Purpose. To reveal the frequency and intensity of callus formation and organogenesis, the effectiveness of microclonal reproduction of various species of the genus Linum L. (Linaceae) in vitro. Methods. For in vitro induction of callus formation and organogenesis, hypocotyl segments of species Linum usitatissimum L. convar. elongatum and convar. usitatissimum, L. tenue Desf., L. bienne Mill., L. corymbulosum Pchb., L. nervosum Waldst. & Kit., L. flavum L., L. campanulatum L., L. perenne L., L. austriacum L., L. grandiflorum Desf., L. strictum L. were cultivated on Murashige and Skoog medium supplementedwith 0.05 mg/l 1-naphthylacetic acid and 1.0 mg/l 6-benzyl aminopurine at 22–24 °C, relative humidity of 60–80%,with 16 hours photoperiod (2500 flux). For microclonal reproduction Murashige and Skoog, White, Gamborg and Eveleigh media and their modifications were used. The measurement results were interpreted by the arithmetic mean, standard error for the sample mean, the leastsignificantdifference and ranked. Results. Different species of the genus Linum to a large extend are capable of forming callus and regenerating shoots under the specified cultivation conditions. The frequency of callus formation for the studied samples on the 35th day of cultivation varied within 81.25–100%, the mass of callus from one explant – 0.21–1.64 g, the frequency of organogenesis – 12.50–100%, the number of shoots – 1.8–7.6 pcs. and the height of the shoots was 0.82–2.12 cm. The following species: L. usitatissimum convar. elongatum, L. tenue, L. bienne and L. strictum were distinguished by a high intensity of callus formation. Intensive organogenesis was pecular to L. tenue, L. bienne, L. flavum, L. austriacum and L. grandiflorum. The efficiency of somaclone obtaining was quite low in L. nervosum and L. campanulatum. In total, for the microclonal reproduction of species of the genus Linum Murashige and Skoog, Gamborg and Eveleighmedia supplementedwith 12.5 g/l glucose were optimal. At the final stages of microclonal propagation, before transferring microclones in vivo, it is advisable to use White medium, which contributes to a high frequency of rhizogenesis. Varieties of L. usitatissimum convar. elongatum and convar. usitatissimum had diffe­rent responses to in vitro culture. Conclusions. The frequency and intensity of callus formation and organogenesis, the effectiveness of microclonal reproduction depended on the genotype of a particular species; therefore it is advisable to select the composition of the nutrient medium and growth regulators for each of them. Some species of the genus Linum have not yet been studied in vitro, so the obtained results allow expanding the scope of their use in practice, in particular in breeding as a new source material with somaclonal variation, interspecific crosses, and ornamental floriculture.

Purpose. The adaptation of regenerant plants to environmental conditions is the final stage of micropropagation. According to a number of authors, when in vitro plants are transferred to in vivo non-sterile conditions, a significant percentage of mortality is recorded. In a previous publication, the regenerative capacity of strawberry (Fragaria vesca L.) in vitro tissues on MS culture medium (Murashige & Skoog, 1962) and a regenerants was obtained (Chornobrov O. Yu., 2019). The objective of the study is to develop an optimal protocol of acclimation of in vitro F. vesca plants to in vivo conditions. Methods. Biotechnological and statistical methods of research were applied. For the research ‘Ruiana’ and ‘Zhovte Dyvo’ cultivars were used with in vitro cultivation cycle of 30–35 days. Prepared plants were planted in 0.33 L plastic contai ners, one piece in a mixture of coconut substrate and perlite (3:1). Plants were kept under high relative humidity (85–90%) conditions for 3–5 days, 6–8 days and 10–14 days. The studies were carried out in the Plant Biotechnology Laboratory of SS of NULES of Ukraine “BFRS” during 2019–2020. Results. The duration of Fragaria vesca regenerant plants exposure in conditions of high relative humidity significantly affected adaptation efficiency. The proportion of ‘Ruiana’ and ‘Zhovte Dyvo’ plants adapted to the greenhouse conditions were 47.6 ± 2.5% and 60.0 ± 1.7%, respectively, when the plants were kept for 10–14 days. A significant efficiency of plant adaptation (more than 70%) was obtained under condition of preliminarily exposure the roots of the plants in an auxin solution for 25–30 minutes with daily application of 30% solution of glycerine as foliar spray. The plants adapted to the greenhouse conditions had pigmentation characteristic of the variety, without signs of chlorosis and vitrification. Conclusions. An optimal protocol for in vitro adaptation of F. vesca cultivars to in vivo conditions was developed and viable plants were obtained. Further research will be aimed at studying the growth and development of F. vesca regenerant plants in open ground.