In Vitro Propagation and NaCl Tolerance of the Multipurpose Medicinal Halophyte Limoniastrum monopetalum

Abstract

Limoniastrum monopetalum is an evergreen perennial shrub native to Mediterranean coastal sands and salt marshes. It has adapted to a variety of environmental stresses and is used in traditional medicine and as an ornamental plant. In the present study, an efficient micropropagation protocol for this species was developed to facilitate the production of selected genotypes and promote its wider use. Research has focused on the effects of various cytokinin types [benzyladenine (BA), zeatin, 6-furfurylaminopurine (kinetin) or 6-γ-γ-dimethylallilopurine (2iP)] and concentrations (0.0–4.0 mg·L−1) and various NaCl concentrations (0.0–20 g·L−1) during all stages of in vitro culture. For in vitro establishment, Murashige and Skoog (MS) medium supplemented with 0.5 mg·L−1 BA and 0.0 or 5.0 g·L−1 NaCl was most appropriate (100% explant response, 3–4 shoots per explant, 2 cm shoot length). The best results for shoot multiplication (100% response, 9 shoots per explant, 0.8–1.0 cm shoot length) were obtained with low (0.5 mg·L−1) BA or relatively high (2.0 mg·L−1) kinetin concentrations in the medium; however, 0.5 mg·L−1 kinetin should be preferred in the case of production of multiple rooted microshoots during one stage. The addition of NaCl at relatively low concentrations (2.5 or 5.0 g·L−1) in a medium supplemented with 0.5 mg·L−1 BA doubled shoot multiplication but did not improve shoot elongation (100% explant response, 16 shoots per explant, 0.8 cm shoot length). For in vitro rooting, half-strength MS medium supplemented with 1.0 mg·L−1 IBA was most appropriate (97% rooting, 9.4 roots per microshoot, 1.2 cm root length). Regarding the effects of NaCl on in vitro rooting, microshoots were relatively tolerant to NaCl concentrations up to 10.0 g·L−1. The effects of NaCl depend on the micropropagation stage; they are synergistic during shoot multiplication and tolerant during rooting. However, explants responded satisfactorily in its absence, indicating that NaCl was not necessary as a medium component. Ex vitro acclimatization and establishment of plantlets was 100% successful in a mixture of peat:perlite 1:1 or 2:1 (v/v).