A new method for in vitro propagation of lilac (Syringa vulgaris L.): regrowth and storage conditions for axillary buds encapsulated in alginate beads, development of a pre-acclimatisation stage

Abstract Axillary buds from three micropropagated varieties of lilac were encapsulated in alginate beads. Best explant regrowth conditions were achieved by culturing the encapsulations in 24-well microplates on Murashige and Skoog agar-gelled medium [Murashige, T., Skoog, F., 1962. A revised medium for rapid growth and bioassays with tobacco tissue cultures. Plant Physiol., 15, pp. 473–497]. The regrowth rate could reach 100% depending on the cultivar and macronutrient supply. When encapsulations were stored at 5°C, explant regrowth rate after 50 days remained above 75%. A pre-acclimatisation procedure was developed under non-sterile conditions, with leaf fertilisation and progressively increased air renewal in the enclosure. One tested treatment allowed survival, growth and hardening of 95% of the plantlets, so they could be transferred to the greenhouse without requiring a saturated humidity stage. For such plantlets, rooting rate after 21 days in the greenhouse reached 81%.