Abstract
The research was conducted with the aim of optimizing the introduction of apple clonal rootstocks (M.9, MM.106) and varieties (Golden Delicious, Zarya Alatau) into the initial in vitro nutrient medium. As a result, the most favorable time for introducing apple explants into the in vitro medium was found to be March - April. A sterilization scheme was developed for one-year-old shoot tips and dormant axillary buds used as initial explants. The most active development of microshoots occurred in the MS-1 nutrient medium. The addition of polyvinylpyrrolidone (PVP) as an antioxidant to the nutrient medium contributed to the inhibition of phenolic compound release and demonstrated that frequent medium renewal was not necessary. The analysis of the obtained data revealed that the development of microshoots depends on the genotypic characteristics of the apple varieties and clonal rootstocks. The highest growth rates of explants were observed in the following apple varieties and clonal rootstocks: Zarya Alatau (98% regeneration ability), Golden Delicious (77%), and clonal rootstocks M.9 (80%). The lowest growth rate was observed in the clonal rootstock MM.106 (43%). The effect of the duration of the vegetative period of apple varieties and clonal rootstocks on the induction of microshoot growth and development has not been investigated.