Alginate-encapsulation, short-term storage and plantlet regeneration from encapsulated protocorm-like bodies (PLBs) of Cymbidium finlaysonianum Lindl.: An endangered orchid of Thailand

Abstract

© 2018, Walailak University. All rights reserved. Synthetic seed technology is becoming popular due to its wide application in germplasm conservation and for exchanges among countries in the floriculture trade. This method was used to study the bead formations and the conversion capabilities of Cymbidium finlaysonianum Lindl. For artificial seeds, new protocorm-like bodies (PLBs) (about 4 - 5 mm in diameter) of Cymbidium finlaysonianum Lindl. were isolated individually from 2-month-old proliferating PLB-clusters cultured in Vacin and Went (VW) liquid medium supplemented with 8.84 μM 6-benzyl-aminopurine (BAP). Different concentrations of sodium alginate (2, 3, 4 and 5 %) and calcium chloride (CaCl2.2H2O) (75, 85 and 100 mM) were tested to prepare bead formation. The ideal bead was obtained using 3 % sodium alginate and 100 mM CaCl2 for 30 min, resulting in uniform spherical beads. Effects of different media (full-strength MS, ½ MS or ¼ MS liquid medium with 3 % (w/v) sucrose) in gelling matrix on artificial seed germination were explored. Of the various gelling matrices for germination, the ¼ MS liquid medium was the most effective in terms of germination percentage (90 %) and germination date (28 days). Germination of the artificial seeds was observed within 28 - 56 days of formation on various gelling matrices. The effects of different storage conditions and intervals on conversion (into plantlets with shoot and root) ability of artificial seeds were determined. Among the 4 temperature regimes of storage (0 ± 2, 4 ± 2, 8 ± 2 and 25 ± 2 °C), artificial seeds were successfully stored at 8 ± 2 °C, till 105 days showed percentage of conversion frequency at 44.0 % when cultured on a VW medium supplemented with 2 % (w/v) sucrose with 0.2 % (w/v) activated charcoal. The complete plantlets derived from germinated-encapsulated PLBs showed 90 % survival rate during their gradual acclimatization to greenhouse conditions after transferal of rooted plantlets to sterilized coconut husks and irrigation with water twice a day for 3 months under 70 - 80 % relative humidity and about 12 h photoperiod. The highest percentage of plantlet survival recorded at 12 months after reestablishment in the forest was 75.8 %.