An improved micropropagation and assessment of genetic stability of micropropagated Salvadora oleoides using RAPD and ISSR markers

Abstract

An improved micropropagation method has been developed for Salvadora oleoides, a valuable tree species of alkaline and arid regions. Nodal explant obtained from a mature tree (30- to 35-year-old) responded optimally (80.0 %) on BAP (2.0 mg l⁻¹) and produced (4.56 ± 0.52) shoots. Shoots were further multiplied by subculturing the in vitro excised shoots and transferring them to MS medium containing either BAP (0.0–2.0 mg l⁻¹) alone or in combination with lower concentrations of an auxin (IAA or NAA 0.05–0.4 mg l⁻¹). Among all the PGRs combination tested, MS medium supplemented with BAP (0.5 mg l⁻¹) and IAA (0.1 mg l⁻¹) formed the maximum number of shoots (68.40 ± 2.74 per culture bottle) with an average height (6.59 ± 0.30 cm), after 6 weeks of culture. Rooting in regenerated shoots was achieved by ex vitro methods and about 92.5 % of shoots were rooted with 5.25 ± 0.64 roots per shoot and an average length of 2.76 ± 0.53 cm after 3 weeks of incubation in the green house. More than (80 %) of hardened plantlets survived in the field conditions. Genetic stability of the discussed protocol was confirmed by two DNA-based fingerprinting techniques i.e. RAPD and ISSR. Of the 10 RAPD primers finally selected, a total of 42 bands (out of 43) were monomorphic and one polymorphic, whereas from 10 ISSR primers selected, all the 43 bands were monomorphic revealing a high level of genetic homogeneity in the regenerated plants and the donor plant. In the present investigation, we achieved significantly more number of shoots during multiplication, which are higher than all previous reports and further evaluated the genetic fidelity of protocol for the first time in S. oleoides, which concludes the clonal (true-to-type) nature of micropropagated plantlets.