Rhizogenesis in clonal apple rootstocks (Malus Mill.) in vitro depending on the influence of abiotic factors

In vitro culture at the rooting stage the aft ereff ect of the use of earlier (during proliferation) growth regulators with cytokinin activity (6-benzylaminopurine and thidiazuron) and the eff ect of lamps of diff erent spectral composition on the percentage of rooting and biometric parameters of the development of the roots of clonal apple rootstocks were studied. The following forms of apple clonal rootstocks were taken as objects of research: 54-118, 57-490, 57-545, ММ 106 and М 26. The research methods used at the stages of in vitro culture studies corresponded to those generally accepted for this section of research. Studies were performed on two variants of explants, one part was cultured at the proliferation stage on media with 6-benzylaminopurine and the other on media with tidiazurone. It was found that explants that were cultivated at the stage of proliferation on media with thidiazuron had a tendency to a subsequent increase in the number of roots (at the stage of rooting) by one microscopic cut, in comparison with cultivation on media with 6-benzylaminopurine, by 1.1-1.3 times, and this regularity was observed in all studied clonal rootstocks of the apple tree. It was noted that when explants were illuminated, explants had a greater percentage of rooting when illuminated with phytolamps in comparison with lighting with lamps with a color temperature of 6500K by 1.1-1.4 times in all studied apple rootstocks, and an increase in the number of roots per one microstalk was observed (for excluding rootstock 57-490), by 1.1-1.9 times. During the research, the specificity of rooting of clonal apple rootstocks was observed under the infl uence of the composition of light and the use of 6-benzylaminopurine and thidiazuron at the stage of proliferation, which was expressed in a higher ability to rhizogenesis of some rootstocks compared to others. The rootstocks MM 106 (83.3-93.9 %) and M26 (87.8-92.7 %) had a greater percentage of rooting, according to the average number of roots per one microcut, rootstocks 57-545 (15.4 pcs.), MM 106 (11.2 pcs.), and M 26 along the average root length (27.0 mm).