Features of rooting microcuttings of black crowberry (Empetrum nigrum L.) during adaptation

Relevance. Black crowberry (E. nigrum L.) is a wild plant that contains high levels of biologically active substances. It is currently attracting increasing interest as both a berry and a medicinal plant. Therefore, it has potential for cultivation as a source of medicinal plant material containing high amounts of flavonoids. There is therefore a need to develop accelerated methods of vegetative propagation, including clonal micropropagation. A critical step in this process is adapting the plant to non-sterile conditions. The aim of our research was therefore to develop methods for adapting and inducing rhizogenesis ex vitro of microcuttings of black crowberry (E. nigrum L.) cultivar 'Irland' grown on various substrates using different rooting stimulants. Methods. The study focused on unrooted microcuttings of black crowberry (E. nigrum L.) plants of the 'Irland' variety, which were obtained through clonal micropropagation in vitro. The crowberry microcuttings were planted in the third ten-day period of November in mini-greenhouses in various substrates (high-moor peat with pHKCl ≤ 3.5-4.0, sphagnum moss, and agroperlite). Experimental microplants treated with root formation stimulants ('Radygreen zelonyy', 'Mycofriend', 'BioKoren', 'KorneWin Ultra') were planted in these substrates. The control variant was a variant without treatment. The mini-greenhouses were located under Zěma ZML-0160 LED phytolamps, with a photosynthetic photon flux density (PPFD) of 120 µmol·s−1·m−2 at a distance of 50 cm from the plants, with a 16/8-hour (light/dark) photoperiod for 45 days. After adaptation to non-sterile conditions, the plants were maintained in a greenhouse (temperature 22-30 ºC, air humidity 70-75%). Results. On the 45th day of adaptation and rooting process of the black crowberry microcuttings', the advantages of cultivating them on an inorganic substrate agroperlite and treating the basal parts of the microcuttings with the mycorrhiza-forming preparation ‘Mycofriend’ was revealed. With a rooting of 88.9%. Significant differences were found in the morphometric indicators of the root system: in the number of roots – 4.00 ± 0.41 pcs., compared to the control 2.52 ± 0.35 pcs.; the total root length – 6.24 ± 0.83 cm, compared to the control – 2.71 ± 0.40 cm. The maximum total shoot growth was obtained in a substrate with acidic peat using the mycorrhiza-forming preparation ‘Mycofriend’ and amounted 6.78 ± 0.88 cm, compared to the control 3.97 ± 0.25 cm. Conclusion. The information is useful in the scientific understanding of the rooting ability of ever- green plants ex vitro, using the black crowberry cultivar 'Irland' as an example. It could also help us to obtain high-quality planting material for large-scale commercial production.