Biotechnology methods in virus-free chrysanthemum varieties production

The paper considers the development of optimal conditions for the production of virus-free regenerants of Chrysanthemum spp. for further reproduction under in vitro conditions. The studies were conducted in 2021–2022. The object was chrysanthemum varieties of different taxonomic ranks: Ch. morifolium, Ch. multiflora and Ch. koreanum, which are affected by chrysanthemum virus B (CVB). Microcuttings with a bud were used as explants. At the stages of clonal micropropagation, the following nutrient media were used: MS + 0.5 mg/l of BAP (in vitro culture) and MS + 0.2 mg/l of kinetin + 0.05 mg/l of IBA (multiplication). The DAS-ELISA method was used to diagnose grafters and retest regenerants for the absence of CVB virus. The testing of regenerants for the presence of endophytic microflora was carried out on a Viss provocation nutrient medium. The effect of exposure time of the sterilant – lysoformin-3000 on the possibility of obtaining aseptic explants was conducted. It was found that treatment with 70 % ethanol (10 seconds) and effect of 2 % lysoformin solution for 10 minutes produces the maximum number of viable explants from 63.3 to 76.7 %, depending on the variety. The data on the effect of high temperature (37 °C) for 1–12 weeks on chrysanthemum plants are presented. A negative correlation was established (r = –0.84…–0.97) of the duration of thermotherapy with the regenerative ability of explants. The possibility of eradication of chrysanthemum plants, both against bacterial and viral infection is shown. An exposure of 9 weeks was noted, at which the rate of regeneration varies from 11.1 to 23.1 % relative to the control, while the efficiency of the recovery is maximum – 100 %.