The article presents the results of research on the optimization of the techniques of preparing somatic buds of cherry (Prunus serrulata L.) initial forms for introduction in vitro, as well as the sterilizer selection, its concentration, processing exposure time and other parameters to perform an effective sterilization. The authors give a description of commonly used and novel sterilizers and their characteristics and describe the optimum conditions for effective sterilization of the initial forms of cherry (Prunus serrulata L.) somatic buds.

While selecting a sterilization technique and a sterilizer, a biotechnologist attempts to clear the surface of the plant material from any present microorganisms, minimizing the explants damage risk caused by sterilizers, which contain toxic substances.

The main goal of this research was to tailor the conditions of sterilization, which present one of the most important stages of microclonal propagation as well as to elicit the characteristics of commonly used and novel sterilizers, and to select the optimum conditions for performing the effective sterilization of somatic buds of cherry initial forms (Prunus serrulata L.).

Explants were represented by somatic buds of cherry which were cut in the laminar box with a scalpel steamed at 180–200 °С and immediately transferred with sterilized tweezers to a growing medium. The growing medium was prepared according to Murashige and Skoog medium protocol modified with 6-benzyl-aminopurine (6-BAP), 1 mg/ml. The sterilizers used in this research were chloramine, biоchloride of mercury and septodor forte of different solution concentration. Prior to sterilization the explants of Prunus serrulata L. were treated with soap and pure water for 15–20 min in order to remove surface fungal and/or bacterial contamination.

The amount of the bedded material counted 50 units for all modes of sterilization. The rest of the manipulations with plant material were performed in compliance with the standard procedures.

This research has shown that the sterilization exposure time up to one minute provides no sterile cuttings. With exposure increase from one to ten minutes sterile viable explants output was almost equal for 0.05 % mercury dichloride and septodor forte and amounted about 50-58 %, and sterilization of plant material with 10 % chloramine gave the lowest yield of cuttings varying from 14 % to 20 %.

It has also been noted that exposure time increase up to 20 minutes, as well as 0.01 % mercuric chloride application resulted in plant tissue failure as they could not withstood the load.

Explants necrosis was recorded in all the research variants, but the largest number of dead cuttings demonstrated 5-10 % chloramine sterilizer with 20-minute exposition.

The studies prove that the most effective sterilizer of somatic buds of cherry (Prunus serrulata L.) initial forms is a 15 % chloramine solution with 15-minute exposition that allows 90 % output of the sterile material.

Sterilization time increasing up to more than 20 minutes ensured 20-25 % output of non-infected material, but the plants were not viable.

Key words: initial plant material, cherry, plant breeding, explants, sterilization, in vitro, biotechnology, introduction, morphological characteristics.