Submitted to: The Scientific World
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 17, 2013
Publication Date: December 13, 2013
Citation: Sakhanokho, H., Pounders, C. and Blythe, E. 2013. Alginate Encapsulation of Begonia Microshoots for Short-Term Storage and Distribution. The Scientific World Journal, Article ID 341568, DOI:10.1155/2013/341568. Interpretive Summary: Production of synthetic seeds or synseeds is achieved by artificial encapsulation of explants (or portions) such as shoot tips, cell aggregates or any other tissue of a plant. Synthetic seed technology is useful for many reasons. For example, it is useful for the propagation of rare hybrids, elite genotypes, and genetically engineered plants whose seeds are either too expensive or not readily available. Also, cold storage of encapsulated or synthetic seeds has the potential to reduce the cost of maintaining germplasm cultures. Finally, this technology could play a role in reducing the spread of plant diseases and pests as it has practical application for short-term storage of plant germplasm and the exchange of pathogen-free plant materials between laboratories, both nationally and internationally. Begonias are among the most popular ornamental plants and also one the largest angiosperm genera, containing about 2000 species with new ones continuing to be discovered in various parts of the world. The main purpose of the current study was to establish an encapsulation method for Begonia shoot tips as explants for short term storage and germplasm exchange. Two Begonia semperflorens cultivars, Sweetheart Mix and BabyWing White, were used. Thanks to the protocol developed, plantlets obtained from encapsulated shoots were successfully acclimatized and established in potting soil. Encapsulated shoot tips could still be converted to plants even after two-month storage duration, but when the non-encapsulated (control) shoot tips were stored for just one month, only 13% conversion rate was obtained.
Technical Abstract: Synthetic seeds were formed from in vitro grown Begonia cultivars (Sweetheart Mix and BabyWing White) shoot tips using 3% sodium alginate in Murashige and Skoog medium (MS) salt solution as the gel matrix and 100 mM calcium chloride for complexation. Synthetic seed formation was achieved by releasing the sodium alginate/explant combination into 100 mM calcium chloride (CaCl2•H2O) solution aseptically for either 30 or 45 min. The control consisted of nonencapsulated shoots. Both control and encapsulated shoots were transferred into sterile Petri dishes and stored at low temperature (4 °C) or at room temperature (~22 °C) for 0, 2, 4, 6, or 8 weeks. Conversion of synthetic seeds into plantlets for both storage environments was assessed in either MS medium or peat-based substrate (PBS; Jiffy 7 peat pellets). No significant difference was found between the 30 and 45 min CaCl2•H2O treatments or the two cultivars. Encapsulation of explants improved survival rate over time irrespective of the medium type or storage environment. Survival rates of 88, 53, 28, and 11% for encapsulated microshoots vs. 73, 13, 0, and 0% for control explants could be achieved after storage for 2, 4, 6, and 8 weeks, respectively. Overall, the best results were obtained when synthetic seeds were stored at low temperature (4 °C) and germinated on MS medium. Low germination (8%) was achieved in MS after 8 weeks of storage at ~22 °C, but this procedure has the advantage of avoiding costs associated with refrigeration equipment. Plantlets obtained from encapsulated shoots were successfully acclimatized and established in potting soil.