + gibberellic acid 0.58 μM + indole-3-butyric acid 0.3 μM. The culture period for all the treatments was fixed to 52 days.Simultaneous regeneration response of somatic embryos, adventitious roots and shoots differed according to the length of the kinetin + naphthaleneacetic acid treatment and to the absence or the presence of growth regulators in the transfer medium. In the absence of growth regulators, only somatic embryos and roots were regenerated; the number of somatic embryos increased from the 0 day to the 6–9th day of treatment with kinetin + naphthaleneacetic acid, while root regeneration showed the opposite trend. After the 9th day, the production of somatic embryos decreased up to the 15th day and then stabilized, while roots showed only very small reduction up to the end of the experiment. In the presence of growth regulators in the transfer medium, adventitious shoots were regenerated together with somatic embryos and roots. The highest number of shoots was observed when the leaves were directly transferred from 2,4-dichlorophenoxyacetic acid treatments to growth regulator medium. Increasing the length of kinetin + naphthaleneacetic acid treatment, shoot regeneration decreased and by the 12th day no more shoots were produced. Somatic embryo regeneration peaked on the 6th day of culture with kinetin + naphthaleneacetic acid and showed the same trend as in the absence of growth regulators in the transfer medium, while root formation tended to increase with prolonging the kinetin + naphthaleneacetic acid treatment.