Features of clonal micropropagation of plum PK SK 1 clonal rootstock

Abstract

Methodological features of the main clonal micropropagation stages of plum PK SK 1 clonal rootstock (of NCFSCHVW selection) are described. The rootstock is characterized by a high adaptability to soil and climatic conditions of the region. In particular, it exhibits good winter hardiness, resistance to overwatered soils, tolerance to drought, and the capacity to grow on heavy soils. Plum seedlings on this rootstock develop a powerful root system. These advantages render the development and improvement of methods for clonal micropropagation of plum PK SK 1 clonal rootstock highly relevant. The research was carried out in 2019-2022. The period of active shoot growth, i.e., the first and second decade of may, was established to be the most optimal period for introduction of explants into in vitro culture. In this period, regeneration reaches 78.1–93.8 %. Eff ective shoot multiplication proceeds on MS medium with Fe-EDTA or MS medium with Fe-EDDHA and 6-BAP in the amount of 1 mg/L, with the highest number of shoots formed from one explant following the fourth passage (on average, 11.7 and 12.3 shoots per explant). A signifi cant eff ect of the 6-BAP concentration on the number of shoots formed was observed. The combined eff ect of the form of chelated iron and 6-BAP concentration on the number of shoots formed was established only after 3-5 passages on MS medium with Fe-EDDHA. The rooting stage of PK SK 1 rootstock can also be carried out on a hormone-free MS medium with Fe-EDDHA. The rooting effi ciency reaches 57.1–61.8 %. On average, 2.4 roots are formed per shoot with a length from 1.2 to 5.1 cm, with the root quality being high (not cartilaginous and not brittle). For the adaptation stage, rooted shoots with a height of at least 2 cm having two or more roots with a length of at least 2-3 cm are selected. A mixture of the Agrobalt plant nutrient soil, vermiculite, and perlite in a ratio of 3:1:1 can be used as a substrate. Following four weeks of adaptation, the number of adapted plants averaged 87.5 %.