Efficient axillary shoot proliferation and in vitro rooting of apple cv. 'Topaz'

Abstract

'Topaz' is a modern Czech apple cultivar well accepted by consumers and scab-resistant, providing reasons for the significant spread of cv. 'Topaz' in European orchards, especially in the organic fruit production industry. Growing the apple trees on their own roots provides some advantages in comparison with grafted trees. Micropropagation is the method of choice for plantlet production for this purpose as well as for the establishment of healthy mother stock trees as a source of scions. The efficiency of axillary shoot proliferation was examined on four media differing in plant growth regulators and their concentrations, and from three explant types: intact or decapitated and defoliated microshoots placed vertically and one-nodal segments placed horizontally. All media consisted of Quoirin and Lepoivre (QL) macroelements and Murashige and Skoog (MS) microelements. Furthermore, rooting efficiency on six different media/treatments was analyzed. Media with 1 mg/L 6-benzylaminopurine (BA) or BA (0.5 mg/L) + 1.5 mg/L kinetin (Kin) produced similar number of microshoots per inoculated one (2.5 and 2.4, respectively). Medium with 1 mg/L thidiazuron (TDZ) produced significantly higher number of shoots (3.6) but they were fasciated. Three different explant types also produced similar numbers of microshoots. High rooting efficiency (68.7%), a high number of roots per shoot (6.6) and the best quality of shoots were obtained in rooting medium containing 2 mg/L of indole-3-butyric acid (IBA). An efficient method of shoot proliferation was established, and, since rooting was the most critical step, an efficient procedure for rooting apple cv. 'Topaz' was established.