Multiplication of apple 'Gala' (Malus domestica L) by thidiazuron (Germination, In vitro root-based regeneration, and micrografting)

In apple Malus domestica, improvement of in vitro propagation methods is required to generate healthy and good quality apple trees in order to meet the demand for large quantities of planting material in the market. The combination of seed coat removal and application of thidiazuron (TDZ) improved germination rate in seeds extracted from ‘Red delicious’, ‘McIntosh’, ‘Gala’, and ‘Fuji’ fruits (100% after 8-10 days). A study the effect of exposure time and TDZ on endogenous components in ‘Gala’ apple seedlings root showed that TDZ changed the levels of endognous salicylic acid, isopentenyladenine and gibberellic acid in the roots of apple seedlings. A novel and highly efficient regeneration protocol was developed from seedling-derived root explants, with ‘Gala’ as the preferred cultivar and using 10 µM TDZ as an elicitor. Histological studies revealed that pericycle and inner cortex cells are the origins of shoot buds regenerated from the roots in ‘Gala’. In a novel approach, regenerants from ‘Gala’ roots were successfully micrografted onto rooted ‘G202’ rootstocks under in vitro conditions.