In vitro growth responses of the 'Pyrodwarf' pear rootstock to cytokinin types

The present paper deals with the effect of different concentrations (1, 2, 5, 10 and 15 mu M) of 6-benzyladenine (BA) and thidiazuron (TDZ), combined with indole-3-butyric acid (IBA) at concentrations of 0, 0.5, 2.5 and 4.9 mu M on in vitro multiplication of the pear rootstock 'Pyrodwarf'. Murashige and Skoog (1962) (MS) was the basal medium used in all combinations. The multiplication index as well as the length of axial and lateral shoots were monitored The highest multiplication index (2.89) was obtained on the medium supplemented with 5 mu M BA and 0.5 mu M IBA. Higher concentrations of TDZ (more than 2 mu M TDZ), in combination with IBA. brought about fasciation of shoots, which was confirmed by SEM technique. On the rooting medium consisting in 1/2 MS supplemented with 5 mu M IBA and 0.3 mu M giberellic acid (GA(3)), the higher rooting percentage and other superior rooting parameters were also recorded in the case of the shoots originated from BA media. The obtained results suggest that to gain good multiplication parameters it is recommended to use good quality shoots for further subcultivation. In order to avoid the occurrence of fasciation it is required to use the cytokinin BA or to limit the concentration of TDZ in the multiplication phase of pear 'Pyrodwarf' rootstock.