Synseed Production in Spilanthes mauritiana DC. for Short-Term Storage and Germplasm Exchange

Abstract

Aims: The present study provides an efficient protocol for short-term storage and germplasm exchange of a potent medicinal herb, Spilanthes mauritiana using encapsulated nodal segments. Study Design: For in vitro conversion of synseeds, 5 beads were placed in each flask having Murashige and Skoog (MS) medium supplemented with different combinations of plant growth regulators (PGRs). While for ex vitro conversion, 5 synseeds per thermocol cups having different planting substrates were directly sown. The data for each experiment were collected after 6 weeks. All the experiments were conducted with a minimum of 20 replicates per treatment and each experiment was repeated thrice. Place and Duration of Study: Plant Biotechnology Lab, Department of Botany, AMU, July 2012 to November 2013. Methodology: Concentration of two different manufacture grade of Na-alginate (purchased from Central Drug House and Loba Chemie) were compared for the production of ideal synseeds. Conversion of synseeds was tested under in vitro and ex vitro conditions. A low temperature storage (4ºC) experiment was also carried out to understand the explants’ ability to revive physiological activity leading to plantlet development. Results: A gelling matrix of 4% Na-alginate (CDH) or 3% (Loba Chemie) with 100 mM calcium chloride (CaCl2∙2H2O) was found most suitable for the production of ideal Ca-alginate bead. However, CDH grade Na-alginate (74.4% conversion) was found to be better than Loba Chemie (62% conversion) in terms of in vitro conversion of synseeds into complete plantlets when cultured on MS basal medium. Supplementation of Plant Growth Regulators (PGRs) to the MS basal medium further enhanced the conversion frequency of the synseeds. Maximum conversion (83%) was recorded on MS basal medium supplemented with 5.0 µM 6-benzyladenine (BA) and 0.5 µM indole-3-acetic acid (IAA). Synseeds, stored at 4ºC for 1-8 weeks showed successful sprouting with variable percent in successive weeks of transfer, followed by development into complete plantlets when returned to regeneration medium. Ex vitro conversion of synseeds also occurred when synseeds were sown directly into SoilriteTM moistened with quarter-strength MS salts. Plantlets regenerated from non-stored and stored synseeds were successfully hardened, acclimatized and established in soil with a success of 90%. While plantlets recovered from direct sowing of synseeds exhibited 80% survivability. Conclusion: Being small in size, synseeds provide an effective tool for conservation, storage and exchange of this valuable medicinal plant species, potentially overcoming many of the difficulties associated with long-distance transport of plant germplasm.