Micropropagation of Plum rootstock (Prunus domestica L.) of ‘Wavit’ variety

Background. ‘Wavit’ is a valuable Plum rootstock hybrid of Prunus domestica (P. cerasifera × P. spinosa). It reduces tree vigor and exhibits a high winter hardiness, increases fruit size, shows good compatibility with all types of plums and apricots, and consistently produces high yields. The aim of this study is to propose a suitable in vitro propagation protocol for the ‘Wavit’ rootstock. This includes micropropagation based on the analysis of two base media for shoot proliferation: Driver Kyniyuki Walnut (DKW), and Quorin & Lepoivre (QL) with different combinations of plant growth regulators and two forms of iron chelate. Additionally, the study explores an in vitro protocol for rooting with different concentrations of Indole-3-butyric acid (IBA), and an ex vitro adaptation period. Material and Methods. Research was conducted by cultivation under in vitro conditions of ‘Wavit’explants with following stages: shoot proliferation was exmained by using two basal media DKW, and QL supplemented with Walkey vitamins and diffe­rent contents of IBA, meta-topolin (MT), 6-benzylaminopurine (6-BAP) and iron chelate: ferric-sodium salt of ethylenediaminetetraacetic acid (FeNaEDTA) and ethylenediamine di-2-hydroxyphenyl acetate ferric (FeEDDHA). After 4 weeks of cultivation shoot length, number of shoots, % of vitrification and multiplication rate were measured. Rooting medium was consistent with ½ Mourashige & Skoog (MS) medium supplemented with Walkey vitamins and different concentrations of Indole-3-butyric acid. After 4 weeks of cultivation shoot length, root length, number of roots and % of rooted nodal segments were measured. Acclimatization was conducted in the greenhouse. For the experiments, shoots were divided into 3 groups: unrooted, 1–3 roots, >3 roots, and cultivated for a month after which survival rate was measured. Results. The research involved the cultivation of ‘Wavit’ explants under in vitro conditions, comprising several stages. At the stage of shoot proliferation after 4 weeks of cultivation, the highest value with a significant difference in shoot length was found in variants DKW 0.5 MT, 0.1 IBA, FeNaEDTA; DKW 0.5 MT, 0.5 BAP, 0.1 IBA, FeNaEDTA; DKW 0.5 MT, 0.5 BAP, 0.1 IBA, FeEDDHA; however, the highest number of vitrified shoots was observed in the last two listed variants. A significant difference was also found in the multiplication coefficient in the variant DKW 0.5 MT, 0.5 BAP, 0.1 IBA, FeEDDHA, which was the lowest among all DKW medium variants. Subsequently, the data obtained at the rooting stage showed dependency on root formation with increase of IBA concentration in nutrient media. Addition of 1,0, 1,25 and 1.5 mg/L significantly increased percentage of rooted shoots, number of roots and root length, however 1.5 mg/L decreased the shoot length of the explants. After 1 month of acclimatization, only 25 % of the group without root survived, the survival rate of groups with 1–3 roots and more than 3 roots was 87.5 % and 92 % respectively. Conclusions. The present study describes a standard in vitro protocol for the mass propagation of a valuable plum ‘Wavit’ rootstock from stem nodal segments. Driver Kyniyuki Walnut medium supplemented with 0.5 mg/L meta-topolin, or with 0.5 mg/L meta-topolin and 0.1 mg/L indole-3-butyric acid with FeNaEDHHA, showed the overall increased performance during shoot proliferation. For the rooting stage, ½ Mourashige & Skoog with indole-3-butyric acid at concentrations of 1.0 and 1.25 mg/L demonstrated better results. Additionally, we observed the advantage of obtaining rooted plant material before the acclimatization stage, which significantly increased the survival rate of plants.