OPTIMIZATION OF THE NUTRIENT MEDIUM FOR THE PRIMARY STAGES OF COMMON WALNUT MICROCLONAL PROPAGATION IN VITRO

SummaryAim. To optimize the processes of microclonal propagation of Juglans regia in vitro by selecting the composition and consistency of the nutrient medium. Methods. The methods of in vitro culture establishment of initial explants and microclonal propagation were used. Parts of the stem and buds of young sprouts, germinated by the mini-greenhouse method from the seeds of Juglans regia, were used as initial explants. Murashige&Skoog (MS) and Driver&Kuniyuki (DKW) nutrient media were used to establish Juglans regia explants in vitro. Agar was used as a gelling agent. The solid, semi-liquid, and liquid media were prepared with addition of 7 g/l, 3.5 g/l and 0 g/l of agar, respectively. All experimental variants of the media were modified by adding the phytohormone of the cytokinin group 6-BAP. The pH of the medium was controlled at the level of 7.1–7.2. The established explants in vitro were cultivated at a temperature of + 25°C, a light intensity of 2500 lux, a relative humidity of 56–70% and a photoperiod 16/8 h light/dark. On the 3rd, 7th and 14th day, the survival rate, growth and development parameters of the initial explants were estimated. Results. It was found that the optimal nutrient medium for in vitro establishment and cultivation of Juglans regia is the DKW medium, on which the high survival rate of explants was observed (80%), as well as accelerated swelling of buds and their proliferation. It is proposed to use semi-liquid nutrient media for in vitro establishment of initial Juglans regia explants. The use of semi-liquid nutrient medium DKW for the initial stages of common walnut micropropagation in vitro contributed to the acceleration of the processes of reproduction of this culture by 2 days and improved the survival rate by 20% compared to solid medium. Conclusion. The use of semi-liquid nutrient medium DKW for introduction into the culture and cultivation of walnut (Juglans regia) in vitro is recommended to increase the survival rate of explants by 20%, as well as the accelerated activation of buds (2 days) and their further proliferation.